Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Posts Tagged ‘health physics

Fukushima updates; March 18.

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I’m going to focus this post on radiation dosimetry – because radiation dosimetry is what really matters in terms of deciding whether anybody can actually get hurt. So far, nobody around Fukushima has been hurt by radioactivity, although of course tens of thousands are still dead or missing because of this great tragedy.

It doesn’t matter what you do or don’t do to the reactors or the used fuel, or what condition they’re in – at the end of the day, the radiation dose to the public is how we measure the effect of this incident on the public and its potential for harm.

To be honest, I’m really not concerned much with what the dose rates are in the plant itself.

The men and women who work there understand dose rates and health physics quite well. They routinely work in areas of elevated above-background dose, and they know how to work safely in those environments. They understand how to measure and quantify the radiation field in the working environment, and the accumulated doses that they’re personally receiving.

They understand how to manage shielding, exposure time, radiation measurement and dosimetry in order to get the work done safely and effectively.

Even with abnormally significantly elevated radiation fields in some areas as a result of these incidents, they still know how to work safely. If the radiation dose rate in some particular area is so highly elevated that it cannot be entered safely for any length of time at all, then they won’t be entering it.

It’s pointless to scare the public with elevated on-site dose rate measurements. They’re not working on the site. Leave that for the people with health physics training. I’m much more interested in off-site dose rate measurements, personally, as those are the measurements that are actually of relevance to the public.

Off-site radiological dose rates

The KEK accelerator physics complex in Tsukuba (165 km from Fukushima) has a webpage showing their real-time measurements of the environmental gamma dose rate (counted with a GM tube). They’re currently measuring 0.17 μSv/h, at the time I write this, which has been fairly constant over the last few days, except for a brief, narrow spike up to 0.6 μSv/h, which they observed on the 16th.

(NOTE: Just to avoid any ambiguity, “m” means milli, 10-3. “μ”, or “u” if you don’t have access to the Greek alphabet in your software, means micro, 10-6. And when I say milli I’m quite sure I mean milli, and when I say micro I’m quite sure I mean micro. Because these terms are important, personally, I make damn sure to get them right.)

Each year, a resident of the United States receives an average total dose from background radiation of about 3.1 mSv. This is the radiation dose from natural background sources; from natural radioactivity in the Earth, and cosmic rays from space. That’s equal to 0.354 μSv/h.

In practice, the average dose that a person receives each year in the United States is significantly higher than that natural background dose, about twice that, once you’ve added on the dose from medical imaging and things like that.

The radiation dose rate being measured in Tsukuba right now, after the Fukushima accident, is less than half of the average natural background radiation dose rate that a person receives in the United States. This includes all sources of radiation in Tsukuba, including natural geological radioactivity, cosmic radiation, and any radioactivity released at Fukushima, as well as any ionising radiation from the particle accelerators at KEK, which is what these sensors are actually intended to monitor.

That brief, narrow spike seen in the radiation field measured at KEK doesn’t really concern me. The radiation dose you’ll receive if you hang around in that area for an extended period of time is the area under the graph – the integral – over that period of time. For such a short, sharp spike, the overall potential dose is still quite small.

In order to quantify the potential harm from a significant release of radioactivity, it would make more sense to “filter” that dose-rate data from the detector as a rolling average, to make it simpler to make a more straightforward interpretation of the potential to receive any significant radiation dose.

KEK is also measuring the concentration of 131I and the short-lived fission product 132Te in the atmosphere and reporting regular updates to this data online. The concentrations we’re looking at here are extremely small – on the order of 10 microbecquerels per cubic centimeter – but they are concentrations which they are able to accurately measure at KEK, using a high-volume air sampler and a high-purity germanium gamma-ray spectrometer.

This site gives us a continually updated log of the gamma-ray dose rate in Tokyo.

The environmental gamma-ray dose rate measured in Tokyo between 11 pm and 12 am, averaged across one hour, on March 18th, was 0.0471 μSv/h. This radiological monitor in Tokyo returned its highest reading yet on the 16th, from 05:00 to 05:59, at a dose rate of 0.143 μSv/h.

So, that most recent figure from Tokyo is 13% of the average natural background radiation dose rate in the United States. One banana dose is something like 0.1 μSv, so what we’re measuring in Tokyo at the moment comes in at just under 0.5 banana per hour. (One banana per hour, and you’re going to triple that dose rate.)

The highest figured measured at all in recent days, 0.143 μSv/h, is equal to 40% of the average natural background in the United States.

The radiation level in Saitama, outside Tokyo, is also being recorded and charted on the web. As of 21:00 on the 18th of March, they report a dose rate of 0.058 μSv/h. The maximum value reported, at 1 am on March 17, is 0.067 μSv/h. These figures are 16% and 19% of US natural background, respectively.

Two things are apparent from this data.

(a) Japan has very low levels of natural background radiation compared to the continental United States. (This is interesting in itself! It’s probably a combination of both low elevation providing shielding from cosmogenic radiation and a relatively low abundance of uranium and its daughter products in the ground.)

(b) The background ionising receive dose rate that people receive across Japan has not been elevated significantly at all, at least outside the immediate vicinity of the plant, as a result of the Fukushima damage.

There’s an extremely interesting, valuable plot of dose-rate measurements on this page. Units are μSv/h.

(ASIDE: If you can’t read Japanese – I can’t – a little bit of Google’s automatic translation goes a long way in helping you sort through this important data.)

If we look at the 5 monitoring sites closest to the 30 km radius marked on the chart, we see that the last three measurements marked on the chart, for each of those sites are 52, 52, 52, 140, 140, 150, 40, 45, 45, 8.5, 9.0, 8.7, 1.6, 1.6, and 2.0 μSv/h.

This tells us that there is detectable radioactivity which is moving in a narrow plume in the atmosphere – it is not distributed out isotropically, which is indeed exactly what you would expect from thinking about the meteorology.

This chart of compiled radiation measurements also tells us a very similar story.

At that 30 km radius, the average dose rate from that monitoring station which reports the high outlier values – the one corresponding to the location of the plume – is 143 μSv/h.

I wonder what radionuclides are present in that plume? The presence of 131I, 132Te and 133Xe would tell us that this radioactivity has come from a reactor, the absence of these short-lived fission products will tell us it has come from used fuel in the pool. A little bit of gamma spectroscopy, and we would have the answers.

The presence of these radionuclides as measured at KEK confirms that at least a tiny bit of radioactivity has been released from the reactors themselves.

That’s fairly high, but it’s not obviously high enough to hurt people. If you stood in the location of that plume for an entire week, you would receive 24 mSv over the course of a week – which is a dose figure which would be consistent with a relatively-high-dose nuclear imaging procedure using something like 201Tl to make an image of a tumor, or something like that.

If we remove those three outliers corresponding to the plume location from the above set of numbers and we take the mean of the remaining values, this gives us a rough idea of the mean dose rate elsewhere along the 30 km radius, outside the location where the source term of radioactivity is passing in a plume of wind. That mean value, then, is 26 μSv/h.

If you were standing in that radiation field, 26 μSv/h, for five hours per day every day for a year, you would reach a total annual dose of 47 mSv, which is just above the allowed occupational radiation dose – above natural and non-occupational background – of 50 mSv per year, for people working around radioactivity, such as nuclear power plant employees. (This is the limit set in the United States by the NRC; I’m not sure what the corresponding dose limit is in Japan, but it will be something loosely similar.)

But it’s well worth remembering that that radioactivity that is present now, in very low levels, will not be sticking around for a whole year. It is dispersing rapidly, and it drops away exponentially as you move away from the Fukushima site. As we move further out from the 30 km radius marked on that map, the dose rates recorded are all at harmless levels, consistent with background radiation dose rates experienced by people in the United States and elsewhere across the world.

In Ramsar, Iran, the natural background radiation dose rate is unusually high, at 260 mSv per year in some places. That is 30 μSv/h, which is higher than the mean value of about 26 μSv/h measured at these monitoring stations 30 km west of Fukushima, as I described above.

The people of Ramsar experience a background radiation dose significantly above that which most other people across the world experience – but they do not seem to experience any ill health effects at all from this.

I hope all the above helps to put these dose rates in context.

Used-fuel radiochemistry

The composition of the radionuclides that are responsible for most of the radioactivity in used nuclear fuel that has been stored in a cooling pool for a few months is very different than in nuclear fuel in a reactor that is operating, or has just been shut down.

Fuel straight out of an operating reactor contains a number of rather short lived, rather high specific activity fission product radionuclides which are of the largest health physics significance in the time immediately following severe reactor accidents.

Some of these short-lived fission products include iodine-131, xenon-133, xenon-135, tellurium-131, tellurium-132, and ruthenium-105. These short-lived fission products were very significant contributions to people’s radiation doses in the environment around Chernobyl in the time immediately following the Chernobyl disaster, for example, when they were dispersed from “hot” nuclear fuel from the reactor.

However, they are not present to any significant level in stored nuclear fuel, because they decay away relatively fast, and they cannot contribute any significant source term into the environment in some sort of accident scenario involving used nuclear fuel which has been stored for a month or three post-defueling.

So, what radionuclides are present in stored fuel? The main ones of interest here are the longer-lived fission products. 137Cs, 85Kr and 90Sr are the most significant ones. Of these, 85Kr is a gas, and has the most potential to be readily released from the fuel into the atmosphere. 137Cs accounts for most of the radioactivity of the used nuclear fuel, and it is usually the most feared radionuclide in the used fuel inventory, in terms of the potential source term released from an accident with a used-fuel pool.

Fuel-pool water evaporation

“In this house, we obey the laws of thermodynamics!”
— Homer Simpson

With the used fuel heating the water in the Unit 4 fuel transfer pool, how long will it take for all the water to be boiled away? It is actually possible to know this, without any real speculation. The physics is pretty simple.

We know that there is a full core-load of used fuel in the Unit 4 defueling pool, which was put there after the reactor was shut down for inspection on November 30.

(Assumption I’ve made here which may possibly be wrong: That that single core-load of fuel is the only fuel in the pool. Is there additional fuel in the pool? If there is, somebody needs to tell me how much and how long it has been cooling for, so we can re-run the numbers – or you can take what I’ve explained here and re-calculate it for yourself.)

That fuel has been cooling for the last 3.5 months, or approximately 9.2 * 106 s.

After this time, the radiothermal power output of the used fuel is small. Looking at this decay heat chart, we read that the decay heat is approximately 2 MWt. However, this chart is for a power reactor with a thermal power rating of 3000 MW. (And I’ve done a not-really-precise job of eyeballing that chart.)

But the Fukushima-I Unit 4 reactor has an electrical power capacity of 784 MW; that’s about 2352 MW thermal. So, we need to scale back the above figure commensurately; it’s approximately 1.6 MWt, from the entire core load of fuel.

The latent heat of vaporisation of water, at 100 C, is 2260 kJ/kg. (Let’s assume, conservatively, that the water in the pool is boiling; it’s at 100 degrees C, and the only route of energy dissipation from the system is through vaporisation of the water. This also assumes that none of the energy released is stored in the water by means of a rise in the water’s temperature, because it’s already at boiling point, and that there is no functioning mechanism for otherwise cooling that water.)

1.6 MW / (2260 kJ/kg * 1000 g/L) = 0.7 litres per second. 61 cubic meters per day.

The used fuel pool at Vermont Yankee, which is also a GE BWR-4, is 40 feet long, 26 feet wide and 39 feet deep, and is normally filled with 35,000 cubic feet of water. I will make an assumption that the Fukushima I Unit 4 used fuel pool has the same dimensions.

The level of water in the used fuel pool is normally 16 feet above the top of the fuel assemblies. With the water level evaporating at the rate described above, the water level will drop by 2 feet per day.

Uncovery of the fuel assemblies will take eight days. (Beginning from the point where the water level reached boiling point, after active cooling ceased.)

(Working assumption which you may subject to some skepticism: That there is no form of leakage or other water loss pathway from the used fuel pool.)

It seems plausible that a fire hose or something can be used to add water to the pool at a rate equal to this loss rate of 700 ml per second. The Chernobyl-style helicopter drops seem like overkill, and they are doing an effective job of whipping up “Chernobyl again” fear, and images that the newspapers are having a field day with.

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Written by Luke Weston

March 18, 2011 at 6:19 pm

Health physics implications of the ionisation smoke detector.

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It’s still occasionally heard from some sources, even after the technology has been in widespread use for many, many years, that the common household ionisation smoke detectors, which contain a very small radioactive source, present some kind of health hazard.
They don’t.

Such devices usually contain a sealed source, of 0.9 to 1.0 μCi of Americium-241. The source itself is a tiny little thing, about three millimeters in diameter – it’s a point source. *

241Am principally decays by emission of an alpha particle at 5.49 MeV, but this is not of any significance, since the α-particle cannot escape the device at all. However, 241Am also emits some low-energy gamma photons as it decays, principally a gamma ray of 59 keV, and it is this γ-radiation that can pass through the device and conceivably result in some dose to the householder, possibly.

The specific gamma-ray dose constant (“Γ factor”) for 241Am is 0.314 rem m2 Ci-1 h-1, or 3.14 x 10-9 Sv m2 μCi-1 h-1

(Here’s my source, a useful little reference table for this type of health physics information for several common, important, industrial, scientific and technical radionuclides.)

The dose rate, then, to the whole body from an external exposure to a point radioactive source which is emitting photon radiation is just the Γ-factor for the particular nuclide, multiplied by the activity of the source, multiplied by the familiar old inverse-squared distance term.

Suppose you’ve got such a detector on the ceiling, right next to your bed, which would place you about , say, 3 m away from the source. Suppose, additionally, that you spend your entire life in that bed. Of course, here I’m taking the most conservative scenario possible, to set an upper bound on the plausible dose.

3.14 x 10-9 Sv m2 μCi-1 h-1 x 1 μCi x 8765.8 hours x (3 m)-2 = 3.06 microsieverts per year.

Of course, the average worldwide dose from natural background radiation is almost 1000 times that – around 2.4 to 3 millisieverts per year, and in some places, far, far higher.

However, there is a more surprising and interesting context that we can put such a dose rate in. If you sleep in bed next to your partner every night, then the ionising radiation dose that you receive, due to the radioactivity of your partner’s body, from 40K and things like that, is about five microsieverts per year. [Source]

That’s assuming a realistic amount of sleep each day, of course – if you were actually in bed 24 hours per day, the dose from this source would be three times as much; 15 μSv per year.

Thus – the dose from sleeping next to your partner is 4.9 times what it is from the smoke detector. Surprising, isn’t it?

Obviously there is no reason to expect any significant health physics implications of any kind at such extremely low doses. Heck, such low doses are probably even too small to have potential significance with regards to radiation hormoesis. But we do know they’re proven to be extremely effective at protecting against the threat of fire destroying your home.

* Just as an aside, although technically illegal in the US and possibly in other localities as well, people (usually physicists and people that do know what they’re doing) do often remove these sources, and use them for educational demonstrations of radioactivity, of Geiger-Marsden style scattering, charged particle absorption, and to test and calibrate alpha and X-ray detectors – it’s quite tempting, since these devices are far, far less expensive than purchasing exactly the same sort of tiny sealed radioactive sources through “proper” channels, and no more dangerous.

Written by Luke Weston

October 23, 2008 at 10:33 am

Case-control study of lung cancer risk from residential radon exposure in Worcester County, Massachusetts.

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A few months ago, a rather interesting-sounding paper was published in Health Physics:

Case-control study of lung cancer risk from residential radon exposure in Worcester County, Massachusetts; Thompson et. al. Health Physics 94(3):228-241; 2008.

Home exposure to radon, a naturally occurring radioactive decay product of radium, has been thought to be the second leading cause of lung cancer, after cigarette smoking. Chemically inert, it can percolate out of the ground into basements.

The study was initiated and managed by Donald F. Nelson, now professor emeritus of physics at WPI, during the 1990s, a time when concern over the link between residential radon exposure and lung cancer was growing. Nelson says the aim was to try to establish what level of radon exposure actually correlated with significant lung cancer risk and to establish a safety zone for home radon levels.

The results of the study were described by their own authors as “surprising” and “stunning”: Clear evidence of radiation hormesis. It looks like Bernard Cohen has been vindicated after all.

“We were certainly not looking for a hormetic effect,” says co-author Joel H. Popkin of Fallon Clinic and St. Vincent Hospital in Worcester. “Indeed, we were stunned when the data pointed to that conclusion in such a strong way.”

A study of lung cancer risk from residential radon exposure and its radioactive progeny was performed with 200 cases (58% male, 42% female) and 397 controls matched on age and sex, all from the same health maintenance organization. Emphasis was placed on accurate and extensive year-long dosimetry with etch-track detectors in conjunction with careful questioning about historic patterns of in-home mobility. Conditional logistic regression was used to model the outcome of cancer on radon exposure, while controlling for years of residency, smoking, education, income, and years of job exposure to known or potential carcinogens. Smoking was accounted for by nine categories: never smokers, four categories of current smokers, and four categories of former smokers. Radon exposure was divided into six categories (model 1) with break points at 25, 50, 75, 150, and 250 Bq m-3, the lowest being the reference. Surprisingly, the adjusted odds ratios (AORs) were, in order, 1.00, 0.53, 0.31, 0.47, 0.22, and 2.50 with the third category significantly below 1.0 (p < 0.05), and the second, fourth, and fifth categories approaching statistical significance (p < 0.1). An alternate analysis (model 2) using natural cubic splines allowed calculating AORs as a continuous function of radon exposure. That analysis produces AORs that are substantially less than 1.0 with borderline statistical significance (0.048 <= p <= 0.05) between approximately 85 and 123 Bq m-3. College-educated subjects in comparison to high-school dropouts have a significant reduction in cancer risk after controlling for smoking, years of residency, and job exposures with AOR = 0.30 (95% CI: 0.13, 0.69), p = 0.005 (model 1).

There is more discussion and commentary at PhysOrg, here.

It will be very interesting to keep an eye on research in this area in the future, especially given the famous debates between the likes of Bernard Cohen and William Field over their radon dose response research.

Written by Luke Weston

August 12, 2008 at 12:31 pm

Quote of the week.

with 4 comments

A beautiful analogy to explain why the LNT hypothesis seems like it might be something of a stretch:

DV82XL Says:
July 22nd, 2008 at 12:04 am

If the LNT were applied to falling as it is to radiation, we might note that 100 percent of those falling onto concrete from 100 feet are killed, but only 50 percent of those falling from 50 feet die. With these data we would linearly extrapolate to say that 10 percent falling from 10 feet and one percent of those falling from one foot would die. Armed with this “linear no-threshold falling theory,” we could confidently assert that jumping rope should be banned on all school playgrounds since statistically anyone making 100 one-foot jumps would die.

Written by Luke Weston

July 23, 2008 at 2:45 pm

Not your average anti-nuclear-power group.

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This is worth checking out.

EFMR Monitoring Group

I will quote a few sentences from the website, to show what this group is generally about.

The EFMR Monitoring Network is a non-profit, non-partisan organization which monitors Three Mile Island Unit 1 (TMI) and Peach Bottom Atomic Power Stations 2 & 3. The Group was formed out of a Settlement with GPU Nuclear in 1992 relating to Post-Defueling Monitored Storage at TMI-2. In January 1999, the new owners of TMI-1, AmerGen, (PECO Energy & British Energy) agreed to terms with EFMR through 2006. Additionally, EFMR expanded its monitoring and research activities to include Peach Bottom 2 & 3 as a result of Universal Settlement relating to the merger of PECO Energy with Commonwealth Edison.

This is not your average dogma-packed “no nukes, no nukes, no nukes” activist group. Nowhere in their mission statement does it call for or support the closure of existing, operating, safe fission power plants.

EFMR maintained five low-volume air samplers on the east and west shores of the Susquehanna River opposite of TMI from 1993-1999. Dickinson College Physics Department collected the filters and cartridges of these monitors on a weekly basis. Analyses performed included, but were not limited to, weekly gross beta and alpha measurements, monthly gamma isotopic analysis, weekly Iodine-131 analysis, and semi-annual Strontium-90 analysis. The last collection occurred in December, 1999.

In November, 2000, EFMR deployed a low-volume air sampling station at Peach Bottom.

This is a neat idea! Of course, every nuclear power plant meticulously monitors any discharge of the very small amounts of radionuclides into the atmosphere or other effluents, and these records are all meticulously filed with the NRC, and are a matter of public record.

However, if they want to provide an extra layer of data, and extra monitoring apparatus, by themselves, then so much the better.

Having such data collected by independent means, and analysed by local college physicists, has every potential to:

a) Eliminate any community distrust of nuclear utilities.

b) Dispel the myth that nuclear power plants emit any aetiologically significant amounts of radioactivity into the environment at all during their operation.

c) In the event of a severe incident such as the Three Mile Island accident, improbable as though it may be, provide independent data to confirm the true magnitude of any release of radioactivity, and dispel baseless and false speculations or claims of very large and aetiologically significant releases of radioactivity being “covered up”

e) Educating people about natural background radiation and radioactivity and its sources, including atmospheric nuclear weapons testing, cosmic radiation and fossil fuel combustion, as well as about basic radiation instrumentation and health physics.

The only potential for a problem that I can foresee with this is that controversy may be generated over very small radioactivity releases which can be detected above background by sensitive instruments, which are however not in excess of NRC and EPA regulatory limits, and are of no public health significant – just like the controversy surrounding tritium effluents at certain nuclear generating stations in the US in recent years.

PECO has also agreed not use Mixed Uranium Oxide (MOX) fuel at Peach Bottom 2 & 3, Limerick Nuclear Station Units 1 & 2, and Salem Nuclear Station 1 & 2.

Well, I must say, I don’t agree with that. What is their reasoning behind making such a demand of the utility? What’s so bad about the use of MOX? I can think of several good points to be made of the use of MOX as a fission reactor fuel.

AmerGen has ensured that its work force meets or exceeds NRC staffing requirements and has agreed to pay excess decommissioning costs for TMI-1. AmerGen also agreed not to conduct business with any company, organization or nation that the United States of America is boycotting for economic or military reasons.

Well, how can you argue with any of that? Of course, the owner pays decommissioning costs for TMI-1, just like they pay the costs of decommissioning any other unit. I don’t think this represents any shift away from the obvious, in terms of the utility’s policy – the only difference being that TMI-2 will of course cost a bit more to decommission completely than the average reactor. I see no reason to believe that the TMI-2 accident will in any way affect the decommissioning of TMI-1 at the end of its life.

Of course any nuclear utility should meet or exceed anything the NRC requires of it. (If the NRC’s requirements are thought to be inappropriate, or too strict, or too soft, or whatever, then you take that up with the NRC – but of course the utilities should be by the book.)

EFMR has on-line access to AmerGen’s Reuter-Stokes, gamma monitoring system. This sensitive system collects samples, analyzes them, and prints out data on an hourly basis from 16 separate collecting stations located within a four mile radius of Three Mile Island. EFMR continues to attend NRC meetings, and receive regular briefings and updates from AmerGen, Exelon, and PECO Energy.

To monitor radiation levels surrounding the Three Mile Island Nuclear Station and the Peach Botom Atomic Power Station so that any deviation from normal background radiation levels are immediately detected and reported. This allows for a prompt response from our citizens network to provide independent data, especially in the event of another accident or any radiological release in the area.

If abnormal levels are detected, EFMR may report the data to proper authorities including the PA Department of Environmental Protection, the US Nuclear Regulatory Commission and others.

The network is comprised of ordinary citizens whom each record five radiation measurements per day. Each person had been provided a geiger counter equipped with an electronic timer to measure radiation levels.

At the end of each minute, it displays the counts in a liquid crystal display window. That user then writes the count on a data sheet along with the time and weather conditions. The monthly data sheets are collected and reviewed by professional advisors.

We also utilize five stationary low-level air samplers located within a two mile radius around Three Mile Island. These monitors are able to distinguish and record Alpha and Beta radiation. The data is collected by the Dickinson College physics Department and analyzed quarterly. A control station low-level air sampler is located a Dickinson College for comparison.

EFMR has distributed 75 RadAlert radiation monitors at 50 stations in an eight county area around Three Mile Island, including numerous colleges, high schools and community-based organizations. Several additional monitors are deployed in northern Maryland close to the York County border. In addition, EFMR will deploy 30 rad alerts in close proximity to Peach Bottom as a result of its Agreement with PECO Energy.

This all sounds good to me. Of course, the data taken needs to be analysed by those who understand what they’re doing, and in the event of any unusual and potentially release of radioactivity, the NRC and authorities need to be notified so that they may determine the most safe, prudent and rational course of action – of course, the utility will almost certainly be the first to notify the NRC, in any accident scenario.

The anti-nuclear lobby, and many environmentalist groups, could do well to learn from this group.

The battle for Chernobyl.

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Last month I got into a discussion with some people about the Chernobyl disaster, following the 22nd anniversary of the catastrophic Soviet reactor accident, and this documentary film was mentioned:

The Battle for Chernobyl.

To put it lightly, this film is an astonishing bunch of rhetorical baloney.

I’m not trying to downplay the public health consequences of the Chernobyl accident – but I’m downplaying the inaccurate or false claims made by certain groups, as distinct from the body of evidence of real, documented and substantiated (and very significant impacts).

Despite the known public health impacts, some people continue to make claims that are either just not true or are completely unsubstantiated – for example any claim that there are children, today, with an increased incidence of thyroid cancer, which just isn’t true – any children who were exposed to the short-lived iodine-131 source term in 1986 are adults today, 22 years later, and the iodine-131 decayed away quickly, within months.

Now, to look at the video:

From the gaping hole, a spray of fire, charged with radioactive particles in fusion, sprays a thousand meters into the sky.

Right from the outset, it’s completely obvious that for the next hour and a bit, science is tossed aside, and rhetoric is the first and only order of affairs.

The radioactive fallout is going to be 100 times greater than the combined power of the two atomic bombs dropped on Hiroshima and Nagasaki.

Some simplistic comments have often been made in which the radioactive release of the Chernobyl event is claimed to be 300 or 400 times that of the bomb dropped on Hiroshima. However, in sensible terms of radiological impacts, the two events can not be simply compared with a number suggesting that one was x times larger than the other.

Radioecology after Chernobyl – some good literature.

The total combined energy yield of both of the nuclear weapons used in Japan was about 35 kilotons of TNT equivalent – or about 41 gigawatt-hours. The Chernobyl Unit 4 reactor, with a thermal power output of about 3 gigawatts, produced that same amount of energy, and created about the same amount of fission-product activity, every 13.6 hours or thereabouts. Given that a nuclear power reactor contains fuel that has provided that kind of power output for perhaps as long as several years, of course there’s a larger inventory of radioactivity contained in the reactor fuel.

Iodine tablets swallowed to counteract the effects of radioactivity.

Iodine prophylaxis only prevents the body from uptaking iodine from the environment – which might be contaminated by radioactive iodine-131. It in no way “counteracts the effects of radioactivity”.

“The radiation level above the reactor is over 3500 R, almost nine times the lethal dose.”

3500 R over what length of time? The strength of an ionising “radiation field” in such a situation can only sensibly be expressed as roentgens (or sieverts or similar unit) per hour (or per unit of time).

0:36:40

If over six hundred pilots were “fatally contaminated with radiation”and killed, and this is known to be true, why have the Chernobyl Forum, the IAEA, the WHO, the UNDP, the UNSCEAR, Russian or Ukrainian governments never mentioned it? Can it be proven to be true, before the international community, by these people?

0:37:08

Why does none of this film show any artefacts on the film resulting from radiation damage?

0:38:20

The infamous “elephant’s foot” “magma” doesn’t look “white-hot” at this stage, although that’s how it’s described.

0:43:45

Again, the level of radioactivity is implied to be so very high – and it was high – yet it was not high enough to leave artefacts on the camera film. I don’t know exactly what sort of radiation dose is required to effect a piece of photochemical film (Remember that stuff, that was used before digital photography?), but I really expect it to show some damage under these conditions.

0:44:45

If you’ve got documentary evidence of these lives lost as a direct result of the disaster, that don’t appear in any of the UN’s findings, then I’m sure the UN would love to hear about it.

0:52:30

Oh dear – it’s “imagined” health physics, romanticised Hollywood fiction style.

“It finds a way in, and knocks you out”.

1:03:00 or thereabouts:

7000 R/hr – and still no effect on the video camera film. I wonder how strong the ionising radiation field needs to be to affect it?

1:12:30 –

“…The visit stirs up painful memories. He was fatally exposed to radiation during the seven months he spent covering the battle. Since then, he’s had to be hospitalised for over two months each year.”

He was fatally exposed to radiation? Oh, really? So you’re reanimated a dead man to interview for the program?

Chernobyl showed us the true nature of nuclear energy in human hands

No, Chernobyl showed us the potential for folly associated with the Soviet way of doing things back then. Keep in mind that the non-Soviet world has never even come remotely close to experiencing such an accident.

1:31:20:

“Inside, there are 100 kilograms of plutonium.

One microgram is a lethal dose for a human being. That means there is enough plutonium to poison 100 million people.”

Even assuming that “one microgram of plutonium is a lethal dose for a human being”, which it isn’t, I expect that somebody who is really a nuclear physicist should know how to count, and not allow such a glaring error of arithmetic to go uncorrected.

“The half-life of plutonium is 245,000 years.”

In order of descending half-life:

Pu-244: 80 million years

Pu-242: 373,300 years

Pu-239: 24,100 years

Pu-240: 6564 years

Pu-238: 87.7 years

Pu-241: 14.35 years

Pu-236: 2.858 years

The nuclides bolded are the most common ones. I don’t know about you, but Iexpect someone who is a nuclear physicist to get that right, and not just pull some nonsense number out of thin air! Again, not one of these plutonium nuclides has the half-life claimed in the film. What’s more, no credible nuclear physicist would state that “the half-life of plutonium is such-and-such” without specifying which nuclide he was talking about.

But wait – if you’ve watched the video, there are a couple more scenes that you almost certainly haven’t overlooked:

“Yet, it is thanks to these men that the worst was avoided. A second explosion, ten times more powerful than Hiroshima, which would have wiped out half of Europe.”

Yes, you heard that correctly. They claim that a  150 kiloton nuclear detonation could have happened. See below, for what I think of that.

0:34:00 – 0:35:00

The ensuing chain reaction could set off an explosion, comparable to a gigantic atomic bomb.

“Our experts studied the possibility, and concluded that the explosion would have had a force of three to five megatons. Minsk, which is 320 kilometres from Chernobyl, would have been razed, and Europe rendered uninhabitable.”

A 3 to 5 megaton nuclear detonation.

I apologise for putting this bluntly, but there’s only one thing I can say to that. What complete and utter bullshit.

They trump out the nuclear weapon explosion stock footage and everything. This is quite possibly the most blatantly shameless, ridiculous, completely falsifiable and utterly ridiculous example of shameless and absurd anti-nuclear-power propaganda I have ever seen.

Written by Luke Weston

May 8, 2008 at 3:27 pm

New laser pointer restrictions for Australians.

with 5 comments

Stupid politicians – and even stupider tabloid press – are not a good combination.

To let me set the background or context for this post, here are some relevant press articles:

http://news.theage.com.au/nsw-govt-may-ban-laser-pointers/20080330-22eu.html

The NSW government is considering a ban on laser pointers after six planes had to alter their flight paths into Sydney after being targeted in a “cluster attack” on Friday.

NSW Police Minister David Campbell on Sunday said he was now considering a ban on the laser pointers.

“There are some penalties that police can impose now, but we’re looking to make these items a prohibited weapon in certain circumstances which would lead to substantial fines and possible jail terms,” he told Macquarie Radio.

There already exist laws under the Civil Aviation Safety Act posing severe penalties for prejudicing the safe operation of an aircraft, or interfering with an aircraft. If people commit such acts, then absolutely, by all means, throw the book at them.

But what about our civil liberties? Kitchen knives, for example, are a useful, important tool, which can be misused by some antisocial idiot who wants to do the wrong thing. So, do we prohibit all kitchen knives? No – we find those using them for the criminal purposes and though the book at them.

“Western Australia only announced in the last couple of weeks that they were going to make it a prohibited weapon, Victoria has already done that,” Peter Gibson said.

Not even the [over the top] Victorian legislation applies to all laser pointers. I mean – all laser pointers? Come on. Next it will be high-intensity keyring LED lights for finding your keyhole in the dark banned.

http://www.news.com.au/story/0,23599,23505696-2,00.html

ONE of the first people to be prosecuted in Australia for shining a laser at an aircraft has been sent to jail.

Lanfranco Baldetti, 23, of Adelaide, was sentenced to two years and three months’ jail today after pleading guilty to prejudicing the safe operation of an aircraft.

Obviously the existing legislation is sufficient to prosecute – and hopefully to ultimately deter, if combined with better enforcement – this antisocial behaviour.

http://www.smh.com.au/news/travel/sydney-plane-attacked-with-laser/2008/04/02/1206850941540.html

Australian Federal Police, ASIO and other government agencies plan to meet in Canberra today to work out a strategy to tackle the problem of laser attacks on passenger jets.

The meeting will be urged to ban the sale of the high-powered lasers, The Australian reports today.

Under penalties introduced last year, perpetrators are liable to up to two years’ jail and fines of up to $30,000.

http://www.abc.net.au/news/stories/2008/04/21/2222662.htm

The New South Wales Government has announced that it is banning laser pointers after a spate incidents involving aeroplanes.

The new laws mean that the lasers will be illegal without a prohibited weapons permit.

“I cannot underestimate the potential, the catastrophic consequences if a plane is brought down by one of these fools, these idiots,” he said.

Come on – “if a plane is bought down”? I agree that this antisocial behaviour in unacceptable, but you’re misrepresenting real risk as an excuse for draconian legislation.

NSW Police Commissioner Andrew Scipione says making it illegal to carry lasers will help police crack down on the improper use of the devices.

It’s already completely possible, within the letter of the existing law, for authorities to “crack down on improper use of the devices”, whether it’s assulting a person with it, or interfering with the operation of an aircraft. The laws already exist to police these antisocial behaviours – and rightly so.

The Government says people like astronomers will be allowed to have lasers if they apply for a permit.

Well, that’s somewhat promising, I guess. But how much bureaucracy, red tape, restrictions and fees will be applied? If enforcement is left to average police officers frisking people, how do they determine who is a student, lecturer, or amateur astronomer, and who isn’t, reasonably and effectively?

http://www.smh.com.au/news/national/ban-to-stop-laser-plane-attacks/2008/04/05/1207249536609.html

THE importation of high-powered laser pointers, similar to those used to target passenger planes landing at Sydney Airport, will be banned by the Federal Government.

Since there’s nobody manufacturing those things in this country, a ban on importation indirectly means a total ban, doesn’t it? That’s not fair at all!

Mr Debus said the Government would ban the import of high-powered lasers by classifying them as a dangerous weapon.

“The Government will introduce a new regime to restrict certain laser items which could operate in the same way as the existing controls on firearms and weapons. Recent attacks on pilots have highlighted the seriousness of the problem. ”

Mr Debus said exemptions were available for legitimate uses for lasers, such as surveying, astronomy, mining and construction.

We’ll see how well that goes, if enforcement of such laws is left to every beat cop on the street, instead of being left to the likes of the Australian Radiation Protection and Nuclear Safety Agency, or similar state-level organisations, tasked with policing the complex and subtle issues associated with laser safety or any other form of health physics.

NSW Police Minister David Campbell said he supports the ban and was stunned to hear the attacks had not let up despite the publicity.

The antisocial behaviour which you’re clearly not policing effectively will obviously increase if you saturate it with media publicity, and the media publicity demonstrates that you’re not able to police it effectively, you idiot.

http://www.abc.net.au/news/stories/2008/04/22/2223521.htm

A plan to ban laser pointers in New South Wales has been labelled as nothing more than a stunt after Premier Morris Iemma admitted pet owners would have an excuse for possessing one.

Possession of high-powered laser pointers will be illegal in NSW without a prohibited weapons permit, and laser pointers of all strengths will be banned in public without a reasonable explanation.

But Mr Iemma told the ABC an excuse could be using the pointer to entertain a pet cat.

“A pet would be a reasonable excuse but having a pet in the house and using it for the pet and then aiming at a pilot would not be,” he said.

Well, there’s all of Iemma’s credibility gone.

Captain Mike Glynn from the Australian and International Pilots Association says a nationwide ban on laser pointers is the next logical step.

“We’ve had a couple of our pilots who’ve actually had harm done to their eyes when these lasers have been shone in their eyes,” he said.

What a bunch of baloney. This guy is a twit, he’s just BAN BAN BAN, and incapable of seeing the bigger picture.

http://www.smh.com.au/news/national/backlash-over-laser-ban/2008/04/21/1208742851975.html

AMATEUR astronomers, teachers and surveyors will have to justify carrying lasers under new bans aimed at avoiding “mass murder” if aircraft are targeted.

The Premier, Morris Iemma, warned that all high-powered lasers would soon be classified as prohibited weapons and carrying any kind of laser – even harmless classroom pointers – without a good reason could result in two years’ jail or a $5000 fine.

Critics said the new laws were impractical and accused the Government of failing to back its tough talk with resources for enforcement.

Mr Iemma said banning hand-held lasers would “stop the potential for mass murder”.

“I cannot underestimate the … catastrophic consequences if a plane is brought down by one of these fools, these idiots, these reckless individuals who want to use these high-powered hand-held lasers and think it’s a joke.”

Previously police needed to prove a laser had been used improperly in order to prosecute. Under the new laws they would be able to frisk people for lasers and ask why they carried them.

The laws will affect professions such as teachers, surveyors and astronomers. If questioned by police, they must prove they need a laser pointer or face two years’ jail. Anyone who carries a high-powered laser faces 14 years in jail.

Unbelievable, isn’t it?

Catching the culprits can be expensive: late last year, police used two helicopters as well as ground officers in a fruitless search for a laser in Bondi.

The Federal Government recently banned the importation of high-powered lasers.

The president of the Australian Optical Society, Professor Hans Bachor, said the blanket ban was an overreaction. “You can’t point [low-powered lasers] at any aircraft over a distance – the effect wouldn’t be big enough,” he said.

The laws could create a headache for police and the public, he said.

Too right it’s a headache for police – more laws designed to satiate the demands of those who follow the tabloid media, and more laws that cannot be effectively enforced on top of existing law that cannot be enforced.

The Opposition’s police spokesman, Mike Gallacher, described the announcement as a media stunt. Only enforcement would determine how effective the new laws would be, yet the Government was not offering police any extra money.

Outlawing a legal object would also be difficult, he said.

“I suspect it will be much like most of the State Government’s quick-fix, media-driven solutions aimed at grabbing a headline rather than fixing a problem.”

Too right!

But the acting president of the Australian and International Pilots Association, Mike Glynn, welcomed the ban, saying the problem had become serious over the past two years. “It’s not an overreaction – there’s real potential to cause a problem.”

Bob Lipscombe, the deputy president of the NSW Teachers Federation, said enforcement of the new bans should focus on people who posed a threat. “We don’t think teachers would pose a threat,” he said.

John O’Byrne, from the Astronomical Society of Australia, hoped police would be reasonable. “Our understanding is that the intent is clearly not to inhibit legitimate use of lasers.”

Now, this next report is certainly my favourite.

http://www.abc.net.au/science/articles/2008/04/07/2209657.htm

Australian scientists have attacked the federal government ban on importing high-powered laser pointers as using a “sledgehammer to crack a nut”.

And vision experts say people using the lasers to distract pilots would have to be good shots to make the beam temporarily blind the pilot.

Professor Hans Bachor, president of the Australian Optical Society, says the ban is an overreaction and researchers may be left to deal with the bureaucracy if it proceeds.

He urges the government to consult with scientists over the issue.

“It’s like banning the kitchen knife because we have people using the knives incorrectly,” says Bachor, director of the Australian Research Council Centre of Excellence for Quantum-Atom Optics.

Dr John Greenhill, at the University of Tasmania‘s School of Maths and Physics, says a ban could affect amateur astronomers who use laser pointers to help align telescopes and in delivering public talks.

He says lasers of about 3-4 milliwatts are used to point out stars in the night sky.

But Greenhill says more powerful pointers are illegal and questions “how putting a ban on something that is already illegal can help”.

“The dangers of high-powered lasers have been recognised for quite a while,” he says.

“[The ban] is like using a sledgehammer to crack a nut. There must be better ways of solving the problem.”

A home affairs spokesperson says the government is yet to determine the classes of laser pointers to be banned, but adds that they will be subject to restrictions similar to those for guns and other weapons, with exemptions available for legitimate use.

Bachor says scientists would be concerned if lasers were put on an equal footing with guns as a weapon and a large bureaucracy for their use was created.

Professor Michael Collins, at Queensland University of Technology‘s School of Optometry, says pilots face minimal danger from the lasers.

“You’d have to be a pretty good shot to get [the laser beam] directly into the pilot’s eyes,” he says.

“And the distance the pilots are from the source gives a great deal of protection.”

But he says pilots landing at night would be scanning for visual cues and may be attracted to a flash of light.

They could be temporarily blinded by the laser beams if they looked at them, in the same way that a flash on a camera can cause problems.

The intensity of the light will determine how long pilots take to recovery, he says. But that it “can take up to minutes”.

Neryla Jolly, an orthoptics researcher at the University of Sydney, agrees.

“A dazzle can take 2-3 minutes to recover, which is vital when you’re flying,” she says.

But because of the distance the laser beam travels, Jolly says it is unlikely to do any physical damage to the pilot’s eye.

There are legitimate reasons for pointing lasers into the night sky, says Professor Warrick Couch at Swinburne University‘s Centre for Astrophysics and Supercomputing.

He says research astronomers often do this to create artificial stars and so correct for air turbulence.

But he says such lasers are already only used under clearance from aviation authorities and any ban is unlikely to affect research astronomy.

While Bachor is concerned that scientists may face red tape if they want to buy lasers for legitimate research, he says the wider community should have restricted access.

“The first move should be to somehow limit the free purchase of lasers if [the buyers] have no professional use for them,” he says.

He says it is possible to buy green lasers more than 20 milliwatts in power over the internet.

The issue of people pointing lasers at planes is not new.

Peter Gibson of the Civil Aviation Safety Authority, is reported as saying there are cases almost daily.

Last year the ABC reported that the federal government passed new laws providing for up to two years’ jail and fines of A$30,000 for directing mini-laser lights toward planes.

http://www.smh.com.au/news/national/laser-lunatics-face-5000-fines/2008/04/21/1208629786565.html

Police will have powers to frisk people they suspect of carrying lasers and those without reason to have them – such as educators, architects or astronomers – will be fined up to $5000.

NSW Premier Morris Iemma said today the Government would ban the most powerful laser pointers and make it a summary offence to carry any laser pointer without a lawful reason.

Class three and four laser pointers will be declared prohibited weapons and carrying them could attract a maximum penalty of 14 years’ jail, he said.

There are already [fairly strict] restrictions on laser pointers in most states of Australia. In fact, so strict as to be utterly stupid, in my opinion.

In New South Wales, laser pointers, defined as hand-held battery operated laser products that produce a single beam of radiation, cannot be sold unless they comply with the requirements for a Class 1 or Class 2 laser product in the Australian/New Zealand Standard AS/NZS 2211.1 :1997
That is, any laser pointer with a Class IIIR or Class IIIb laser is illegal in NSW already, and has been for some time.

(Note that the “safety classes” for laser devices are pretty uniformly standardised throughout the world.)

In Victoria the existing law states that a “hand-held, battery operated laser pointer” emitting a laser beam with an accessible emission limit of greater than one milliwatt is considered a prohibited weapon.

[So too, according to the Victorian legislation on prohibited weapons, is a “cat of nine tails” with knotted lashes a prohibited weapon. I’m sure you can still go to a sex shop and buy something like that, though.]

The Class II category, if I recall correctly, corresponds to an accessible emission limit of 1 mW, for a continuous laser at at a visible wavelength. Therefore, the existing Victoria and NSW legislation, introducing restrictions over 1 mW, are pretty much exactly the same.

Any laser product with an accessible emission level greater than the accessible emission limit of a Class 3B (Restricted) laser product as defined by the accessible emission limit given in AS/NZS 2211.1:1997 – that is, all Class 3B (not Class 3R) and Class IV lasers – is already legally controlled on a federal level – under the Australian Radiation Protection and Nuclear Safety Regulations 1999. That includes all the extra-high power output laser pointers with emission power levels of many tens or hundreds of milliwatts, such as those sold by places like Wicked Lasers.

Such laser devices are not banned – but they are subject to many restrictions regarding licencing and regulation so as to provide for the safe use of potentially dangerous devices, and rightly so, too.

The point is, though, that these laws are nothing new. There are multiple different layers of existing legislation that should stop bogan idiots misusing laser pointers with power outputs of tens or hundreds of milliwatts – but it does not stop them.

Introducing new laws means absolutely nothing, and does absolutely nothing if the laws cannot or will not be enforced. This is especially clear when the current laws should be stopping the problem, but are not.

I completely support seeing Class IIIb laser pointers regulated under the existing ARPANS legislation, with police acting to enforce against obvious public misuse, assuming that ARPANS licencing requirements for Class IIIb laser pointers are not overly restrictive, financially prohibitive or demanding of individual citizens who use such lasers for astronomy.

I possess [illegally…] such a laser pointer. [10 mW 532 nm Nd:YAG SHG] The main thing that I use it for [responsibly] is as a teaching tool when performing astronomical observation in a dark-sky environment with a group of people. These laser pointers are fantastically useful for this purpose.

Now, you will never find a suitable dark-sky environment for serious astronomy in suburbia. If anybody is pointing a bright laser beam into the night sky in the suburbs, then there’s a high likelyhood that stupid antisocial behaviour is involved, and the police should check it out.

But how much danger does a laser pointer with a power output of say 5-10 mW [10 mW is amply sufficient as a pointer for dark-sky astronomy, and 5 mW is marginally OK, too] actually present to a person, especially in an aircraft at any realistic altitude?

The key thing to consider here is the divergence of the laser beam – what optical energy flux (i.e. power density) could actually be entering a person’s eye, and for what length of time?

Here’s a primer on the relevant (freshman level) physics – perhaps the politicians would do well to take note.

The physics says that these aircraft “attacks” are not, opthalmologically speaking, especially dangerous.

But wait, there’s more…

http://www.smh.com.au/news/national/channel-10-traffic-reporter-lasered/2008/04/23/1208743030294.html

Channel 10 traffic reporter Vic Larusso has tonight become the latest victim of a laser attack – his right eye hit by a high-powered green beam as his helicopter returned to Bankstown Airport.

“It was blurry for about 10 seconds just a bit sore, like when you rub your eye and it’s red,” Mr Larusso, who also does the traffic on commercial radio, told smh.com tonight.

What a load of rubbish. Could or would any ophthalmologist confirm such symptoms as the expected result of such an exposure? I doubt it.

“I looked down into [the laser].”

Mr Larusso, who was flying over Church Street in Parramatta at the time, said his main concern was for the pilot, who he told to look ahead.
“If your pilot got shone in both eyes, I don’t want to think what the result could be.”

Mr Larusso was also concerned by the location of the attack, noting that it could easily have affected pilots carrying children into Westmead Hospital.

“I don’t know how people can get their kicks out of this,” he said.
Mr Larusso said he would see how his eye felt in the morning and may go to a doctor if it had not improved.

But here’s the kicker:

April 23, 2008
POLICE say bright lights from an art installation are to blame after Sydney traffic reporter Vic Larusso feared he and his helicopter pilot were the victims of a laser attack.

Larusso, who works for Network 10 and commercial radio, told The Sydney Morning Herald online the pair were flying over Church Street, in Parramatta in Sydney’s west, this evening when he was struck in the right eye by a green laser beam…

But police said they believed the light did not come from a laser but from a council art installation in the Parramatta CBD.

Good going, media dilettantes.

We’re going to see this problem a lot – when anybody sees any bright colored light source at night… Oh no, it’s criminal lasers!

Written by Luke Weston

April 24, 2008 at 7:56 am