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Just a quick question that I’m trying to find an answer to.

We all know that when used fuel is discharged from a reactor, it’s highly radioactive.

But exactly how radioactive? Considering, say, typical used uranium oxide PWR fuel material at a typical burnup, what is the activity of the used fuel at discharge, in terms of, say, curies per GWh, or curies per gram?

I’m looking for a specific number, like that – can anybody direct me to it?

Written by Luke Weston

March 28, 2008 at 1:34 pm

Posted in Uncategorized

6 Responses

1. The radiation dose measured at a distance of 30 cm from a used CANDU fuel bundle, is ~5000-6000 Sv/h at removal, ~500-600Sv/h after one day. One year following discharge, it would be about 50 – 60 Sv/h, and the level drops to about 1 Sv/h after 50 years, 0.3 Sv/h after 100 years, and less than 0.001 Sv/h after 500 years.

These are AECL’s numbers for a CANFLEX bundle removed from a CANDU-6. I have no numbers for any other type of reactor, sorry.

DV82XL

March 28, 2008 at 2:48 pm

2. The name of the study is “Dose Rate Estimates from Irradiated LWR Fuel Assemblies in Air.” You can find two tables (pages 2 and 4) on how much radiation a person would receive based on how far they stand from a PWR or BWR fuel assembly and how long the assembly has been out of the reactor. Data is in rems/hour. This is a study NEI references for various things.

March 28, 2008 at 4:35 pm

3. Found some data for LWR.

The radioactivity of 1 MT spent fuel (50 MWd/kgU burnup) discharged from a pressurized water reactor/PWR (4.5% initial enrichment) are approximately 214 MCi at discharge, 25 MCi after one week, 13 MCi after one month, and 3 MCi after one year, respectively.

The the thermal powers of 1 MT spent fuel (50 MWd/kgU burnup) discharged from a PWR (4.5% initial enrichment) are approximately 2 MW at discharge, 200 kW after one day, 100 kW after one week, and 13 kW after one year, respectively.

Hope this helps

DV8

DV82XL

March 28, 2008 at 4:57 pm

4. I assume that “MT” means metric ton? I seriously doubt it means megaton.

enochthered

March 28, 2008 at 5:47 pm

5. Metric tonne of course

DV82XL

March 28, 2008 at 5:52 pm

6. The well known paradigm for radiation protection involves three factors – exposure time, distance, and shielding

I’m assuming your question has some health physics aspect to it. You can get decay data by isotope here