Re: Carbon 14 and PWR

[Charles Willis <caw@nrc.gov>]

Fred,

I do not remember when attention was first directed to carbon 14 in reactors but I believe the knowledge that carbon 14 can be the result of an (n,p) reaction with nitrogen 14 dates back to about 1941, so its presence as an activation product should have been recognized early.  Shoupp, Coe and Wiidman addressed carbon 14 in connection with Yankee Rowe at the 1958 Geneva Conference.  Concern about carbon 14 is another matter.

The release of carbon 14 was limited in the operating license for Yankee Rowe in 1964.  Joe Logsdon and R. Chissler of the Bureau of Radiological Health  reported on carbon 14 in reactor effluents in 1970.  The EPA addressed carbon-14 in 1971.  Interest in carbon 14 in effluents was associated in the AEC requirement to keep releases as low as practicable, which led to 10 CFR Part 50, Appendix I.  For this, the AEC/NRC supported considerable work on reactor effluents, including carbon 14.

There seems to have been relatively little concern about carbon 14 in wastes before the development of 10 CFR Part 61, which was published in December of 1982.  The 8 curies per cubic meter criterion for carbon 14 has proven problematic.  It might be said that the regulation created the problem.

There seems to be little that can be done about the production of carbon 14.  As long as we use UO2 as fuel, we will produce about 3.5 curies/GW(e)-yr in the fuel largely by the O(n, alpha)  and the N(n,p) reactions.    Carbon 14 production in the coolant  from the same reactions may be on the order of 10 curies/GW(e)-yr but there is considerable variation between reactors.  The oxygen reaction is dominant so reducing the nitrogen content  would be of limited value.

I hope this little background information is helpful.  Someone else will have to address the resin disposal problem.

Charlie Willis
caw@nrc.gov


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