Modeling the Production of Tritium, Carbon-14 and Cobalt-60 in Irradiated Graphite from a UK Magnox Reactor

Abstract

ABSTRACTThe Tritium, Carbon-14 and Cobalt-60 content of a trepanned sample from one of the Wylfa Magnox reactor have been experimentally determined using beta liquid scintillation counting and gamma spectroscopy. The WIMS9a reactor code and FISPACT-2007 neutron activation software have also been used to calculate this inventory for the sample, considering only a model which is isolated from the reactor circuit. Comparison between experimental and calculated results has shown that the calculated values for 14C are within 26%, 60Co within 24% and 3H 120%. These results show that the original impurity levels are sufficient to explain the experimentally determined end of life activity, without additional consideration of contamination from other materials in the reactor circuit, in this type of simulation. Additionally the calculations show that the production of 14C from 14N is approximately equal to that produced from 13C. These results are only applicable to the isolated system models developed here, and do not explicitly model existing reactor conditions, where external operating conditions may interact with the graphite and the core environment