Pu-breeding feasibility in irradiation channels of research reactors

The objective of this study is to investigate the breeding potential in irradiation channels of research reactors. These reactors differ considerably from commercial power reactors in characteristics, purpose and so non-proliferation aspects. Research reactors are easily accessible and allow rapid core configuration modification to achieve high neutron fluxes, because usually they are not sealed by IAEA. From the three possible proliferation path ways for research reactors: (1) diversion of fresh fuel for U235 extraction; (2) diversion of spent fuel for plutonium extraction; (3) clandestine plutonium production via irradiation facilities, this paper addresses the last pathway. It is of particular interest because there is no way to determine exactly which kinds of experiments are taking place every moment in irradiation channels. Moreover, irradiation time can be optimized in order to breed high quality weapon grade plutonium. With regard to the safeguards measures currently adopted, IAEA concentrates its efforts on those reactors whose thermal power is greater than 25 MWth, because it was calculated that a 25 MWth LEU-fuelled reactor produces not more than one Significant Quantity of Pu (8 kg) per year in its spent fuel and a HEU-fuelled reactor of this power would require an annual reload of not more than one Significant Quantity of U235 (25 kg). This paper investigates whether it would be possible to determine an analogous power level threshold in order to estimate the clandestine plutonium production capability of different research reactors. The Monte Carlo method was used to determine the neutron flux in the irradiation channels and to calculate the plutonium breeding potential for three different reactor types: (1) a Triga Mark II with 250 kWth, representative for a small size research reactor; (2) a Material Test Reactor (MTR) with 5 MWth, representative for a medium size research reactor; (3) a High Flux Reactor (HFR) with 45 MWth, representative for a large size research reactor. It was observed that the most important factors for plutonium breeding are the neutron flux (to which reaction rates are proportional) and the available space to place irradiation samples. The breeding capability scales fairly well with the reactor power level and from about 10 MWth onwards the proliferation concern raises with increasing power level and available sample space.

TOMANIN Alice;  PEERANI Paolo;  JANSSENS-MAENHOUT Greet; 

2011-02-02

ELSEVIER SCIENCE SA

JRC58942

0029-5493,   

www.elsevier.com/locate/nucengdes,    https://publications.jrc.ec.europa.eu/repository/handle/JRC58942,   

10.1016/j.nucengdes.2010.11.015,