G. Pshakin

The BFS-1 and BFS-2 critical assemblies[50] at the Institute for Physics and Power Engineering in Obninsk (Figure 2-11) provide a good example of reactors that cannot be converted to LEU fuel. These reactors, which are fueled with HEU and plutonium, were constructed in the late 1950s and early 1960s as part of the Soviet Union’s fast breeder program for nuclear energy development. Although these assemblies cannot be used for design­ing commercial-scale fast breeder reactors, they are useful for simulating fast breeder reactor cores, for fuel cycle research, and for studying the transmutation of minor actinides. This fuel used in these assemblies is not self-protecting[51] and therefore poses special security concerns.

Converting these facilities to LEU fuel cannot be accomplished without sacrificing the current mission. Moreover, even if the uranium enrichment of the fuel could be reduced, plutonium would still be required to simulate the cores of fast breeder reactors.

There are two options for addressing the security concerns associated with these facilities: (1) shut down the facility and remove all nuclear ma­terials; or (2) organize a state-of-the-art materials protection, control and accounting (MPC&A) system and enhance the culture of personnel through proper training, motivation, and support. The second option is obviously preferable.

The facility has cooperated with the United States to develop an MPC&A system. It includes a non-destructive analytical system based on high-resolution germanium detectors for isotopic measurement of ac­counted items; neutron coincident counters for nuclear material mass mea­surements; and specially designed access and monitoring systems. This program has to protect more than 100,000 HEU and plutonium discs that are used to model the cores of fast breeder reactors.