Pyrochemical conversion of weapons plutonium into plutonium mononitride, monocarbide and mixed uranium-plutonium fuel for fast reactors

Abstract

The main directions and results of research on pyrochemical reprocessing of weapons plutonium in fuel for fast reactors are presented. It is shown that this technology is economical and ecologically validated, compact, fire and explosion safe, especially for reprocessing in carbide-nitride as well as oxide fuel for fast reactors. It satisfies the principle of nonproliferation. For reprocessing weapons plutonium in oxide fuel with deep removal of 241 Am and Ga, a combined process which combines pyrochemical conversion of plutonium into oxide or nitride powder, and dissolution in acids and extraction of impurities. It is shown that the fuel kernels made from nitride, carbide, and oxide powers both from individual PuN, PuC 0.86 , and PuO 2 powders as well as mixed plutonium compounds with uranium are fabricated by means of the conventional regime and provide the required density and content of gallium of <0.001 wt. %.Weapons plutonium is considered to be a very important initial energy material for fabricating fuel for future commercial nuclear power facilities. A necessary condition for converting weapons plutonium into nuclear fuel is it regeneration from irradiated fuel and re-fabrication, i.e., the development of a closed nuclear fuel cycle. In the absence of a closed fuel cycle the use of weapons plutonium becomes its actual destruction, and the enormous renewable source of energy is lost.Fast reactors with liquid-metal coolant are most promising and cost-effective for use of weapons plutonium, and they give the required breeding ratio (BRC ≥ 1.05). They make it possible to realize an inexhaustible resource for obtaining energy and to decrease the ecological load as a result of the closed fuel cycle and burning of long-lived fission products. Only fast reactors can use most effectively the enormous stores of waste uranium, including in combination with weapons and power plutonium.Thermal reactors are also being considered to salvage weapons plutonium. Salvaging of weapons plutonium in lightwater reactors will result in substantial losses (to 60%) of the energy potential and a three-fold increase in the radiotoxicity index as compared with fast reactors.An increase of the scientific-technical interest noted at beginning in the 1960s to develop a liquid-salt reactor which uses nuclear fuel in a form admitting continuous adjustment of the composition and control of the nuclear-physical, chemical, and thermophysical processes during operation. The investigations showed that such reactors can find application in electric power production for transmutation of long-lived transuranium actinides, burning spent power plutonium as well as weapons plutonium, and solving other problems.