New radiochemical technologies of spent nuclear fuel reprocessing V.I. Volk, А.V. Vatulin , P.P. Poluektov, А.Yu. Vakhrushin, L.P.Sukhanov A.A. BOCHVAR ALL-RUSSIA RESEARCH INSTITUTE OF INORGANIC MATERIALS 1

New technology of spent nuclear fuel (SNF) reprocessing should be decide following major problems: -separation of fissile materials for recycling in nuclear fuel cycle; separation of actinides and fission products in form of two factions, one of which should contain heat generated cesium and strontium, and second - long-lived minor actinides: neptunium, americium and curium; immobilization of the two factions in matrix materials meet the requirements to reliable and safe supervised storage (Cs, Sr) and transmutation or disposal (Np, Am, Cm). 3

SNF rerocessing technology developing for RT-2 plant In the long term there is supposition of new complex creation for domestic and foreign SNF reprocessing. For this complex is designing the drastically new technology based on operations of embrittlement and chopping of clad material, gaseous conversion of fuel oxides in nitrate salts, crystallization separation of bulk of uranium and mother liquor extraction reprocessing.

New items in SNF reprocessing technology. “REPA - process” Reprocessing tasks Fission materials separation for recycling into nuclear fuel cycle; Transplutonium elements and fission products separation as two faction, as minimum. First faction must contain heat-regenerating Cs and Sr, and second one - super-longlived minor-actinides: Np, Am, Cm; immobilization of obtaining factions into matrix materials, corresponding to the request of reliable and safe storage (Cs, Sr) and transmutation or storage (Np, Am, Cm) Potential advantages Ecological acceptability Technological support of non-proliferation Compactness Possibility of coat creation over the reprocessing plant Thermo-mechanical destruction of clade Gaseous conversion of U-oxide to nitrate U separation and affinage by HNU fission cake crystallization Extraction with simultaneously partitioning SNF CO2-N2O4 Mother liquor Hexahydrate of uranyl nitrate (HNU) Isolation of radioactove noble gases and tritium Gas-mixture adjustment Leaching of HNU fission cake Jacket materials U + Pu REE/TPE & FP faction Cs/Sr & FP faction Compactization Conversion into UF6 and adjustment of isotope composition Fuel for thermal reactors MOX-fuel for Fast Reactors Immobilization into mineral-like matrix Immobilization into the glass Cs & Sr isolation for commercial use TPE separation for transmutation

The principle scheme of head operation and unit of gas conversion from oxides to nitrates Clade materials washing FA dismantling. Brittle failure of Zr – jackets and FA destruction Oxidizing re-crystallization. NSF separation from clade material Conversion to nitrates N2+ О2 1200-1250 оС Т from clade, ~ 1% J, 1% Kr, 1% Xe 300-350 оС ~ 98% C ~ 98%J, 98% Kr, 98% Xe NO2 O2  5 % Zr + ~1%U3O8 95% Zr HNO3 UO2(NO3)2*6H2O UO2(NO3)2*6H2O, Pu,Minor actinides, FP  800 g/l H2O U3O8 (UO3) + 5% Zr  = 3,3 г/см3 N2O4 O2 <2% J, <2% C <2% Kr, <2% Xe, <2% T CO2 Periodically ourput Heat-exchanger Aerosol purypying iodine-129 recovery Tritium oxidizing to НТО, СО to СО2 НТО recovery СО2 recovery Xe recovery Kr recovery Iodine reprocessing to the product forms for storage Gas vent to atmosphere GAS-purifying system WWER-1000 fuel assembly (FA) Fultration

Equipment with СО2–N2O4 natural circulation for conversion from actinide oxides to nitrate salts (“Radium Inst.”) Equipment with СО2–N2O4 natural circulation for conversion from actinide oxides to nitrate salts (GHK)

Hot cell experimental model of crystallizer

Components distribution on main technological flows during the process of HNU continuous crystallization

Technology compactization Extraction process uranium flow 100 g/l Crystallization process uranium flow 1000 – 1100 g/l

Extragent regeneration TPE / REE re-extraction Flow sheet of improving extraction cycle Extractant washing U+Pu re-extraction U+Pu extraction SNF solution 8 М HNO3 0,5 М HNO3 U+Pu re-extract 0,1 М HNO3 U+Pu extractant Extragent regeneration Na2CO3 solution Soda regenerate Evaporation Adjustment TPE / REE extraction TPE / REE re-extraction Recycling extragent Still Cs+Sr faction To vitrification (boron-silicate glass ) TPE/REE faction To partitioning and immobilization into mineral-like matrix raffinate

- U-Pu faction obtaining; - Cs-Sr faction obtaining; Extraction cycle ~ 15 % feed flow Purposes: - U-Pu faction obtaining; - Cs-Sr faction obtaining; - МА-REE faction obtaining

The parameters of partitioning and separation of MA, REE, Cs, Sr The flow sheet of RAW partitioning process in improving extraction cycle F Re1 S E1 E2 E3 E4 E5 E6 E7 E8 1 2 3 4 5 6 7 8 R4 R3 R2 R1 Re3 Re2 R5 Re4 F – initial solution; S – extragent; En – extractant after “n” stage; Rn – raffinate after “n” stage; Ren – re-extragent after “n” stage. The parameters of partitioning and separation of MA, REE, Cs, Sr MA-REE output, % 98,5 Cs–Sr output, % ≥ 99 МА content in Cs–Sr fraction, % 1,5 Cs–Sr content in МА fraction, % ≤ 1