Nitride Fuel and Pyrochemical Process Developments for Transmutation of Minor Actinides in JAERI Masahide Takano, Mitsuo Akabori, Kazuo Minato, Yasuo Arai Japan Atomic Energy Research Institute OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov. 2004

>Background >PROMINENT program >Fabrication of MA nitrides Carbothermic synthesis of (Pu,Am,Cm)N & (Pu,Am,Cm,Zr)N >Property Measurements of MA nitrides Hydrolysis & Evaporation behavior of AmN & (Am,Zr)N >Pyrochemical process Pu nitridation in Pu-Cd alloy >Irradiation test (Pu,Zr)N & PuN+TiN >Conclusion Content

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Nitride fuel cycle - background > JAERI has proposed double strata fuel cycle for MA transmutation, based on U-free nitride fuel, ADS, and pyrochemical reprocessing. > Expected on nitride fuel: Good thermal properties, Mutual solubility among MA nitrides, High heavy metal density > Experiments on MA nitride: Limitation in facility, apparatus, handling, material amount, High purity inert atmosphere required > We have studied on: Fuel fabrication technology Property measurements Irradiation behavior Pyrochemical process

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov PROMINENT program Pyrochemical Process Technology Fuel Irradiation Experiment Nitride Fuel Cycle Fuel Fabrication Reprocessing Pu/MA burning Fuel Fabrication Technology Fuel Property Measurement Research areas in PROMINENT program > JAERI, Osaka Univ, MMC, NDC, JAPC > Started Nov. 2002, five year program > Development and demonstration of elemental technology for nitride fuel cycle in laboratory scale PROMINENT: Property Measurements, Pyrochemical Process and Irradiation Experiments Needed for Nitride Fuel Cycle Technology.

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Fabrication of MA nitrides (1) 243 Am 2 O 3, ( 240 Pu, 244 Cm)O 2, ZrO 2 amorphous carbon > Starting materials > Fabrication method Carbothermic reduction of oxides mixture MO x + xC + 1/2N 2 MN + xCO Nitridation: N ºC Decarburization: N 2 +4%H ºC > Analyses X-ray diffraction N,O,C analyses (Pu,Am,Cm)N (Pu,Am,Cm,Zr)N Process temperature and CO gas release > Pu+Am+Cm+(Zr) nitrides 30~40 mg scale

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Fabrication of MA nitrides (2) Expected product Pu/Am/Cm/Zr molar ratio C/O molar ratio Mixture weight (mg) (Pu,Am,Cm)N(Pu,Am,Cm,Zr)N /0.34 /0.21 /00.14 /0.10 /0.06 / Composition of the oxides and carbon mixtures

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Fabrication of MA nitrides (3) (Pu,Am,Cm)N (Pu,Am,Cm,Zr)N XRD profiles of products > (Pu,Am,Cm)N Single phase solid solution nm ( nm by Vegard’s law) No oxide phase Low carbon content (<0.05 wt%) > (Pu,Am,Cm,Zr)N Double phases with NaCl structure different (Pu,Am,Cm)/Zr ratio Low oxygen content (0.15 wt%) High carbon content (1.3 wt%)  remained as carbonitride

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov AmNAm(OH) 3 Am 2 O 3 Property measurements (1) Hydrolytic behavior > MA nitrides are reactive with moisture > Hydrolysis of AmN and (Am,Zr)N observed in ambient air > AmN reacted with moisture to form Am(OH) 3 > (Am 0.1 Zr 0.9 )N retained the phase over 1000h Weight gain of AmN, (Am,Zr)N and (Dy,Zr)N in air and moist N 2

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Property measurements (2) Evaporation behavior > Am has high vapor pressure > Evaporation behavior of AmN & (Am,Zr)N in He gas flow AmN = Am(g) + 1/2N 2 > Evaporation rate constant, k (s -1 ) v = -(dN/dt) = kN > AmN retained the phase while heating, no metallic phase > Selective evaporation of AmN on (Am,Zr)N  change in composition > k of AmN in (Am,Zr)N depressed Arrhenius’ plots of k

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Property measurements (3) New apparatus > Apparatus for thermal property measurements installed > Thermal diffusivity ~ laser flash method sample diameter 3~5 mm installed in Ar atmosphere > Specific heat capacity ~ drop calorimeter sample sealed in Pt capsule > Designed for nitrides and small sized samples > Thermal expansion ~ high temp. XRD installed in Ar atmosphere

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Pyrochemical process of nitride fuel > Anodic dissolution of PuN in LiCl-KCl eutectic salt examined > Recovery of Pu into liquid Cd cathode demonstrated with high current efficiency Schematic diagram of pyrochemical process for nitride fuel > Pu in Pu-Cd alloy converted to PuN > Experiments on Am-containing nitride will start soon at “TRU-HITEC”

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Nitridation of Pu in Pu-Cd alloy (a) N 2 bubbling process Cd N 2 gas Pu-Cd PuN Furnace (b) Nitridation-distillation combined process > N 2 bubbling process U in U-Cd: 100% recovery Pu in Pu-Cd: only 10% recovery  decrease in Pu activity in Pu-Cd > Nitridation-distillation combined process Pu: 99% recovery PuN with high purity obtained Pu-Cd (12wt% Pu) Recovered PuN Crucible N 2 gas Pu-Cd melt PuN LiCl-KCl 723K 973K

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Irradiation test ongoing (Pu,Zr)N PuN+TiN > (Pu,Zr)N & PuN+TiN pellets Pu: 20wt%, He-bond > Irradiation ongoing at JMTR Linear power: ~40kW/m Target burnup: 20 at% of Pu > Basic irradiation behavior of U-free nitride fuel Irradiation: May 2002 ~ Nov PIE: Apr ~ Irradiation test schedule > Irradiation of (Pu,Np,Zr)N pellet scheduled at JOYO with JNC

OECD/NEA 8 th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov Concluding remarks > (Pu,Am,Cm)N and (Pu,Am,Cm,Zr)N synthesized by carbothermic reduction of the oxides  Mutual solubility among PuN-AmN-CmN was demonstrated. > Hydrolysis and evaporation behavior of AmN and (Am,Zr)N studied > Pu nitridation in Pu-Cd alloy investigated  AmN was chemically and thermodynamically stabilized by formation of solid solution with ZrN.  Simultaneous nitridation-distillation process yielded high purity PuN.