Session 5.1. Advanced Fast Reactor Fuel Development – I

Session 5.1. comprised six presentations, two from Republic of Korea, two from the Russian Federation, one from France and one from India.

J. Park (Republic of Korea) presented a fabrication process of metallic fuels for Sodium cooled Fast Reactors (SFR) developed using the injection casting. U-Zr-RE(Nd-Ce-Pr-La) fuel slugs were fabricated and characterized to optimize the injection casting process. The microstructure examined by SEM showed that inclusions were uniformly distributed over the fuel slug. The reaction between the melt and the crucible was found to be significant in the fabrication of rare earths (RE)-containing fuel slugs compared to U-Zr fuel slugs. The pressurized injection casting method was also developed to fabricate the fuel slugs containing volatile elements. U-Zr-Mn fuel slugs were fabricated as a surrogate for Am-bearing metallic fuels under three different melting pressure conditions. From the chemical composition analysis by the ICP-AES method, no evaporation of manganese was detected in the fuel slugs fabricated under argon atmosphere higher than 400 torr.

B. Tasarov (Russian Federation) presented a new concept for metal fuel fabrication for fast reactors lowering swelling effect. To get that, it is proposed to create an open porosity of 15 to 25% of the entire volume of the fuel pellet by applying the technique of powder metallurgy based on electromagnetic compaction methods. The particle size from 15 μm to 3000 mm was made from alloys uranium with molybdenum and zirconium by mechanical means, and by means of a hydrogenation-dehydrogenation. It was shown that the optimum powder fabrication technology is the mechanical grinding followed by grinding in a ball mill. Pycnometric analysis showed the presence of open (connected) porosity with weak dependence of density on the pressing pressure, and the size of the starting powders. Measurement of thermal conductivity of porous fuel pellets showed the thermal conductivity is decreasing with increasing porosity.

Thermophysical calculation of temperature fields in a fuel rod showed the possibility of using porous metal fuel in fast reactors.

L. Zabudko (Russian Federation) presented the development of uranium-plutonium nitride fuel. The work has been carried out in accordance with the comprehensive programme of computational and experimental validation of the performance of mixed nitride fuel for BN-1200 and BREST-OD-300. The technology of manufacturing pellets of mixed uranium-plutonium nitride fuel by carbothermic synthesis method had been developed. More than 500 fuel elements were produced to be tested in MIR, BOR-60 and BN-600 reactors (more than 60 fuel elements of different modifications with mixed nitride fuel were loaded into the BOR-60 and 15 experimental fuel assemblies with mixed nitride fuel were delivered to the BN-600).

Researches are continuing to improve the composition and structure of MNUP fuel in order to increase ductility, reduce crack resistance and fuel swelling speed. An industrial production is scheduled to be launched by 2020. Post-irradiation examinations confirmed that all fuel elements remained at their work capacity.

V. Blanc (France) presented the design of the fuel and radial shielding sub-assemblies for the ASTRID CFV v4 core at the end of the conceptual design phase (AVP2). Innovative design choices have been made to meet the ASTRID project requirements, marking a break with the former Phenix and SuperPhenix French SFRs. Fuel sub-assemblies ensure a low sodium void worth (CFV core), thanks to axially heterogeneous fuel pins, a wide cladding/small spacer wire

bundle, a sodium plenum above the fuel pins, and upper neutron shielding with B4C sodium-bonded pins. The upper neutron shielding helps to reach a low secondary sodium activity level and would be made removable on-line through the assembly head so as to meet washing constraints. Studies had been performed to increase the stiffness of the stamped spacer pads on the wrapper tube in order to analyze its effect on the core mechanical behaviour during hypothetical radial core flowering and compaction events. ASTRID specification for ²⁴Na activity in secondary loops appears to be reachable.

B. Nashine (India) presented the development of electromagnetic devices for sodium cooled fast reactors such as electromagnetic pumps, magnetic flow meters and sodium level probe.

The design and development of sodium submersible annular linear induction pump (ALIP) by employing mineral insulated (MI) cable for fabricating winding of ALIP addressed the problem of development and non-availability of high temperature electromagnetic pump (ALIP) for draining of primary radioactive sodium from main vessel of pool type sodium cooled fast reactor. The submersible ALIP can be also used for pumping sodium in integrated cold trap system submerged in primary sodium of pool type sodium cooled fast reactor and any other application where pumping is needed in pump submerged condition. Use of samarium cobalt magnet in flowmeter has facilitated reduction in weight and increase in sensitivity. Similarly, the development of electromagnet based flowmeter has overcome constraints of high temperature operation. Development of eddy current based ex-vessel allows the measurement of discrete sodium level in side vessel without need of penetration in the vessel.

J. Kim (Republic of Korea) presented the chemical interaction of irradiated metallic fuel and T92 cladding conducted at 750°C. In the case of U-10Zr slug with T92 specimen, eutectic reaction layer was observed and element distribution indicates that significant migration of elements occurs and neodymium, plays a significant role in increasing penetration depth. The measured penetration rate is almost similar but slightly higher than the reference value. It is thought that the difference comes from the furnace cooling. On the other hand, no eutectic melting region was found in the case of irradiated U-10Zr-5Ce with T92 specimens by fuel slug oxidation. Therefore, to minimize the oxidation of specimen at high temperatures, special rig for the heating test was made. Preliminary examination using the rig showed that rig is effective in preventing the oxidation.

TABLE 1. PRESENTATIONS FROM SESSION 5.1. – ADVANCED FAST REACTOR FUEL DEVELOPMENT – I

Chair: V. Troyanov and C. Sowrinathan

Id Presenter Country Title

CN245-198 PPT-198

J. Park (Invited)

Korea, Republic of

Fabrication Characteristics of Injection-cast Metallic Fuels

CN245-347 PPT-347

B. Tarasov Russian

Federation

Metal fuel for fast reactors, a new concept

CN245-62 PPT-62

L. Zabudko Russian

Federation

Development of innovative fast reactor nitride fuel in Russian Federation: state-of-the-art

CN245-128 PPT-128

V. Blanc France Conceptual design of fuel and radial shielding sub-assemblies for ASTRID

CN245-174 PPT-174

B. Nashine India Development of Electromagnetic Devices for Sodium Cooled Fast Reactor Application

CN245-106 PPT-106

J. Kim Korea,

Republic of

Fuel Cladding Chemical Interaction Tests of Irradiated Metallic Fuel