Kunihisa Soda

Nuclear aerosol codes

Codes used to simulate aerosol behavior inside containments of nuclear power plants after assumed severe accidents are described. The basic aerosol physical equations of all codes are the same worldwide. Only minor differences can be detected regarding some special aerosol physical processes. These differences are not inherent but caused by boundary conditions, which are of special interest for the code users. The comparison of the single codes also shows that the general agreement achieved by the numerical treatment of the aerosol equation requires an appropriate discretization of the distribution function to yield stable solutions under all arbitrary conditions. The application of solutions based on special distribution functions should, therefore, be restricted to certain scenarios.

Fire Behavior and Filter Plugging During a Postulated Solvent Fire in the Extraction Process of a Nuclear Fuel Reprocessing Plant

A solvent fire in the extraction process of a fuel reprocessing plant is postulated. Because of the high concentration of fission products and large amount of nuclear fuel materials in the extraction process, it is necessary to demonstrate that these radioactive materials can be confined by the air ventilation system during a solvent fire. Large-scale tests are performed in a fire/filter facility to evaluate the effectiveness of a ventilation system including high-efficiency particulate air (HEPA) filters to confine radioactive materials. It is demonstrated that the integrity of the filters in the ventilation factor of HEPA filters for smoke particles, which might contain radioactive materials, is sufficiently high during a postulated solvent fire.

Small-scale component experiments of the penetration leak characterization test in the ALPHA program

A small-scale penetration leak characterization test has been performed as a part of the ALPHA program at Japan Atomic Energy Research Institute (JAERI). Two series of experiments were performed using test sections which simulate relevant parts of an EPA (Electrical Penetration Assembly) used in Japanese PWR containments. One of the test sections simulates an alumina module and the other includes the silicone resin portion of the EPA. The test section was heated in a leak test vessel which simulated thermal-hydraulic conditions inside and outside of the containment in a severe accident. From the experimental results, it was concluded that although the silicone resin may melt at high temperature, the alumina module will remain intact under severe accident conditions. The EPA as a whole is estimated to maintain leak-tightness during a severe accident. It was found in the experiments that heat conduction along the metal portion of the test section had a strong influence on the melt progression of the resin. It was also found that the measured strain of the alumina module was predominantly caused by the elevated temperature. Therefore, the thermal load will be more of a threat to the EPAs integrity rather than the pressure load.

Structural analysis of Japanese PWR steel containment vessel under internal pressure loading

Abstract Elastic—plastic structural analyses of a typical Japanese PWR steel containment vessel under static or dynamic internal pressure loading representing conditions of a typical severe accident were performed using the finite-element analysis code “ADINA”. In the analysis, static pressure was applied up to 1 MPa, simulating the conditions of a severe accident. Dynamic pressure loadings were assumed, such as a triangular pressure pulse with 10 ms duration and 1 or 2 MPa peak pressure, representing dynamic conditions of hydrogen burn or steam explosion in a containment. It was found in the present analysis that the containment behaves elastically as a whole up to 0.8 MPa in the statically applied loading.

Structural analysis of a Japanese BWR MARK-I containment under internal pressure loading

Abstract This paper describes the elastic-plastic analysis of the Japanese BWR MARK-I steel containment vessel under pressure loadings by a general purpose finite element method code ADINA. The present study is focused on the entire deformation of the vessel rather than the stress or strain concentrations around the structural singularities such as penetrations. Elastic deformation limits, displacements and equivalent stress distributions are discussed.

Finite element dynamic bifurcation buckling analysis of torispherical head of BWR containment vessel subjected to internal pressure

Abstract In this paper the bifurcation buckling pressure for the torispherical head of the Mark II type BWR containment vessel subjected to dynamically applied internal pressure is calculated, using a finite element program for a dynamic analysis. Three kinds of dynamic loadings, that is, step loading, ramp loading and pulse loading are considered in the present analysis. The minimum bifurcation buckling pressure is predicted for the respective loadings. The minimum bifurcation buckling pressure for dynamic loading is much lower than the bifurcation buckling pressure for static loading.

Analysis of Hydrogen Burn in the Three Mile Island Unit 2 Accident with the CONTAIN1.1 Computer Code

The hydrogen burn that occurred in the Three Mile Island Unit 2 (TMI-2) accident raised a concern on the possible threat to the containment integrity of a light water reactor during a severe accide...

Thermal-Hydraulic Analysis of the Initial Phase of the Three Mile Island Unit 2 Accident

A thermal-hydraulic analysis of the initial 174 min of the Three Mile Island Unit 2 (TMI-2) accident was performed using the THALES (Thermal-Hydraulic Analysis of Loss-of-Coolant, Emergency Core Co...