[en] General influence of fission and corrosion products in primary system on MONJU plant design is reviewed. Various research and development works are now in progress to decrease the generation rate, to remove the products more effectively and to develop the methods of evaluation the behaviour of radioactive products. The inventory and distribution of fission and corrosion products in the primary circuit of MONJU are given. The radiation levels on the primary components are estimated to be several roentgens per hour. (author)

[en] An international project, the PHEBUS Fission Project Program (von der Hardt et al., 1994), is being carried out at Cadarache, France. Six integral in-pile tests, FPT0--FPT5, have been planned in the project to evaluate the behavior of fission products (FPs) released from a light water reactor during a severe accident. This paper describes numerical analysis of the PHEBUS FP steady-state benchmark problems and the first in-pile transient test, FPT0. A two-dimensional code has been newly developed to predict thermal hydraulics in the containment vessel, including air, steam and hydrogen transport and steam condensation. A degradation factor correlation, which plays an important role in the predictions for the condensation heat transfer in the presence of noncondensable gases, has been developed and incorporated into the code. The calculation results show that the code can accurately and rapidly predict complicated phenomena in the PHEBUS containment vessel

[en] In order to evaluate the behavior of fission products released from a core at a nuclear power light water reactor during a severe accident, the Phebus FP program is under way at CADARACHE (FRANCE) as an international project. In this program, the fission products released from the core are injected via a steam current into a containment vessel which is 1/5000 in volume of the actual plant. The Phebus FP program is unique in that it is the first in the world to study the transport of real fission products from their release in the fuel to their behavior in the circuit and containment. In NUPEC, MELCOR has been applied for thermal-hydraulic pre-test analysis of the first test of the Phebus FP program (test FPT-0) to study the applicability of the code for analysis of fuel bundle degradation phenomena and to confirm that the targeted constant test conditions can be attained in the circuit and containment. This paper presents the Phebus FPT-0 pre-test analysis by MELCOR version 1.8.2. (J.P.N.)

[en] Iodine release associated with sodium pool combustion was determined by heating 20 gr sodium containing sodium iodide, which was labelled with ¹³¹I and dissolved in the sodium in concentration of 1∼1,000 ppm, to burn on a nickel crucible in conditioned atmosphere in a closed vessel of 0.4 m³. Oxygen concentration was changed in 5∼21% and humidity in 0∼89% by mixing nitrogen gas and air. Combustion products were trapped by a Maypack filter composed of particle filters, copper screens and activated charcoal beds and by a glass beads pack cooled by liquid argon. Iodine collected on these filter elements was determined by radio-gas chromatography. When the sodium sample burned in the atmosphere of air at room temperature, the release fractions observed were 6∼33% for sodium and 1∼20% for iodine added in the sodium. The release iodine was present in aerosol at a ratio of 98%, and the remainder in the gas form. The release fraction of iodine trended to decrease as oxygen concentration and humidity in the atmosphere increased. No organic iodide was detected in the combustion products. (author)

[en] Energy release associated with sodium spray combustion was determined and a computer code was developed to analyze combustion of sodium particles in the atmosphere depleted of oxygen. Liquid sodium heated at 300∼500 deg. C was injected as much as 400 gr into a closed vessel of 2 m³. Atmosphere in the vessel was controlled by mixing nitrogen gas with dry air and wet air 0∼21% in oxygen concentration and 0∼75 in humidity. Temperatures and pressure of the atmosphere were recorded to observe their rises and drops with time during and after sodium injection. Peak pressure rose with increases in oxygen concentration and temperature of injected sodium being more sensitive to the concentration than the temperature. The peak pressure did not reach a level which was obtained from theoretical energy release from sodium spray combustion because of incomplete combustion and heat transfer to the vessel wall. It was assumed in the computer code that heat and mass transfer was controlled respectively by heat conduction and mass diffusion inside a reaction zone and the transfer was governed by convection outside the reaction zone. Calculation results revealed that combustion rate per unit area on the sodium particle was in proportion to oxygen concentration in the ambient gas but in reverse to the particle sizes, and that decreasing rate of square of particle sizes was about 7x10^-4 cm²/s, being smaller in one order of the value of fuel oils. Change in the pressure obtained from the calculation was on the whole in agreement with that observed in the experiment. (author)