Improvement of JASMINE code for ex-vessel molten core coolability in BWR

Matsumoto, Toshinori; Kawabe, Ryuhei*; Iwasawa, Yuzuru; Sugiyama, Tomoyuki; Maruyama, Yu

Annals of Nuclear Energy, 178, p.109348_1 - 109348_13, 2022/12

https://doi.org/10.1016/j.anucene.2022.109348

The Japan Atomic Energy Agency extended the applicability of their fuel-coolant interaction analysis code JASMINE to simulate the relevant phenomena of molten core in a severe accident. In order to evaluate the total coolability, it is necessary to know the mass fraction of particle, agglomerated and cake debris and the final geometry at the cavity bottom. An agglomeration model that considers the fusion of hot particles on the cavity floor was implemented in the JASMINE code. Another improvement is introduction of the melt spreading model based on the shallow water equation with consideration of crust formation at the melt surface. For optimization of adjusting parameters, we referred data from the agglomeration experiment DEFOR-A and the under-water spreading experiment PULiMS conducted by KTH in Sweden. The JASMINE analyses reproduced the most of the experimental results well with the common parameter set, suggesting that the primary phenomena are appropriately modelled.

Basic test on sodium fire protection systems (III); Simulation Test, Run-B3 of a design basis sodium leak from the Monju IHTS

Himeno, Yoshiaki; ; Kawada, Koji*; Kawabe, Ryuhei*; *; *; Miyaguchi, Kimihide

PNC TN941 85-130, 65 Pages, 1985/09

PNC-TN941-85-130.pdf:2.49MB

Test of sodium fires in an auxiliary building of the fast reactor has been conducted by use of a test rig in which reduced scale models of a sodium pipe, a floor liner, a sodium drain pipe, and a smothering tank were installed to simulate the configuration of fire mitigation systems in the reactor. In the test, a 150kg sodium at temperature of 505 C was spilled from the model sodium pipe at flow rate of 1 /sec for 3 minutes. Then a whole accident sequence that starts from a sodium spill and ends at a self-extiguishment of fire within the smothering tank was studied. From the test results obtained and through their analysis, the following conclusions were drawn. (1)A whole sodium leak and fires accident sequence proceeded as expected in the Monju design, i,e., a spilled sodium was smoothly drained into the smothering tank via the floor liner and the drain pipe, then sodium fire was self-extinguished in the smothering tank. (2)In regard to the model sodium pipe, failures of the thermal insulation jackets due to sodium corrosion and due to generated sodium combustion heat are not found. The thermal insulation jackets kept its original geometries and functioned propely as a barrier to prevent the dispersion of spilled sodium into the atmosphere during the test. No flow blockage of a spilled sodium occured both on the floor Liner and in the drain pipe. Combustion heat of mixed fires (a columnar fire and a pool fire) that occured within an accident cell of the test rig was determined to be 1.6 times of that of a pool fire. This value is not so large as expected and indicates that the mild fires proceeds during the test. (3)With the smothering tank, temperatures data of sodium, steel liner, perlite concrete, and structural concrete were obtained. The data of concretes indicated that the structural concrete was not heated so high as to interfere its structural integrity. A total water released from the concretes per unit surface area of the liner ...

Comparison of Sofire-MII Predictions with the Results of German FAUNA F5 and F6 Tests

Miyake, Osamu; Kawabe, Ryuhei; Himeno, Yoshiaki; Miyaguchi, Kimihide

PNC TN941 85-67, 43 Pages, 1985/03

PNC-TN941-85-67.pdf:0.78MB

The SOFIRE-MII code, which was developed based on the U.S. SOFIRE-II code, analyzes a sodium pool fire accident in the LMFBR plant to predict the pressure and temperature of atmosphere as well as the structural temperatures within a reactor building. To date, the code has been validated by test data at low oxygen concentrations. However, the code validation at high oxygen concentration has been incomplete. To complete this validation, the calculations of pool fire test results that were obtained with an air-filled closed vessel, are conducted. The test results used for this purpose are those taken from the FAUNA F5 and F6 tests. FAUNA is a large sodium fire test facility installed in Kernforschungszentrum Karlsruhe (KfK), Federal Republic of Germany. The calculations include sensitivity studies on the important input parameters in SOFIRE-MII; the burning ratio, S (weight ratio of sodium/oxygen consumed by a the radiation heat exchange coefficient, F between a pool and the atmospheric gas, and the heat removal rate from the external surface of the test vessel. Enhancement of sodium combustion at the initial stage of the test due to sodium filling by a columnar high-speed sodium flow from an open nozzle over the pan is also evaluated. The result indicates that, as a whole, the test results are predicted fairly well by SOFIRE-MII with the S value of l.44that represents the sodium combustion generating 100% sodium peroxide as its reaction products and with F=0.65. The sensitivity studies of these parameters indicate that the S value has a significant effect, while the F value does not. The heat removal rate from the external surface of the vessel has also a little effect on the gas pressure and temperature, although the vessel wall temperature is significantly affected by this. Contribution of a columnar combustion during the sodium fill at, the initial stage of the test is found to be significant to the initial gas temperature and pressure spikes.

Basic test on sodium fire protection systems

Kawabe, Ryuhei*; Himeno, Yoshiaki; *; *; *

PNC TN941 84-124, 56 Pages, 1984/08

PNC-TN941-84-124.pdf:3.89MB

At Sodium Leak-Fire Basic Test Rig (SOFT-1), three tests were performed, which were : (1)Run-A1 : For the aim of understanding the sodium combustion phenomena, 180 sodium was burnt in an open pool, and temperature transients in sodium was measured and burning rate were determined. (2)Run-B1 : For the evaluation of efficiency of fire suppression board, burning sodium was covered by a slitted board and change in burning rate was observed and drain test was performed using 530 C sodium to confirm the function and integrity of draining pipe. (3)Run-B2 : In order to clarify the burning-hydraulic behavior of sodium on liner, 505C, 180 sodium was discharged onto 1.2m2.4m steel plate with 1/100 gradient, and temperature transients and mass of residuum were measured. Following results were obtained. (i)When sodium was heated up to 400C and exposed to air, the sodium was ignited. (ii)The surface temperature reached 650 C, 7 min. after the ignition and the temperature was almost constant from that. (iii)Under a conservative condition where air flowed over the fire suppression board by forced convection, the sodium burning rate and the aerosol generating rate where pool surface were covered by fire suppression board (opening area 1%) was about 3 % and 5 % of those in open pool burning respectively. (iv)The maximum heat flux to the draining pipe wall reached 1.210 W/m. Any cracking, however, was not found on the draining pipe wall even by color check. (v)In the liner test Run-B2, on the liner there remained large amount of sodium oxide, which worked as wick, and the soaked sodium burned after sodium supplying finished, resulting liner temperature 643 C which was higher than the supplied sodium temperature. The amount of sodium oxide was 8.7kg/m on the liner after the test. (vi)The maximum temperature, flow velocity and burning rate of sodium on liner and maximum heat ...

Study on molten core coolability under precautionary water injection into containment vessel, 3; Improvement of melt spread model in the JASMINE code

Kawabe, Ryuhei; Matsumoto, Toshinori; Sugiyama, Tomoyuki; Maruyama, Yu

no journal, , 

no abstracts in English

Study on molten core coolability under precautionary water injection into containment vessel, 1; Development of breakup particle agglomeration model in JASMINE

Matsumoto, Toshinori; Kawabe, Ryuhei; Ajima, Kohei; Sugiyama, Tomoyuki; Maruyama, Yu

no journal, , 

no abstracts in English

Evaluation of molten core coolability in containment vessel using JASMINE code

Iwasawa, Yuzuru; Matsumoto, Toshinori; Kawabe, Ryuhei; Ajima, Kohei; Sugiyama, Tomoyuki; Maruyama, Yu

no journal, , 

For assessment the molten core coolability during severe accident in LWRs, we improved the models in the JASMINE code regarding to agglomeration of melt particles and melt spreading in containment vessel based on the DEFOR-A and the PULiMS experiments conducted by KTH. The improved models generally show good agreement with these experimental results.