Abstract
Some of PWR severe accidents are initiated by loss of all AC power. In these cases, accident would proceed while the primary system pressure is still at high level. Thus it is proposed that an intentional depressurization of the primary system has a potential to enhance core cooling by lowering the system pressure, actuating the accumulator injection system and cooling the core. It would delay reactor pressure vessel meltthrough and prevent HPME (High Pressure Melt Ejection) and DCH (Direct Containment Heating). Effectiveness of an intentional primary system depressurization was investigated by performing analysis with MARCH3.0 for cases in which an operator was assumed to open PORVs during a TMLB` sequence of a PWR severe accident. The present analyses showed that: (1) If an effective depressurization is performed by an operator before reactor vessel meltthrough, core melt, core collapse and reactor pressure vessel meltthrough could be delayed up to about 160 minutes by early initiation of accumulator injection. Furthermore HPME and DCH could be prevented even if reactor pressure vessel meltthrough occurs. (2) Timing of depressurization initiation has little effect on the timing of reactor pressure vessel meltthrough and an overall accident progression. However, early depressurization would delay melt initiation. (3)
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Hidaka, Akihide;
Sugimoto, Jun;
Soda, Kunihisa;
[1]
Yabushita, Yukihisa
- Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
Citation Formats
Hidaka, Akihide, Sugimoto, Jun, Soda, Kunihisa, and Yabushita, Yukihisa.
Severe accident management of PWR by an intentional primary system depressurization.
Japan: N. p.,
1991.
Web.
Hidaka, Akihide, Sugimoto, Jun, Soda, Kunihisa, & Yabushita, Yukihisa.
Severe accident management of PWR by an intentional primary system depressurization.
Japan.
Hidaka, Akihide, Sugimoto, Jun, Soda, Kunihisa, and Yabushita, Yukihisa.
1991.
"Severe accident management of PWR by an intentional primary system depressurization."
Japan.
@misc{etde_10117120,
title = {Severe accident management of PWR by an intentional primary system depressurization}
author = {Hidaka, Akihide, Sugimoto, Jun, Soda, Kunihisa, and Yabushita, Yukihisa}
abstractNote = {Some of PWR severe accidents are initiated by loss of all AC power. In these cases, accident would proceed while the primary system pressure is still at high level. Thus it is proposed that an intentional depressurization of the primary system has a potential to enhance core cooling by lowering the system pressure, actuating the accumulator injection system and cooling the core. It would delay reactor pressure vessel meltthrough and prevent HPME (High Pressure Melt Ejection) and DCH (Direct Containment Heating). Effectiveness of an intentional primary system depressurization was investigated by performing analysis with MARCH3.0 for cases in which an operator was assumed to open PORVs during a TMLB` sequence of a PWR severe accident. The present analyses showed that: (1) If an effective depressurization is performed by an operator before reactor vessel meltthrough, core melt, core collapse and reactor pressure vessel meltthrough could be delayed up to about 160 minutes by early initiation of accumulator injection. Furthermore HPME and DCH could be prevented even if reactor pressure vessel meltthrough occurs. (2) Timing of depressurization initiation has little effect on the timing of reactor pressure vessel meltthrough and an overall accident progression. However, early depressurization would delay melt initiation. (3) If depressurization rate is not large enough, reactor pressure vessel meltthrough would occur before accumulator injection under the condition of large pressure difference between the primary system and containment, and HMPE could not be prevented. It is also found that depressurization rate more than 45.1kg/s for saturated steam, which is equivalent to two PORVs capacity, is needed for an effective depressurization. (author).}
place = {Japan}
year = {1991}
month = {Oct}
}
title = {Severe accident management of PWR by an intentional primary system depressurization}
author = {Hidaka, Akihide, Sugimoto, Jun, Soda, Kunihisa, and Yabushita, Yukihisa}
abstractNote = {Some of PWR severe accidents are initiated by loss of all AC power. In these cases, accident would proceed while the primary system pressure is still at high level. Thus it is proposed that an intentional depressurization of the primary system has a potential to enhance core cooling by lowering the system pressure, actuating the accumulator injection system and cooling the core. It would delay reactor pressure vessel meltthrough and prevent HPME (High Pressure Melt Ejection) and DCH (Direct Containment Heating). Effectiveness of an intentional primary system depressurization was investigated by performing analysis with MARCH3.0 for cases in which an operator was assumed to open PORVs during a TMLB` sequence of a PWR severe accident. The present analyses showed that: (1) If an effective depressurization is performed by an operator before reactor vessel meltthrough, core melt, core collapse and reactor pressure vessel meltthrough could be delayed up to about 160 minutes by early initiation of accumulator injection. Furthermore HPME and DCH could be prevented even if reactor pressure vessel meltthrough occurs. (2) Timing of depressurization initiation has little effect on the timing of reactor pressure vessel meltthrough and an overall accident progression. However, early depressurization would delay melt initiation. (3) If depressurization rate is not large enough, reactor pressure vessel meltthrough would occur before accumulator injection under the condition of large pressure difference between the primary system and containment, and HMPE could not be prevented. It is also found that depressurization rate more than 45.1kg/s for saturated steam, which is equivalent to two PORVs capacity, is needed for an effective depressurization. (author).}
place = {Japan}
year = {1991}
month = {Oct}
}