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Severe accident management of PWR by an intentional primary system depressurization

Technical Report:

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)  More>>
Authors:
Hidaka, Akihide; Sugimoto, Jun; Soda, Kunihisa; [1]  Yabushita, Yukihisa
  1. Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
Publication Date:
Oct 01, 1991
Product Type:
Technical Report
Report Number:
JAERI-M-91-175
Reference Number:
SCA: 210200; PA: JPN-91:012209; SN: 92000659243
Resource Relation:
Other Information: PBD: Oct 1991
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; PWR TYPE REACTORS; OUTAGES; PRIMARY COOLANT CIRCUITS; DEPRESSURIZATION; MELTDOWN; HIGH PRESSURE COOLANT INJECTION; M CODES; PRESSURE VESSELS; REACTOR SAFETY; 210200; POWER REACTORS, NONBREEDING, LIGHT-WATER MODERATED, NONBOILING WATER COOLED
OSTI ID:
10117120
Research Organizations:
Japan Atomic Energy Research Inst., Tokyo (Japan)
Country of Origin:
Japan
Language:
Japanese
Other Identifying Numbers:
Other: ON: DE92768131; TRN: JP9112209
Availability:
OSTI; NTIS (US Sales Only); INIS
Submitting Site:
JPN
Size:
73 p.
Announcement Date:
Jun 30, 2005

Technical Report:

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}
}