Abstract
Many experiments have been conducted on accidents and transients of pressurized water reactor (PWR) employing the rig of safety assessment/large-scale test facility (ROSA/LSTF). Recent research activities concerned with the OECD/NEA international joint projects included experimental investigation via the ROSA and ROSA-2 Projects, and counterpart testing with thermal-hydraulic integral test facilities under collaboration of the PKL-2, PKL-3, ATLAS, and ATLAS-2 Projects. Major results of the related integral effect tests (IETs) with the LSTF were reviewed to experimentally identify thermal-hydraulic phenomena involved, regarding the PWR accident sequences in accordance with the new regulatory requirements for the Japanese light-water nuclear power plants. Future separate effect test using the LSTF is planned to simulate loss of emergency core cooling system (ECCS) recirculation functions in a large-break loss-of-coolant accident (LOCA). Key results of the recent IETs utilizing the LSTF and future plans were presented relevant to multiple steam generator tube rupture accident with recovery operation, small-break LOCA with accident management measure on core exit temperature reliability, and small-break LOCA with thermal stratification under cold water injection from ECCS into cold legs. Also, main outcomes of the LSTF IETs were indicated for wide spectrum LOCA with core uncovery and anticipated transient without scram following small-break LOCA under totally failed high-pressure injection system.
Highlights
In the SB-PV-09 test, the core power was automatically lowered to a certain low level because the maximum cladding surface temperature became above the criterion of 958 K, which affected the peak cladding temperature (PCT) greatly
The PCT of 989 K was observed at Position 5 which is placed at a level of about 1/2 of the active core height
A series of integral effect tests (IETs) by use of the LSTF simulated Multiple Steam Generator Tube Rupture (MSGTR) accident with recovery operation being coupled with severe multiple system failure
Summary
Japan Atomic Energy Agency has been operating the rig of safety assessment/ large-scale test facility (ROSA/LSTF) [1] [2] since 1985, triggered by the Three. The following five accident sequences belong to beyond DBAs are involved in the PWR events that must be postulated in the new regulatory requirements; 1) station blackout (SBO), 2) loss of reactor shutdown functions, 3) loss of emergency core cooling system (ECCS) water injection functions, 4) loss of heat removal functions from secondary cooling water system, and 5) loss of ECCS recirculation functions. Foremost results of related integral effect tests (IETs) with the LSTF for the accident sequences of 1) through 4) were surveyed for experimentally specifying thermal-hydraulic phenomena concerned. PWR events involving specific thermal-hydraulic phenomena and transient responses, included 1) multiple steam generator tube rupture (MSGTR) accident with recovery operation, 2) small-break loss-of-coolant accident (LOCA) with accident management (AM) measure on core exit temperature. No more IETs are planned for the SBO transient with loss of the primary coolant with the AM actions
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