ML20168A569
| ML20168A569 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1971-099-00 | |
| Download: ML20168A569 (5) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
66996 Date:
October 10, 1971
Title:
Pressure Transient and Blowdown at Millstone Point 1 The failure sequence was:
- 1. A malfunction in the turbine pressure control system (not specified) caused a pressure transient which resulted in a reactor trip on high neutron flux.
- 2. The turbine was manually tripped.
This caused the turbine bypass valve to open as expected.
- 3. The #1 bypass valve failed to close so the operator manually closed the MSIVs.
- 4. The blowdown continued through an open relief valve until the reactor pressure reached 263 psig when it reseated. The valve's main disk was wire drawn and badly eroded.
(See attached page)
Corrective action:
- 1. The relief valve was ground,rebuilt, and tested prior to being reinstalled.
- 2. The turbine control problem was thought to be with. the linkage however this was being investigated.
Design purpose of failed system or component:
Relief valves provide for reactor pressure control Unavailability of system p er WASH 1400:* Relief valve failure to reset:
1-10-'/D Unavail~ability of component per WASH 1400:*
Unavailabilities are in units of per demand D
.Failure rates are in units of per hour HR-1.
- 5. The operator initiated the isolation condenser and proceeded with a controlled cooldown.
A total of 75,000 gallons of water was lifted from the torus, however it was not stated how the water was injected into the core.
The turbine control system The operator manually The bypass valve The relief valve The operator malfunctions which resulted tripped the turbine remained open so failed to reset successfully in a system blowdown.
which caused the tur-the operator juntil the pres-started the and reactor trip bine bypass to open closed the MSIVs sure dropped to IC and a relief valve 265 psig to lift__________I________________
Potential Severe Core Damage No No, EGGS avail-able No No, ECCS avail-able No No, ECCS avail-able No NSIC 66996 -
Actual Occurrence of a Pressure Transient and Blowd iat Millstone Point 1
Loss of Reactor 11PCI/RCIC ADS/LPCI Long Coolant Maintained Response(I' CS Term Accident Subcritical Adequate
Response
Core Adequate Cooling Potential Severe Core Damage Sequence No.
No 1
2 Yes No 3
Yes Yes Yes 4
5 6
NSIC 66996 -
Sequence of Interest for Pressure Transient and Blowdown at Millstone Point 1 1Millstone Point 1 utilizes ICj and FWCI instead of RCIC and HPCI.
2 Stuck open relief valve.
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
66996 DATE OF LER:
October 22, 1971 DATE OF EVENT: October 10, 1971 SYSTEM INVOLVED:
Turbine control system, pressure relief COMPONENT INVOLVED: Relief valve CAUSE:
erosion and wire drawn seat SEQUENCE OF INTEREST:
Loss of Coolant Accident (small)
ACTUAL OCCURRENCE:
Pressure transient and blowdown at Millstone Point 1 REACTOR NAME:
Millstone Point 1 DOCKET NUMBER:
50-245 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING:
660 MWe REACTOR AGE:
1 yr VENDOR:
GE ARCH ITECT-ENG INEERS: Ebasco OPERATORS:
North East Nuclear Energy Company LOCATION:
5 miles SW of New London, Conn.
DURATION:
N/A PLANT OPERATING CONDITION:
680MWe SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; (c) made inoperable;O failed to close.
DISCOVERY METHOD:
Operational event COMMENT:
-