ML17286A275
| ML17286A275 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 08/28/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17286A274 | List: |
| References | |
| IEB-86-002, IEB-86-2, NUDOCS 9009050273 | |
| Download: ML17286A275 (3) | |
Text
. s.4'EQV
> ++
Ci 4u C
O 0
~
i4p*y+
t t
UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION-BY THE OFFICE OF NUCLEAR REACTOR-REGULATION RELATED TO DIFFERENTIAL PRESSURE STATIC "0" RING. SWITCHES AT WASHINGTON PUBLIC-POWER. SUPPLY SYSTEMS NUCLEAR-PROJECT UNIT 2 DOCKET-NO. 50-397
1.0 INTRODUCTION
Following an event at LaSalle County Station, Unit 2 on June 1, 1986, that resulted in low water level in the reactor vessel, one'f four low water level trip,channels (which use Static "0" Ring LSOR] differential pressure
[dpsviitches) actuated, resulting ir a half scrarri condition.
The operator recovered the viater level, cleared the half scram condition and continued power operation.
Subsequent review by the licensee raised.
a concerri that the water level may have dropped to a level at which a full scram should have occurred.
Based on this concern and following a series of discussions arid meetings v;ith the NRC, the staff issued IE Bulletin (IEB) 86-02 on SOR/DP svritches on July 18, 1986.
The Bulletin focused on SOR Yodel 102 and 103 dp switches which were in use at many boiling water reactors.
Specifically, the Bulletin stated that operation of the subject SORs had been found to be erratic viith little correlation between the setpoints established duririg atIIiospheric pressure (PSIG) calibrations and switch actuations under normal reactor system pressure conditions (approximately 1000 psig).
The Washington Public Power Supply System responded to IEB-86-02 on July 29, 1986, and a supplerrental response on November 7, 1986.
Review of the licensee response revealed that only four SOR hlodel 103 dp switches were in use at Nuclear Project Unit 2.
The primary function of these sviitches is to provide a sigrial of a low reactor water level condition to initiate closure of the main steam isolation valves to stop the loss of reactor water invertory through the main steam lines following a feedwater system malfunction or break in the primary coolant system.
The same four SOPs also provide signals to initiate isolation of the Containment and Reactor Building Heating and Veritilation Systems, and the Reactor Water Clean Up (RWCU) system.
The licensee reported that in addition to revising the plant operator training program in order to include the actions needed i.o identify a 9009050273 900828 PDR ADOCK 05000397 P
PNU malfunctioned SOR and to verify proper system isolations, they had also conducted special tests to compensate for an inherent shift of the trip setpoint between 0 and 1000 psig that had been experienced with SOR calibration efforts.
At that time, the licensee concluded that since the inherent setpoint drift had been determined and then compensated for during instrument calibration no long term corrective action was appropriate.
2.0 EVALUATION The staff has reviewed the licensee's response to IE Bulletin 86-02 and agrees that monthly checking and recording of the "as-found" trip setpoint as measured at atmospheric pressure and the change of this setpoint to compensate for its shift due to reactor operatino pressure, provides an acceptable means of addressino the primary concerns identified in IE Bulletin 86-02.
Also the Region V follow-up Inspection Report identified as 50-397/86/34 issued on December 3, 1986, verified that the licensee had satisfied all related action requirements specified in IEB 86-02.
In
- addition, NUREG/CR-5294 entitled, "Closeout of IEB-86-02:
Static "0" Ring Differential Pressure Switches" dated October 1989 lists the status of LJNP-2 as "closed".
In addition to the above findings, a recent (August 22, 1990) telecon with the licensee on the operational history of the subject SOR switches at their plant since issuance of the Bulletin in 1986, revealed that other than the failure described in the licensee's response to IEB-86-02 dated July 2., 1986, no failures or violations of technical specification limits have been noted ot the Static "0" Ring Switches, Series 103 at MNP-2.
.0 CONCLUSION Based on review of the licensee's response to IEB 86-02, the IEB 86-02 closeout-YUREG/CF-5294, and the recent information gathered from the licensee on the historical operating data of the subject SORs at MNP-2 since
- 1986, SICB finds the licensee's response to IEB-86-02 and the corrective actions taken to resolve the chronic drift problem associated with the subject SOR to be acceptable.
SICB considers the action requested by TAC No. 61816 satisfied and plans no further action on the issue.
Principal Contributor:
Vince Thomas, SICB Dated:
August 28, 1990
4
~
~