ML19340D885
| ML19340D885 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 12/05/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8101050504 | |
| Download: ML19340D885 (1) | |
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NUCLEAR REGULATORY COMMISSION Ur o
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- e December 5, 1980 v
1 Docket Nos. 50-133, 50-275, 50-323 i
Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 i
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Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel
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Gentlemen:
The enclosed Information Notice is provided as an early notification of a possibly significant matter.
Recipients-of this notice should review the information for possible applicability to their facilities.
- However, no specific response is requested at this time. After further NRC evalu-ations we expect a bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
$Il bw,,xlh l
R. H. Engelken Director i
Enclosures:
1 1.
IE Information Notice No. 80-43 l
2.
Recently Issued i-IE Information Notice-I cc w/ enclosures:
-J. D. Shiffer W. Raymond, PG&E!
i-l R. C. Thornberry, Plant Manager j.
E. Weeks, PG&E, Humboldt Bay
- E. B. Langley, Jr., PG&E l
i 8101050 Nf I
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i SSINS NO.: 6835 Accession flo.
8008220279 IN 80-43 h
UNITED STATES WM NUCLEAR REGULATORY COMMISSION
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OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 December 5, 1980
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IE Information Notice No. 80-43:
FAILURES OF THE CONTINU0US WATER LEVEL MONITOR FOR THE SCRAM DISCHARGE VOLUME AT DRESDEN UNIT NO. 2 Descrintion of Circumstances:
On December 2,1980, following a reactor scram at Dresden Nuclear Power Station Unit 2, the licensee discovered that the recently installed scram discharge volume (SDV) continuous water level monitoring system had failed to respond as expected. The continuous water level monitoring system was designed and supplied by Nortec Corporation, and utilizes a single transmit /
receive transducer for each of the four level monitoring channels.
Following installation of the continuous level monitoring system, the licensee verified its operability by tripping each alarm channel while its sensor was connected to a calibration standard consisting of a section of 4 inch pipe identical to the SDV piping.
No in situ test of _ the equipment was accomplished.
The expected high level annunciator alarms were not received in the control i
room following scram when the SDV filled with water.. An investigation 4
to determine the cause was initiated and once per shift checks of the SDV level on both Units 2 and 3 were re-instituted. The reactor scram system functioned normally and post scram manual ultrasonic tests on the SDV verified proper system drain.
Investigations by the licensee determined that the ultrasonic detectors were inadeauately coupled to the SDV piping. The coupling was improved and testing performed to show that the system could detect water flow into the SDV during single control rod scram tests. The unit was taken critical and was heating up on December 4,1980, at approximately 400 psig when a reactor scram occurred. The expected SDV high level annunciator alarms were not received in the control room immediately following the scram, but were received about 10-15 minutes later when the SDV was -draining.
Following an additional scram at approximately 20 psig with control rods inserted these alarms were received properly.
Investigation identified
' level detection system operability problems as evidenced by a low signal to noise ratio.
Arranaements are being made for replacement components (including transducers} to improve the signal ' characteristics and reduce
-system noise.
Until-the improvements are installed and demonstrated adequate by in situ testing, use of the ultrasonic detection system is being augmented with manual ultrasonic checks of level in the SDV, using the previously required once per shift check. A manual check will be performed af ter each reactor scram. At Dresden Unit 2 the licensee will
IN 80-43 December 5,1980 Page 2 of 2 complete the system improvements and required testing within 7 days in accordance with the Immediate Action Letter issued by Region III on December 4, 1980.
The above operating experience indicates the need for a demonstration of the operability of ultransonic systems recently installed to continuously monitor for water in the SDV.
Until demonstrated coerable by in situ testing, these systens should not be solely relied on for detection of water in the SDV.
Use of new ultrasonic detection systems should be augmented by manual checks for water in the SDV each shift and after reactor scram until in situ testing is performed.
It is important that a high degree of reliability be established in operability of these continuous water level monitoring systems in order to support plant operations in the interim until final scram discharge system modifications are performed.
This IE Information Notice is provided as an early notification of a possibly significant matter that is still under review by the NRC staff.
Recipients should review the infornation for possible applicability to their facilities.
No specific response is requested at this time.
Pending further NRC evaluations, we expect licensee actions will be requested or required.
No written response to this IE Information Notice is required.
If you have any auestions regarding this matter, please contact the Director of the appropriate NRC Regional Office, t
i
IN 80-43 December 5, 1980 RECEtlTLY ISSUED IE IflFORt1ATI0tl NOTICES Information Date of flotice flo.
Sub,iect Issue Issued to 80-42 Effect of Radiation on 11/24/80 All power reactor Hydraulic Snubber Fluid facilities with OL or CP 80-41 Failure of Swing Check 11/10/80 All power reactor Valve in the Decay Heat facilities with an OL Removal System at Davis-or CP Besse Unit No. 1 80-40 Excessive Nitrogen Supply 11/10/80 All nuclear power Pressure Actuates Safety-facilities with Relief Valve Operation to OL or CP Cause Reactor Depressur-ization 80-39 italfunctions Of Solenoid 10/31/80 All light water reactor Valves flanufactured By facilities holding Valcor Engineering Corporation power reactor OLs or cps 80-38 Cracking In Charging Pump 10/30/80 All PWR facilities Casing Cladding with an OL or CP 80-37 Containment cooler leaks 10/24/80 All nuclear power and reactor cavity facilities holding flooding at Indian Point power reactor OLs Unit 2 or cps 80-36 Failure of Steam 10/10/80 All nuclear power Generator Support Bolting reactor facilities holding power reactor OLs or cps 80-35 Leaking and dislodged 10/10/80 All categories G and Iodine-124 implant seeds G1 medical licensees 80-34 Boron dilution of reactor 9/26/80 All pressurized water coolant during steam reactor facilities generator decontamination holding power reactor OLs 80-33 Determination of teletherapy 9/15/80 All teletherapy timer accuracy (G3) licensees
- Operating Licenses or Construction Permits
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