ML19340D941
| ML19340D941 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 12/08/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | William Jones OMAHA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 8101050611 | |
| Download: ML19340D941 (1) | |
Text
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NUCLEAR REGULATORY COMR4lSSION LPDR 2,
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ARLINGTON, TEXAS 76011 December 8, 1980 Docket No.
50-285 Omaha Public Power District ATTN:
W. C. Jones, Division Manager -
Production Operations 1623 Harney Street Omaha, Nebraska 68102 Gentlemen:
The enclosed IE 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 facility.
However, no specific response is requested at this time.
After further NRC evaluations we expect a bulletin will be issued to recomend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
i Sincerely,
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Enclosures:
1.
IE Information Notice No. 80-43 2.
List of Recently Issued IE Information Notices cc:
S. C. Stevens, Manager Fort Calhoun Station Post Office Sox 98 Fort Calhoun, Nebraska 68102 8101 050 ((!-
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SSINS NO.:
6835 Accession No.
8008220279 DhO' UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information Notice No. 80-43 December 5, 1980 Page 1 of 2 FAILURES OF THE CONTINUOUS WATER LEVEL MONITOR FOR THE SCRAM DISCHARGE VOLUME AT DRESDEN UNIT NO. 2 Descriotion 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 room following scram when the SDV filled with water.
An investigation 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 l
SDV verified proper system drain.
l Investigations by the licensee determined that the ultrasonic detectors l
were inadequately coupled to the SDV piping.
The coupling was improved I
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 j
alarms were not received in the control room immediately following the scram, but were received about 10-15 minutes later when the SDY was draining.
l Following an additional scram at approximately 20 psig with control rods inserted these alarms were received properly.
Investigation identified I
level detection system operability problems as evidenced by a low signal j
to noise ratio.
Arrangements are being made for replacement components (ingluding transducers) to improveUntil the improvemer.9.he signal characteristics an syshem noise.
s are installed and demonstrated l
adectuate by in situ testing, use of?the ultrasonic detection system is 9
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IE Infctmation Notice No. 80-43 December 5, 1980 Page 2 of 2 1
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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 after each reactor scram.
At Dresden Unit 2 the licensee will complete the system improvements and requireo 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 operable by in situ testing, these systems should not be solely relied on for detection of water in the SDV.
Use of new ultrasenic detection systems should be augmented by manual checks for water i., 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 ender review by the NRC staff.
Recipients should review the information.'or 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 questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
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IE Infor<.iation Notice No, 80-43 December 5, 1980 LISTING OF RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 1
80-38 Cracking in Charging 10/30/80 All Pressurized Water Pump Casing Cladding Reactor Facilities holding power reactor 1
Operating Licenses (OLs) and Construction Permits (cps) 80-39 Malfunctions Of Solenoid 10/31/80 All light water reactor Valves Manufactured By facilities holding Valcar Engineering Corporation power reactor Operating Licenses (OLs) or Construc-tion Permits (cps)
I 80-40 Excessive Nitrogen 11/7/80 All power facilities Supply Pressure wich an Operating License Actuates Saidty-Relief (OL) or Construction Valve Operation to Permit (CP)
Cause Reactor Depressuriza-i tion 80-41 Failure of Swing Check 11/10/80 All power reactor Valve in the Decay Heat facilities with an cperating Removal System at Davis-License (OL) or Cor.struction Besse Unit No. 1 Permit (CP) 30-42 Effect of Radiation 11/24/80 All power reactor on Hydraulic Snubber Fluid facilities with an Operating License (0L) or Construction Permit (CP)
Enclosure r
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