ML19340D948
| ML19340D948 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 12/08/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 8101050619 | |
| Download: ML19340D948 (1) | |
Text
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December 8, 1980 EcM m
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Docket Nos. 50-445/IE Information Notice No. 80-43 0
ru 50-446/IE Information Notice No. 80-43 Texas Utilities Generating Company ATTN: Mr. R. J. Gary, Executive Vice President and General Manager 2001 Bryan Tower Dallas, Te:sas 75201
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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 facilities. 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.
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Sincerely,
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Karl V. Seyfrit
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Director
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Enclosures:
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IE Infomation Notice No. 80-43 2.
List of Recently Issued IE Infonnation Notices i
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SSINS NO.:
6835 Accession No.
8008220279 UNITED STATES
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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 ut.'lizes 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 wa:s 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 cy the licensee cetermined that the ultrasonic detectors 4ere inaaecuately couoled to the SDV piping.
The coucling was improved and testing performed to snow that the system could detect water flow into the SDV curing single control rod scram tests.
The unit was taken critical and was heating uo on Decemoer 4, 1980, at acoroximately 100 osig wnen a reactor scram accurrec.
The exoectea 50V hign level annunciar" alarms were not receivec in ne controi room immediately following ne scram, but nere receivec aoout 10-15 minutes later wnen tne SDV sas craining.
Following an additional scram at accroximately 20 psig witn control rocs insertec these alarms were received precerly.
Investigation identified level detection system oceracility oroolems as evidencea by a low signal to noise ratio.
Arrangements are being made for reciacement comoonents (incluaina transaucers) to imorove the signal cnaracteristics ana reduce system noise.
Unt1: the improvements are installed anc cemonstratec acecuate by in situ testing, use of the ultrasonic detection system is
IE Information Notice No. 80-43 December 5, 1980 Page 2 of 2 i
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 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 i
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 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 information for possible applicability to their facilities.
No specific response is requested at this time.
l Pending further NRC evaluations, we expect licensee actions will be l
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 Information Notice No. 80-43 December 5, 1980 LISTING OF RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 80-38 Cracking in Charging 10/30/80 All Pressurized Water Pump Casing Cladding Reactor Facilities holding power reactor Operating Licenses (OLs) and Construction Permits (cps) 80-39 Malfunctions Of Solenoid 10/31/80 All light water reactor Valves Manufactured By facilities holding Valcor Engineering Corporation power reactor Operating Licenses (OLs) or Construc-tion Permits (cps) 80-40 Excessive Nitrogen 11/7/80 All power facilities Supply Pressure with an Operating License Actuates Safety-Relief (OL) or Construction Valve Operation to Permit (CP)
Cause Reactor Depressuriza-tion 80-41 Failure of Swing Check 11/10/80 All power reactor Valve in the Decay Heat facilities with an Operating Removal System at Davis-License (OL) or Construction Besse Unit No. 1 Permit (CP) 80-42 Effect of Radiation 11/24/80 All power reactor on Hydraulic Snubber Fluid facilities with an Operating License (0L) or Construction Permit (CP)
Enclosure
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