ML19340D942
| ML19340D942 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 12/08/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8101050612 | |
| Download: ML19340D942 (1) | |
Text
CENTRAL FILES
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UNITED STATES PDR:HQ
,*,7 NUCLEAR REGULATORY COMMISSION DR j
REGloN IV g
11 RYAN PLAZA oRtVE. SUITE 1000 0,
?,,,,,8 ARLINGTON, TEXAS 76011 STATE December 8, 1980 Docket No. 50-267 Public Service Company of Colorado ATTN: Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
The enclosed IE Information Notice is provided as an early notification of a possibly significant matter.
Recipients of this notice should review the infomation for possible applicability to their facility.
However, no specific response is requested at this time. After further NRC evaluatior._
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,
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Karl V. Seyfri, l
Director
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Enclosures:
1.
IE Information Notice No. 80-43 l
2.
List of Recently Issued IE Information Notices c:::
D. W. Waremoourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance l
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1 SSINS NO.:
6835 Accession No.
8008220279 UNITED STATES 2
NUCliAR REGULATORY COMMISSION c
0FFICE tr INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information Notice No. 80-43 December 5, 1980 Page 1 of 2 FAILURES OF THE CONTINU0US WATER LEVEL MONITOR FOR THE SCRAM DISCHARGE VOLUME AT DRESDEN UNIT NO. 2 Description of Circumstances:
On December 2, 1980, following a reactor scram at Dresden 'aclear Power Station Unit 2, the licensee discovered that the recent', 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 wcs 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 fellowing scram when the SDV filled with water.
An investigation to determine the cause was initiated and once per shift checks of the SDV level oc 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 di&ia.
Investigat ons by the licersee determined that the ultrasonic detectors were inadequately coupled to the SDV piping.
The coupling was improved and testing performed to show tha' the system could detect water flow into the SDV during single contro, rod scram tests.
The unit was taken i
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.
Arrangements 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 c
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IE Information Notice No. 80-43 December 5, 1980 Page 2 of 2 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 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 inforration for possible applicability to their facilities.
No specific rasponse 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 tne appropriate NRC Regional Office.
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j IE Information Notice No. 39-13 December 5, 1980 LISTING OF RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To j
Notice No.
Issued 80-38 Cracking in Charging 10/30/80 All Pressurized Water Pump Casing Cladding Reactor Facilities i
holding power reactor Operating Licenses (0Ls) and Construction Permits (cps) 80-39 Malfunctions Of Solenoid 10/31/80 All light water reactor i
Valves Manufactured By facilities holding Valcor Engineering Corporation power reactor Opceating Licenses (0L,1) or Construc-tion Permits (cps) 80-40 Excessive Nitrogen 11/7/80 All power facilities Supply Pressure with an Operating License 4
Actuates Safety-Relief (OL) or Construction Valve Operation to Permit (CP) l Cause Reactor Depressuriza-tion i
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) cr Construction Besse Unit No. 1 Permit (CP) i 80-42 Effect of Radiation 11/24/80 All power reactor on Hydraulic Snubber Fluid facilities with an Operating License (0L) or Construction i
Permit (CP) 1 Enclosure t
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