ML20050E217
| ML20050E217 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 04/01/1982 |
| From: | Mclendon G LOUISIANA POWER & LIGHT CO. |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, W3K-82-0193, W3K-82-193, NUDOCS 8204130113 | |
| Download: ML20050E217 (4) | |
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l.OUISIANA
,42 ouAnoNoe srnEu POWER & LIGHT P O BOX 6008
- NEW CRLEANS LOUISIANA 70174. (504) 366 2345 SSk!sYNO April 1, 1982 G. D. McLENDON Senior wce President W3K-82-0193 Q-3-A35.07.37 Mr. John T. Collins, Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76012
SUBJECT:
Waterford SES Unit No. 3 Docket No. 50-382 Interim Status Report of Significant Construction Deficiency No. 37
" Temperature Detectors (RTD's) Failure"
Reference:
LP&L Letter W3K-81-0420 to USNRC dated November 20, 1981
Dear Mr. Collins:
In accordance with the requirements of 10CFR50.55(e), we are hereby providing two copies of the Interim Status Report of Significant Construc-tion Deficiency No. 37, " Temperature Detectors (RTD's) Failure."
If you have any questions, please advise.
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Very truly yours, EECQygg s
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CDMcL/LLB/grf eb Attachment cc:
1)
Director Of fice of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 (with 15 copies of report)
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- 2) Director f
Office of Management jF Information and Program Control U. S. Nuclear Regulatory Commission Washington, D. C. 20555 (with 1 copy of report) hO
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LOUISIANA POWER & LIGHT COMPANY WATERFORD SES UNIT No. 3 l
Interim Status Report of Significant Construction Deficiency No. 37
" TEMPERATURE DETECTORS (RTD'S) FAILURE" Reviewed by 3 2/
2.-
R. J. Mi f - Site Manager
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~Date Reviewed by K If s - Project Superi tendent Date 35/b Reviewed by N
h_e-h J. Hart - Proj e Eicensing Engineft' Date Reviewed by 3/w/vi J. D
- ESSE Project En ineer
/ Ifate
/M 3k/bb hh Reviewed by J. Gutierrez
. A. Site. Supervisor p' Date March 31, 1982
INTERIM STATUS REPORT OF SIGNIFICANT CONSTRUCTION DEFICIENCY NO. 37 TEMPERATURE DETECTORS (RTD'S) FAILURE INTRODUCTION This report is submitted pursuant to 10CFR50.55(e).
It describes a deficiency regarding unreliable temperature signals from Rosemount, Inc., resistance temp-erature detectors (RTD's).
The RTD's supply reactor coolant system (RCS) cold leg temperature signals to the reactor protection system.
This problem is con-sidered reportable under the requirements of 10CFR50.55(e).
This problem was identified to the Nuclear Regulatory Commission on July 10, 1981, by a utility owner of a C-E NSSS.
DESCRIPTION OF PROBLEM On July 27, 1981, C-E Power Systems notified Ebasco Services, Incorporated, that errors in the RCS T-cold signal could result in a non-conservative thermal margin /
low pressure (TM/LP) trip setpoint and could permit possible operation in excess of departure from nucleate boiling (DNB) limits.
C-E does not believe that such operation is likely to occur because the RTD drif t is easily detectable by cross channel comparison and simultaneous multiple failures are not deemed credible.
The utility has determined that the cause of the erroneous RTD signals was due to resistance changes in the RTD circuitry as a result of corrosion degradation of the RID leads at the terminal block connection in the head of the RTD assembly.
The corrosion was believed to be caused by a galvanic reaction between the dis-similar metals in the RTD leads and the terminal blocks.
The utility placed the plant in hot standby for approximately twenty-four hours while all accessible safety and non-safety related Rosemount RTD's were refur-bished. This refurbishment consisted of replacing all components in the head of the RTD assemblies including the crimp type terminals on the RTD field leads and the terminal block. A gasket was also added to each of the RTD assembly heads to limit ingress of water vapor into the RTD head assembly, and surveillance of the inaccessible safety related RTD's was increased.
The utility is planning to re-place all Rosemount RTD's with comparable equipment from an alternate vendor during the next unit refueling outage.
SAFETY EKPLIC' TIONS A
The documents referenced together with NY I&C's evaluation recognize that the failure of subject RTD's is significant and could compromise the safe operation i
of NSSS.
The subject RTD's are used predominantly in safety-related systems.
Sixteen are installed in steam generator's hot and cold leg and provide input to Plant Pro-tection System; four of these will be used for subcooled margin calculator.
Six additional are used for display.
The galvanic corrosion in RTD's head introduces parasitic resistance into the in-strumentation loop.
This results in unreliable signals which would essentially indicate lower than actual temperature and adversely affect protective system re-sponse.
Thus, the safety of the plant could be compromised if lef t uncorrected.
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.. CORRECTIVE ACTION New York Instrument & Controls (I&C) has issued a Design Change Notice (DCN-NYC-IC-654) to implement the corrective action. The procedure will be to:
- 1) Leave extra cable slack in sensor termination head for future maintenance.
2)
Provide silver soldered splice connections.
3)
Insulate splice with Raychem heat shrinkable tubing.
4)
Equip RTD sensors with cable termination seal assemblies.
An unrelated Nonconformance Report (NCR W3-3413) which was holding work on this corrective action has been closed.
Corrective action will be accomplished by May 28, 1982; and a Final Report will be submitted to the USNRC on or before June 15, 1982.
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