ML20009H610

LER 81-018/03L-0:on 810701,Channel I (PI-474) of a Steam Generator Steam Line Pressure Indicated High Compared to Two Redundant Channels.Caused by Throttled Root Isolation Valve MSV-14.Valve Reopened

ML20009H610
Person / Time
Site:	Robinson
Issue date:	07/31/1981
From:	Cox H CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009H604	List: ML20009H603 ML20009H610
References
LER-81-018-03L, LER-81-18-3L, NUDOCS 8108100292
Download: ML20009H610 (3)

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NRC F oRM M6. U. S. NUCLE AR REGULATORY COMMISSION 0 77)

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/ 8 60 61 NUMBER EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h I o 12 I lon July 1,1981, with the unit at 93% power, the Control Operator observed that Channell lT[5] lI (PI-474) of "A" Steam Generator Steam Line Pressure was indicating high compared to l l o 14 j lits two redundant channels. Channel I was declared inoperable at 1128 hours0.0131 days <br />0.313 hours <br />0.00187 weeks <br />4.29204e-4 months <br />. The l lo is] l Channel I bistables were tripped to maintain the minimu:: degree of redundancy. However) g Ithe apparent inoperability of Channel I, prior to tripping its bistables, resulted in l g l exceeding the minimum degree of redundancy required by Technical Specification Table l lOIsl 13.5-3 which is reportable pursuant to 6.9.2.b.2. l 80 7 8 9 SYS TEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE o o l C l C l@ W@ LA_J@ l v l A l t l v I E l X lh W@ [D_j 20 7 8 9 10 11 12 13 18 19

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33 34 35 36 3/ 40 41 42 43 44 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l i l o l lThe Channel I deviation was caused by a throttled root isolation valve (MSV-14) on l 3 i [the instrument sensing line. MSV-14 was opened, and Channel I was declared operable l

, 7 jat 1440 hours0.0167 days <br />0.4 hours <br />0.00238 weeks <br />5.4792e-4 months <br />. Operating personnel have been cautioned as to the importance of l 3 3 l insuring that instrument sensing line root isolation valves are fully open, and all l employees have been reminded that no valve operation is to be done by unauthorized or I i l 41 juntrained personnel. l 7 8 9 80 SA S  % POWER OTHER ST ATUS DISC R DISCOVERY DESCRIPTION 1 5 [J j@ l O l 9 l 3 l@l N/A l lAl@l Operator Observation l ACTIVITY CO TENT RELE ASED OF RELEASE AMOUNT OF ACTIVITY LOCATION oF RELEASE 1 6 N/A l l N/A l 7 8 9

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• • " * '8 7 8 8108100292 810731 DR ADOCK 05000 Howard T. Cox peong: (803) 383-4524 E,

SUPPLEMENTAL INFORMATION FOR LICENSEE EVENT REPORT 81-018

1. Cause Description and Analysis At approximately 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> en July 1, 1981, with the unit at 93%

power, the Control Operator observed that Channel I (PI-474) of "A" Steam Generator Steam Line Pressure was indicating high compared to its two redundant channels. These Steam Line Pressure Channels supply signals for sensing high differential steam pressure between the steam generator line and the steam header which provide steam line break protection. At 1128 hours0.0131 days <br />0.313 hours <br />0.00187 weeks <br />4.29204e-4 months <br />, Channel I was declared in-operable and its bistables tripped using Operating Work Permit (OWP)

RP-ll.

Instrumentation and Control personnel verified that the problem was not in the Channel I electronics. It was suspected the problem was due to sludge blocking the instrument sensing line. When flush-ing the sensing line failed, an operator proceeded to close the root isolation valve (MSV-14) so the line could be disconnected and back-flushed. The operator discovered MSV-14 to be throttled. This throttled position of MSV-14 caused the steam line pressure signal to be dampened and reduced the ability of Channel I to respond to short duration steam line pressure changes. This created the channel deviation observed by the Control Operator. MSV-14 was opened and Channel I (PI-474) returned within the deviation limits of its two redundant channels. An investigation was conducted to determine how valve MSV-14 could have been misplaced into the throttled position.

The most recent valve lineup documentation was reviewed and the operator who made the lineup was questioned as to the last known posi-tion of the valve. The operator stated that on June 9, 1981, when the valve w s last checked, it was in the fully opened position. A review of past maintenance records indicates that no work has been done on the valve since June 9, 1981. In addition, a review of' operating conditions at the valve indicate that local vibrations are not of sufficient magnitude to cause the valve position to change.

Therefore, although the operator stated positively that the MSV-14 valve had been fully opened, operator error cannot be ruled out as the most probable cause for this event.

Channel I was checked for proper signal levels and declared operable at 1440 hours0.0167 days <br />0.4 hours <br />0.00238 weeks <br />5.4792e-4 months <br /> in accordance with OWP RP-ll. Throughout this event, the other two. redundant channels of "A" Steam Generator Steam Line Pressure were operational. This provided the necessary indication and safety signals. There was no threat to the public health and safety. However, the apparent inoperability of Channel I prior to tripping its bistables resulted in exceeding the minimum degree of redundancy required by Technical Specification Table 3.5-3 which is reportable pursuant to 6.9.2.b.2.

2. Corrective Action The immediate corrective action was to fully open MSV-14. This restored Channel I to within the deviation limits. The instrument sensing was flushed as an added precaution.

3. Corrective Action To Prevent Recurrence 1

3 This event appears to be the result of either mis-operation or not' assuring the valve was in its fully open position. Therefore, Operating personr.el have been cautioned as to the importance of 7 assuring that instrument sensing line root valves, which are required to be open, are fully opened. Also, Operating personnel will review this LER for its lessons to be learned. In addition, all plant i

personnel will be reminded by August 15, 1981, that no valve opera-tion is to be done by unauthorized or not properly trained personnel.

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