ML20054H456

Ro:On 820428,PT-9.13 Revealed Failure in Power Supply to Damper Relay Panel B1 (Train B) Concurrent W/Failed Relay for Zone 10 (South Cable Vault) on Panel A1 (Train A). Correction in Progress & Completion Expected by 821231

ML20054H456
Person / Time
Site:	Robinson
Issue date:	06/18/1982
From:	Starkey R CAROLINA POWER & LIGHT CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
RSEP-82-1091, NUDOCS 8206240077
Download: ML20054H456 (2)

Text

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Carolina Power & Light Company d[// ri ,

H. B. ROBINSON STEAM ELECTRIC PLANT 4 POST OFFICE BOX 790 8* g/

HARTSVILLE, SOUTH CAROLINA 29550 JUNI 81982 Robinson File No: la?.aC Serial: RSEP/82-1091 Mr. James P. O'Reilly Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Northwest Suite 3100 Atlanta, Georgia 30303 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261 LICENSE NO. DPR-23 30 DAY SPECIAL REPORT - FIRE DAMPER POWER SUPPLIES

Dear Mr. O'Reilly:

In accordance with Technical Specification (TS) 6.9.3.g this special report on the inoperability of fire dampers is submitted pursuant to TS 3.14.7.2.

With the plant in the refueling shutdown condition with fuel removed from the containment vessel, periodic testing (PT's) revealed inoperability of circuits which would have prevented automa tic actuation of fire dampers in certain fire zonen. These dampers, however, were capable of closing via fusable links.

Specifically, on April 28,1982, PT-9.13 revealed a failure in the power supply to the damper relay panel B1 (train B) concurrent with a failed relay for Zone 10 (South Cable Vault) on panel A1 (train A). This resulted in the auto-matic actua tion feature (from both redundant trains) for the fire dampers in Zone 10 being inoperable.

On May 2,1982 while performing PT-9.14, the power supplies for damper relay s

panels A2 and B2 were discovered ' de-energized. This resulted in the loss of the automatic actuation feature (both trains) for the fire dampers in Zone 19 (Cable Spread Room) .

Investigatiori of the above events revealed that although the plant was in a condition not requiring them, these circuits may have been inoperable during previous periods of plant operation, thereby identifying these events as repo r tab le. This was identified on May 21, 1982.

8206240077g i PDR ADOCK PDR s - @yFICIAL COPY

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Letter to Mr. Jamss P. O'Reilly .

,Sarials RSEP/82-1091 7 Page 2 g ,,

1 In the case of panel A1, the relay failure was identified as random; the failed relay was repl'ced on June 5,1982; ar.d the circuit was returned to serv ice.  :

The failure of the B1 panel power suppl) was attributed, to a voltage regulator failure. No specific cause for the failure was determined. The voltage regulator will be replaced upon receipt of materials. If this circuit is not fully restored to operation prior to its being required, the appropriate ,.

corpensatory actions as outlined in the Technical Specifications will be taken.

The de-energizing of the A2 and B2 panels was apparently caused by improperly set over-voltage protection (set too low)'resulting in spurious opening of the i supply breakers. Since the supply breakers (electrical protection) also serve '

as the on-of f switch and by design have nq '_' trip-free" position, a fault-trip of the circuits cannot be easily distinguished from a manual turn-of f of the circuit. On this occasion, however, a deliberate effort was made to  :

evaluate the reason for the switches being of f. It was found that the resetting of certain alarms created suf ficient voltage"fluctuatigns in the power supply to " trip" the switches. Verification of these setpoints was not included in the installation procedures, apparently through oversight. We trip setpoints on the over-voltage devices were, set properfy, ands the circuits were- returned to se rvice. -

In addition, supervision will be installed in all four circuits to provide annunciation of damper power supply failure or de-energiza tion of the circuit. This supervision should be available, pending procurement of any ma terials, by Sep tember 1,1982. .,

15 y i

/e The discovery of the above items prompted ,a thorough review of the entire fire detection actuation system. This r.sview revealed a number of minor deficiencies which have not impacted system operability,, but when corrected

. will provide a substantial improvement in overell system : performance and -

reliability. Correct tod of these items is currently in progress and is' 1/- (" '+

expected to be complet'ed by December 31, 1982. ,

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If you have any questions, please contact my staff. ,

Very truly yoursg id it

. R. B. Starkey, r.

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General Manager

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li. B. Robinson SIE Plant FG/bs -( \

cc: Richard C. DeYoung (30)/

R. A. Hartfield (3) s

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