ML20045B438

LER 93-005-00:on 930518,notified That Control Circuit for Makeup & Purification Sys Letdown Isolation Valve Did Not Meet Electrical Isolation Criteria Due to Human Error.Mod in Development Will Be expanded.W/930610 Ltr

ML20045B438
Person / Time
Site:	Crystal River
Issue date:	06/10/1993
From:	Boldt G, Stephenson W FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0693-06, 3F693-6, LER-93-005, LER-93-5, NUDOCS 9306170362
Download: ML20045B438 (4)

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Florida Power COAPORAYiOA Crystal River Unit 3 Docket No. 50-302 June 10, 1993 3F0693-08 U. S. Nuclear Regulatory Commiss'on Attention: Document Control Desk Washington, D. C. 20555

Subject:

Licensee Event Report (LER) 93-05

Dear Sir:

Enclosed is Licensee Event Report (LER) 93-05 which is submitted in accordance with 10 CFR 50./3.

Sincerely, hi$b';ff G. L. Bo'ldt Vice President Nuclear Production EEF: mag Enclosure xc: Regional Administrator, Region II Project Manager, NRR Senipr Resident Inspector

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F AaliTY NAME (1) DOCFIT NUMBER C2) PAGE (3)

CRYSTAL RIVER UNIT 3 (CR-3) 0l 5l 0l 0l 0l 3l 0l 2 1 lOFl 0 l3 TIT Li (4)

Lack of isolation Device Between Safety Related and non-Safety Related Portions of a Control Circuit Results in a Condition Outside Design Basis ET3ENT DATE (5) LER NUMBER (6) EPORT DATE (7) OTHER F ACILtTIES INVOLVED (B)

SEQUENTIAL REVISION F ACILITY NAMES DOCKET NUMBER (S)

MONTH DAY YEAR VEAR NUMBER NUMBER MONTH DAY YEAR NiA 0l5l0l0l0l l l 0l6 1 l8 9 3 9l3 -

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0l0 0l6 1l 0 el3 wA 015]0l010l l l E?ERATING THIS KPORT OR SUBMITTED PUR9UANT TO THE KQulKMENTS OF 10 CFH 6: (CNECW ONE OR &#0RE OF THE Fot.LowwG) (11)

MODE (9) 1 20.432(b) 20.405(c) 50.73(aK2Xw) 73.71(b)

R 2c.405(aX t gr) 50.3rXcX1) _

50.73(ag2Xv) 73.71(c)

(to) l1 1 0l 0 20.405(aX1Xil) -

50.36(cK2) 50.73(aK2Xvil) -

OTHER ispeco re>4cerrect see- and m Tart, NRC For.

20 405(aX1Xiii) 50.73(ax2X;) 50.73(s.;(2XvinXA) seus 20.405(aK1Xw) X 50 73(aK2X'l) 50.73(aX2Xvli;XB) 20 405(axtXv) 50.73(aK2 mil) 50.73(aX2X4 LICENS[E CONT ACT FOH Tits LER(12)

NAME 1ELLPHOteE NUMBER AREA CODE W. A. Stephenson, Nuclear Safety Supervisor 9] O l 4 7l 9 l 5 l- l 6) 4 l 8 [ 6 COMPLETE ONE L8NE FOR EACH OOMPONENT FAILURE IN TH4S KPORT (13)

CAUSE SYSTEM COMPONENT M ANUF AC. FCPORTABLE CAUSE SYSTEM COMPOt4ENT MANUF AC- REPORTABLE TURER TO NPRDS TURER TO NPRDS I I i l i I I I I I I I I I >

I I I I I l I I I I I I I I SUPPLI. MENTAL KPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION

] YES (a rea sampem EWECTED SseanSSON DATEJ P40 DATE (15) l l l j ABST RACT nans m isap ereews. t e . awnsmenem& rmeen sepowmace tmewrmen enee (16)

On May 18, 1993, Crystal River Unit 3 (CR-3) was in Mode 1 (POWER OPERATION) at 100% Rated Thermal Power producing 870 Megawatts. The Nuclear Shift Supervisor was notified that the control circuit for the Makeup and Purification System letdown isolation valve (MUV-49) did not meet the electrical isolation criteria for IE and non-lE components. MUV-49 is a containment isolation valve located outside the containment. In addition to its safety related functions, MUV-49 also has a non-safety related function to automatically close on a high temperature signal to protect the demineralizers in the letdown system. During original plant design, an isolation device was not specified for installation between the safety related and non-safety related portions of the control circuit for MUV-49, thus placing the unit in a condition outside the design basis. A modification is being developed which will install isolation devices for the non-safety related temperature control circuit. Current design standards prevent this condition from recurring.

NRC Form See (6-69)

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EVENT DESCRIPTION: i On May 18, 1993, Crystal River Unit 3 (CR-3) was in Mode 1 (POWER OPERATION) at i 100% Rated Thermal Power producing 870 Megawatts. A routine review of electrical I isolation was being conducted as part of plant modification preparation. At IS50, l the Nuclear Shift Supervisor was notified that the control circuit for the Makeup  !

and Purification System [CB] letdown isolation valve (MUV-49) [ISV] did not meet the electrical isolation criteria for IE and non-lE components.  !

MUV-49 is a containment [NH] isolation valve located outside the containment. The safety function of the valve is to close upon a letdown line rupture or loss of coolant accident, upon receipt of a high Reactor Building Pressure or Diverse Containment Isolation (HPI) signal. There are other valves located inside i containment which provide redundancy for this function. MUV-49 also has a non-safety related function to automatically close on a high temperature signal to protect the demineralizers [FDM] in the letdown system. The portion of the control circuit associated with the high temperature closure is non-safety related.

There is no electrical isolation device (fuse) between the two circuits which is contrary to the plant design basis for electrical isolation.  !

l l CAUSE:  ;

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This condition is considered to be a result of human error during original plant design. Based on an investigation, it was concluded the engineer believed that i

by running a safety related cable into the Non-Nuclear Instrumentation (NNI) i l cabinet, the design was correct without an isolation device. The investigation j also indicated that if the engineer had properly run a non-safety related cable,  !

an isolation device would have been installed. The confusion in dealing with a l safety related cable and a non-safety device may have been a result of the vague '

i guidance present in the industry star.dards at the time of initial plant design.

l l Failure to use an isolation device in connecting a non-safety to a safety related circuit was not in direct violation of the standard used to design CR3 protective systems (draft IEEE 279, August 1968 " Proposed IEEE Criteria for NUCLEAR POWER l PLANT PROTECTION SYSTEMS") as written, primarily due to the lack of detail in- the draft standard addressing isolation requirements. However, the lack of an i isolation device is not in accordance with the intended design bacis. l Presently there is no isolation device installed between the safety related and i non-safety related portions of the control circuit for MUV-49. Thus, this report is submitted in accordance with 10CFR50.73 (a)(2)(ii)(B).

l l EVENT EVALUATION:

In order for the non-safety circuit to render MUV-49 inoperable, a fault would have to develop to blow either of the valve control fuses [FU]. The probability of this i i

NRC Form 386A (5-88)

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0l0 0 l 3 lOFl 0 l 3 TIXT (# amare asear e swowtod use sentwof NRC Fom 3864 e (17) occurring is extremely unlikely. The loss of control power to MUV-49 would only pose a safety problem if there was a Loss of Coolant Accident (LOCA) or a letdown line rupture with concurrent failure of the redundant inside containment isolation valves. Although this scenario could result in an increased risk of radiation release to the surrounding environment, the probability of such a combination of circumstances occurring is so small that this is not considered a realistic concern.

CORRECTIVE ACTIONS:

A modification already in development will be expanded to include installation of an isolation device for the non-safety related temperature control circuit. The installation of this modification is scheduled for the next refueling outage. To prevent recurrence in today's designs, updated design criteria have been developed which, in conjunction with improved industry standards, provide specific guidance in this area.

PREVIOUS SIMILAR EVENTS:

This is the first report concerning design basis deficiencies related to MUV-49.

A similar isolation discrepancy was reported in LER 89-034. ,

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i MtC Frsm 386A (6-89)