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LER 80-012/01T-0:on 800311,while Facility Was Operating at Less than 2% Power,Orifice Valves Not Set for Equal Flows & Temp Limit Was Exceeded.Caused by Inability to Close Orifice Valve to Equal Flow Position.Valve Freed Up
	ML19305C728
Person / Time
Site:	Fort Saint Vrain
Issue date:	03/25/1980
From:	Gahm J; PUBLIC SERVICE CO. OF COLORADO
To:	; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19305C725	List: ML19305C724; ML19305C728;
References
	LER-80-012-01T, LER-80-12-1T, NUDOCS 8003310334
	Download: ML19305C728 (9)
	v • d • e

NRC FORM 384 U.S. NUCLEAR REGULATO%Y COMMISSION csm Q' LICENSEE EVENT REPORT CONTROL 8 LOCK: l 1

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7 8 60 61 DATE 75 REPORT DATE EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h 10121 l On Thursday, March 13,1980, at 0830 hours0.00961 days 0.231 hours 0.00137 weeks 3.15815e-4 months , while the plant was operating at less l l0l3l l than 2% power, it was determined that due to the orifice valve in region 31 being l gl more open than the orifice valves in the other seven-column regions, all orifice l lo lsi l valves were not set for equal flows and the temperature limit of LCO 4.1.9, Figure l l0 is l l 4.1.9-2 was exceeded. This is being reported per Fort St. Vrain Technical Specifi- l l 0 l 71 l cation AC 7.5.2(a)2. No accompanying occurrence. No affect on public health and l loIal I safety. l 7 8 9 80 E CODE SL8C DE COMPONENT CODE SUSCODE SU E 10l9l 7 8 l R l B l@ W@ lZ l@ l Zl Zl Zl Zl Zl Zlh W@ W @

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44 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l3 lO; j Inability to close orifice valve to equal flow position, coupled with personnel I gl interpretation of Technical Specifications, resulted in operation outside the limits I l i 121 l of LCO 4.1.9, Figure 4.1.9-2. Valve freed uo. Personnel re-i n s truc te rt . Personnel l I,l j l instructed that written record to be maintained on future interpretations. Techni- l gl cal Specification LCO 4.1.9 to be amended for clarification. I 7 8 9 80

$A % POWER OTHER STATUS Ol$ RY DISCOVERY DESCRIPTloN l1 15 l W@ l0 l0 l1 l@lN/A l l A l@l Personnel Observation l A T1vlTY CO TENT RELEASED QP RELEASE IIl6l [_Z_j @ W @ lN/A AMOUNT OF ACTIVITY lN/A @ lLOCATION oF RELEASE @ l PERSONNEL EXPOS ES NuMSER TYPE oESCRiPTiON @

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March 13, 1980 MR. KARL V. SEYFRIT REGION IV REGULATORY OPERATIONS NUCLEAR REGULATORY COMMISSION 611 RIAN PLAZA DRIVE, SUITE 1000 ARLINGTON, TEXAS 76012 ON THURSDAY, MARCH 13,1980, AT 0830 HOURS, WHILE THE PLANT WAS OPERATING AT LESS THAN 2% POWER, IT WAS DETERMINED THAT DUE TO THE ORIFICE VALVE IN REGION 31 BEING MORE OPEN THAN THE ORIFICE VALVES IN THE OTHER SEVEN COLUMN REGIONS, ALL ORIFICE VALVES WERE NOT SET FOR EQUAL FLOWS AND THE TEMPERATURE LIMIT OF LCO 4.1.9, FIGURE 4.1.9-2 WAS EXCEEDED. ALTHOUGH THE BASIS OF LCO 4.1.9 ADDRESSES LOW HELIUM FLOW RATES WHICH WOULD RESULT FROM A CLOSED ORI-FICE VALVE, THE LCO DOES NOT ALLOW FOR INTERPRETATION OF ONLY THAT CONDITION.

AN INVESTIGATION IS IN PROGRESS TO IDENTIFY THE CAUSE.

THIS EVENT APPEARS TO BE REPORTABLE OCCURRENCE NO. 50-267/80-12/01-T-0 AND IS REPORTABLE PER FORT ST VRAIN TECHNICAL SPECIFICATION AC 7.5.2(a)2.

PLEASE CONFIRM RECEIPT OF THIS TRANSMITTAL BY CALL BACK TO J. W. GAHM AT (303) 785-6300.

J. W. GAHM NUCLEAR GENERATING STATION FORT ST. VRAIN PUBLIC SERVICE CONPANY OF COLORADO 550 FIFTEENTH STREET, DENVER, COLORADO 80202 I

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REPORT DATE: March 25, 1980 REPORTABLE OCCURRENCE 80-12 ISSUE O OCCURRENCE DATE: March 11. 1980 Page 1 of 7 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/2 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/80-12/01-T-1 FINAL IDENTIFICATION OF OCCURRENCE:

On Thursday, March 13,1980, at 0830 hours0.00961 days 0.231 hours 0.00137 weeks 3.15815e-4 months , while the plant was operating at less than 2% power, it was determined that due to the orifice valve in region 31 being more open than the orifice valves in the other seven column regions, all orifice valves were not set for equal f18ws and the temperature limit of LCO 4.1.9, Figure 4.1.9-2 was exceeded.

This is being reported per Fort St. Vrain Technical Specification AC 7.5.2(a)2.

CONDITIONS PRIOR-TO OCCURRENCE:

Routine startup.

The major plant parameters at the time of the event were as follows:

Reactor Power 7.58 MRth, 0.9%

Electrical Power 0 MWe Secondary Coolant Pressure 876 psig Secondary Coolant Temperature 223*F.

Secondary Coolant Flow 423,900 #/hr.

Primary Coolant Pressure 366 psia Primary Coolant Core Inlet Temperature 212*F.

Primary Coolant Core Outlet Temperature 242*F.

Primary Coolant Flow 277,000 #/hr., 7.9%

Circulator 1A Self-Turbining Circulator 1B 2,200 RPM Circulator 1C 2,200 RPM Circulator 1D Self-Turbining

REPORTABLE OCCURRENCE 80-12 ISSUE O Page 2 of 7 l

DESCRIPTION OF CCCURRENCE:

Prior to reactor startup on March 11, 1980, core orifice valves had been adjusted for equal flow settings, with the exception of the region 31 orifice valve, which was stuck in a position more open than that required for equal flows.

The reactor was taken critical at 2120 hours0.0245 days 0.589 hours 0.00351 weeks 8.0666e-4 months on March 11, 1980. At that time, requirements of LCO 4.1.7 and 4.1.9 dealing with core orifices and region temperature rise were met. With the core orifice valves set for other than equal flows, the provisions of LCO 4.1.9, Figure 4.1.9-2 were applicable.

When verification of compliance with Technical Specifications occurred at approximately 2300 hours0.0266 days 0.639 hours 0.0038 weeks 8.7515e-4 months on March 11, 1980, requirements of LCO 4.1.7 were still being met, but the temperature rise limits of LCO 4.1.9, Figure 4.1.9-2 had been exceeded for a number of core regions. In checking the requirements of LCO 4.1.9, the operator noted that the basis of this speci-I fication is addressed to prevent very low flow conditions which would exist l as the result of a nearly closed orifice valve. With the region 31 orifice i

I stuck in a more open position, the LCO requirements did not appear to be applicable. The operator discussed his interpretation of the Technical Specification requirements with supervisory personnel. It was determined that the intent of the LCO was met, and that no excessive fuel temperatures would be expected with the temperature rise across some regions outside the allowable limits of LCO 4.1.9, Figure 4.1.9-2. Based on this inter-pretation, no action was required, and none was taken.

The interpretation outlined above was discussed with on-coming shif t personnel, and reactor operation continued at a fairly constant power level of approximately 1.8%. Continued attempts to close the valve to equal flow position were unsuccessful, .ad a Plant Trouble Report was initiated at 0510 hours0.0059 days 0.142 hours 8.43254e-4 weeks 1.94055e-4 months on March 12, 1980. Technical Specification com-pliance verifications utilizing the above interpretation continued until 1615 hours0.0187 days 0.449 hours 0.00267 weeks 6.145075e-4 months on March 12, 1980, at which time the valve was freed and returned to the proper setting, and equal flow conditions were restored.

j For equal flow conditions, Figure 4.1.9-2 is not applicable. Subsequent compliance verifications indicated that the requirements of both LCO 4.1.7 and LCO 4.1.9, Figure 4.1.9-1 were met.

APPARENT CAUSE OF OCCURRENCE:

Inability to close the orifice valve in region 31 to the equal flow position, coupled with the interpretation of the Technical Specification taken by operations personnel, resulted in a condition where the temperature rise limits of LCO 4.1.9, Figure 4.1.9-2 were exceeded.

REPORTABLE OCCURRENCE 80-12 ISSUE O l Page 3 of 7 ANALYSIS OF OCCURRENCE:

Prior to taking the reactor critical, verification is made to assure com-pliance with all applicable Technical Specifications. At the time of the reactor startup on March 11, 1980, core orifice valves had been set for equal flow conditions, with the exception of the orifice valve for ;

region 31. For startup conditions, equal flow settings of 17% open for seven column regions and 10% open for five column regions are utilized. 1 The orifice valve for region 31 (a seven-column region) was sticking at a 26% open position.

A verification of Technical Specification compliance indicated that re-quirements of both LCO 4.1.7 and LCO 4.1.9 were met. LCO 4.1.7(b) requires that for core average outlet temperatures less than or equal to 950*F.,

individual region outlet temperatures are not to exceed the core average outlet temperature plus 400*F. This LCO also specifies that the requirements of LCO 4.1.9 must be met. For the conditions which existed with core orifices 3 set at other than equal flow positions and the reactor pressurized to greater l than 50 psia, the maximum allowable helium coolant temperature rise across !

a region as a function of power level is specified by Figure 4.1.9-2. I Technical Specification compliance was again verified at approximately 2300 hours0.0266 days 0.639 hours 0.0038 weeks 8.7515e-4 months on March 11, 1980, j ust prior to shif t change. At that time, i l

it appeared that the temperature rise limits of LCO 4.1.9, Figure 4.1.9-2 l had been exceeded for some core regions. At the time of the compliance verification, total helium flow was approximately 8.5% with a reactor power level of approximately 0.4%. This "overblowing" condition ensures ;

that very low helium coolant flow rates could not exist in any coolant i channel. Based on this condition, the operator on duty initiated a review of the basis of LCO 4.1.9. Af ter noting that neither low helium flow rates nor excessive temperature conditions existed, the operator further noted that the basis of the LCO had been directed to conditions which would exist if an orifice valve were stuck in a more closed position than required for equal flows. This review seemed to indicate that the LCO was not ap-plicable under the conditions prevailing at the time - an interpretation which was agreed to by supervisory personnel. Based on the interpretation that Figure 4.1.9-2 limits were not applicable, it was determined that l requirements for compliance with LCO 4.1.9 had been satisfied. No action with regard to meeting Figure 4.1.9-2 temperature requirements was required.

Although no written record of the interpretation was entered in the logs, on-coming personnel were made aware of the interpretation being used to verify compliance with LCO 4.1.9, concurred, and used this interpretation for subsequent compliance verifications.

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REPORTABLE OCCURRENCE 80-12 ISSUE O Page 4 of i ANALYSIS OF OCCURRENCE: (Cont'd)

Continuing attempts were made to close the valve and establish equal flow corditions. At 0510 hours0.0059 days 0.142 hours 8.43254e-4 weeks 1.94055e-4 months on March 12, 1980, a Plant Trouble Report was initiated regarding inability to close the region 31 orifice valve to the equal flow position. At approximately 1615 hours0.0187 days 0.449 hours 0.00267 weeks 6.145075e-4 months on March 12, 1980, the valve was feed and closed to the equal flow position of ap-proximately 17%. Following return to equal flow conditions, the requirements of LCO 4.1.9, Figure 4.1.9-2 were no longer applicable. At that time, total helium flow was 8.9%, which was well above the Figure 4.1.9.1 re-quirement of 7% for the 1.2% power level which existed at the time.

At 0830 hours0.00961 days 0.231 hours 0.00137 weeks 3.15815e-4 months on March 13, 1980, a review of the logs and Plant Trouble Reports for the time period beginning at 2152 hours0.0249 days 0.598 hours 0.00356 weeks 8.18836e-4 months on March 11, 1980, indicated that although the intent of LCO 4.1.9 was not violated, the LCO makes no provisions for the type of interpretation taken by the personnel involved. The intent of the LCO is to prevent very low helium flow rates and corresponding excessive fuel temperatures. The temperature rise limits of Figure 4.1.9-2 were developed based on the assumption of a nearly closed orifice valve. Neither low flow rates nor excessive temperatures existed during the period of unequal flow settings. Upon return to equal flow settings, no abnormal temperature changes were observed, indicating that no stagnant flow conditions had existed. Refer to Figure 1 for comparative information at 1100 hours0.0127 days 0.306 hours 0.00182 weeks 4.1855e-4 months on March 12,1980, (with unequal flow conditions) and 1100 hours0.0127 days 0.306 hours 0.00182 weeks 4.1855e-4 months on March 13,1980 (with equal flow conditions) . Orifice positions and temperatures for the region with the stuck orifice valve are boldly outlined. Note that the change in shim group and rod position was due to rod insertion to compensate for Xenon burn-out.

Although a review of the data available and the basis of the LCO supports the interpretation that Figure 4.1.9-2 requirements were not applicable, a strict interpretation of the Technical Specifications provides no leeway for the more open orifice valve position or for conditions of "overblowing" the core which existed at the time. Thus, this situation is being reported per AC 7.5.2(a)2.

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, - .. FIGURE 1- REPORTABLE OCCURRENCE 80-12 ORIFICE POSITIONS ISSUE O AND REGION OUTLET Page 5 of'7' TEMPERATURES n' n s, ne m a Orifice 16.7. 10.1 Positions

16.7 " 460 421 0.0 " Region Outlet 8

(% OPan 16.8 1* "

Temperatures 451 i. '

17.1 " " 413 "

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437 M9 .

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16.7 '

451 '

451 n

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16.9 = n 587 n 16.4 " "

17.0 17.0 i

, 9,9 490 6.8 17.1 401 . 430 400

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550 543 a

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570 *

, 17.0 438 , 384 16.7 16.8 . E, "

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4 = 17.2 6.6 .

426 388 17.2 a 441 a Untq l 17.0 a 10. 15 a M n 386 ,

17.2 "

Flow Po-0.1 16.8 432 382 sition 401 ,

1 Data / Time: March 12, 1980, 1100 hrs. Operating Circulators: A and C l

Reactor Power: 1.6% Reactor Pressure: 407 psia Primary Coolant Flow: 8.6% -

Shim Group / Position: 4B/41.5"

, Avarage Temperature Rise: '172*F.

n n n n Orifice " "

16.6 10.1 468 425 Positions a 16.8 s'

374 n )

(% oPsn 10.0 " 17.2 Region Outlet "

p 16.7 Tempe ratures 463 " 386

,, , ,, 407 9 ,,

1 .0 16.7 ,

16.7 456 3 ' l 17.0 , ,

408

" 16.9 " " 438 l n , u 560 a 584 ,

17.1 17.1 , 478 .

,7 17.1 4.9 391 . 432 408 l

- " 53 u *g 16.9 u n 545 543 n

10.

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386

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483 435

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16.7 16.6 451 406 ,

" 386 n 419 l 17,1 n 429 17.4

Equal 16.9 " 415 "

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sition 10.1 16.8 377 409 439 Dats/ Time: March 13,1980,1100 hrs. Operating Circulators: A and D Reactor Power: 1.9% Reactor Pressure: 394 psia Primary Coolant Flow: 8.8% Shim Group / Position: 2A/138.5" Avarage Temperature Rise: 175'F.

REPOT. TABLE OCCURRENCE 80-12 ISSUE O Page 6 of 7 CORRECTIVE ACTION:

Continued attempts to close the stuck crifice valve to the equal flow po-sition were successful, and the valve is now operable.

Personnel have been instructed to make a literal interpretation of the LCO.

Operations personnel were instructed that if interpretations are made in the future, a written record of the interpretation is to be entered in the logs.

An amendment to clarify the intent and applicability of LCO 4.1.9 is being prepared and will be submitted to the commission for approval and imple-mentation upon completion.

No further corrective action is anticipated or required.

FAILURE DATA /SIMILAR REPORTED OCCURRENCES:

None PROGRAMMATIC IMPACT:

None CODE IMPACT:

None l

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REPORTABLE OCCURRENCE 80-12 ISSUE O Page 7 of 7 Prepared By: tC tr -

f. 2c!)

Cathy C.fHirsch Technical Services Technician Reviewed By:

f.W.Gahm Technical Services Supervisor Reviewed By:

Frank M. Mathie Operations Manager Approved By: /b M4;< [e Don Warembourg g Manager, Nuclear Production

ML19305C728

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