ML18113A640

LER#78-035/01T-0 on 781109:study of Calibr Techniques Showed That SI Accumulators Indicated Level Would Be Lower than Actual Level.Discovered After Rigorous Review of Factors Affecting Instru

ML18113A640
Person / Time
Site:	Surry
Issue date:	11/20/1978
From:	Baucom T VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18113A639	List: ML18113A638 ML18113A640
References
LER-78-035-01T, LER-78-35-1T, NUDOCS 7811280238
Download: ML18113A640 (3)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION

{7.77) ..

• LICENSEE EVENT REPORT.

CONTROL BLOCK:  !-----'---'l'--__._l_..,___,__-c'I CD (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 6

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~~~~~~. ~JC~ I o I s I o I o I o I 2 I s I o 101 1 I 1 I o I 2 I 1 I a I© I 1 I 1 I 2 I oI 1 I s 10 60 61 DOCKET NUMBER ' 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@

!An engineering study of tank level instrument ca]ihration techniq11es demonstrated

~ I that the indicated level of SI Accumulators would be lower than actual level. The

[:QID I condition is conservative for minimum level requirements but maximum 1 eve]_ 1 imi ts a.i=

((II] jT.S. 3.3 may be exceeded by 5.7 cu. ft. on Unit 1 and 8.0 cu. ft. on Unit 2. Actual

[QJI] !level differences are 0.7 inches on Unit 1 and 0.99 inches on Unit 2, Event is rPportd

[§J2] !able per T.S. 6.6.2.a.(2) and applies to Surry Unit Nos. 1 and 2.

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7 8 9 80 SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

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7 9 10 11 12 13 18 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION Q LER/RO CVENT YEAR REPORT NO. CODE TYPE NO.

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47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @

jThe condition was discovered by a rigorous review of factors affecting the instrument, DJJJ ji.e. calibration standard, b*oron concentration, pressure effects and temperature

[I))] teff_ects. The levels of the accumulators were brought into an operating band that is IJJJJ jconserv~tive for high and low volume requirements.

OJil 7 8 9 80 FACILITY METHOD OF A STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION ~

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ITII1 LU@ ~@._I_____NA_ _ _____. NA 8 9 10 11 44 45 80 PERSONNEL EXPOSURES ~

t*UMBER r:;:;-. TYPE DESCRIPTION~

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ITI~] IO IO 10 l@L--_N_A_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _~ - - - - J 7 8 9 11 12 80 LOSS OF OR DAMAGE TO FACILITY '43" TYPE DESCRIPTION ~

[IE)~@ NA 7 8 9 10 80 PUBLICITY r::'\ NRC USE ONLY ISSUED~ DESCRIPTION~ "'

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'all 1 ]. 2 § 0 ~ ' 68 69 80 ;;;

NAME OF PHEPARER I* L Baucom PHONE: _ _ (8_0_4..;..)_3_5_7_-_3_1_8_!}_ _ _ _ ~ J

Attachment, pag~* of 2)

Surry Power Station, Unit 1 Docket No: 50-280 Report No: 78-035/0lT-0 Event Date: 11-09-78 Safety Injection Accumulator Errors

1. Description of Event:

An engineering study of tank level instrument calibration techniques demonstrated that the indicated level in Safety Injection (SI) accumulators is lower than the actual level. As a result, the maximum volume limits stated in Technical Specification 3.3 may have been exceeded but the minimum volume requirements have always been met. In the worst case condition (maximum indicated level and 650 psia) the excess volume is 5.7 cubic feet (over 989) for Unit 1 and 8.0 cubic feet (over 1089) for Unit 2 *. These excess levels decrease the pressurized gas volume by no more than 1.15% in Unit 1 and 2.0% in Unit 2. In actual level, the differences amount to 0.7 inches in Unit 1 accumulators and 0.99 inches in Unit 2 accumulators. This event is reportable in accordance with Technical Specification 6.6.2.a.(2) and is applicable to Surry Units 1 and 2.

2. Probable Consequences/Status of Redundant Systems:

The consequence of a higher-than-indicated level would be to reduce the volume of pressurized gas available to inject the accumulator contents. Accident analyses are conducted based on minimum level and minimum pressure conditions. Maximum levels are specified to assure that the accumulator contains sufficient pressurized gas to accomplish the injection. In the worst case identified by the study, the maximum possible level reduced the gas *volume by 2% but this was at a condition of gas pressure 8% over minimum required pressure. It is considered that even in "worst case" level error, the accumulator systems would have performed the intended function fully. Therefore, the health and safety of the public were unaffected.

3. Cause:

The condition was discovered as the result of a rigorous review of the factors affecting the output of a differential pressure type liquid level indicator system. The factors included in the study were calibra-tion standards. and techniques, boron concentrations, pressurized gas density variations, and variations in ambient temperature of the accumu~

lators.

4. Immediate Corrective Action:

The accumulator levels were lowered to the indicated levels recommended by the study on 11-9-78.

Attachment, Surry Power Docket No:

Report No:

page 2 of 2 Station, Unit 1 50-280 78-035/0lT-0 Event Date: 11-9-78 Safety Injection Accumulator Errors

5. Subsequent Corrective Action:

The station administrative documents for accumulator setpoints were changed on 11-15-78.

6. Actions Taken to Prevent Recurrence:

Future level requirements for accumulator levels will be verified by the calculational methods outlined in the study.

7. Generic Implications:

No other analagous situation is known to exist at Surry Power Station.