ML20085M579

Updated LER 75/021A:on 751124,during Preventive Maint Check, Number of Reactor Bldg Pressure Relief Louvers Did Not Function as Required.Caused by Normal Outside Ambient Conditions.Preventive Maint Program Initiated

ML20085M579
Person / Time
Site:	Fort Saint Vrain
Issue date:	05/26/1978
From:	Hillyard H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Madsen G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
LER-75-021A, LER-75-21A, P-78080, NUDOCS 8311090019
Download: ML20085M579 (6)

Text

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I CCENSEE EVENT REPORT O "ro^tt CoNTnot 8toCx

1 l l l 1 I I (PLEASE PRWT A UMED WFIRM ATIO'j) 1 6 AME LEENSE NUMBER P TYPE

! oi Ic 10 I vi siv li l l o l 01-1 ol ol of ol 01-1o 101 14111112 l o l I o f 31 7 89 14 15 25 26 30 31 32 CAftcORY T Pf h0N OOCKET NUMBER EVENT OATE REPORT DATE Q CONTl l l y y l 0 l 5 l 0l-l 0 l 2l 6l 7l l1 (1-l2 l 4 l 7 l 574l 68 69 l 0 l 5 l 2l 6l 7l 8l 75 80 7 8 57 58 59 60 61 EVENT DESCRPTION gg lDuring a routine preventive maintenance check, personnel noted that some of the l 7 89 80 3E l reactor building pressure relief louvers did not fully open. l 7 89 80 EI 7 89 80 I

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OE CODE COMPONENT CODE ACT R WOLATON E I x 1 x I [3_l Iz Iz Iz Iz1 z1 7i L7J lzI9I9I91 -

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7 89 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION l

Q l Normal outside ambient conditions deteriorated the surfaces on which louver seals 80 7 89 .

BE l slide. Installed springs were thus unable to fully open some louvers. l 7 89 80 DE I l 5 US  % POWER OTHER STATUS DISCOVERY ' DISCOVERY DESCRIPTON

@ lG_) 1010101 I N/A I iBI I Preventive Maintenance Check l 7 8 9 10 12 13 44 45 46 80 0 OF RE AMOUNT OF ACTMTY LOCATON OF RELEhSE QG lZjASE l N/A l l N/A .

l 7 8 9 10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTON DE l 0 l 0 l 0]

7 89 11

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PERSONNEL INJUAIES NUMBER DESCR@ TON E 101 0l0 I I v/s 80 I

7 89 11 12 OFFSITE CONSEQUENCES

• h lN/A 1 7 89 86 LOSS OR DAMAGE TO FAC:LITY TYPE DESCRIPTON

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PUBLICITY 17 l N/A l 7 89 80 8311090019 780526 ADDITIONAL FACTCRS PDR ADOCK 0500026 8 l

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Public Service Comp:my W Cac2ti:

• P. O. Box 361, Platteville, Colorado 80651

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May 26, 1Q78 Fort S t. J. rain Unit-No. J..

P .78080 .

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Mr. G. L. }bdsen, Acting Director ~

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Nuclear Regulatory Commission J Region IV Office of Inspection and Enforcement Suite 1000 Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 Docke t No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Unusual Event Report No. 50-267/75-21A, Final Supplement, submitted per the requirements of Technical Specifi-cation AC 7.6.

Also, please find enclosed one copy of the Licensee Event Report for Unusual Event Report No. 50-267/75-21A.

Very truly yours, f

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Frederic E. Swart Nuclear Production ihnager FES/alk g cc: Director, MIPC 7915100 p bl

O O REPORT DATE: May 26. 1978 UNUSUAL EVENT 75-21A Page 1 o f 4 OCCURRENCE DATE: November 24, 1975 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/75-21A Final Supplement: Complete Revision IDENTIFICATION OF OCCURRENCE:

A number of the reactor building pressure relief louvers did not function as required by a preventive maintenance check. This was identified as an unusual event per Fort St. Vrain Technical Specification AC 7.6, Non-Routine Repor ts , (C) 2. A preliminary report, Unusual Event Report No. 50-267/75-21, was submitted December 23, 1975.

4 EVENT '

DESCRIFFION:

While performing a routine preventive maintenance check during cold shutdown conditions , test personnel noted that some reactor building pressure felief louvers did not open fully. The results were as follows: 22 louvers opened fully, 35 louvers opened between 75% and 100%, 30 louvers opened between 50%

and 75%, and 7 louvers opened between 25% and 50%. The preventive maintenance check did not address the question of partially open louvers. Consequently, the available free floa area used for overpressure protection could not be determined. .

Discussions between the prime contractor and the louver manufacturer indi-cates that a linear relationship exists between the amount of louver opening and f ree flow area, e.g., halfway open is 50% free flow area. Based on that criteria and using the most conservative value of louver position (i.e., all louvers between 50% and 73% open are 50% open, etc.) the total free flow area available was calculated to be 781 square feet.

CAUSE DESCRIPTION:

i The cause of the failure of some of the louvers to open fully was the result of normal outside ambient conditions. Refer to Figure 1. The louvers nor-mally have atmospheric pressure on the outside and -1/4" water with respect to atmospheric pressure on the inside. They also have rubber seals on all sides o f each vane. Due to wind, dust, and water vapor, the surfaces on which the rubber seals slide, deteriorated. Thus, additional force tc cause full louver opening was necessary. The installed springs used for opening the louvers were unable to fully supply the additional force. Consequently, the total free flow area of the system decreased.

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O . o UNUSUAL EVENT 75-21A Page 2 o f 4 l

CORRECTIVE '

ACTION:

A total of 1,130 square feet of louver free flow area is presently installed.

Evaluations by the prime contractor, General Atomic Company, indicate 760 square feet is the minimum opening required to prevent exceeding the reactor building design pressure of 10" water above the refueling floor, in the limiting accident case which is failure of the PCRV bottom head access penetration.

Since only 760 square feet of the total 1,130 square feet is actually required, the calculated value of 781 square feet provided sufficient overpressure pro-tection.

A preventive maintenance program to exercise the louvers quarterly, will be initiated. Icplementation of the program will be contingent upon obtaining a necessary Technical Specification revision.

No further corrective action is anticipated or required.

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l , UNUSUAL EVENT 75-21A Page 3 of 4

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Sliding Surface Area of De terioration

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r-Actuating Arm TOP VIEtJ Rubber Seals Upper Rubber Seal pen M

Van Pivot Point for Vane Opening M

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Actuating A O

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Open P O O j ___

Top Section of Adjacent Vane " Piston Rod (Down to Open)

MN SIDE VIEtJ FIGURE 1 LINKAGE 'AND LOUVER ARP.ANGEMENT

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UNUSUAL EVENT 75-21A Page 4 of 4 Prepared by: fr M /! /

Charles H. Fuller Technical Services Technician Reviewed by: t / [4 -_ I

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~W.'~ Niljyard, TechnicaY Servie6sfy' Supervisor Reviewed by: L4vf H. Larry Brey, Superintendent, Operation;s ,,

\ Approved by:

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(redericE. Swart Nuclear Production Manager

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