05000282/LER-1998-001, :on 980117,leakage Through CR Steam Exclusion Dampers Found to Exceed Value Assumed in HELB Analysis. Caused by Actuator Being Out of Adjustment.Repaired & Replaced Dampers

:on 980117,leakage Through CR Steam Exclusion Dampers Found to Exceed Value Assumed in HELB Analysis. Caused by Actuator Being Out of Adjustment.Repaired & Replaced Dampers

ML20203A536
Person / Time
Site:	Prairie Island
Issue date:	01/17/1998
From:	Kivi J NORTHERN STATES POWER CO.
To:
Shared Package
ML20203A502	List: 05000282/LER-1998-001, :on 980117,leakage Through CR Steam Exclusion Dampers Found to Exceed Value Assumed in HELB Analysis. Caused by Actuator Being Out of Adjustment.Repaired & Replaced Dampers
References
LER-98-001, LER-98-1, NUDOCS 9802240054
Download: ML20203A536 (4)

LER-1998-001, on 980117,leakage Through CR Steam Exclusion Dampers Found to Exceed Value Assumed in HELB Analysis. Caused by Actuator Being Out of Adjustment.Repaired & Replaced Dampers

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2821998001R00 - NRC Website

text

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e NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150 0104 4 99 EXPIRES 04/30/98 ISilMATED SURDEN PER RESPON$t TO COMPLY WITH TMi$ MANDATORY INFORMATich COLLICil0N RIQUEST: 50.0 HRS. REPORTfD LISSONS Lt ARNED ARE INCORPORATED INTO LICENSEE EVENT REPORT (LER) syys,'1lj!5s,glo,0,s,Ac,gwgouleonc,gR,ggjgM,y,NTS I r

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,- m Prairie Island Nuclear Generating Plant Unit 1 05000 282 1 OF 4 m.

m Leckage Through Redundant Control Room Steam Exclusion Dampers Found to Exceed Value A2::umed in the HELB Analysis svana LATE (53 LER NuncER (6)

REPGRT LATE (7)

OTHER FACILIIIES INVOLVED (5)

MUNIH DAY YLAR YLAR SLOUtNIiA(

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On January 17,1998, Units 1 and 2 were operating at 100% power. As a part of the in-leakage testing being conducted on the control room envalope (to support habitability assumptions for post-accident control room dose analysis), the control room outside air supply dampers were tested individually for Isakage. These outside air dampers also serve as steam exclusion dampers in the event of a high ensrgy line break (HELB) outside of containment. Testing of these dampers revealed that damper leckage exceeded that assumed for steam exclusion purposes on each of the two in-series dampers

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on one train of outside air supply.

An LCO was declared (per Technical Specification 3.4.C.2) due to two redundant steam exclusion dampers being inoperable. One of the dampers was repaired and re-tested and resultant leakage was acceptable. The damper was declared operable and the LCO exited. Currently, one steam exclusion damper in each train is inoperable. Redundant (operable) dampers are maintained in the closed position (per Technical Specification 3.4.C.1.a), until repair or replacement of the inoperable dampers.

9902240054 900212 PDR ADOCK 05000202 g

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.U.S. NUCLEAR REGULATORY COMMISSION M l9 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (I)

DOCKET LER NUMBER (6)

PAGE (3)

NUMBER (2) i Prairie Island Nuclear Generating Plant Unit 1 05000 282 YEAR N

2 OF 4

98 -- 01 00 I

TEXT (Jt more space as requared, use adda t2onal cop 2es of NRC Form 366A)

( 7)

EVEllT DESCRIPTION On January 17,1998, Units 1 and 2 were operating at 100% power. As a part of the in-leakage testing being conducted on the control room envelope (to support habitability assumptions for post-accident control room dose analysis), the control room outside air supply dampers' were tested individually for I:akage. These outside air dampers also serve as steam exclusion dampers in the event of a high energy line break (HELB) outside of containment. Steam exclusion damper leakage limits for purposes of the test were based on values given in Appendix l of the Updated Safety Analysis Report (USAR).

Tha tracer gas testing of these dampers indicated that damper leakage on each of two redundant steam exclusion dampers exceeded these leakage limits for steam exclusion.

Damper testing first revealed that one of the control room outside air supply dampers (CD-34180) exceeded the steam exclusion damper leakage limits. The redundant damper (CD-34177) was then closed (per Technical Specification 3.4.C.1.a). During testing of damper CD-34177, damper CD44180 was repaired. Results of testing CD-34177 revealed that it also exceeded the maximum leakage limits for steam exclusion. Both dampers CD-34180 und CD-34177 were declared inoperable An LCO was declared (per Technical specification 3.4.C.2) based on two redundant steam exclusion dampers being inoperable. Damper CD-34180 was immediately re-tested and resultant leakage was accaptable. Damper CD-34180 was declared operable and the LCO exited. Damper CD-34180 as well as damper CD-34145 are currently maintained in the closed position (per Technical Specification 3.4.C.1.a), until damper CD-34177 is repaired or repited.

Similar damper testing on the opposite train of control room outside air supply dampers revealed Isakage in excess of the acceptable limit for damper CD-34176 (the functional counterpart of CD-34177). However, neither of its redundant dampers were found to have leakage in excess of acceptable limits, thus, no LCO was declared for this train with respect to Technical Specification 3.4.C.2. Currently, dampers CD-34178 cnd CD-34142 are being maintained in the closed position (per Technical Specification 3.4.C.1.a), ur.til CD-34176 is repaired or replaced.

CAUSE OF THE EVENT

2 CD-34180 is a butterfly damper in a rounc duct. CD-34177 and CD-34176 are louvered dampers in rectangular ducts. The cause of the failure on damper CD-34180 was due to the actuator being out of adjustment. The repaired damper (CD-34180) was repaired by adjustment of the actuator - the actuator

' (Ells Component Identifier. CDMP)

(Ells Component identifier: DUCT)

MC FOCM 366A M 99 g

eU.S. NUCLEAR REGULATORY COMMISSION 6499 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION I

FACILITY NAME (1)

DOCKET LER NUMBER (6)

FAGE (3)

NUMBER (2)

Prairie Island Nuclear Generating Plant Unit 1 05000 282 YEAR jgf MV 3

Op 4

98 01 00 TEXT (Jt rnore space as required, use adda t2onal copies of NRC Fonn J66AJ (17) had not driven the damper to a fully seated position. The cause of the failures of CD-34177 and CD-34176 is not yet known, however, it appears to be associated with aging of the non metal portions of the dampers.

ANALYSIS OF THE EVENT

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The assumed post-accident control room environment is 82.5 degrees F (dry bulb) and 50% relative humidity. An evaluation was performed to determine an acceptable damper leakage limit for steam exclusion purposes (assuming one train of control room ventilation system was operating) tc assure that such leakage would not result in a control room environment beyond the usumed post-accident control room environment. However, the control room exterior atmosphere assumed in the evaluation was assumed to remain at wors+ case conditions. No account was taken of the transient heat load in the are. ind the time required u.aat the structure and equipment within the control room.

The oaceluation also assumes complete failure of the ducts between the affected dampers and outside air. Tt.c affected dampers art Jotected against the effects of a HELB outside of containment, however, the ducts between these dampers and the outside air are not protected and are conservatively assumed to fail.

In their as-found condition, the affected steam exclusion dampers leaked in excess of the acceptable limit determined by evaluation and were, thus, declared inoperable. Inoperability of redundant steam exclusion dampers is a condition that c nild have prevented the safety function of the steam exclusion system and thus is reportable under 10 Cr'P 50.73(a)(2)(v).

CORRECTIVE ACTION

1.

The long term corrective action will be to repair or replace dampers CD-34177 and CD :4176.

Th:se dampers will be post maintenance tested to ensure they meet acceptable steam exclusion liskege lim!ts.

2.

Maintenance procedures associated with these dampers will be updated appropriately b22ed on the final resolution of the first action (repair or replacement) and final determination of the failure mechanism.

3.

Based on the results of the above two actions, the need for additional testing of the control dzmpers in the steam exclusion system will be evalustad.

NRC PMI 303A M 99

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.U.S. NUCLEAR REGULATORY COMMISSION M 9W LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER (6)

FAGE (3)

NUMBER (2)

Prairie Island Nuclear Generating Flant Unit 1 05000 282 YEAft jQU IAL RE N

4 OF 4

98 01 --

00 TnxT ut osoie space sa required, use additional cop 1es or nac rorm 3ssA) (11) l FAILED COMPONENT IDENTIFICATION The cause of the failure on damper CD-34180 was due to the actuator being out of adjustment. The cause of the failures of CD-34177 and CD-34176 is not yet known, however, it appears to be associated with aging of the non-metal portions of the dampers.

PREVIOUS SIMILAR EVENTS

Prairie Island has previously reported other instances where steam exclusion dampers have failed.

These instances were reported in LER's 75-43 (Inoperability of Steam Exclusion Damper),82-03 (One Stcam Exclusion Damper Found Inoperable During Annual Inspection), and Unit 1 LER 92-10 (Technical Specification Surveillance Requirements for Steam Exclusion Check Dampers not being Met).

NRC FOR3 366A R 99

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