05000282/LER-1998-001, :on 980626,leakage Through Redundant CR Steam Exclusion Dampers Was Found to Exceed Value Assumed in HELB Analysis.Caused by Actuator Being Out of Adjustment.Will Implement Design Change & Repair or Replace Dampers

:on 980626,leakage Through Redundant CR Steam Exclusion Dampers Was Found to Exceed Value Assumed in HELB Analysis.Caused by Actuator Being Out of Adjustment.Will Implement Design Change & Repair or Replace Dampers

ML20236T412
Person / Time
Site:	Prairie Island
Issue date:	07/27/1998
From:	Kivi J NORTHERN STATES POWER CO.
To:
Shared Package
ML20236T406	List: 05000282/LER-1998-001, :on 980626,leakage Through Redundant CR Steam Exclusion Dampers Was Found to Exceed Value Assumed in HELB Analysis.Caused by Actuator Being Out of Adjustment.Will Implement Design Change & Repair or Replace Dampers 05000282/LER-1998-001-01, Forwards LER 98-001-01 Re Leakage Through Redundant CR Steam Exclusion Dampers Found to Exceed Value Assumed in HELB Analysis.Licensee Has Modified Three NRC Commitments Made in Original Ler,As Noted by Corrective Actions in
References
LER-98-001, LER-98-1, NUDOCS 9807280168
Download: ML20236T412 (5)

LER-1998-001, on 980626,leakage Through Redundant CR Steam Exclusion Dampers Was Found to Exceed Value Assumed in HELB Analysis.Caused by Actuator Being Out of Adjustment.Will Implement Design Change & Repair or Replace Dampers

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

text

e NRC MRM 366 U.S. NUCLEAR REGULATORY CCH4ISSION APPROVED kY CNB NO. 3150-0104 (4 gg

• EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 PRS. REPORTED LESSONS LEARNED ARE INCORPORA LICENSEE EVENT REPORT (LER)

EIN 585 ATE Ib8* ^II0Eu'ATi!N SA"O EECOROs$"A TH U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE

1. A[3g$T0N

" PROJECT (3150-0104L OFFICE OF MANAGEMENT AND BUDGET.

, E" (See reverse for required number of 20 3.

digits / characters for each block)

FACILITY MAME (1)

DOCKET NUMDER (2)

FAi3E (3)

Prairie Island Nuclear Generating Plant Unit 1 05000 282 1 OF 5 TITIE (4)

Le kage Through Redundant Control Room Steam Exclusion Dampers Found to Exceed Value A% umed in the HELB Analysis EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR GEQUENTIAL REVISION MONTH DAY YEAR FACILITY NAME DOCfET NUMBER

"""*E"

""8'"

Prairie Island Unit 2 05000 306 06 26 98 98 -

01 01 7

27 98 F^'1L m N^M' "T""

05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT IO Tk2, REQUIREMENTS OF 10 CFR S: (Check one or moIe) (11) 1 20.220ico) zo.2203(ex2)(v) so.73(a)(2xi) so.73(a)(2)(vui)

POWER 20.2203(ax1) 20.2203(a)(3)(i) 50.73(a)(2)(ii) 50.73(a)(2)(x) 100 20.2203(ax2xi)

Zo.2203(ax3xn>

so.73(a)(2)(iii) 73.73 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2xiv)

OTHER m

Zo.2203(ax2xin) bo.36(c)(3)

V bo.73(ax2)(v) gggn Abs ra below or 20.2203(a)(2)(sv) 50.36(cx2) 50.73(a)(2)(vn)

LICENSEE CONTACT FOR THIS LER (12) hedL i ti,La Mer, NJ13LE ilhbiude AIta LuGt)

Jeff Kivi 612-388-1121 CCHPLETE ONE LINE FOR EACH CCHPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTAB(E

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPRDS X

VI CDMP Po14 N

3 4 SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAV YEAR YES y

NO SUBKISSION (If yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limit to 1400 spaces, i.e.,

approximately 15 single-spaced typewritten lines)

(li)

On June 26,1998, follow-up testing (a corrective action from the originalissuance of this LER) found cn cdditional pair of inoperable steam exclusion dampers. Dampers CD-34146 and CD-34147 were t:st::d individually for leakage and were found to leak in excess of limits delineated in the USAR. Both drmpers were declared inoperable and closed in less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, per Technical Specification 3.4.C.2. In addition, a blank was installed over the affected duct within approximately one hour of the det:rmination that the dampers were inoperable.

Tha blank will remain until CD-34146 and CD-34147 are repaired or replaced and post-maintenance t:sted to ensure they are operable.

980728016e 980724 PDR ADOCK 05000282 S

PDR NRC FORM 368 (4 951

MRC FCIDI366A U.S. NUCLEAR REGULATORY CChetISSICtt 14 est,

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACII.ITY MADE (1)

DOCKET 1.ER NUMBER (6)

PAGE (3)

MhdBER (2).

Prairie Island Nuclear Generating Plant Unit 1 05000 282 YEAR KUUN L R

2 OF 5

98 -- 01 01 i

TEKT UE more space is requiredo use additional copies of NRC Form 366A) (17) l i

i

EVENT DESCRIPTION

l On January 17,1998, Units 1 and 2 were operating at 100% power. As a part of the in-leakage testing bring 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 lerktge. These outside air dampers also serve as steam exclusion dampers in the event of a high en:rgy 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) j exceeded the steam exclusion damper leakage limits. The redundant damper (CD-34177) was then l

closed (per Technical Specification 3.4.C.1.a). During testing of damper CD-34177, damper CD-34180 was repaired. Results of testing CD-34177 revealed that it also exceeded the maximum leakage limits i

for steam exclusion.. Both dampers CD-34180 and CD-34177 were declared inoperable.

l 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 acceptable. 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 replaced.

Similar damper testing on the opposite train of control room outside air supply dampers revealed I:akege in excess of the acceptable limit for damper CD-34176 (the functional counterpart of CD-l~

34177). However, neither of its redundant dampers were found to have leakage in excess of j

ecceptable limits, thus, no LCO was declared for this train with respect to Technical Specification L

3.4.C.2. Currently, dampers CD-34178 and CD-34142 are being maintained in the closed position (per Technical Specification 3.4.C.1.a), until CD-34176 is repaired or replaced.

On June 26,' 1998, Units 1 and 2 were operating at 100% power. As a part of in-leakage testing of the Steam Exclusion Dampers undertaken as part of Corrective Action 3 of the originalissuance of this Licensee Event Report, the Control Room Exhaust Air Dampers CD-34146 and CD-34147 were tested individually for leakage. These exhaust air dampers also serve as steam exclusion dampers in the evsnt of a HELB outside of containment. Steam exclusion damper leakage limits for purposes of the l

tnt were based on values given in Appendix I of the USAR. Dampers CD-34146 and CD-34147 were dstsrmined through testing to exceed the steam exclusion damper leakage limits as delineated in the

- USAR.

' (Ells Component identifier. CDMP)

Imc FOR'1386A 14954

{

sec poses 3c64 U.s. isUCLEAR REGULATORY C0bedISSICat WW.

LICENSEE EVENT REPORT (LER) t TEXT CONTINUATION FACILITY ltAbe (1)

DOCIET LER madBER (6)

PAGE (3)

DIUteER (2)

Prairie Island Nuclear Generating Plant Unit 1 05000 282 WAR MgE R

3 OF 5

98 -- 01 --

01 TEXT (11 more space is required, use additional copies of NRC Form 366A)

(1*l) l Both dampers'were declared inoperable and closed in less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, per Technical Specification 3.4.C.2. In addition, a blind flange was installed over the affected duct within approximately one hour 2

of the determination that the dampers were inoperable. The blind flange will remain until CD-34146 and l

CD-34147 are repaired or replaced and post-maintenance tested to ensure they are operable.

i

CAUSE OF THE EVENT

CD-34180 is a butterfly damper in a round 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 I

edjustment. The repaired damper (CD-34180) was repaired by adjustment of the actuator - the actuator hid not driven the damper to a fully seated position.' The cause of the failures of CD-34177 and CD-l 34176 is not yet known, however, it appears to be associated with aging of the non-metal portions of the l

dampers.

l" CD-34146 and CD-34147 are louvered demnerc in rectangular ducts. The cause of the failure on CD-34146 and CD-34147 is not yet knowr twevar, it appears to be associated with aging of the non-L matal portions of the dampers.

1

ANALYSIS OF THE EVENT

l Tha assumed post-accident control room environment is 82.5 degrees F (dry bulb) and 50% relative l

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) to assure that such leakage would not result in a control room environment beyond the assumed post-accident control i

room environment. However, the control room exterior atmosphere assumed in the evaluation was assumed to remain at worst case conditions. No account was taken of the transient heat load in the l

area and the time required to heat the structure and equipment within the control room.

Tha evaluation also assumes complete failure of the ducts between the affected dampers and outside

. cir. The affected dampers are protected against the effects of a HELB outside of containment, howsver, the ducts between these dampers and the outside air are not protected and are conservatively assumed to fail.

I l

2 (Ells Component identifier: DUCT) mconesawm i

0-_-_-_.---.._

lU.S. NUCLEAR REGUIATCaY ColeIISSION 84 95) e LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER (6)

PAGE (3)

NUMBER (2)

Prairie Island Nuclear Generating Plant Unit 1 05000 282 YEAR MOUE IAL M

4 OF S

98 01 --

01 TEXT (If more space is required, use additional copies of NRC form 366A) (11)

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 could have prevented the safety function of the steam exclusion system and thus is reportable under 10 CFR 50.73(a)(2)(v).

In their as-found condition, CD-34146 and CD-34147 leaked in excess of the acceptable limit determined by evaluation and were, thus, declared inoperable, inoperability of reduridant steam exclusion dampers is a condition that could have prevented the safety function of the steam exclusion system and thus is reportable under 10 CFR 50.73(a)(2)(v).

CORRECTIVE ACTION

1.

The long term corrective action will be to: (a) implement a steam exclusion system design ch:nge, or(b) repair, or(c) replace dampers CD-34177, CD-34176, CD-34146, and CD-34147.

Thue dampers will be post-maintenance tested to ensure they meet acceptable steam exclusion l

leakage linkits.

I 2.

Based on the final determination of the failure mechanism and final resolution of the first l

ccti:n (design change, repair or replacement), maintenance procedures associated with steam l

exclusion dampers will be updated appropriately.

3.

Based on the results of the above two actions, the need for additional testing of the control d:mpers in the steam exclusion system will be evaluated.

FAILED COMPONENT IDENTIFICATION The cause of the failure on damper CD-34180 was due to the actuator being out of adjustment. The l

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.

Th3 cause of the failures of CD-34146 and CD-34147 is not yet known, however, it appears to be cssociated 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.

Th::e instances were reported in LER's 75-43 (inoperability of Steam Exclusion Damper),82-03 (One__________-_____--_--_- __ - -_______-- - _______

w.0, twgEED CBEEGiw dEni!i0DiKT 14 951 LICENSEE EVENT REPORT (LER)

+

TEXT CONTINUATION FACILITY NAME (1)

DCCKET LER NUMBER (6)

PAGE (3)

N%BER (2)

Prairie Island Nuclear Generating Plant Unit 1 05000 282 YEAR SEQUENTIAL REVISION 5

0F 5

l NUMER NUMER 98 -- 01 --

01 Text tit more space is required, use additional copies or upc Form 366A) (17) l Stsam Exclusion Damper Found inoperable During AnnualInspection), and Unit 1 LER 92-10 (Technical Specification Surveillance Requirements for Steam Exclusion Check Dampers not being Mat).

l i

1 l

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1 h__________-_-_____--_-__---__--__a