ML20093K314

Forwards Rev 1 to DECO-04-2468, Assessment of Purge Valve Pressure Differential Capabilities & Responses to Items Pending from Sser 3.Submittal Should Close Issue

ML20093K314
Person / Time
Site:	Fermi
Issue date:	10/11/1984
From:	Jens W DETROIT EDISON CO.
To:	Youngblood B Office of Nuclear Reactor Regulation
Shared Package
ML20093K317	List: ML20093K314 ML20093K319
References
RTR-NUREG-0798, RTR-NUREG-798 EF2-72272, NUDOCS 8410170275
Download: ML20093K314 (6)

Text

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Wayne H. Jens -

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FermF2 6400 North Dwe Highway I%7VI I (313) s86 4isQAM. Newport, Mc.higan 48166 October 11, 1984 EF2-72272 Director. of Nuclear Reactor Regulation Attention:

Mr.

B. J.-Youngblood, Chief Licensing Branch No..1~

Division of Licensing U..S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Youngblood:

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Reference:

(1)

Fermi 2 NRC Docket No. 50-341 (2)

NU REG- 0798, Supplement 3,

" Safety Evalua-tion Report Related to the Operation of Enrico Fermi Atomic Power Plant, Unit 2",

dated January, 1983

Subject:

Purge Valve Operability Chapter 22,Section II.E. 4.2 of Supplement 3 to the Fermi 2 Safety Evaluation Report (Reference 2) provided the NRC evaluation of the Fermi 2 purge valves.

The discussion identified several items that required additional informa-tion from Detroit Edison to support NRC resolution of'the issue. Attachment 1 identifies the items pending from SSER 3 and provides the Edison discussion responding to these items.

This submittal should allow closure of. this issue.

If you have any questions or require supplemental information, please contact Mr. O. K. Earle at 313-586-4513.

Sincerely, cc:

Mr.

P.

M. Byron Mr.

M. D.

Lynch Mr.

R. Wright

• USNRC Document Control Desk Washington, D.C.

20555

• With attachment 8410170275 841011 j

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'Mr.. B.J. Youngblood October 11',

1984

- EF2-72272

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a SSER"3' Purge' Valve'Open. Items L Att'achment.12 M

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u The $ followind. disedssion presents -additional informatilon to support NRC re-review. of ithe. purge valve ' issues ' identified

.in ChapterE22:ofithe Fermis 2 SSER'3.i(page.22-8).. Relevant

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'information isip'rovided for=each of the-results documented t

.,in SSER 3 ;aslindicated ;below.,

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1.

= " Torque; loads ;calculatedffor the 6, inch valves using s.

3-the.drywell peak containmen_fpressure=and~ maximum t

' torque coefficients-from-theiTamesburyJcurves for 6--

' inch-valves.(withL50% margin)lindicatetthe-torque

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11oads'used.intthe stress analysis'are more conser-1 n

Lvative.

• Closure time-for-these~ valves.is therefore

' limited only-by then.:5 secon'd requirement."

Response

Edison' concurs with this: position.

i 2.

" Torque] loads calculated in;this mannersfor'the'10J-

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inch 1 valve would; exceed the loads used rin :the stress i

analysis.

A closuret time ofliess' than! 2 ' seconds would -

c be. required for-these' valves."'

Response

JIhis comment-was' provided to.the NRC. via a.

Brookhaven National Laboratory L(BNL). evaluation 1 report (Reference 1)'of..the-Fermi 2-' purge valves.

The:BNL evaluation had used a breaking torque'(the torque:

required to either seat or unseat the valve)1 of 730 ft-lbs for ^ thE 10- inch valve to dev'elop a' P valve capability of 3 4.3 psi.

I As reflected in Attachment 2 (Reference.2)',

the

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original stress report'(in whichfEdison had t

transmitt ed the 730: ft-lb value) did not include the U

dynamic torque -exerted on-the valve by - the j

compressible flow of drywell gases' during.a LOCA.

Ene reanalysis, provided in Attachment ~2,' includes this

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dynamic torque, and concludes'that the'. differential' l-pressure capability of ~ the 10 : inch valves is not exceeded during.a DBAL (The valve is shown to be operable against a differential pressure of 56 psi -

the maximum containment' pressure in a LOCA-environment.)LTherefore, the current ~ Technical l"-

Specification fclosure ' limit of. 5 seconds is adequate to ensure valve operability and, further, no additional limitations beyond'the requirements of l

ASME,Section XI, Article IWV-3417 need to be. imposed i

for-measuring closure times.

3.

"The 20- inch valves are connected to the wetwell with a maximum potential pressure " of '2 5 psig.. The torque i

is used in the' stress analysis for these' valves corre-'

i sponds 'to 'a pressure 1 of 23 psig.; As it would take

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.psig,ithe15-second closure-time = requirement is more C

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1 Response:

Edison concurs (with.thi~s1 position.-

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- The calculated: torque 5at' peak drywell' pressure'for

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'4 D the 2 4-inch--valve ' would be considerably higheri thani

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the/ torque usedin the stress analysis..)In;that the 1s1 ess:

1 differentialipressure=' capability of theLvalve7 than..the< peak drywell' pressure,,aflimi.tation11_ sire-quired on 'the' valve ' closure time consistent with' the

, stress ' analysisL limitations and the: 5-second closure-

. time requirement."

Response:. - Similar to -Item 2 - above', 'this comment was

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provided.in the BNL' report and was based on a breaking-torque of 3200 sft-lbs which, again, ndoes 'not1 reflect 1

- the : dynamic torque exerted > on the' valve bys the'.drywell'.

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atmosphere during a'LOCA. >

Attachment:

2'provides'-the?

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reanalysis of-this valve,_ incorporating the dynamic; 0

t'orque, - and concludes that the. differential pressure capability of the 24 inch ' valve:is not exceeded during the-required 5-second closure' time'.- gTherefore,.as-

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with the.10 inch valve, the current. Technical-SpecificationLclosuremlimit of 5-seconds"isiadequate i

to-ensure valve operability,.and that no additional limitations, beyond the requirements of ASME,Section XI, Article IWV-3 417, need to be imposed'for measuring; closure times.

5.

"In addition, valves experiencing a' pressure load may?

close slower than valves in a no-load condition. : As -

inservice inspection tests are performed in the

'no-load condition, stroke time acceptance ) times should provide'a margin to account for the extended closure' times under load."

Response

Due to the analysis discussed in Items 2' and 4 above, and in previous Edison correspondence' which:have been reviewed by BNL and/or NRC, more restrictive stroke time requirements are not deemed necessary.- The analysis proves that the-valves'are-capable of closing against the containment pressures arising from LOCAs.

In addition, these valves are governed.by _ASME,Section XI, Article IWV-3417 which requires:

"If, for power operated valves an increase in stroke time...

from the previous test...

of 5 0% '

.or more"for valves with full stroke times.less than - or _ equal to '10' seconds is observed, test' frequency shall be increased to once each month'

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unti1~ corrective' action is taken..."'

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This requires that if, for exan.ple, a valve which normally closed in 2 seconds is found to take 3 seconds to close, its test frequency will be increased to monthly.

This increased surveillance will continue until the cycling time returns (via maintenance or cycling exercise) to the expected 2 second range.

This will further ensure the t any valve degradation that occurs.during-operat' ion will be identified and monitored until corrected.

6.

"As the purge valves.do include handwheels, provisions should be made by administrative procedures or auto-matic reengagement to ensure that valves are not inad-vertently left in the handwheel mode.

Response

As reflected in Detroit Edison to NRC letter EF2-57430 (dated May 12, 1982), the valve will operate automatically even in the manual handwheel mode.

The handwheel clutch is disengaged when this occurs.

In addition to those items discussed above, one other issue was identified in SSER 3 under the heading " Evaluation Summary" (page 22-9) which requested the following:

" Valve and valve disc orientations are to be modified so that valve shafts are "in plane" with upstream el-bows or bends, and valve discs are to be installed with the shaft side downstream."

Via Detroit Edison to NRC letter EF2-55980, dated January 4,

1982, Edison previously committed to " reorient and maintain all of the purge valves with an in-plane orientation with shaft relative to an upstream elbow" and the valves have been installed accordingly.

The valve discs are oriented with the shaft side downstream, with the exception of valves VR3-3013 and VR3-3015.

Valves VR3-3013 and -3015 are the inboard isolation valves on each of the two torus purge lines.

Edison has located both the inboard and outboard torus purge line isolation valves outside the torus to maximize valve accessibility and remove the valves from the torus environment.

Both inservice inspection requirements and maintenance considerations dictated that the inboard valves (i.e., VR3-3013 and -3015) be oriented with the valve shaft upstream.

This is contrary to our commitment in EF2-55980, but, as indicated below, does not adversely impact the operability of these valves under accident conditions.

Reference 3 provided stress and closure analyses for these two valves and reflected loads that are comparable to the maximum dynamic torque values identified in the BNL report (Reference 1).

Based upon Reference 3, BNL had concluded

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' that - the -valves had a structuralf capability 'of 23 psig

[using-worstLcase valve torque coefficients';(Ct)]..

. torus pressure =is.25_psig.(100% ofivalve structurcl. The ABA l capability). ' If the analysis methodology;(i.e., f ratioing -

of stress loads)' utilized in: Attachment 2 wereLapplied to:

theseTtwo valves an eight percentE(8%)1 increase would

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-result.

Reference 3 indicates that the stress capability sfor these-valves: ranges from 122 percent to;150' percent of allowable..Therefore, the valves will be capable of oper-ating againstia pressure differential of,25 psig.-

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Further the structura1' capability limitiof 23 psig identified by BNL is based on a-150. percent factor for.the valve torque coefficient.. 1This is conservative due-toithe 50% margin and' the combination of? maximum torque coefficient coincident.with maximum torus pressure.

Lastly, VR3-3013 Eand VR3-3015 are installed with -the valve shafts in-plane with upstream elbows.

As noted in

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Reference 1, the magnitude of-the dynamic torque is likely to be equivalent 1for the "in-plane, :shaf t upstream elbow" configuration and the straight piping upstream configuration.. Therefore, no additional loads 'are applied-for: this L aspect: of.the. valve's configuration.

Therefore, based upon the. need. to orient the valves as

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described, to support. inservice inspection'and maintenance activities, and the fact that the valve capability envelops the loads to be encountered in a-DBA environment,

, Edison concludes the valves' are acceptable.

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References:

1.

Letter from T. J. Restivo.(Brookhaven National-Laboratory) to M. Haughey (NAC-EQB), dated January 20, 1982.

2.

Report No. DECO- 04-2 468, Assessment'of Purge Valve Pressure Differential Capabilities", dated Septenber 1984.

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3.

Detroit Edison to NRC letter, Purge Valve i-Operability", EF2-55980, dated January 4, 1982.

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