ML19327B595
| ML19327B595 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/10/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19327A642 | List:
|
| References | |
| TAC-55417, TAC-55418, TAC-73427, NUDOCS 8911020170 | |
| Download: ML19327B595 (4) | |
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Inclosure 1 i
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR RfCULATION PLANT $Y$TEMS BRANCH e
PROPOSED TECHNICAL 5PECIFICATIONS CONTAINMENT PURGE i
ZION NUCLEAR POWER STATION, L' NITS 1 AND 2 i
DOCKET N05, 50 295 and 50 304 j
1.0 INTRODUCTION
Comonwealth (dison, the owner of the nuclear power plants Zion Units 1 and F, proposed in a letter to H. Denton dated February 21,The amendment proposed 1986, en amendment to Facility Doerating License his. OpR-3g and DPR 48.
changes to the Technical Specifications (TS) relat M to vent and purge i
operations as well as restricting the maximum purge valve pocition. These thanpes were in response to an NRC request in a $afety Evaluation Report cated i
Apri 3, 1984 Simply stated, the request was-to reflect the permissible 9Miration of the purge and vent valves into the T5. The submittal contains tse requested chaages, j
'l 2.0 EVALUATION l
t The proposed changes related to renttictions in purge and vent operations.
Specifically they include the allowable angle the purge supply and exhaust valves can be, opened, the nus6er of valves that can be used at one time, the valve closure time, and the pool for purging time in one year. Each of these changes will be discussed be ow.
i Nowever before the individual T$ clianges are discussed, there is one surviellence test that was reewunended in the staff SER that was not added to the proposed Ts The staff had recomended the periodic leakage testing i
of the valves with resilient seals. The frequency was to be once per three months during operating Modes 1 through 4, if the valvet were considered to be active.
l fn response to this request, the licensee indicated that the additional i'
surveiller.:= requirement was not needed for the valves at Zion because the isolation valve seal rater system and penetration pressurization system are designed to continuously detect any leakage during plant operation. If leakage is detected, an alarm f s sounded in the control room. The staff has reviewed the licensee's justification for not perfoming the added leakage L
' tests. As part of their justification, the licensee, in the basu Section 3.a of the TS, indicated that the seal water is tatroduced at a pressure of 50 L
psig. This pressure is slightly higher than the peak containment post accident pressure. Further, the seal water system and penetration pressurization system are included in T$ Sectio: 3.g.1 ane 3.g.2 which l
l includes 11mitin3 condition for operation (LCu) and surveillance reeutrements.
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l Based on the above, the staff concludes that the continuous leakage detection tystems now in place at Zion Units 1 and 2 satisfy the requirsments of the s6rve111ance leakape tests referenced in the staff's $ER.
In addition, the current TS on the eskaje systems meets the intended purpose of the. suggested added T5. Therefore, t3e staff concurs with the licensee tnat no additional I
surveillance testig or added T$s are necessary.
The ptsposed TS indicating that the purge supply and exhaust valves shall not l
beopenedmorethan50deg.reetisconsietrntwiththestaff'sSERdatedApril3, 1994 Therefore the sta' finds the proposed T$ acceptable. The acceptance of the allowable opening angle is based in part, on the demonstration of acceptable stresses titain the valve. Inequallyimportantparameterin 1
determining the closure stresses is the closure time. The staff concluded, as i
dor:umented in the April,1984 SER, that acceptable closure times range between i
5 and 8 seconds. The proposed 73 change, in this eegard is to change the i
survie11av.e test value from the curre.it 60 seconds to 7, seconds. The revised l
closure time reflects the acceptable stress analysis and is therefore acceptable, j
Another proposed charge is to assure that the containment puree valv n shall
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not be open concurrently with the containment vent valves. This operational i
l res':riction is consistent with the guidelines set forth in $Rp Sec+1on 6.2.4 to minimize the number of Sachways open at any one time. Based en this compliance with the SRP, tr.e staff finds the operational guidance provided for r
vent and purge operation acceptable.
l An important consideration in the development of an effective program is i
the selection of a usage factor as well as the reasons for vent and purse operation. The itcensee has proposed a goal cf 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> per year. This time has been established based upon the literste's estiaste to limit the concentration of radioactive materials in the containment atmosphere to less than 100 times the maxinum permissible concentrailon per 10 CFR 20. After i
review of the purping criteria, the staff has concludd that the program including the goa established by the licensee is acceptable. However, due to the importance the staff has placed on the need to minimite purging or venting of the containment, the staff believes that additional clarification should be added to the T5 to ensure that purging be perforined enty for safety related A marked up copy of the appropriate T5 page is enclosed which the reasons.
staff would find acceptable. The licensee has agreed to the staff's proposed rarkup in a series of telephone conferences. Based on the verbal agreement of the marked up changes, the staff finds the proposed use of the purge sad vent systams acceptable.
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An additional consideration must he included in the overall evaluation of the purging program, in light of the fact that large diameter valves are being For these conditions, $RP L
used for time, periods greater than 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br />.
Section 6.2.4 indicates that the radiological consequences of a LOCA concurrent The with the purge / vent valves assumed open at time zero must be calculated.
I analysis should show that 10 CFR part 10011mits are not exceeded.
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-3 Guidance is provided in the SRP concerning t.Ne source term to be used for the riose consequences due to the release through the valves until calculating'he guide indicates that for valve closure times within five closure.
setor.ds, isolation is assured prior to enset of fuel failure. interpreted by the s This
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pike need to be considered in determining primary coolant activity without thi need for further justification. For closure times sltshtly beyond 5 seconds, the staff has evaluated the merits of assuming no fuel failure on a case by case basis.
Consideratior has included the transport times necessary to sweep the source from the failed fuel into the reactor coolant, from the fuel pins to the postulated pipe rupture, from the pipe enture u the nearest pipe inlet of the open purge line, and finally through the duct to the isolation valve.
Based on this retit, rale, the staff has concluded that there will be a substantial time delay between the onset of fuel failure and the actual release of products from the containment as a result of the fuel failure.
Additionally, there will be a finite minimum time before initiation of fuel failure can occur. Using the above rationale, the staff has concluded that a l
i more reasonable upper bound of velve closure time for which no source term contribution due to fuel failure can be conservatively assumed is 15 seconds.
for the Zion closure time of seven seconds, the staff has concluded I
Th'..vfore, failure need not be considered. Based on the above, the staff has
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that feel concluded that only the pre existing iodine spike need be considered.
the above source i
The licensee has computed the deu consequences consideriN131 spike at the i
term. The results show that usi.1 a 60 ve/gm equivalent time of the accident, the site boundary thyroid dose due to iodine up until i'
Wher. added to the containment leakaae dose of 123 valve closure is 52 res.
rem yields a total dose of 175 rem. Thisiswellwithin10CIR100 I
requirements of 300 rom.
i The staff has performed an inh pendent calculation of the dose contribution I
due to releases through the purge / vent pathways. The results confirm the 11censee's value. Based on this a reement, the staff finds that the dose vences due to purging operat ons ate acceptable and within 10 CFR 100
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3.0 CONCLU$10N lased on the above evaluation, the steff concludes that the preposed changes to the Zion Units I and 2 Technical Specifications for limitation on purge and t
-vent valve operation above cold shutdown are more restrictive than current T$s and consistent with the comitments identified in the staff SER on the same l
subject. Therefore, the staff fir.ds the proposed changes acceptable.
5520 NAME: Zion TACS 55417/8 L
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$PLS $ ALP INPUT l
Units 1 and 2 Zion Nuclear Generation $tations, Operation I
Plant Name:
Containment Purge and Vent Valve j
'SfR
Subject:
TAC Nos.:
55417/8 I
5t m ry of Review /!nsoection Activities l
The licensee initially proposed Technical Specification changes for j
containment purge and vent valve operation needed revision. However, i
j data revisions adequately addressed the concerns, gettre Discussion of Licensee Performance. Functional Area The licensee's approach for resolution of generic concerns related to the j
demonstratior,of containment purge and vent valve was viable and sound from a safety standpoint.
' Authors: J. Kedrick and C. Li t
Date: May 10,1989 I
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