ML20199B208
| ML20199B208 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 11/03/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20199B200 | List: |
| References | |
| NUDOCS 9711180245 | |
| Download: ML20199B208 (5) | |
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SAFLTY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.114 TO FACILITY OPERATING LICENSE NO. NPF 42 WOLF CREEK NUCLEAR OPERATING CORPORATION t
WOLF CREEK GENERATING STATION DOCKET NO. 50 482
1.0 INTRODUCTION
By letter dated October 17, 1997. Wolf Creek Nuclear Operating Corporation (WCNOC. the licensee) requested changes to the Technical Specifications (TS)
(Appendix A to Facility Operating License No. NPF 42) for the Wolf Creek Generatir Station (WCGS). The proposed changes would revise TS 4.5.2b and associate Bases to eliminate the requirement to vent the centrifugal charging pump casings.
2.0 EVALUATION The emergency core cooling system (ECCS) pumps are normally in a standby, non-operating mode. As such, flow path piping has the potential to develop voids and pockets of entrained gases. Maintaining the piping from the ECCS pumps to the reactor coolant system (RCS) full of water by venting pump casings and accessible discharge piping high point vents ensures that the system will perform properly, injecting its full capacity into the RCS upon demand.
Venting of the non operating subsystems ensures that the piping is full of water and provides confioence that a potential water hammer event which could result from voiding would not result in unacceptable dynamic loads.
The proposed TS amendment would eliminate the requirement to vent the centrifugal charging pum) casings. TS 4.5.2b requires verifying that the ECCS piping is full of water )y venting the ECCS pump casings and accessible discharg piping high points at least once every 31 days. However, the centrifu al charging pumps, which are ECCS pumps. were designed and installed to be se f venting, and are not provided with casing vent valves. The design of the pum) places the suction and discharge piping at the top of the pump casing. T1e c3ntrifugal charging pump suction piping is in communication with either the refueling water storage tank or the volume control tank, Both of theses sources provide a net positive suction pressure for the pumps.
The design of the centrifugal charging pumps is such that significant noncondensible gases do not collect in the pumas, whether they are running or not. The suction and discharge lines are on tie top of the ) umps and the internal cavities in the pump that do not communicate with tie nozzles are small enough that significant gas accumulation in the pump casings will not
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occur. Noncondensible gases that may collect in the discharge pipino will be vented at the discharge piping high points every 31 days per TS 4.5.2b.1).
i Operating experience has shown that no significant voiding has occurrad in the i
affected piping which will continue to be vented at a high point every 31 days per TS 4.5.2b.1). The pump vendor informed the licensee that small amounts of gases can be swept through the pump without causing damage to the pump. Wolf Creek has had the pumps disassembled and ins)ected by the vendor. Only normal i
signs of marking and wear were observed on tie pump 1mpeller.
l is designed to be self venting and Thecentrifu$eswillal charg noncondensib o$1 in high points which are vented every 31 days.
t As a resuit, the removal of this venting requirement will not affect the i
operability of the centrifugal charging pump.
The limiting condition for operation (LCO) associated with the pump is not affected and removal of the reugirement does not meet any of the four criteria for retention in TS as defined by 10 CFR 50.36.
Based on the.above, the staff concludes that the elimination of the requirement to vent the centrifugal charging pump casings will make the TS surveillance requirements consistent with the design of the ECCS system. and that the TS surveillance. as modified, will provide continued confidence that unacceptable accumulations of gases will not occur.
3.0 DESCRIPTION
OF EX1 GENT CIRCUMSTANCES WCGS shut down on October 4.1997, for a refueling outage and is currently in l
Mode 6.-
On October 14. 1997, WCNOC personnel determined that WCGS was not being operated in compliance with the technical specifications in that the centrifugal charging pump casings were not being vented as recuired by Technical Specification 4.5.2b.
The pump casings are designec without casing vents since noncordensible gases can escape through the top mounted suction 1
and discharge nozzles. Therefore, a change to TS 4.5.2b and associated Bases is needed to specify that only the safety injection and residual heat removal pumps require vent of the pump casings. The licensee promptly sebmitted the amendment request.
Restart of WCGS is planned for early November, with Mode 4 expected on November 10. 1997 (changed from November 4. 1997, as stated in the October 17, 1997, letter due to an extension in the outage). Technical Specification LC0 3.5.3 requires one operable centrifugal charging pump in Mode 4 and Surveillance Requirement 4.5.3.2 requires the centrifugal charging pump be demonstrated operable per the requirements of Specification 4.6.2, which currently. includes venting of the pump casings.
The exigent situation exists and cannot be avoided because (1) the TS noncompliance was not identified by WCNOC until October 14. 1997, and (2) WCGS i
cannot be returned to Mode 4 without the change.
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The staff finds the 11censee acted in a timely manner, the licensee has not abused the exigent provisions and there is not sufficient time to process this amendment request in the routine manner as described in 10 CFR 50.91 without causing an unnecessary delay in startup of WCGS.
4.0 FINAL NO SIGNIFICANT HA7ARDS CONSIDERATION DETERMINATION The Comission has made a final determination that the amendment involves no significant hazards consideration. Under the Commission's regulations in 10 CFR 50.92(c), this means that operation of the facility in accordance with the proposed amendment would not (1) involve a significant increase in the presability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
The staff evaluated the proposed changes against the above standards as required by 10 CFR 50.91(a) and has concluded that:
1.
The proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
The proposed change will align the surveillance requirements with the installed system design and normal o)erating conditions.
The conduct of surveillances required by teclnical specifications is not postulated to initiate an accident. The intent of the surveillance ensures operability of the centrifugal charging pumps by verifying that the emergency core cooling system (ECCS) p131ng is full of water and not subjected to gas binding or water lammer.
The design of the centrifugal charging pumps is such thct significant noncondensible gases do not collect in the pumps, whether they are running or not.
Therefore it is unnecessary to require periodic pump casing venting to ensure the equipment will remain operable.
In addition operating experience has shown that no significant voiding has occurred in the affected piping which will continue to be vented at a high point every 31 days per Surveillance Requirement 4.5.2b.1).
Theref ore, no increase in the probability or consequcrces of an occid:nt will occur as a result of this change.
2.
The proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
The proposed change will not result in new failure modes because no new (;uipment is installed and installed equipment is not operated in a new or different manner. The design of the centrifugal charging pumas is such that significant noncondensible gases do not collect in tie pumps, whether they are running or not.
Therefore, it is unnecessary to require periodic pump casing venting to ensure the equipment will remain operable. Manual venting operations have been performed which minimizes the potential for voids in system p1pirg. Accordingly, this change will not create the possibility of a new or different kind of accident.
3-4 3.
The proposed change does not involve a significant reduction in a margin of safety.
The margin of safety is not significantly reduced because the proposed change provides assurance that locations where-noncondensible gases can collect will be vented.
Eliminating the requirement to vent the centrifugal charging pump casings where gases cannot collect has no functional effect on the system. This assures pro >er system functioning.
Additionally, operating experierce las shown that no significant voiding has occurred in the affected piping which will continue to be vented at a high point every 31 days per Surveillance Requirement 4.5.2b.1).
Therefore, this change will not involve a significant reduction in the margin of safety.
Accordingly, the Comission has determined that this amendment involves no significant hazards consideration.
5.0 PUBLIC COMMENTS The NRC received coments from two members of the public questioning the exigency of the TS amendment.
In addition, one of the members of the public asked (1) how many times the licensee performed the surveillance, (2) were the centrifugal charging pumps originally designed without casing vents, and (3) is the licensee at fault for not having detected the TS problem in the past.
Further. it was requested that the NRC not grant the license amendment request until it has been processed in accordance with federal regulations.
As discussed in 10 CFR 50.91(a)(2)(11), under the normal amendment-process, a 30 day coment aeriod is required after publication of the pro)osed amendmer.t in the Federal Reaister. Section 50.91(a)(6) indicates that w1en the Comission finds that exigent circumstances exisr. in that time does not permit the Comission to publish a Federal Register notice allowing 30 days for prior public comment, the Comission may process the request under exigent circumstances and provide a two week prior comment period if the Commission determines that the licensee acted in a timely manner did not abuse the exigent provisions, and there was not sufficient time to process the amendment request in a routine manner, in lieu of the two week notice. Section 50.91(a)(6) further states that the Comission mau use local media to provide reasonable notice to the public in tN area surrou.11ng the facility and a reasonable opportunity for the public to coment.
As discussed in Section 3.0 of the Safety Evaluation, on October 14, 1997.
WCNOC identified that WCGS was not being operated in compliance with the TS in that the centrifugal charging pump cesings were not being vented as required by'TS 4.5.2b.
ThissituationwasnotidentifieduntilWCNOCbecameawareofa similar-siutation at another licensed facility and initiated a review to determine'the applicablity to WCGS. The pumps were not designed with casing vents since noncondensible g nes can escape through the to p mounted suction and discharge nozzles, Without casing vents venting of tie pump casings is not possible and further. is not needed. As such. the TS surveillance has
-never been performed, p
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-5 based on the above. WCNOC submitted a request for a TS amendment on October 17. 1997.
At the time of the request. WCGS was in a refueling outage with Hode 4 (the first Mode at which compliance with TS 4.5.2b would be needed) expected to be entered on November 4. 1997 (however due to a change in the refueling schedule. Mode 4 is currently expected on November 10.
1997). The licensee requested that the amendment be processed under exigent circumstances to allow startup of WCGS at the end of the outage since processing the amendment in a routine manner would delay startup of WCGS.
As such, on October 24, 1997, the Comission used local media (Coffey County Today newspaper) to provide reasonable notice to the public in the area surrounding the facility and a reasonable opportunity (5 days) for the public to coment on the proposed TS amendment.
Based on the above, and the staff's determination (see Section 3.0 of the Safety Evaluation) that the licensee acted in a timely manner, did not abuse the exigent provisions, and there was not sufficient time to process the request in a routine manner. the staff has concluded that processing the licensee's TS amendment request under exigent circuc tances is in accordance with the regulations.
6.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Kansas State Official was notified of the proposed issuance of the amendment.
The State official had no coments.
7.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements.
The NRC staff has determined that the amendment involves no significant increase in the amounts. end no significant change in the types, of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Comission has made a final no significant hazards consideration with res)ect to this amendment.
Accordingly the amendment meets the eligi)ility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
8.0 CONCLUSION
The Comission has enncluded, based on the considerations discuss 7d above.
that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
K. Thomas Date:
November 3, 1997
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