ML19260A829
| ML19260A829 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/20/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19260A828 | List: |
| References | |
| NUDOCS 7912040128 | |
| Download: ML19260A829 (5) | |
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3 UNITED STATES b
'k NUCLEAR REGULATORY COMMISSION j J[f'I
- hh,j}*j WASMNGTON. D. C. 20555 a
\\; -Q SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 22 TO FACILITY OPERATING LICENSE NO. OPR-70 PUBLIC SERVICE ELECTRIC AND GAS COMPANY, PHILADELPHIA ELECTRIC COMPANY, D_ELMARVA POWER AND LIGHT COMPANY, AND ATLANTIC CITY ELECTRIC COMPANY SALEM NUCLEAR GENERATING STATION, UNIT NO. 1 DOCKET NO. 50-272 Introduction Facility Operating Licensa No. OPR-70 for Salem Unit No. I contains a condition that limits the secondary side water level rise rate in each steam generator when the secondary side water level is belcw the level of the feedwater sparger. This condition was icoosed as an interim measure to prevent water hammers until the licensee demonstrated that secondary side flow instability would not result in unacceptable consequences.
By letter dated August 23,1979 (Reference 1) the licensee referred to the restrict'on in Section 2.C(3) of Facility Ocerating License No. DPR-70 as a possible unreviewed safety question and proposed that it should be lifted.
This document presents the staff's avaluation of the license coadition and concludes that this license condition should be lifted.
Discussion Section 2.C(3) of Facility Operating License No. DPR-70 reads as follows:
Steam Generator Wa*.er Rise Rate Except for the purpose of performing secondary side ficw stability tests, Public Service Electric and Gas Comoany shall, whenever the secondary side water level in a steam generator is below the level of the feedwater soarger, limit the secondary water level rise rate in each steam generator to less than 1.2 inches per minute cnd shall reduce the rise rate to wi*nin this limit within two (2) minutes. This condition will be removed Dy anencrent of tnis license when ?ublic Service Electric and Gcs C=cany ceconstrates to the satisfaction of the Comission that seconcary sice flow instability (water hamer) does net result in unacce: aole consequences.
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This condition was deternined to afford adequate measures against water hamer while the staff and the licensee further assessed the significance of water hanner considerations at Salem Unit No.1.
The purpose of limiting the water level rise rate in the steam generator was to limit the flow of subcooled water in the feedwater piping and feedring when the subcooled water is in contact with steam in the feedwater piping arid feedring.
The staff has completed a review of steam generator water hammer at Salem Unit No.1 (Reference 2) and has determined that the provisions that have i
been made for minimizing the likelihood of water hamer events due to the rapid condensation of steam in the feedwater systems at Salem Unit No. I are acceptable.
The licensee has proposed to provide more effective procedural control of the feedwater flow in lieu of the license condition. Our evaluation addresses the need for such procedures under normal, transient, and emergency modes of operation.
Evaluation Tests performed at Indian Point Unit No. 2 under conditions where subcooled water is in contact with steam in the feecwater piping and feedring showed 2
that there were indications of water haccer at a ficw of 240 gpm but there were no indications at 200 gpm and lower ficws.
The results of those tests are given in Reference 3.
It was estimated that 200 gpm corresponded to a steam generator water level rise rate of approximately 1.2 inches per minute, including appropriate margins for error.
It was further assumed that whenever the level of water in the steam generator dropped below the feedring, the ring would drain rapidly, and, in approximately two minutes, steam would enter the feedring and piping and come in contact with subcooled water. Based on the result of those tests, it was considered prudent to ir. corporate the flow limitations of Section 2.C(3) into the license for Salem Unit No.1.
Some of the assumptions that formed the basis for the license condition aoply only to a feedring that discharges from the bottom. The design of the Salem Unit No. I feedrings was revised to include "J" tubes that discharge from the top of the ring. When a feedring discharges from the top, the water does not drain quickly. Under transient conditions, such e
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3-as a plant trio with loss of feedwater, the steam generator water level will drop below the feedring but the feedring will be kept filled by the auxiliary feedwater that.is automatically actuated upon a low water level signal in the steam generator. Administrative restrictions on flow are not necessary under these conditions.
There may be situations, however, wheri cperator inattention or failures in the auxiliary feedwater system would leed to the introduction of subcooled water into the steam-filled feedwater ring and piping.
Therefore, procedures for refilling a steam generator should include precautions to restrict feedwater flow to 200 gallons per minute when, coincidentally, all water flow to the feedring has been interrupted for five minutes or more and the water level in the steam generator is below the top of the feedring.
Such a precedure does not require restrictions of flow nor intervention by the operator in the event of a plant trip or a loss of feedwater event.
After a plant trip, the operator will usually throttle auxiliary feecwater flow to prevent overtooling of the reactor coolant system or overfilling of the steam generator.
If for some reason, the operator is confronted with an overheating situation, maximum feedwater flow will take precedence over water hamer considerations.
3 We have evaluated the potential for steam generator water hamer at Salem Unit No. I and have concluded that modifications are not necessary to reduce further the likelihood of a damaging steam generator water hame r.
We agree that this license condition should be lifted because it is nisleading and may cause actions to be taken that would unnecessarily
' restrict the flow of auxiliary feedwater.
The objective of this license condition will better be accomplished by specific operating procedures.
We have set forth herein the criteria for such procedures.
The procedures will be established by the licensee and verified by an NP.C inspector.
In establishing appropriate operating procedures, the licensee will:
(1) modify the procecures for auxiliary feedwater system operation to include precautions to limit auxiliary feedwater flow to 200 gallons per minute when coincidentally all water flow to the feedring has been interrupted for more tnan five minutes and the water level in the steam generator is below the top of the feedring, (2) issue a memorardum to licensed operators providing the background and the basis for these procedures, and (3) place a cancionary tag in the vicinity of the controls for the auxiliary feedwater system.
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. Environmental Consideration We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR Sl.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have found that the license condition in Section 2.C(3) of Facility Operating License No. DPR-70 for Salem Unit No.1 could mislead the licensee to restrict the flow of auxiliary feedwater unnecessarily. We have concluded that the intent of this condition will be accompl!shed more effectively by the procedures proposed by the licensee. Therefore, we have determined. that Section 2.C(3) should be deleted from Facility Operating License No. OpR-70.
We have concluo0d, based on the considerations discussed acove, that:
3 (1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amencnent does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the procosed manner, and (3) such activities will be conducted in comoliance with the Comission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date:
November 20, 1979 1478 H5 Referenc es 1.
Letter, PSEG (Librizzi) to NRC (Grier), dated August 23, 1979.
Reportable Occurrence 79-52/0lT.
2.
Letter, NRC (Schwencer) to PSEG (Libriz:i) dated Noventer 3,1979.
3.
NUREG-0291, "An Evaluation of PWR Steam Generator Water-Harr er,"
June 1977.
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