ML20077F593

Forwards Response to NRC Request During 910513 Telcon in Support of 910424 Application for Amend to License NPF-86 Re Operation of Safety Injection Pump in Modes 5 & 6

ML20077F593
Person / Time
Site:	Seabrook
Issue date:	06/14/1991
From:	Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-17, NYN-91096, NUDOCS 9106190391
Download: ML20077F593 (6)

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New Hampshire Ted C. Feigenbaum h h President and Chief Executive Officer NYN- 91096 J une 14,1991 United States Nuclear Regulatory Commission Washr!9n, D.C. 20555 Attention: Document Control Desk

References:

(a) Facility Operating License No. NPF-86, Docket No. 50 443 (b) USNRC Generic Letter 8817 dated October 17,1988, " Loss of Decay Heat Removal" (c) NilY Letter NYN-90211 dated December 14, 1990, " Safety injection Pump Operability in a Reduced Inventory Condition", T. C. Feigenbaum to USNRC (d) NHY Letter NYN-91067 dated April 24, 1991, " Request for License Amendment: Safety injection Pump Operability in hiodes 5 and 6",

T C. Feigenbaum to USNRC

Subject:

Request for Additional Information Regarding Safety injection Pump Operability in hiodes 5 and 6 Gentlemen:

New Hampshire Yankee has enclosed herein additional information in support of its license amendment request regarding the operation of a Safety injection Pump in Modes 5 and 6 [ Reference (d)]. This information is provided in response to questions from the NRC staff during a telephone call on hiay 13, 1991. We trust that the infr mation will provide satisfactory responses to the staff's questions.

Should you have any questions regarding this matter, please contact hir. James hl.

Peschel, Regulatory Compliance Nianager, at (603) 474-9521, extension 3772.

Very truly yours, ed C.I'cig- aum TCF:J M P/act Enclosure 9106190391 910614 FDR ADOCK 05000443 i

P PDR l , ,, ,s y New Hampshire Yankee Division of Public Service Company of New Harrpshire s' U U U J P.O. Box 300

• Seabrook, NH 03874

• Telephone (603) 474-9521 oOg

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'- 'Urited States Nuclear Regulatory Commission June 14,1991 Attention: Document Control Desk . Page two ec: Mr. Thomas T. Martin Regional Administrator United States Nuclear Regulatory Commission Region I l

475 Allendale Road King of Prussia, PA 19406 Mr. Gordon E Edison, Sr. Project Manager Project Directorate 13 Division of Reactor Projects U.S. Nuclear Regulatory Commission Washington, DC 20555 Mr. George L. Iverson, Director Office of Emergency Management l State Office Park South -

107 Pleasant -Street I Concord, nil 03301 l-

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Mr. Noel Dudley ,

l .- NRC Senior Resident Inspector i

P.O.130x 1149 Seabrook, NII 03874 L

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New Hampshire Yankee J une 14,1991

> ENCLOSilRE TO NYN-0109q l

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e Question: What is the required size of the Reactor Coolant System vent area to ensure I that the Appendix G limits are not exceeded when a Safety injection Pump is j made operable in Mode 5 or Mode 6? '

R e s po ng.

The minituum Reactor Coolant System vent area to ensure that the Appendix G liuits are not exceeded when operating one Centrifugal Charging Pump and one Safety injection Pump while in Mode 5 or Mode 6 with the reactor vessel head on is 2.92 square inches. This value was determined in YNSil calculation S13C 363. Revision 3, "Mid Loop Operation Analysis",

I As stated- in our April 24, 1991 submittal (Reference (d)) a vent area larger than that required based upon Appendix G overpressure protection requirements was conservatively specified atter consideration was given to two other factors influencing mid loop operation as discussed below:

.. If operating with SG nozzle dams in place, in order to avoid potential exposure of plant personnel to reactor coolant due to postulated nozzle dam failure, it is necessary to provide a vent capable of maintaining the pressure in the RCS hot and cold legs lower than the allowable pressure differential across the nozzle dams in order to preclude failure. The 18 square inch vent area specified is sufficient to limit the pressure differential across the SG nozzle dams during the new mass addition event to 33 psig, which is less than the 56.5 psig design pressure differential of the nozzle dams which may be used at Scabrook. In the event of a loss of Residual Heat Removas (RilR) cooling during mid-loop operation, the 18 square inch vent area (as provided by removal of a single pressurizer SV) also provides adequate steam relief capacity to prevent RCS pressure from exceeding the SG nozzle dam design pressure differential assuming the plant has been shutdown for at least 48 horrs, The equilibrium RCS pressure is expected to be 46 psig following a loss of RilR shutdown cooling, during mid-loop operation, 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after shutdown utilizing best estimate decay heat and no makeup flow so that decay heat is removed by vaporization of saturved liquid.

. . In addition to the SI pump and the CCP, gravity feed from the Refueling Water Storage Tank (RWST) to the RCS is possible at Seabrook subject to RCS (hot leg) pressure and RWST level, With an RWST level of 25%, gravity feed is possible with _

- RCS pressures up to 32 psig. With a full RWST, gravity feed is po:sible up to-an RCS pressure cf 45 psig. The RCS pressures discussed abose are substantially below the Appendix 0 pressure limit. A vent path -larger than the 1,58 square inches specified in TS 3.4.9.3c is required to meet Appendix G limits and to allow gravity feed from the RWST. Removal of a single pressurizer SV from its flange (which provides a vent area slightly greater than the 18 square inches specified in the proposed change to TS 3.5.3.2) is the smallest vent path under consideration for this purpose. This vent path is sufficient to pass the steaming rates associated with decay heat removal via saturated steam cooling while maintaining RCS hot leg pressures 145 psig, for shutdown times in excess of 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> (7 days); and maintaining RCS hot leg pressure 132 psig, for shutdown times in excess of 360 hours0.00417 days <br />0.1 hours <br />5.952381e-4 weeks <br />1.3698e-4 months <br /> (15 days).

Gravity feed from the RWST is a backup means of providing RCS makeup and cooling. The primary method is to utilize the RIIR system. If RHR were to fail the 1

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a Charging System, using the CCP, and the Safety injection System, using the Si pump are _the primary backups systems to provide additions to the RCS inventory. Gravity feed from the 1(WST is also available to backup these systems in the unlikely event that both the CCP and Si pumps are unavailable after a loss of RilR.

The 18 square inch vent area specified in the proposed change to TG 3.5.3.2 therefore represents a conservatively large vent area wit h respect to Appendy G overpressure protection requirements, and a minimum desirable vent area with respt et to these other considerations. Seabrock Station procedures will include administrative controls to ensure that a vent path of at least 18 square inches is established prior to makirig the Si pump available to flow to the Reactor Coolant System.

Question: NUREG-1410, describes the potential for failure of seal table temporary seals during a loss of RilR cooling with the reactor vessel head tensioned. lias NilY considered the potential for temporary seal. failure relative to its proposed Technical Specification change.

. R esponse:

New Hampshire Yankee has reviewed NUREG 1410 with regard to the temporary thimble tube seals and has determined that the preparations for refueling have adequately addressed the use of temporary thimble tube seals and that no special trquirements are required with regard to the proposed Technical Specification change. At Seabrook Station, the seal table and'the location of the temporary thimble tube seals is 1 1/2 inches below the elevation of the reactor vessel flange. The temporary thimble tube seals are designed to withstand the static head-of approximately 10 psig produced by the elevation e' water (approximately 23 feet) that results when the refueling cavity is flooded.

i The normal sequence of events in preparation for a refueling outage as provided in NilY I Procedure OS1000.09 Refueling Operations" requires that the incore detectors be withdrawn l' and the temporary seals be installed shortly before the reactor vessel head is detensioned and removed. The upcoming refueling schedule indicates that there may be a short periou of time, up to one day, when the temporary seals- are installed before the head is removed.

New llampshire Yankee has recognized that during this short period of time a Safety injection Pump could be. made operable while the head is tensioned and the temporary thimble tube seals are installed. Therefore NilY has inciuded a precaution and a caution in procedure OS1000.09 to prevent a Safety injection Pump from being made available while the temporary thim_ble tube seals are installed and the reactor vessel head is installed. Once the reactor: vessel head is detensioned. a significant gap of I to I 1/2 inches is created between the- reactor vessel and the head creating a vent area many times the 18 square inches specified in the proposed Technical _ Specification which obviates concerns regarding reattor coolant- system pressurization.

' The proposed Technical Specification change, allows a Safety injection Pump to be made operable only after a vent area - equal to or greater than 18 square inches has been established in the Reactor Coolant- System._ The Safety injection Pump is intended to be made operable to support operations at a reduced inventory level (mid loop operations) or to accommodate check valve flow testing. 110th of these evolutions will _bc performed _ in Mode 5, and not while the preparations are being made to detension and remove the head.

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A final considtration with regard to the potential pressuritation of the Reactor Coolant System while the reactor vessel head is tens.ioned and the temporary thimble tube seals are installed was considered. in order for this condition to occur, the Residual llcal Removal (RllR) System would have to be assumed to be unavailable, followed by the unavailability of the Charging System and the Safety injection System. Given the low probability of these three system's unavailability, followed by the lost of the ability to provide a gravity feed from the Refueling Water Storage Tank (RWST) to the Reactor Coolant System this hypothetical or postulated event sequence is of an extremely low probability of occurrence. Only after these sources of Reactor Coolant System makeup capability were lost would the Reactor Coolant System be able to increase in temperature and pressure. Even if this were to be a credible esent under these conditions the postulated failure of a temporary thimble tube seal (or seals) would provide vent area in addition to the 18 square inches required by the proposed Technical Specification change, thus providing additional vent area for further protaction against RCS overpressurization. Therefore, New Hampshire Yankee considers it to be highly unlikely that the four inventory addition systems, R11 R, Charging, Safety Injection and RWST gravity feed would become unavailable during the short period of time that the temporary thimble tube seals are installed and the reactor vessel head is tensioned and instalied.

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