B12885, Provides Info on Open Items Re HPSI Pump Miniflow Mods & Gate Valve Flow Throttling Ability to Enable NRC to Complete Review of ECCS

Provides Info on Open Items Re HPSI Pump Miniflow Mods & Gate Valve Flow Throttling Ability to Enable NRC to Complete Review of ECCS

ML20151R535
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	08/02/1988
From:	Mroczka E CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
B12885, TAC-62974, NUDOCS 8808120207
Download: ML20151R535 (6)

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MEAST UTILITIES cenerai ottice. . seioen street. Beriin. connect cui EN2 I U ARTFORD. CONNECTICUT 06141-0270 k k 1J ",o. Ys d ,[ [ , (203) 665-5000 August 2, 1988 Docket No. 50-213 B12885 Re: 10CFR50, Appendix A, GDC-35 l 1

U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Reference:

(1) D. M. Crutchfield letter to E. J. Mroczka, "Extension of the Temporary Exemption from the Single Failure Criterion (GDC No. 35)," dated September 2, 1987.

j Gentlemen:

! Haddam Neck Plant ECCS Modifications (TAC 62974)

By Reference (1), the NRC granted Connecticut Yankee Atomic Power Company (CYAPC0) a one cycle extension to the exemption the single failure criterion that had been granted on April 28, 1986. ( 3jrom This extension to the exemption and its associated safety evaluation report (SER) identified two open items pertaining to the high pressure safety injection (HPSI) pump miniflow modifications and the gate valve flow throttling ability. The purpose of this submittal is to provide information on these open items so the NRC Staff can complete its review of this issue.

Gate Valve Flow Throttlina Presently, flow control valve RH-FCV-796 is locked in the throttled position to prevent excessive residual heat removal (RHR) pump flow and resultant RHR pump damage. However, the long term ECCS modifications require RH-FCV-796 to be fully opened to assure adequate net positive suction head for proper HPSI pump performance. In order to address excessive RHR pump flow during long term recirculation, CYAPC0 intends to operate with one of the redundant core deluge paths closed and the other path throttled by remote operation of a gate valve. The NRC Staff stated that throttling with a gate valve is not a recommended industrial practice and questioned the acceptability of long term operation in this mode.

In order to ensure that throttling could be achieved using a gate valve, CYAPC0 performed an ECCS flow test with the valves aligned in the long term recirculation position. During this test, flow to core deluge was varied from approximately 200 to 1800 gpm in 200 gpm increments by using the core deluge l

1 i (1) F. J. Miraglia letter to J. F. Opeka, "Exemption from Single Failure Criterion (GDC 35) - Haddam Neck Plant," dated April 28, 1986.

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.U.S. Nuclear Regulatory Commission B12885/Page 2 August 2, 1988 isolation gate valve SI-M0V-871A. Flow was simultaneously delivered to the loop 2 cold leg at 200 gpm using a charging pump. At the time of the test, the RCS was depressurized.

The test ran smoothly and there were no unusual vibrations or noises that would indicate that the valve could not remain in a throttled position for an extended period of time. Based on the results of this flow test, CYAPC0 believes that the post 1989 long term recirculation procedures which utilize a throttled gate valve are valid.

HPSI Pumo Mini-Flow Modifications A detailed description of the HPSI pump miniflow modification that will be completed during the 1989 refueling outage is attached. Briefly, these modifi-cations include:

o Replacement of the existing miniflow lines and associated manual isola-tion valves (SI-V-857A and B) with rerouted piping and manual stop-check valves.

o Replacement of the existing air operated flow control valve (SI-FCV-875) and piping as necessary with two motor operated valves (M0V) in series.

o Installation of a relief path to provide HPSI suction overpressurization protection.

These miniflow modifications do not change the conclusion that pump damage will not occur g Haddam Neck as stated in the June 30, 1988 response to Bulletin 88-04. A proposed license amendment will be submitted prior to the next refueling outage to include the modifications in Technical Specifica-tions 3.6 and 4.3.

We hope you find this information satisfactory, and we remain available to answer any questions you may have.

Very truly yours, CONNECTICVT YANKEE ATOMIC POWER COMPANY

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Senior Vice President l cc: W. T. Russell, Region I Administrator l A. B. Wang, NRC Project Manager, Haddam Neck Plant l J. T. Shedlosky, Senior Resident Inspector, Haddam Neck Plant l (2) E. J. Mroczka letter to U.S. NRC, "Response to NRC Bulletin 88-04, Potential Safety Related Pump loss", dated June 30, 1988.

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Docket No. 50-213 812885 Attachment l Haddam Neck Plant l HPSI Pump Mini Flow Modifications 1

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August 1988 l

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1 Miniflow Line The purpose of the miniflow line is to provide a minimal amount of cooling water through the HPSI pumps if the pumps were pumping against a dead head condition (no flow). Per manufacturer recommendations, a miniflow of at least 32 gpm should be maintained when a HPSI pump is operating dead headed. In March 1987, a test was run to determine if the flow in the bypass line was sufficient to operate a HPSI pump long-term on just miniflow. During this test, temperature and vibration readings were taken until the HPSI pump temperature stabilized. No unacceptable conditions were noted.

The individual miniflow lines from each HPSI pump contain a manual isolation valve which is locked open. The common miniflow line downstream of the manual valves contains an air operated valve which is blocked open. This ensures that a miniflow path is always available during the injection phase of a LOCA when HPSI could be dead headed.

By procedure prior to April 1986, the HPSI pumps were not used in the recircu-lation phase of a LOCA and miniflow did not have to be isolated from the refueling water storage tank (RWST). After the discovery of the small break LOCA problem, procedures were modified to include use of a HPSI pump being fed from an RHR pump during sump recirculation. This necessitates isolation of the miniflow line to prevent flow of potentially highly contaminated water back to the RWST.

Procedures developed under the interim exemption to the single failure crite-rion require an operator to locally isolate the miniflow line during switchover to sump recirculation. This modification eliminates the need for operator action outside of the control room and satisfies the single failure criterion.

As shown in Figure I, the manual isolation valves (SI-V-857A and B) on the flow line for each pump will be replaced with stop check valves. They will provide isolation for maintenance, but will prevent backflow through the miniflow line. These valves will be locked in the open position during operation.

Valve SI-FCV-875 on the common miniflow line will be replaced with two M0Vs in series. These valves will be operable from the control room normally open during operation, and the manual operator for these valves will be locked open. Each valve will be powered from a separate vital power source to ensure that at least one valve will close during switchover to sump recirculation, assuming a single failure.

HPSI Suction Overoressure Protection l The HPSI pump suctions presently do not have overpressure protection. Prior

! to 1986, HPSI was not used for sump recirculation and the suction piping

! always remained open to the RWST. By interim procedures developed for the time between the 1986 and 1989 refueling, HPSI suction isolation is accom-plished by closing valve SI-M0V-24 in the common HPSI suction line. Any pressure buildup caused by leakage past the check valve in the HPSI discharge l piping into an idle pump suction would be relieved by bleeding through the l common line into the operating pump suction.

After 1989, overpressurization of an idle pump suction could occur due to leakage past the discharge or miniflow check valves. This condition could only occur if the idle pump HPSI suction valve was closed upon entry into sump recirculation and the crosstie valve associated with the idle pump failed to open (single failure). This would create a condition where pressurized fluid from the discharge of the operating pump could leak past the idle pump discharge or miniflow check valves causing a suction overpressurization.

This modification provides a relief path from the idle pump suction piping to the operating pump suction piping to prevent overpressurization.

As shown on Figure I, each HPSI pump suction pipe will be equipped with a spring loaded poppet-type check valve with a differential crack pressure of approximately 10 psid as the pressure relief device. The check valve will permit pressure relief flow from an isolated HPSI pump suction line to the HPSI/RHR crosstie line, but inhibit flow from the crosstie line into the HPSI suction line. Manual ball or gate valves will be installed upstream and downstream of each relief valve so that it can be removed or maintained without declaring both HPSI pumps inoperable. These valves will be locked l open during operations.

Check valve leakage will be limited to 1 gpm each for the main line check valves (SI-CV-856 A and B) and 1 gpm total for the new stop check valves when tested simultaneously. Total leakage into an idle pump suction should not exceed 2 gpm. The poppet check valve will be sized to pass at least 10 gpm without exceeding pump suction design pressure. The safety valves, therefore, will provide at least a 5 to 1 safety factor.

It should be noted that the poppet check valve will not open unless a single failure occurs (i.e., the suction valve for an idle HPSI pump closes but the crosstie valve fails to open) and the discharge or miniflow check valve leaks.

If the poppet check valve were to open and fail to close, the amount of flow which would be diverted back to the operating pump suction would be small and l

would not adversely impact ECCS performance.

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• NORTHEAST UTILITIES SERV CONN YANKEE ATOMIC POWER CO, PROPOSED HPSI PUMP MINIFLOW AND ALTERNATE SUCTION OVER PRESSURE PROTECTION MODIFICATIONS 87 )i. R. B13151 c <,. W. AFP, OATC 4333 O&it 04TE 0A'E q u. e m ,tes i, x g. o. ,O' ,*L FIGURE I

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