ML20085A768

Safety Evaluation Supporting Amend 3 to License NPF-86

ML20085A768
Person / Time
Site:	Seabrook
Issue date:	07/15/1991
From:	Office of Nuclear Reactor Regulation
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ML20085A758	List: ML20085A753 ML20085A768
References
NUDOCS 9107260221
Download: ML20085A768 (5)

Text

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UNITED ':T ATES 83

'n NUCLEAR REGULn!ORY COMMISSION

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%...* / SAFETY EVALUATION BY THE OFFICE OF HUCLEAR REACTOR REGULATION SUPPORTING AliEf4DMENT NO. 3 TO FACILITY OPERATINC LICENSE fl0. NPF-86 PUBL1CSERV1Cf,,CpfPANYpF,NERpAliP,SHJFE

} E A,B,Rpp,K,,5,T,A,TJ ph _U N I T NO. 1 DOCKET NO. 50-443 LO 1,N.TR,000CT 10N by letter dated April 22, 1988 (Ref. 1), the Westinghouse Owners' Group (WOG) submitted Topical Report WCAP-11736 entitled " Residual Heat Removal System Autoclosure Interlock Removal Report for the Westinghouse Owners' Group," for flRC review. Westinghouse Report WCAP-11736 documents the analyses performed to justify deletion of the autoclosure interlock (AC1) on the Residual Heat Removal System (RHRS) suction / isolation valves at four reference plants:

Salem Unit 1, Callaway Unit 1, North Anna Unit 1, and Shearon Harris Unit 1.

The reference plants represent the lead plant in each of four groups into which WOG participating plants were categorized based on similarity of RHRS configuration and design characteristics. The proposed ACI deletion addresses NRC concerns regarding potential failure of ACI circuitry resulting in isolation of the RHRS with attendant loss of decay heat r:moval capability during cold shutdown and refueling.

A Safety Evaluation Report (SER) documenting the NRC review of WCAP-11736 was issued on August 8, 1989 (Ref. 2). The SER concluded that a net safety benefit would result from removal of the RHRS ACI provided that five plant improvements delineated in the SER are implemented.

In addition, the SER concluded that the information contained in WCAP-11736 may be referenced to supplement licensees' plant-specific submittals requesting removal of the RHRS ACI.

However, such reference would only be used to show compliance with those items that are generic to the WOG plants. A plant-specific submittal would be required of each licensee seeking approval to remove the RHR ACI.

The above referenced plant improvements are listed below:

(1) An alarm will be added to each RHR suction valve which will actuate if the valve is open and the pressure is greater than the open permissive setpoint and less than the RHR system design pressure minus the RHR pump head pressure.

(2) Valve position indication to the alarm must be provided from stem-mounted limit switches and power to these switches must not be affected by power loclout of the valve.

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-2 (3) The procedural improvements described in WCAP-11736 should be implemented.

Procedures themselves are plant-specific.

(4) Where feasib1e, power should be removed from the RHR suction valves prior totheirbeingleak-checked (plant-specific).

(5) The RHR suction valve operators should be sized so that the valves cannot be' opened against full system pressure (plant-specific).

2.0 EVALUATION By letter dated January 24, 1991, New Hampshire Yankee, licensee for the Seabrook Stetion, subnitted an application to revise Technical Specifications (TS) 4.5.2.d.1, 3.4.9.3.a, and 4.4.9.3.2 (a and b) (Ref. 3).

Supplementary information was provided by letter dated May 16,1991(Ref.4). These TS revisions have been proposed in support of the licensee's plans to remove toe RHRS ACI during their 1991 refueling outage. The proposed revision to TS 4.4.9.3.2 deletes the surveillance requirement to verify once every 31 days that one of the two in-series suction valves in each RHRS train is in the open position with its power removed, and to verify once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that the second suction valve in each train is open. This is replaced by the requirement to verify once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> that both suction valves in each train are open. The TS applies when the RHR suction relief valves are being used-for cold overpressure protection. The proposed revision to TS 3.4.9.3.a reduces-the RHR section relief valve setpoint upper limit from 450 psig t 3 percent to 450 psig + 0, - 3 percent.

Regarding TS 4.5.2.d.1, the proposed revision deletes the surveillance requirement for verifying ACI operability (the open permissive interlock surveillance remains-unchanged).

-As noted above, the NRC-approved Westinghouse report WCAP-11736 provides the underly1ng basis for justifying the licensee's planned action. The WCAP-11736 reference plant for Seabrook.is Callaway Unit 1.

The licensee's submittals (Refs. 3 and 4) include a plant-specific analysis of the planned ACI deletion Las a supplement to WCAP-11736. The submittal includes a delineation of the relevant design / operational differences that exist between Seabrook and the reference plant as described in WCAP-11736.

The licensee has examined these

. differences to determine their impact on ISt.0CA potential, RHRS availability, low-temperature overpressure protection,.and on the conclusions reached in

-WCAP-11736.

In addition, the licensee has addressed each of the five plant improvements set forth in Reference 2 and listed above. Where deviations from these improvements are proposed by the licensee, analyses are presented to demonstrate that equivalent levels of safety exist.

.With regard to the above mentioned five plant improvements, the' licensee's January 24 and May-16, 1991 submittals have provided the following responses:

Concerning Improvement-1, the existing Seabrook design already incorporates an alarm for'each RHRS suction valve which will-activate if i

the valve is not fully closed when RCS pressure exceeds the alarm setpoint. The retpoint (365 psig) is consistent with the WCAP-J1736

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3-guidance.

Also, in accordance with WCAP-11736, the open permissive interlock (OPI) for each'RHRS suction valve will remain intact and unchanged.

Concerning Improvement 2, the Seabrook design utilizes existing motor oper-ator limit switch contacts for valve position input to the existing alarms.

These contacts are different from the limit switch contacts which provide valve position on the main control board.

Furthermore, valve position alarms remain operational during valve power lockout.

The original intent of using stem-mounted limit switches in the alarm circuit was to provide a diverse means of valve position indication.

Since the existing design already provides this diversity, the licensee does not plan to install stem-mounted limit switches.

Concerning Improvement 3, the licensee has reviewed the Seabrook operating procedures to determine the effect of ACI removal and has committed to make the appropriate revisions. The p.ocedures reviewed include those delineated in Reference 2.

If an open RHR suction valve cannot be closed upon receipt of an alarm, operators will be directed to halt RCS pressurization and the plant will be returned to the shutdown cooling mode.

To further ensure alarm operability, instrument loop calibration procedures will be revised.

Concerning Improvement 4, the licensee does-not plan to remove power from the RHRS suction / isolation valves prior to Mak testing.

The original intent of this recommended improvement was to :nsure that the valves remained in the tested configuration during testing.

Leak testing of the RHRS suction / isolation valves at Seabrook is normally performed in Mode 4, 5, or 6.

Closure and power removal from these valves is required only prior to entering Mode 3.

One advantage of performing leak testing prior to entry into Mode 3 is that the amount of cooldown required to perform valve maintenance in the event the valve exhibits greater than allowable leakage is minimized.

The two RHR trains are leak tested consecutively.

When testing is completed on one train, that train is returned to serv-ce.

Removal of valve power prior to testing in Modes 4, S, and 6 (and subsequent restoration of power) would increase procedural complexity and time without offering a safety benefit.

Increased testing time would decrease the avail-ability of the RHRS to remove decay heat and for the RHRS suction relief valves to assist in low-temperature overpressure protection.

It also should be noted that, since the operable loop as well as the inoperable loop would be subjected to any unlikely pressure transients occurring during Modes 4, S. or 6, removal of power to the suction valve being tested (on the inoperable locp) would not alter the impact of a pressure transient in RHRS piping inside or outside of containment.

Concerning Imorovement 5, the licensee has stated that the RHRS suction valves potentially have the capability of opening against full RCS pressure.

However, these va;ves are provided with an OPI feature which prevents opening when RCS preasures exceed 365 psig.

The OPI is tested in accordance with TS 4.5.2.d.1 once every 18 months.

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these valves are de-energized during power operation.

Therefore, the likelihood of an ISLOCA scenario owing to an inadvertent open signal when the RCS is at full pressure is extremely low. On this basis, the licensee does not plan to downsize the motor actuators.

We have completed our evaluation of the licensees January 24 and May 16, 1991 submittals and have concluded the following:

The licensee has adequately identified differences in RrtRS configuration and design / operational characteristics that exist between Seabrook and the reference plant (Callaway) addressed in WCAP-11736. Because these differences are insignificant, the analyses and conclusions presented in WCAP-11736 for Callaway are direct'y applicable to Seabrook.

The licensee has adequately addressed the five plant improvements delineated in Reference 2.

Where deviations between these :mprovements and the licensee's proposed actions were identified, the licensee has adequately demonstrated that the proposed actions provided at least an equivalent level of safety.

TheproposedchangetoTS4.5.2.d.1(i.e.}todeletethesurveillance requirement for verifying ACI operability is consistent with the licensee's plans to remove the ACI feature from the RHRS suction valves.

This change is, therefore, acceptable.

The proposed change to T.e 3.4.9.3.a (i.e., to reduce the RHRS suction relief valve setpoint upper limit from 450 psig 3 percent to 450 psig +

0, - 3 percent) provides additional margin for overpressure protection and thus represents a change in a conservative direction.

This revision is, therefore, acceptable.

The proposed change to TS 4.4.9.3.2 (a and b) includes several revisions (see earlier description).

The current TS requirement to periodically verify that power is removed from one of the two in-series RHRS suction / isolation valves in each train is intended to ensure that a single failure of either of the two common pressure transmitters (which provide the ACI signal to these valves) does not result in both RHRS trains becoming isolated from the RCS.

With the planned removal of the ACI circuitry, hcwever, the only mechanism that can cause an isolation of both RHRS trains is now eliminated.

Therefore, valve power removal and its associated surveillance requirement become unnecessary. The revised TS requires only that these valves be verified open at least once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Additionally, for the second of the two in-series isolation valves in each RHRS train, verification of the open position is changed from once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> surveillance frequency for the isolation valves is consistent with that specified for the reference plant (Callaway) in the already approved WCAP-11736.

This frequency now becomes identical to the existing surveillance frequency for verifying the open position of the power operated relief valves (PORVs).

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3.0 STATE CONSULTATION

p in accordance with the Commission's regulations, the New Hampshire State official was notif.ied of the proposed issuance of the amendment. The State official-had no comments.

4.0 ENVIRONMENTAL CONSIDERATION

This amendment involves a change in a requirement with respect to the installa-tion or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and 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 Commission has previously published a proposed 1Inding that the amendment

-involves-no significant hazards consideration and there has been no public commentonsuchfinding(56FR27048). Accordingly, this amendment meets the eligibility 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 this amendment.

5.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above that (1) there is reasonable assurance that the health and safet not be endangered by operation in the proposed manner, (2) y of the public will i

such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

6.0 REFERENCES

1.

R. A. Newton, Chairman WOG, letter to NRC, dated April 22, 1988.

2.

A. Thaoani (NRC) letter to R. A. Newton, Chairman 4'0G, " Acceptance for Reference UCAp-11736, Rev. O, ' Residual Heat Removal System, Auto Closure Interlock IACl) Removal Report' in Plant Specific Submittals," dated August 8,1989.

3.

T. C. Feigenbaum (NHY), letter to NRC, dated January 24, 1991.

4 T. C. Feigenbaum (NHY), letter to NRC, dated May 16, 1991.

Principal Contributor: Dr. Harvey Albelson Date: July.15, 1991 l

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r AMENDMENT NO. 3-TO NPF-86 SEABROOK' STATION DATED ' July 15 ' 1991 DISTRIBUTION:

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