ML20059K204
| ML20059K204 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 09/11/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059K200 | List: |
| References | |
| NUDOCS 9009210216 | |
| Download: ML20059K204 (5) | |
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o UNITED STATES -
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NUCLEAR REGULATORY COMMISSION E
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,o SAFETY EVALUATION BY THE OFFICE OF' NUCLEAR REACTOR REGULATION RELATED TO AMENDNENT NO.112 TO FACILITY OPERATING LICENSE NPF-9 AND AMENDNENT NO.94 TO FACILITY OPERATING LICENSE NPF-17=
DUKEPOWERCOMPAN[
DOCKET NOS. 50-369 AND 50-370' MCGUIkE NUCLEAR STATION. UNITS 1 AND 2 1
1.0 INTRODUCTION
By letter dated July 13, 1990 Duke Power Company (the licensee) proposed -
amendments to the operating licenses for McGuire Nuclear. Station, Unite 1 and 2.
The proposed amendsents would delete a portion'of the surveillance requirements of Technical Specification (TS) 4.5.2.d regarding periodic verification that the suction isolation valvesLofLthe' Residual-Heat Removal (ND) System automatically close on a Reactor Coolant (NC) System signal les~
than or equal to 560 psig.
Issuance of. these amendeants, in effect.:authoriv.
removal of the ND Autoclosure Interlock (ACI) circuitry.'
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The ND System for each McGuire unit includes.twoL. isolation valves arranged in a
series on the inlet line between the high pressure NC; System and the lower pressure ND System. The two motor-operated gate valves are normally closed but are opened for decay heat removal purposes once NC' System' pressure and temperature I
have been reduced to about 425 psig and 350 degrees F.
Each isolation valve is' I
interlocked with one of two independent' NC System pressure signals. -One interlock prevents the valves from being opened when NC System pressure exceeds an actual plant setpoint of about 385.5 psig.- LThissinterlock and its associated TSs are not affected by the proposed amendnents. When thu valves are in'the open position, the other interlock, known as the ACI -causes'the' valves to-automatically close if NC System pressure encreases to an actual setpoint of about 530 psig. These actual setpoints of 385.51and 530 psig are conservative' relative to the corresponding lisiits of 425 and 560 psig presently specified by TS 4.5.2.d.1.
The Consission and industry have previously> recognized the safety benefits of.
removing the ACI circuitry from the ND System.. The Commission's case study on long term decay heat removal, Case Study Report AE00/C503, " Decay Heat Removal'
-Problems at U.S. Pressurized Water Reactors," December 1985, recommended that.
consideration be given to removal of the ACI circuitry to minimize loss of decay. heat removal events. The case study recognized, however, that.in view of the differences among plants, the effects of ACI removal upon plant safety would'need to be evaluated on a plant-spet.ific basis. Also, a study performed for the Commission by Brookhaven National Laboratory, NUREG/CR-5015. " Improved
. Reliability of Residual Heat ~ Removal Capability in PWRs as Related to Resolution.
9009210216 900911 PDR ADOCK 05000369 P
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. of Generic Issue 99," May 1988, listed several' improvements to reduce the risk of loss'of decay heat removal. One improvement was the removal of the ACI circuitry from ND Systems. Also,inGenericLetter(GL)88-17,"LossofDecay Heat Removal," the Commission requested that TSs that restrict or limit the 4
safet,y benefit of actions identified in GL 88-17 should be identified and that appropriate changes should be submitted. One of the items listed by GL 88-17 that could limit such sefety benefits was the ACI.
In parallel with the Commission's activities, the Westinghouse Owners Group evaluated the removal of the ACI circuitry on Westinghouse designed plants and issued WCAP-11736, " Residual Heat Removal System Autoclosu.e ' Interlock Deletion Report for the Westinghouse Owners Group " Volumcs 1 and 2, Revision 0.0,,
February 1988. WCAP-11736 documents the probabilistic analysis performed:on the removel of the ACI circuitry in terms of (1) the likelihood of an interfacing loss-of-coolant accident (LOCA), (2) ND System availability, and (3) low temperature overpressurization concerns. The results show that (1) the frequency of an interfacing system LOCA decreases with the removal of the-ACI circuitry from the ND System accompanied by the addition of a control room alarm and procedural enhancements, (2) removal of the ACI increases ND System availability, and (3) removal of the ACI from the ND System has no effect on heat-input transients, but will result in a small, but not significant, increase in the frequency of occurrence for some types of mass i' put transients with a decrease in others. The net effect of ACI deletion from the ND' System is a net-improvement in safety.
WCAP-11736 was based on four lead plants typical of the different.ND configurations and ND design characteristics among Westinghouse plants. The l
lead plant which best represents the McGuire Station'is Salem Unit 1.
WCAP-11736 also indicated that ACI removal should be accompanied by certain specific improvements.
Five specific improvements applicable to plants such as McGuire were:
(1)AnalarmshouldbeaddedtoeachNDsuctionvalvethatwillactuate if the valve is open and ND System pressure.is high.
(2)Valvepositionindicationtothealarmshouldbeprovidedandpower l
to the switches should not be affected by power' lockout of the vr.lve.
(3)ProceduralimprovementsdescribedintheWCAPshouldbeimplemented.
(4 (4) Power should be removed from the ND suction valves prior to their be'ing leak-checked, if feasible.
(5) ND suction valve operators should be sized such that'the valves cannot 3
be opened against full system pressure, i
TheWCAPalsorecormendedthatalthoughprobabilisticrisk' assessments (PRAs) i had been provided for the lead plants, sufficient PRA and safety analyses ~
should be performed on each specific plant proposing to remove the ACI to ensure that results are consistent with and support the conclusions of the WCAP.
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3-3.0 EVALVATION In support of the application for amendments, the licensee referenced WCAP-11736.
This report was approved by the Commission's staff for reference purposes August 8,1989, subject to applications on a plant-specific basis demonstrating.
j applicability of results and conclusions of the WCAP to that facility, and i
further provided that the five key improvesents in the WCAP are implemented.
Accordingly, the licensee's July 13, 1990, proposal provides analyses to demonstrate that the results and conclusions of WCAP-11/36 are valid for-1 McGuire Units 1 and 2'and describes how the improvements identified by the WCAP will be implemented at McGuire.
The licensee's submittal referenced the-results from WCAP-11736 and presented applicable McGuire information, including results of a series of evaluations.
These results take into account the impact of the removal of the autoclosure interlock (ACI) feature on the ND inlet isolation valves. The licensee concluded that implementation of the proposed design, TS and procedure changes will reduce i
the frequency of an ND overpressurization event and incrasse the ND system availability at McGuire.
The hardware changes proposed for McGuire Station will be the removal of the ACI function from the ND suction valves. The existing open permissive interlock, which has an actual setpoint of 385.5 psig, will remain intact. An alarm
-l (i.e., an annunciator in the-control room) will be added to each isolation valve which will actuate if the valve.is not fully closed (i.e., if the valve is in the "open" or " intermediate" position) and if NC pressure is above the actual setpoint. The. licensee has chosen a value of 440 psig for the alarm setpoint. The licensee has selected a setpoint-of 440 psig because this-value is well below the ND System design pressure of 600 psig and-provides adequate notification of increasing NC pressure while avoiding potential conflicting'
.l interaction with the open permissive setpoint of 385.5 psig. Valve pocition indication will be provided to the annunciator by the setor operator limit switch.
The licensee prefers use of the limit switch because it provides a direct i
position indication that is independent of the motor control circuit. Valve position indication and the NC System pressure signal are sent to the annunciators through isolation devices. This portion of.the circuit is powered by the reliable, battery-backed ~120 volt AC Vital Instrument and Control Power System.
This arrangement provides position indication to the annunciator that is unaffected by power lockout to the valves. The staff concludes that the proposed hardware changes meet the first two key plant improvements identified.
in WCAP-11736 and the associated staff SER and are acceptable.
The licensee has-identified procedural changes that will be completed and implemented by the time the ND ACI is' deleted. These include the following:
1 (1)PiantstartupproceduresandproceduresforNDSystemoperationwillbe sodified to require closure and removal of power from the ND isolation valves at the appropriate times.
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s j (2) The annunciator response procedure used during plant; startup,will be modified to reflect the alarm recognition responses for the added alars..Thei procedure will be written to direct the operator to take necessary actions to close the open ND suction valves upon actuation of the annunciator.
or else cool down to an acceptable value of NC System temperature'.
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(3) The performance procedure for-leak testing ND-System valves'will,be modified to ensure valve closure and removal.of power prior;to the leak test.
Inadditiontothehardwareandproceduralchangesdescribedabove;thelicense'e has reviewed the size and setting of the ND suction. valve's operators regarding the ability of these valves to be opened against full NC System pressure (2485-psig). The Rotork 90NA1 operators are set at maximum opening torque, and:the-valve control circuitry includes a torque switch bypass in both the open and!
closed circuits. This allows the valve actuator to provide its full torque- -
capability to the valve stem during the initial.high-load period of unseatings at. differential pressure conditions, while providing over-torque protection.
during the intermediate to full open position. The licensee finds'that the?
size'and setting of the operators could enable the ND isolation valves to open.
on full NC System pressure. However, the licensee notes that the.ND. valve's open permissive interlock (set at 385.5 psig and discussed above) prevents the i
valves from inadvertently opening during normal plant operation. ; Separate e
pressure transmitter designs made by separate manufacturers provide increased'-
assurance that common mode failures will not occur. -By procedure', both'ND suction valves will have power removed from their operators after-they are--
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closed and, thus, cannot spuriously open. The staff-agrees with the licensee-m that adequate consideration has been given for reasonable assurance thatEthe.
valve will not be opene6 when NC p~resure is excessive.
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Accordingly, the Commission's staff conchdes that r6moval of the'ACI from the McGuire ND System isolation valves, along with removal of power from the.
valves, and implementation of a reliable alarm system with, associated l training and procedures, are in accordance with WCAP-11736 as approved by3 the Cosunission-and GL 88-17. Moreover, these modifications and actions representr ' net; a
improvement in safety. Therefore, the proposed TS' changes reflecting these modifications and actions are acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
,s These amendments involve changes in requirements with respect to'the installation or use of facility components located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. The staff!has determined that the amendments involve no significant increase in the amounts, and:no' o significant change in the types, of any effluents that may be released loffsite and that there is no significant increase in individual or cumulative occupational exposure. The Commission has previously issued a proposed finding that.the' amendments involve no significant hazards consideration,.and there has.been no-public ccament on such finding. Accordingly, the amendments meet 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 L
need be prepared in connection with the issuance of these anendments.
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5.0 CONCLUSION
The Comission's proposed determination that the amendments involve no siorificant hazards consideration was published-in the Federal Relister (55FR32326)onAugust8,1990. The Comission consultea with tie state of North Carolina. No public comments were received, and the state of North Carolina did not have any comunents.
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and r,afety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of these amendments will not be inimical to the cossen defense and security or<
to the health and safety of the public, i
i Principal Contributors:
D. Hood, PDill-3/DPR-I/II M. McCoy, SRXB Dated: September 11, 1990 i
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zi DATED:
Sent#mhnr 11. 1000 AMENDMENT NO.112TO FACILITY-OPERATING t.ICENSE NPF McGuire _ Nuclear Station, Unit 11 AMENDMENT NO. ' 94I0' FACILITY; OPEPATING'clCENSE NPF McGuire Nuclear Station,. Unit-2.-
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DISTRIBUTIO(:-
1 "9edietTileM NRC & Local PDRs' PDII-3 Reading File D. Matthews G. Lainas R.-Ingram D. Hood
- OGC D.n. Hagan E.' Jordan-1 G.11111 a
Wanda Jones i
J. Calvo R. Jones ACRS(10)
GPA/PA OC/LFMB-McGuire P' ant File n
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-Mr. H B. Tucker '
4 A copy of the related Safety Evaluation supporting these amendments is enclosed.
Notice of issuance of amendments will be included in the Commission's biweekly,
Federal Register notice.
Sincerely,
/$
j Darl Hood, Project Manager-Project Directorate 11-3 Division of Reactor Projects 1/II Office of Nuclear Reactor Regulation t
Enclosures:
1.
Amendment No.112 to NPF-9 2.
Amendment No. 94 to NPF-17 3.
Safety Evaluation cc w/ enclosures:
See next page LA:PDII-3,
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