ML20215G134

Accepts Util 860502 & 0625 Requests for Mod of RHR Sys Alarm Logic to Allow Alarm Only If Either Suction Valves 8702A or 8701B Open Above Interlock Setpoints

ML20215G134
Person / Time
Site:	Wolf Creek
Issue date:	10/14/1986
From:	Oconnor P Office of Nuclear Reactor Regulation
To:	Koester G KANSAS GAS & ELECTRIC CO.
References
NUDOCS 8610200085
Download: ML20215G134 (4)

Text

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CocLEt No. 50-482 1 4 OCT 1386 Mr. Glenn L. Koester ~

Vice President - Nuclear Kansas Gas and Electric Company 201 North Market Street Post Office Box 208 Wichita Kansas 67201

SUBJECT:

LOW TEMPERATURE OVER PRESSURE PROTECTION By letter dated May 22,1985 you proposed to add an alam circuit to RHR ~ '

system suction valves 8702A and 8701B. According to the logic of that circuit if any one of the two valves is either open or has no power to its operator and the reactor coolant system (RCS) pressure has reached or exceeded the valve interlock activation setpoint of 682 psig, an alam will sound in the control room. These alams will provide assurance that the RHR system is properly isolated from the RCS suction relief valves for low temperature over pressure protection. The staff has reviewed the above proposed alam circuit and by letter dated August 16, 1985, concluded that it is acceptable..

Subsequently, during the course of completing the detailed design of this alarm circuit you became aware of a design conflict with the existing plant procedures.

By normal operating procedures and in satisfaction of another staff position the plant operator is required to close all RHR suction isolation valves and remove their power before the RCS is pressurized to operating conditions.

Although the RHR valves are now closed, when the RCS pressure is at or above the interlock activation setpoint the alam will be activated and cannot be cleared since one of its conditions is continuously satisfied, i.e., the operators of valves 8702A and 8701B have their power removed. In order to remedy this situation, KG8E proposed, by letter dated May 2,1986 and a supple-ment dated June 25, 1986, to modify the alam logic so that it will alam only if either of the above two valves is open above the interlock setpoint. Valve i position indications will receive their signals from contacts on the limit switch rotor internal to the valve actuator. Power to these signals will be provided by the annunciator system power supply. A diverse alam is provided by the computer annunciator.

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The other two RHR suction isolation valves, 8702B and 8701A, continue to be interlocked independently. If open, these valves close automatically if the pressure setpoint of 682 psig is reached or exceeded. Since the proposed modification provides alanns if any of the subject valves were left inadvertently open, which is that same function as that of the originally proposed alarm circuit, this staff concludes that the proposed modification is acceptable.

Sincerely, Paul W. O'Connor, Project Manager PWR Project Directorate #4 Division of PWR Licensing-A cc: See next page 0

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] 1 4 00 N The other two RHR suction isolation valves, 8702B and 8701A, continue to be interlocked independently. If open, these valves close automatically if the pressure setpoint of 682 psig is reached or exceeded. Since the proposed modification provides alarms if any of the subject valves were left inadvertently open, which is that same function as that of the originally proposed alarm circuit, this staff concludes that the proposed modification is acceptable.

Sincerely, Paul W. O'Connor, Project Manager PWR Project Directorate #4 Division of PWR Licensing-A cc: See next page nMTpimtg

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Mr. Glenn L. Koester Wolf Creek Generating Station Kansas Gas and Electric Company Unit No. 1.

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Mr. Nicholas A. Petrick Mr. Gary L. Haden Director Executive Director, SNUPPS 5 Choke Cherry Road Research & Energy Analysis I Rockville, Maryland 20850 Kansas Co.rporation Commission '

4th Floor - State Office Building Jay Silberg, Esq. Topeka, Kansas 66612-1571 Shaw, Pittman, Potts & Trowbridge 2300 N Street, NW Regional Administrator, Region IV Washington, D.C. 20037 U.S. Nuclear Regulatory Comission Office of Executive Director for Operations l Mr. Donald T. McPhee l 611 Ryan Plaza Drive, Suite 1000 Vice President - Production Arlington, Texas 76011 Kansas City Power & Light Company 1330 Baltimore Avenue Mr. Allan Mee -

i Kansas City, Missouri 64141 Project Coordinator Chris R. Rogers, P.E. Kansas Electric Power Cooperative,Inc.

Manager, Electric Department P. O. Box 4877 Gage Center Station.

Public Service Comission Topeka, Kansas 66604 P. O. Box 360 Jefferson City, Missouri 65102 Resident Inspector / Wolf Creek NPS t

' Regional Administrator, Region III c/o U.S. Nuclear Regulatory Comission U.S. Nuclear Regulatory Comission P. O. Box 311 Burlington, Kansas 66893 799 Roosevelt Road Glen Ellyn, Illinois 60137 Mr. Brian Moline Chief Legal Counsel Brian P. Cassidy, Regional Counsel kansas Corporation Comission Federal Emergency Management Agency Region I 4th Floor - State Office Building Topeka, Kansas 66612-1571 J. W. McCorinack POCH Boston, Massachusetts 02109 Senior Resident Inspector / Wolf Creek NPS Mr. Robert Elliot, Chief Engineer c/o U.S. Nuclear Regulatory Comission P. O. Box 311 Utilities Division Burlington, Kansas 66839 Kansas Corporation Comission 4th Floor - State Office Building Topeka, Kansas - 66612-1571 Mr. Gerald Allen Public Health Physicist Bureau of Air Quality & Radiation Control Division of Environment

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Kansas Department of Health and Environment Forbes Field Building 321 Topeka, Kansas 66620

4 KANSAS CAS AND ELECTRIC COMPANY

,i em eacrac ecwmv June 25, 1986 GLENN L MOESvEm

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Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Cm mission Washington, D.C. 20555 EMLNRC 86-116 Re: Docket No. STN 50-482 Ref: Intter EMIRRC 86-071 dated S/2/86 from GLKoester, KG&E, to HRDenton, NRC '

Subj: Iow Tenperature Overpressure Protection

Dear Mr. Denton:

' Wis letter corrects a discrepancy in the description of the low tenterature overpressure protection (LTOP) alarm circuitry as outlined in the referenced letter.

%e design described in' the referenced letter provides new alarm circuits to valves BB-W-8702A and FJ-HV-8701B such that if the interlock setpoint is reached and either valve is open an alarm will initiate on the main control board. W e referenced letter states that valve position for BB- W-8702A and EJ-HV-8701B will be derived "directly from valve stem mounted limit switches". However, the design utilizes a contact on the limit switch rotor internal to the valve actuator for valve position in31 cation. mis discrepancy does not change the function of the alarm circuitry as previously described.

If you have any questions concerning this subnittal, plasse contact me or Mr. O. L. Maynard of my staff.

Very truly yours, Glenn L. Koester Vice President - Nuclear GLK:see $

cc: PO'Connor (2)

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= = ~ = ~m a May 2, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Comission Washington, D.C. 20555 RMLNRC 86-071 Re: Docket No. STN 50-482 Ref: 1)Ietter RMLNRC 85-122 from GLKoester, KG&E, to HRDenton, NRC, dated 5/22/85 -

2)Ietter from BJYoungblood, NRC, to GLKoester, KG&E, dated 8/16/85 Subj: Low Teperature Overpressure Protection

Dear Mr. Denton:

his letter describes a modification to the design of low tenperature overpressure protection (L'IOP) alarm circuitry described in Reference 1. A schedule for inplementation of this nodified design is also provided.

Reference 1 proposed reliance on existing Technical Specifications and administrative controls with the addition of alarm circuits on certain RHR/BCS suction isolation valves for LTOP. As the alarm circuit was proposed, if either valve BB-W-8702A or EJ-HV-8701B is open or does not have power available and the pressure interlock activation setpoint is reached, an alarm would annunciate in the control room. We NRC approved this design in Paference 2.

During the developnent of the installation package, it was determined that the design proposed in Referen::e 1 would perform its intended function, but would produce alarms that could not be cleared even with correct valve aligment. Wis is because the alarms would be generated above the closure i

interlock activation setpoint of 682 psig when power was removed from BB-W-l 8702A as procedurally required. In order to remedy this situation, Kansas Gas and Electric Capany (KG&E) proposes modified alarm circuits which will alarm if either valve BB- W-8702A or EJ-HV-6701B is open at pressures above the interlock setpoint. A single annunciator window will represent these  ;

two alarm circuits, but they will be alarmed individually on the Balance of '

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201 N. Market - Wichtra, Kanses - Mac Address:RO. Box 206 I nicNta, Kansas 67201 - kephone: Area Code (316) 261-6451

l Mr. H.R. Denton KMWRC 86-071 Page 2 '

May 2, 1986 Figure 1 outlines the design as described in Reference 1 and the modified design. 'Ihe modified alarm circuits do not affect the analysis provided in Reference 1 with regard to conpliance to Standard Review Plans 5.2.2 and 5.4.7 and the corresponding Branch Technical Positions RSB 5-2, and RSB 5-1.

'Ihe valve position inputs for the alarms in the modified circuit come directly from valve stem mounted limit switches rather than from the motor control center inputs as in the previous design. 'Ihe modified circuit continues to provide annunciation in the control room for misaligned valves once the interlock setroint is reached. An alarm response procedure will direct the operator to verify valve closure upon receipt of this alarm.

'Ihe modified design requires new cables to be run- to the valves in containment and requires an outage to conplete. Inplementation of this modification refueling which is scheduled to be empleted prior to startup following is currently planned to begin October 9, 1986. the schedule for inplementation of the modified design is consistant with that outlined in Wolf Creek Generating Station SSERS Section 5.2.2.

If you have any questions concerning this subnittal please contact me or Mr.

O. L. Maynard of my staff.

Very truly yours, Glenn L. Koester GLK:see Vice President - Nuclear i

Enclosure cc: PO'Connor (2)

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e FIGURE 1 .

I Present NRC Approved Design .

(Ref: KMLNRC 85-122) Modified Design BB-PV-8702A or BB-PV-87E2A or EJ-HV-8791B EJ-HV-8701.B 682 psig l OPEN* No Power OPEN** Interlock Setpoint l

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i j 682 psig Interlock Setpoint Conn on Annunciator

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• Position provided by auxiliary relay at MCC

• • Position provided by valve stem mounted limit switches i

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Docket No.: 50-482 Mr. Glenn L. Koester

-Vice President - Nuclear Kansas Gas and Electric Company 201 North Market Street Post Office Box 203 Wichita, Kansas 67201 ~

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Subject:

Wolf Creek - Low Temperature Overpressure Protection The staff has completed its review of your May 22, 1985 submittal regarding p(LTOP) system and procedures.roposed Thetstaff findsmodifications to the plant's that these modifications Low Tempera along iois Uie plant's Technical Specifications provide and adequate LTOP system that meets staff positions.

Accordingly, the staff finds that the submittal requirement of License Condi-tion 2.C.(13) has been met. A copy of the related Safety Evaluation is enclosed.

In addition, we have also enclosed h copy of.the staff's safety evaluation related to the removal of one 345 kV offsite transmission line between Wolf Creek and the West Gardner switching station. This evaluation which was docketed by staff memorandum dated March 14, 1984 is provided for your

. infomation.

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Sincerely, f,. N For B. J. Youngblood, Chief Licensing Branch No. I Division of Licensing

Enclosures:

1. Safety Evaluation Re: Low Temperature Overpressure Protection

2. Safety Evaluation Re: Design Change in -

the Wolf Creek Offsite Power Systein cc: See next page I I ,

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ENCLOSURE

~SAFETY EVALUATION 30LF CREEK GENERATING STATION \

J DOCKET.NO. 50 482

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_kHRS LTOPS MODIFICATION .

Introduction The staff has imposed the followl6g license conditions on the owner of the Wolf Creek nuclear plant, the Kansas Gas & Electric (KG&E) Company: '

13) Low Temperatree Overpressure Protection (Section 15 SSER #3) .

By June 1,1985, KG&E shall submit for NRC review and approval a description of equipment modifications to the residual heat removal system (RHRS) suction isolation valves and to closure circuitry which conform to the applicable staff requirements (SRP 5.2.2).

Within one year of receiving NRC approval of the modifications, KG&E

_ shall have the approved modifications installed. Alternately, by June 1,1985, KG&E shall provide acceptable justifications for.

, reliance on adeinistrati've mean,s alone to meet the staff's RHRS

" isolation requirements; or otherwise, propose changes to Appendix A to this license which remove reliance on the RHRS as a means of low temperature overpressure protection.

To resolve t: .aove license condition, KG&E submitted for staff review certain system and pr::edural modifications by a letter from G. L. Koester, KG&E Company to H. R. Denton, NRC, dated May 2R, 1985. These modifications.are described and evaluated below.

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For the low temperature overpressure protection (LTOP)'of the Reactor Coolant l 1

System (RCS), the plant relies on eMer two power operated relief valves '

l (PORVs) or two residual heat removal (RHR) suction relief valves. The RHR relief valves are located at the suction of the RHR pumps downstream of the RHR

. . l suction valves. The two RHR p6mpt take suction separately from the RCS via two 1 motor operated valves (MOVs) in series.(see attached schematic). The MOVs  ;

closesttopumpsAand5are8701Aand8701Brespectively. The MOVs closest to the RCS are 8702A and 8702B. Both MOVs 8701A and B receive their auto close interlock signal from a single pressure transmitter, while the other two MOVs  !

8702 A and B receive their signal from another pressure transmitter.

The Wolf Creek Technical Specifications (TS) restrict plant operation when the l

reactor coolant is 368'F or colder, such that no more than one centrifugal l charging pump may inadvertently start, and such that an idle reactor coolant pump may not be started if the steam generator water temperature is more than-50*F hotter than that of the reactor coolant.

- l When the LTOP protection to the plant is provided by the RHR suction relief valves, all four RHR suction MOVs are opened to provide the required redundancy of the pressure relieving capacity. However, a single failure in one pressure

, transmitter could actuate the auto close interlock, thus isolating both RHR l trains, causing an everpressure event by the loss of the letdown flow, and I defeating the LTOP protection. To eliminate this single failure and render the LTOP a single-failure proof system KG&E proposes the following.

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• On decraasing RCS temperature and pressure to the RHRS entry conditions, when relying on RHRS for LTOP protection, the licensee proposes to open the four suction MOVs, then remove and lock out the power to NOVs 8702 A and 8701 B.

Valve opening and power removal are specified in the plant's Technical Specifi-cations.

Removing power to these two valves (defeating the interlocks) not only protects the RCS from single faliu're causing isolation of both RHRS suction relief ,

valves (loss of LTOPS), but also provides protection for both RHR pumps, when in operation, from a loss of suction due to a single pressure transmitter failure. Inadvertent isolation of the RHR suction valves has been a concern at other plants and has resulted in damage to a RHR pump.

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On increasing pressure and temperature in addition to the nortial RHRS isolation procedures, KG&E proposes to add the following:

(a) . Administrative procedures to verify that power is restored to valves 8702A and 8701B and the valves are closed prior to exceeding the RHRS suction relief setpoint (this administrative procedure has already been implemented at the plant).

(b) Add an alarm circuit to the valves with the power locking feature, namely 8702A and 8701B, such that if any of these valves are open or do not have power available and the interlock activation setpoint is reached, the alarm would initiate on the main control board. If

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the alars initiates an annunciator alarm response, procedure wo01d require closing or verifying closure of the affected RHR suction isolation valves.

The existing auto close interlock has no visual indication in the control roora (other than valve position in'dication). Therefore, if a signal is generated to close the valve and the valve fails to close, the operator would not be alerted.

With the addition of the proposed alam circuit, if the valve is open or if ,

power is not available and the pressure setpoint is reached, an alarm is generated in the control room giving the operator positive indication. There-fore, protection is afforded if the operator fails to restore power or if the interlock actuates and the valve fails to close. Addition' ally, alarm response procedures would provide positive operator actions.

On increasing pressure and temperature,' if both series suction MOVs in one or

, more RHR trains were inadvertently left open, it would be difficult to continue pressurization. Furthermore, it would be highly unlikely for such a situation to go undetected during a normal startup due to indications such as relief valves lifting, pressurizer relief tank level, and pressure and temperature l alarms. These indications wou' 1 d alert the operator to take action to rectify '

the situation. If the reactor system pressure rises to the intericek setpoint l

despite the relief valve lifting, the operator would be alerted by an alarm.

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If only one suction MOV is inadvertently left open while the other series MOV is closed, then when the reactor system pressure rises to the interlock set-point the open valves would be closed by the auto-close interlock anS an alarm would sound in the control room.

With respect to the ability to'i' blate s the RHR system, should there be a break in the RHR system or a stuck open safety valve, it should be noted that one valve in each flowpath will have power available. Therefore, the operators ,

will retain the ability to isolate the system should the need arise.

Conclusion The staff has reviewed the licensee's proposed system and procedural modifica-tions to the Wolf Creek LTOP system and has reviewed the plant's Technical Specifir.ations and concludes.that in light of the plant's TS these modifica-tions are acceptable and that the LTO.P reliance on the RHRS suction relief valves meets the intent of the Standard Review Plan sections 5.2.2 and 5.4.7 and their associated Branch Techni' cal Positions 5-2 and 5-1 respectively.

Therefore, we conclude that the requirements of License Condition (13) have been met.

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