L-83-246, Forwards Response to Generic Ltr 83-10D Re NRC Criteria for Resolution of TMI Action Item II.K.3.5, Automatic Trip of Reactor Coolant Pumps. Reactor Coolant Pumps Will Be Tripped Following Small Break LOCA

Forwards Response to Generic Ltr 83-10D Re NRC Criteria for Resolution of TMI Action Item II.K.3.5, Automatic Trip of Reactor Coolant Pumps. Reactor Coolant Pumps Will Be Tripped Following Small Break LOCA

ML17345B055
Person / Time
Site:	Turkey Point
Issue date:	04/20/1983
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
TASK-2.K.3.05, TASK-TM GL-83-10D, L-83-246, NUDOCS 8304260489
Download: ML17345B055 (18)

Text

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05000251 AUTH INANE AUTHOR AFFILIATION UHRIGi'R ~ E ~

Florida (Power 8.Light Co,

'RE'CIP ~ NAME RECIPIENT AFFILIATION

.,EISENHUTiDBG ~

Division of Licensin'9

SUBJECT:

Forwards r esponse to Gener ic Ltr 83-10d re NRC crijteria for resolution of TMI Act.ion Item. II,K3'i,"Automatic Trip of Reactor

<<Coolant '.Pumps," <<Reactor'oolant:pumps

'will be tripped following "small 'break LOCA ~

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P OX 14000, JUNO BEACH, FL 3340B FLORIDAPOWER & LIGHT COMPANY Office of Nuclear Reactor Regulation Attention:

Mr. Darrell G. Eisenhut, Director Division of Licensing U.S.

Nucle'ar Regulatory Commission Washington, D.

C.

20555 April 20, 1983 L-83-246

Dear Mr. Eisenhut:

Re:

Turkey Point Units 3 5 4 Docket No. 50-250 8 50-251 Post-TMI Requi rements Automatic Trip of Reactor Coolant Pumps Generic Letter No.83-10d Generic Letter No.83-10d dated February 8,

1983 contained the NRC criteria for resolution of TMI Action Item II.K.3.5, "Automatic Trip of Reactor Coolant Pumps".

Florida Power 8 Light Company is a member of the Westinghouse Owners Group.

The attachment to this letter contains the Owners Group and Florida Power 5 Light Company's plan for resolution of this item.

Very truly yours, Robert E. Uhrig Vice President Advanced Systems 8 Technology REU/PKG/js Attachment cc:

Mr. James P. O'Reil ly, Region II Mr. Harold F.

Rei s, Esquire 8304260489 830420 PDR ADGCK 05000250 P

PDR PEOPLE... SERVING PEOPLE

ATTACHMENT PLAN FOR RESOLUTION OF TMI ACTION ITEM II.K.3.5 "AUTOMATIC TRIP OF REACTOR COOLANT PUMPS" INTRODUCTION The criteria for resolution of TMI Action Plan Item II.K.3.5, "Automatic Trip of Reactor Coolant Pumps" were stated in. letters from Mr. Darrel G. Eisenhut of the Nuclear Regulatory Commission to all Applicants and Licensees with Westinghouse designed Nuclear Steam Supply Systems (83-10 c and d) dated February 8, 1983.

The following represents the plan for demonstrating com-pliance with those criteria.

In order to avoid confusion, the overall philosophy and plan will first be stated.

Then, each section of the attach-ment to NRC letters 83-10 c and d will be addressed as to how the overall plan responds to each NRC criteria.

OVERALL PLAN In the four years. that have passed since the event at Three Mile Island,

~

Westinghouse and the Westinghouse Owners Group have held steadfastly to several positions relative to post accident reactor coolant pump (RCP) operation.

First, there are small break LOCAs fov. which delayed RCP trip can result in higher fuel cladding temperatures and a greater extent of zircalloy-water reaction.

Using the conservative evaluation model, analyses for these LOCAs result in a violation of the Emergency Core Cooling System (ECCS) Acceptance Criteria as stated in 10CFR50.46.

The currently approved Westinghouse Evaluation Model for small break LOCAs was used to perform these analyses and found acceptable for use by the NRC in letters 83-10 c

and d.

Therefore, to be consistent with the conservative analyses per-formed, the RCPs should be tripped if indications of a small break LOCA exist.

Secondly, Westinghouse and the Westinghouse Owners Group have always felt that the RCPs should remain operational for non-LOCA transients and accidents where their operation is beneficial to accident mitigation and recovery.

This position was taken even though a design basis for the plant is a loss of off-site power P1an.t safety is demonstrated in the Final Safety Analysis Reports for all plants for all transients and accidents using the most conservative assumption for reactor coolant pump operation.

In keeping with these two positions, a low RCS pressure (symptom based)

RCP trip criterion was developed that provided an indication to the operator to trip the RCPs for small break LOCA but would not indicate a need to trip the RCP for the more likely non-LOCA transients and accidents where continued RCP operation is desirable.

The basis for this criterion is included in the

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generic Emergency

Response

Guideline (ERG) Background Document (E-0 Basic Revision, Appendix A).

Relevant information regarding the expected results of using this RCP trip, criterion can be derived from the transients which resulted from the stuck open steam dump valve at North Anna in 1979, the

. steam generator tube rupture at Prairie Island in 1980 and the steam generator tube rupture at Ginna in 1982.

The RCPs were tripped in all three cases.

However, a study of the North Anna and Prairie Island tran-sients indicated that RCP trip would not have been needed based on the application of the ERG trip criterion.

The Ginna event, however, indicated a need to review the basis for the RCP trip criterion to allow continued RCP operation for a steam generator tube rupture for low head SI plants.

Thirdly, it has always been the position of Westinghouse and the kestinghouse Owners Group that if there is doubt as to what type of transient or accident is in progress, the RCPs should be tripped.

Again, the plants are designed to mitigate the effects of all transients and accidents even without RCP operation while maintaining a large margin of safety to the public.

The existing emergency operating procedures reflect this design approach.

Lastly, it remains the position of Westinghouse and the Westinghouse Owners Group that RCP trip can be achieved safely and reliably by the operator when required.

An adequate amount of time exists for operator action for the small break LOCAs of interest.

The operators have been trained on the need for RCP trip and the emergency operating procedures give clear instructions on this matter.

In fact, one of the initial operator activities is to check if indications exist that warrant RCP trip.

Westinghouse and the Westinghouse Owners Group will undertake a two part pro-gram to address the requirements of NRC letters 83-10 c and d

based on the aforementioned positions for the purpose of providing more uniform RCP trip criteria and methods of determining those criteria.

In the first part of.

the program, revised RCP trip criteria will be developed which provides an indication to the operator to trip the RCPs for small break LOCAs requiring such action but will allow continued RCP operation for steam generator tube

ruptures, less than or equal to a double-ended tube rupture.

The revised RCP trip criteria will also be evaluated against other non-LOCA transients and accidents where continued RCP operation is desirable in order to demon-strate that a need to trip the RCPs will not be indicated to the operator for the more likely cases.

Since this study is to be utilized for emergency response guideline development, better estimate assumptions will be applied in the consideration of the more likely scenarios.

The first part 'of the program will be completed and incorporated into Revision 1 of the Emergency

Response

Guidelines developed by Westinghouse for the Westinghouse Owners Group.

The scheduled date for completion of Revision 1 is July 31, 1983.

The second part of the program is intended to provide the required justifi-cation for manual RCP trip.

This part of the program must necessar'ily be done after the completion of the first part of the program.

The schedule for completion of the second part of the program is the end of 1983.

The preferred and safest method of pump operation following a small break LOCA is to manually trip the RCPs before.significant system voiding occurs.

P I

No attempt will be made in this program to demonstrate the acceptability of continued RCP operation during a small break LOCA.

Further, no request f'r an exemption to 10CFR50.46 will be made to allow continued RCP operation during a small break LOCA.

DETAILED RESPONSE TO NRC LETTERS 83-10 C AND D Each of the requirements stated in the attachment to HRC lette> s 83-10 c and d will now be discussed indicating clearly how they will be addressed.

The organization of this section of the report parallels the attachment'o NRC letters 83-10 c and d.

I.

Pump Operation Criteria Which Can Result in RCP Trip During Transients and Accidents.

1.

Set oints for RCP Tri The Westinghouse Owners Group response to this section of require-ments will be contained in Revision 1 to the Emergency

Response

Guidelines scheduled for July 31, 1983.

a)

As stated

above, Westinghouse and the Westinghouse Owners Group are developing revised RCP trip criteria which will assure that the need to trip the RCPs will be indicated to the operator for LOCAs.where RCP trip is considered necessary.

The criteria will also ensure continued forced RCS flow for:

1) steam generator tube rupture (up to the design bases, double-ended tube rupture) 2)

the other more likely non-LOCA transients where forced circulation is desirable (e.g.,

steam line breaks equal to or smaller than 1 stuck open POR~I)

NOTE:

Event diagnosis will not be used.

The criteria developed will be symptom based.

The criteria being, considered for RCP trip are:

1)

RCS wide range pressure

< constant 2)

RCS subcooling

< constant 3).

Wide range RCS pressure

< function of secondary pressure Instrument uncertainties'will be accounted for.

Environ-mental uncertainty wi"ll be included i'f appropriate.

II tt

4 No partial or staggered RCP trip schemes will be considered.

Such schemes are unnecessary and increase the requirements for

training, procedures and decision making by the operator during transients and accidents.

b)

The RCP trip criteria selected will be such that the operator will be instructed to trip the RCPs before voiding occurs at tne RCP.

c)

The criteria developed in Item la above is not expected to lead to RCP trip for the more likely non-LOCA and SGTR transients.

However, since continued RCP operation cannot be guaranteed, the emergency response guidelines provide guidance for the use of alternate methods for depressurization.

d)

The Emergency

Response

Guidelines contain specific guidance for detecting, managing and removing coolant voids that result frcm

- flashing.

The symptoms of such a situation are described in these guidelines and in detail in the background document for the guidelines.

Additional ly, explicit guidance for operating the plant with a vaporous void in the reactor vessel head is provided in certain cases where such operation is needed.

The upgraded Emergency Operating Procedures for Turkey Point Units 3 and 4

will reflect the specific guidance contained in the Westinghouse Owners Group's Emergency

Response

Guidelines concerning system voiding.

All licensed personnel will be trained in the use of the upgraded Emergency Operating Procedures pr ior to their impel ementati on.

e)

Operators are provided with information concerning the restoration of reactor coolant pump auxiliary water services in the upgr aded Emergency Operating Procedures.

This includes events where both component cooling water and seal injection water have pr ev i ou sl y b een 1 os t.

f)

Discussed in la and 1c.

2.

Guidance for Justification of Manual RCP Trip The Westinghouse Owners Group response to this section of requirements will be reported separately at the end of 1983.

Florida Power

& Light will finalize its technical justification for treatment of reactor coolant pumps based on the Westinghouse Owners Group report.

A response to this report will be given shortly after the Westinghouse Owners Group report evaluation is complete.

0 a) b)

A significant number of analyses have been performed by Westinghouse for the Westinghouse Owners Group using the currently approved Westinghouse Appendix K,Evaluation Model for small break LOCA.

This Evaluation Model uses the WFLASH Code.

These analyses demonstrate for small break LOCAs o7 concern, if the RCPs are tripped 2 minutes fo')lowing the onset of reactor conditions correspondi ng to the RCP trip setpoi nt, the predicted transient is nearly identical to those presented in the Safety Analysis Reports for all Westinghouse plants.

Thus, the Safety Analysis Reports for all plants demonstrate ccmpliance with requirement 2a.

The analyses performed for the Westinghouse Owners Group will be used to demonstrate the validity of this approach.

Better estimate analyses will be performed f'r a limiting Westinghouse designed plant using the WFLASH computer code with better estimate assumptions.

These analyses wi1 1 be used to determine the minimum time available for operator action for a r ange of break sizes such that the ECCS acceptance criteria of 10 CFR 50.46 are not exceeded.

It is expected that the minimum time available for manual RCP trip will exceed the guidance contained in N660.

This will justi fy manual RCP trip for all plants.

3)

Other Considerations a)

Turkey Point recognizes that some pressure transmitters used for reactor coolant system pressure indication are not lE qualified.

Therefore, the reactor 'coolant pump trip setpoint has been selected based on possible instrument error, while maintaining sufficient subcooling margin.

There are a total of six pressure indications available to the reactor operator in the control roan.

In addition, there is a

pressure transmitter outside containment that gives high head safety injection pr essure indication in the control rocm.

High head safety injection, with flow, occurs at the reactor coolant pump trip setpoi nt.

It is emphasized that thi s pressure transmitter is outside the containment and is thus protected from the hostile LOCA enviroreent.

All licensed operators have been instructed on the use of this instrumentation and the redundancy of information available to them.

The Emergency response Guidelines contain guidance for the timely restart of the reactor coolant pumps when conditions which will support safe pump start-up and operation are established.

The Turkey Point upgraded Emergency Operating Procedures will contain guidance for the timely restart of reactor coolant pumps when conditions are established which support the safe restart and operation of the pumps.

ik

c)

The training program at Turkey Point instructs reactor operators in their responsibility for performing reactor coolant pump trip in the event of a small break. LOCA.

Operators are trained in prioritization of actions following safeguards actuation.

This training includes both classroom and simulator instruction.

II.

Pump Operation Criteria Which Will Not Result in RCP Trip During Transient and Accidents.

The preferred and safest method of operation following a small break LOCA is to manually trip the RCPs.

Therefore, there is no need to address the criteria contained in this section.

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STATE OF Fl OR1DA

)

)

ss.

COUNTY OF PALM BEACH )

Robert E. Uhri being first duly sworn, deposes and says:

That he is Vice President 'f Florida Power 8 Light Company, the Licensee herein; That he has executed the foregoing document; that the statements made in this document are true and correct to the best of his knowledge, information, and belief, and that he is authorized to execute the document on behalf of said Licensee.

Robert F. Uhrig Subscribed and sworn to before me this day of 198&.

V

--- NOTARY.-d.-,UBLIC, in and for the County

, ""of Palm.Beach, State of Florida.

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..., wdte of Ronde at Large My Coinm'ection Expires October 30, 1983 My commission expires:

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