ML20247R738

Forwards Response to NRC Bulletin 88-007, Power Oscillation in Bwrs, & Revised Response to Suppl 1 for Plant.Licensed Reactor Operators & Shift Technical Advisors Thoroughly Briefed on LaSalle Event Described in Bulletin

ML20247R738
Person / Time
Site:	Limerick
Issue date:	03/31/1989
From:	Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-007, IEB-88-7, NUDOCS 8904100046
Download: ML20247R738 (8)

Text

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.._ l PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET j

-3 l P.O. BOX 8699 PHILADELPHIA A. PA.19101 (215)841 45oo JOHN S. KEMPER ssNion vics.pnasIDENT NUCLE Aa March 31, 1989 U. S. Nuclear Regulatory Ccmnission Docket No. 50-353 Attn

Document Control Desk .)

Washington, DC 20555 ] 1

-1

Subject:

Limerick Generating Station, Unit 2 l Response to NRC Bulletin tb. 88-07 and Revised Response to NRC Bulletin No. 88-07, Supplement 1

Reference:

Philadelphia Electric Company Letter to the NRC,.

dated March 7,1989, responding to NRC Bulletin No. 88-07, Supplement 1.

Gentlemen:

Philadelphia Electric Company's response to NRC Bu11etin.88-07,

" Power Oscillations in Bolling Water Reactors" and revised response to.

Supplement No. 1 for Limerick Generating Station, Unit 2 is provided in the attachment.

If you have any questions, or require addltlonal information, please do not hesitate to contact me.

Sincerely, M

ERG /esb/03278901 Attachment Copy to: T. J. Kenny, LGS Senior Resident Inspector W. T. Russell, Region 1 Administrator i fh' I I

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1 8904100046 890331 i PDR ADOCK '05000353 1 o PDC i

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bec: C. A. McNelli - S26-1 S. J. Kowalski - S25-1 E. J. Bradley - 523-1 L. B. Pyrlh - N2-1 E. P. Fogarty - S7-1 l J. M. Madara, Jr. - S7-1 G. A. Hunger, Jr. - N7-1 ,

A. J. Marie - N2-1  !

H. D. Honan - N2-1 l D. P. Helker 1 G. M. Leitch - LGS /MC 200 P. J. Duca, Jr. - LGS /MC AS-1 j C. R. Endriss - LGS /MC A2-2 A. S. MacAinsh - LGS /MC 583-4 W. T. Ullrich - LGS-MC 58 T. E. Shannon - N2-1 ,

R. M. Krich - S7-1 l D. B. Fetters - N4-1 M. S. Iyer - BPC/SF l DAC (NG-8) l l

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BULLETIN 88-07 POWER OSCILLATIONS IN BWRS IbRRDDUCTION Bulletin 88-07, " Power Oscillations in BWRs", describes an unanticipated event at LaSalle in which excessive neutron flux oscillations resulted while the plant was in natural circulation after

a. dual recirculation punp trip. Three actions that nust be taken by BWR Licensees to ensure that correct operator action can and will be taken in the event of uncontrolled power oscillations are' described in 'this bulletin, and are restated prior to the response for each action. The details of conpliance with the requested actions are presented In'the following sections.

LICENSED REACTOR OPERATOR AND SHIFT TECHNICAL ADVISOR BRIEFING Required Action:

" ...BWR licensees should ensure that any licensed reactor 1) operator or Shift Technical Advisor performing shift duties has been thoroughly briefed regarding the March 9,1988-LaSalle, Unit 2 event."

Response

The licensed Reactor Operators and Shift Technical Advisor--(STAS) have been thoroughly briefed on the LaSalle event describeo in Bulletin 88-07.

ADEQUACY OF PROCEDURES AND OPERATOR TRAINING PROGRAMS Required Action:

2) "., BWR licensees sb "d verify the adequacy of their procedures and operocr. training prograns to ensure that all licensed operators anu shift Technical Advisors are q cognizant of: i l

a. those . plant conditlans which nay result in the i Initiation of uncontrolled poner oscillations, b.- actions which can be taken to avoid plant conditions l which nay result in the initiation of uncontrolled  ;

power oscillations, _.

c. how to recognize the onset of uncontrolled power oscillations, and

d. actions which can be taken In response to uncontrolled  !

power oscillations, including the need to scram the reactor if oscillations are not promptly terminated."

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Response

l Applicable procedures and operator training prograns vere reviewed to I verify their adequacy. The three conditions that nay result in uncontrolled power oscillations are: 1) as a result of a recirculation punp(s) trip, 2) during startup and shu+,down, and 3) rod ,

sequence exchanges. Each of the three areas of potential Instability {

delineated above are avoided by procedure or Reactor Engineering l practice at Linerick Generating Station (LGS). Also, startup testing in Test Condition 4 (as described in the LGS Final Safety Analysis )

Report, Chapter 14) will be conducted during the initial startup of j

LGS Uni t 2. This testing is specifically Intended to identify any concerns with transients of this type and any possible resulting instabilities.

k Recirculation Pump Trip Condition j

The nost probable event that could result in a high power / low flow situation is a trip of one or both recirculation pumps. Procedure  !

OT-112, Recirculation Pump Trip, specifically provides an innediate operator action to drive in rods per Reactor Maneuvering Shutdown Instructions to reduce power to less that 35% rated thernal power. In 1 I

addition, the Imnediate actions also specify that if LPRM or APRM noise level exceeds 10% peak to peak while inserting control rods, then the reactor is to be scranged. The follow-up action is to insert control rods as required to reduce reactor power to below the limit specified in Technical Specification Figure 3.4.1.1-1. Maintaining thermal power below this limit makes power oscillations unlikely, and if they do occur, a reactor scram will ensure that the oscillations l are not allowed to increase in magnitude. The Bases for OT-112 specifically address the need for Inserting control rods to eliminate the possibility of sustained power oscillations, and the requirement of a scram should oscillations occur. OT-112 is addressed in the classroom in Licensed Operator Tralning, Course LOT-1540, and j is practiced in the simulator by Simulator Training Scenario, STS-13. )

l Startup and Shutdown Conditions During startup, Recirculation Pump speed is increased to 28% (20%

feedwater runback limit) to ensure that core flow is greater than 45%

as power is increased. GP-2, Nornal Plant Startup, not only raises Recirculation Punp speed to 28%, but at approxinetely 10% rated thernal power, total core flow is verified to be greater than 45%. If core flow is less than 45%, and power is greater than Technical Specification Figure 3.4.1.1-1, ST-6-107-880-2, APRM and LPRM Noise Level Determination is performed to determine APPJi and LPRM noise levels. These baseline noise levels can then be used to monitor core stability as power is increased by 5% increments. GP-2, Normal Plant Startup, is addressed in Licensed Operator Training, course LOT-1530 and is practiced in the sinulator by Sinulator Training Scenarlos, STS-29, 29A, and 30. Technical Specification Figure 3.4.1.1-1 1s specifically addressed in Licensed Operator Training, course LOT-1840, Technical Specification Selected LCOs.

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During performance of GP-4, Rapid Plant Shutdown.to Hot Shutdown, recirculation flow is reduced to mininom, ' and the plant is quickly scrammed so that any high power / low flow situation is quickly exited.

GP-3, Normal Plant Shutdown, instructs the operator to utilize Reactor Maneuvering Shutdown Instructions provided by Reactor Engineering in accordance with RE-201, Reactor Maneuvering Plan Approval. These l Instructions provide for the insertion of sufficient control rods

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prior to reducing both recirculations punps' speeds to minimum, so that reactor poner is belaa the Ilmit in Technical Specification.

Figure 3.4.1.1-1, thus preventing entry into a high power / low flow condition. According to GP-3, Operations personnel verify that reactor power is less than Technical Specification Figure 3.4.1.1-1 when oore flow is less than 45%, .and perform ST-6-107-880-2, APRM and LPRM Noise Level Detennination, if reactor power is above the limit.

Therefore, If a high power / low flow condition is entered, APRM/LPRM noise levels will be monitored. GP-3 and GP-4 are addressed in License Operator Training, course LOT-1530, and plant shutdown is practiced in the simulator by Simulator Training Scenario, STS-17.

Rod Sequence Exchange Conditions

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Since Limerick has a control cell core, Total Sequence A and B exchanges are not performed. Deep / shallow rod exchanges are performed between rod withdrawl groups 9 and 10, but do not occur in areas susceptible to instability. Power and flow are reduced to conduct this reactor maneuver. However, recirculation flow is' not reduced to _minimun, maintaining core flow greater than 45%. The rod sequence exchange between rod withdrawl groups 9 and 10 is perforned and' recirculation flow  ;

Increased. Therefore, conditions favorable to uncontrolled power oscillations are not Ilkely to exist during rod sequence exchanges.

Adequacy of Limerick Procedures - Conclusion Specific details of how to recognize uncontrolled power oscillations and the actions required in response to power oscillations were not previously included in the procedures. The appilcable procedures have been revised to include specific actions, such as instituting a scram and other actions, needed to identify and mitigate excessive power oscillations after control rods are inserted to reduce reactor power to less than the Technical Specification limit. In addition to the initial briefing, Licensed Operator Requallfication training will be given to addressBulletin 88-07, " Power Oscillations in BWRs", and the procedural changes noted above, and will include a simulator demonstration incorporating power oscillations.

The current procedures, therefore, address those plant conditions (recirculation pum trips, startup/ shutdown, and rod sequence exchanges) that can lead to power oscillations. Specific actions (Inserting control rods after a recirculation punp trip, nelntaining core flow greater than 45% on startup/ shutdown, and deep / shallow exchanges) are in the procedures to prevent plant conditions that could result in uncontrolled power oscillations.

4 ADEQUACY OF IN TRUMENTATION An additional requested action presented in the Bulletin is restated below:

" Addressees she>uld also verify the adequacy of the Instrumentation which is relled upon by operators within their procedures."

E l Response:

The existing power range neutron nonitoring instronentation has been evaluated and detennined to be adequate for monitoring neutron flux oscillations. The Local Power Range Monitors (LPRMs) are designed to supply an ionization current proportional to the core neutron flux without suffering fran a loss of saturation plateau. The detector output remains linear (plus or minus 1%) over a range of neutron flux that is sufficient to acconnodate local flux peaks of a magnitude on the order of those experienced at LaSalle.

The applicable drawings have been reviewed, and it has been determined that the Installed Instrmientation has not been modified in such a way as to prevent the detection of oscillations (as had occurred at LaSalle). Limerick has GE power range neutron monitoring instrumentation installed. The adequacy of GE supplied power range neutron nonitoring instrumentation to detect flux oscillation is discussed in GE Service Information Letter (SIL) 380, Rev.1 the methodology of which was endorsed by the NRC as documented in NRC Generic Letter 86-02, " Technical Resolution of Generic Issue B-19: The rmal-Hydraul ic Stabi l i ty". Limerick has implemented SIL 380, Rev. 1.

CONCLUSION As presented in the analyses above, procedures, training, and Instrumentation at Linorick Generating Station adequately fulfills the requirements in the actions requested in Bulletin 88-07, " Power Oscillations in Bolling Water Reactors".

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l GULLETIN 88-07 l SUPPLEMENT 1 q POWER OSCILLATIONS IN BWRS J 1

INTRODUCTION i NRC Bulletin No. 88-07, Supplanent 1: " Power Oscillations in Bolling Water Reactors (BWRs)", dated Decenber 30, 1988, requested that all BWR licensees Implement the General Electric (GE) Interim stability reconnentions described in an attachnent to the Bulletin supplenent and advise the NRC that the requested actions have been completed and implemented prior to fuel loading. The actions requested and taken are described in the following sections.

Actions Requested

1) . ..all BWR licensees should implenent the GE Interim stability recommendations.. .However, for those plants that do rot have effective automatic scran protection in the event of regional oscillations, a nanual scram should be initiated under all operating conditions when two recirculation punps trip (or "no punps operating") with the reactor in the RUN mode, i

2) The boundaries of Regions A, B, and C shown in Figure 1 of the GE recommendations were derived for those BWRs using NRC approved GE fuel. For BWRs using fuel supplied by other vendors, these regions should be adopted in principle, 'but the power / flow boundaries should be based on existing boundaries that have been previously approved by the NRC.

For proposed new fuel designs, the stability boundaries .

should be reevaluated and Justified based on any applicable l operating experience, calculated changes in core decay ratio using NRC approved methodology, and/or core decay ratio measurements. There should be a high degree of assurance that instabilities will not occur under any

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circumstances of operation in Region C.

3) The BWROG recommendations are ambiguous with respect to permissible conditions for entry of Regions B and C. Although the reconnendations state that intentional operation in Region B is not permitted and operation in Region C is permitted only for purposes of fuel conditioning during rod withdrawal startup operations, Intentional entry into Region B or C is also I allowable in situations where rod insertion or a flow increase is required by procedures to exit Regions A and B after unintentional entry. Licensees should ensure that the procedures and training l employed for implementation of these recommendations avoid any similar anbiguity which could lead to operator confusion.

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Response: )

i The GE Interim stability recommendations were implemented for LGS l Unit 1. Since the appilcable LGS Unit 1 procedures and limitations i will be used for the operation of LGS Unit 2, we consider that the GE ,

recommendations have also been ccynpleted and implemented for LGS l

Unit 2.

The requirement for manual reactor trip under all operating conditions

'dien two recirculation purrps trip is not necessary since LGS has a flow biased neutron flux trip.

l LGS Unit 2 will use GE fuel once the OL is granted. Therefore, the j stability boundaries shcun In an attachment to the supplement do not  ;

need to be reevaluated and Justified. Further, we have ensured that the procedures and training provided to LGS operators are not ambiguous j with respect to permissible conditions for entry into certain operating j regions. 1 1

One exception to the implementation of the GE Interim stability recorrmendations will be taken to conduct startup testing in Test j Condition 4 (as described in the LGS Final Safety Analysis Report, j Chapter 10 during the initial startup of LGS Unit 2.

This testing is specifically Intended to identify any concerns with transients of this type and any possible resulting instabilities.

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