ML20154K271

Confirms That Bulletin 88-007, Power Oscillations in BWR, Actions Completed.List of Addl NRC Requests Provided

ML20154K271
Person / Time
Site:	Brunswick
Issue date:	09/15/1988
From:	Mcduffie M CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
IEB-88-007, IEB-88-7, NLS-88-212, NUDOCS 8809230270
Download: ML20154K271 (4)

Text

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O CaeoNna Powee & Ught Company _

P O. Dos 161t . A.9h, N C 27602 SEP 15 DM6 M A SA:DUFfit s n.or vie. P,.. o ni suc4ar o***'* boa SERIAL: NLS 88 212 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSVICK STEAM ELECTRIC PIANT, UNIT Nos.1 AND 2 DOCKET NOS, 50 325 & 50 324/ LICENSE NOS. DPR 71 & DPR 62 RESPOSSE TO NRC BULLETIN 88 07 POWER OSCILLATIONS IN BOILINC VATER REACT 0as Centlemen:

The NRC issued Bulletin 88 07, "Power Oscillations in Boiling Water Reactors" on June 15, 1988. The bulletin requested that licensees perform several actions, described below, and confirm by letter that the actions have been completed. Carolina Power & Light Company hereby submits its confirmation that the requested actions have been completed for the Brunswick Steam Electric Plant (BSEP),

Units 1 and 2.

The NRC requested that licensees ensure that any licensed reactor operator or Shift Technical Advisor performing shift duties has been thoroughly briefed regarding the March 9, 1988 LaSalle Unit 2 power oscillation event. Real time training on this event was conpleted at BSEP on July 5,1988.

The NRC also requested that licensees address the following items:

a) verify the adequacy of procedural and training descriptions of those plant conditions which may result in the initiation of uncontrolled power oscillations, b) verify the adequacy of procedural and training descriptions of  ;

actions which can be taken to avoid plant conditions which may result in the initiation ei uncontrolled power oscillations, c) verify the adequacy of procedural and training explanations of how to recogni:e the onset of uncontrolled power oscillations, l

8809230D70 000915 PDR ADOCK OLO S g i

t Documsnt Control Dask NLS 88 212 / Page 2 i

d) verify the adequacy of procedural and training descriptions of the actions which can be taken in response to uncontrolled power oscillations, including the need to scram the reactor if oscillations are not promptly terminated, and e) verify the adequacy of the instrumentation which is relied upon by the operators within their procedures.

The following are CP&L's responses to the above items, a) The following plant conditions may result in the initiation of I

uncontrolled power oscillations and have been verified as '

adequate in plant procedures: (1) a double recirculation pu'rp trip occurring with a control rod line pattern greater than the 80n rod line and, (2) core flow less than 35 mlbs/ hour and a control rod pattern greater than the 804 rod linci.

b) Actions to be taken to avoid plant conditions which may result in uncontrolled power oscillations are also adequate in plant procedures. If a single recirculation pump were to trip, or if there was a reduction in core flow, the operator is directed to increase core flow to greater the 35 mlbs/ hour using the i unaffected recirculation pump. The operator may also reduce reactor power to a level compatible with core fic- by inserting control rods; the same action is to be taken if two recirculation pumps trip.

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[ c) The local power range monitor (IJM) upscale and LPM downscale l

procedures now indicate that multiple LPM upscale and/or downscale indicating lights spuriously illuminating and clesring is an indication of the reactor operating in a region of thermal hydraulic instability. If the average power range monitors (APMs) or LPMs indicate power oscillations greater I than ,+15% reactor thermal power, plant procedures now require initiation of a manual scram.

Indications from the downscale and upscale LPM alarms and the LPM meters are available on the reactor turbino generator board (RTCB) for observation of flux oscillations. These indications are easily available, requiring only selection of a j control rod to allow the operator to observe individual LPM l readings. The upscale and downscale alarms are bi stable i devices that saturate in either the normal or alarm condition, thus providing a clear indication of the change in state. The use of these indicators for monitoring core instability has i

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• Document Control Dssk N1.5 88-212 / Page 3 been covered in operator training for the LaSalle event and is considered adequate, d) The Brunswick Plant has procedures and operator training programs in place to address uncontrolled power oscillations which are considered adequate. Plant procedures have been revised to address the LaSalle event, as described above.

Also, plane procedures have been revised to clearly indicate the conditions for which the operator shall initiate a manual ,

reactor scram. The training program has also been revised to  ;

make operators more aware of the consequences of operating in the region of thermal hydraulic instability, and to emphasize  ;

the need to manually scram the reactor if the power  !

, oscillations are not promptly terminated. [

e) The instrumentation relied upon by the operators within their procedures in power oscillation events was also verified as requested in the bulletin. The neutron monitoring system at BSEP is representative of the GE Bk% 4 design and is essentially unaltered from its ori inal 5 design. The system has j

been reviewed and found to contain no filters / filtering on the 4

APM recorders, LPM meters, or on the LPM upscale /downscale  !

indicators which would conceal the presence of flux j oscillations from the operator, k'hile the mechanical nature of ,

the APM recorders is such that their response to instantaneous  !

) large step change inputs is incomplete, the frequency of core j

thermal hydraulic instability, defined as oscillation of ~

approximately .4 to .5 Hertz is sufficiently slow to allow the i APM recorders to track power accurately during such an event, 1

j The ability of the APMs and reactor protection system to  ;

j respond to out of phase oscillations in situations where the I APM response may be reduced or degraded is also being i reviewed. An analysis to evaluate this behavior is being j performed by CE, the designer of the neutron monitoring system,  !

for the BkT Ovners' Croup, The results of the analysis will be  ;

1 included in the review of this behavior as they oecome 2

available, Based on the previous discussion, the neutron nonitoring system  !

} has been found to be adequate in responding to core power instabilities and oscillations and in providing accurate indications of core power conditions to operations personnel. ,

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. . . . 4. v Docum:nt Control D:sk NLS 88 212 / Pago 4 Please ref)r any questions regarding this submittal to Mr. Stephen D. Floyd at (919) 836 6901.

Yours very truly, d *b M. A. McDuffie BAB/bab(b8807)

M. A. McDuffie, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Carolina Power & Light Company.

I kho_ 0 . lh-!1M Qf}---

• Notary (Sddl)

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4 My commission expires: (( O[t Y7 cc: Dr. J. Nelson Grace Mr. V. H. Ruland j Mr. B, C. Buckley l

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