ML20216J897

SER Related to General Electric Nuclear Measurement Analysis & Control Power Range Neutron Monitoring Sys Upgrade Southern Nuclear Operating Co,Units 1 & 2

ML20216J897
Person / Time
Site:	Hatch
Issue date:	09/12/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20216J869	List: ML20216J863 ML20216J897
References
NUDOCS 9709180144
Download: ML20216J897 (3)

Text

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4 UNITED STATES

.f 3 NUCLEAR REGULATORY COMMIS8 ION WASHINGTON, o.C. DettHDH

\ .. . . . )l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION MELATED TO GENERAL ELECTRIC NUCLEAR MEASUREMENT ANALYRIS AND.

C.ONTROL POWER RANGE NEUTRON MONITORING SYSTEM UPGRADE SOUTHERN NUCLEAR OPERATING COMPANY. INC.. ET AL.

EDWIN 1. HATCH NUCLEAR PLANT UNITS 1 AND_2 DOCKET NOS. 60 321 AND 60 366

1.0 INTRODUCTION

By letter dated October 26,1996, as supplemented February 19,1997, Georgia Power Company and Southern Nuclear Operating Company, Inc, et al. (SNC or the licensee),

described their intent to replace the existing analog power range mnnitoring system in the Edwin 1. Hatch Nuclear Plant (Hatch), Units 1 and 2, with a digital General Electric (GE)

Nuclear Measurement Analysis and Control (NUMAC) power range neutron monitoring system (PRNMS). The staff approved technical specification (TS) amendments for the average power range raonitoring (APRM) portion of the PRNMS on March 21,1997.

Proposed TS amendments for the oscillation power range monitor (OPRM) portion of the PRNMS were to be submitted by the licensee upon completion of a 6 month testing period.

By letter dated June 20,1997, SNC requested resolution of issues associated with implementation of the OPRM. Preliminary results during the 6 month monitoring period for the OPRM indicated that the response of the OPRM was more sensitive than anticipated.

The licensee, therefore, requested revisions to the OPRM settings to eliminato spurious alarms. To validate these settings, the licensee requested an increase in the OPRM monitoring period for both units. The requested increase extends the monitonng priod in each unit from 6 months to a complete fuel cycle. AddiConally, the licMsee requested <

revisions to the staff's PRNMS safety evaluation (SE) for Hatch to address minor  !

differences between the approved TS Bases amendments and the licensee's October 26, 1996, submittal.

The licensee's proposed TS amendments applicable to the APRM portion of the Hatch TSs were implemented following installation of the NUMAC PRNMS, Originally, the OPRM ,

functions were to be connected to the Reactor Protection System (RPS) trip relays 6fter l 6 months of operation with the NUMAC PRNMS modification Upon completion of this initial operating period, the OPRM specific TS amendments were to be implemented with plant specific setpoints and margins. During this test period, the interim corrective actions for determining and mitigating power oscillations remained in ettst.

The following staff's evaluation addresses the requested extension on the OPRM surveillance period from 6 months to a complete fuel cycle, and the minor revisions of the Hatch, Units 1 and 2, TS Bases.

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2.0 EVALUATION Currently, the OPRM tuning parameter ranges for the corner frequency (2.5 Hz) and period  ;

tolerance 1100 ms) are based on limited reactor noise data from a few plants. OPRM data .

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collected during Hatch, Unit 2, startups in late April and early May 1997, indicated that  !

the OPRM system correctly implements the stability algorithms; however, the response is more sensitive than anticipated. Consequently, the licensee requested changes to the  !

comer frequency and period tolerance to 3.0 Hr and 50 me, respectively.

l 2.1 Manliaring Parind Extanalan l r f

l Since the OPRM tuning parameters must be adjusted to reduce the sensitivity of the OPRM i i

system, the licensee requested an extension of the OPRM monitoring period from 6 j months to a complete fuel cycle. This additional monitoring period will allow the licensee 2

l to evaluate the effect of the tuning parameter changes prior to activating the OPRM  !

automatic RPS trip for mitigation of unacceptable power oscillations.  !

- The requested one complete fuel cycle monitoring period is consistent with the monitoring  !

period identified in approved topical report NEDC 32410P A, " Nuclear Measurement i

Analysis and Control Power Range Neutron Monitor (NUMAC PRNM) Retrofit Plus Option 111 Stability Trip Function." During this additional monitoring period, the licensee will continue to operate Hatch, Units 1 and 2, using the existing laterim corrective actions for determining and mitigating power oscillations. The staff, therefore, finds this extension of -

the monitoring period for the OPRM system to be acceptable.

2.2 Plant Enacific Raviand Technical Snacifications in the following discussion, phrases in the staff's SE for Hatch, Units 1 and 2, dated March 21,1997, for the PRNMS that the licensee has proposed for revision are lined out  ;

. (e.g., mwet-be opeeable), and the licensee's proposed additions are underlined (e.g., me  !

renuired). 1

Section 3.3.6, Page B 3.3 7, of the staff's SE for the Hatch TS Bases states

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...In addition, to provide adequate coverage of the entire core, consistent with the design bases for the APRM Functions 2.a 2.b, and 2.c, at least 17 LPRM llow power range monitor) inputs, with at least three LPRM inputs from each of the four axialinvols at which the LPRMs are located, m:0 5: :;:::S: for e ' each APRM channel. .": "; 0,"i".';:::'d, "; :::;- M, LPRMs are assigned to." cells" of three detectors.' A minimum of three cells, each with a minimum .

of two LPRMt. must be OPERABLE for the OPRM Upscale Function 2.f to be '

OPERABLE.

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i The licensee identified differences between the TS Bases revisions approved by the staff,  !

and requested revisions that were described in a February ig,1997, response to a staff  !

request for additionalinformation. The staff's SE approving the implementation of the  !

NUMAC-PRNM Hatch units inadvertently omitted the licensee's discussion regarding the APRM TS Bases paragraph thet described LPRM inputs for APRM Functions 2.a; 2.b,2.c, i and 2.f. The corrected Bases state: l

...In addition, to provide adequate coverage of the entire core, consistent with the  !

. design bases for APRM Functions 2.a. 2.b, and 2.c, at least 17 LPRM inputs, with l

' at least three LPRM inputs from each of the four axial levels at which the LPRMs 1 are located, are renuired for each APRM channel. For APRM Function 2.f. OPRM Unscale. LPRMs are assigned to *oells' of three detectors with a minimum of 1  ;

detector per cell. The minimum number of LPRM inputs for APRM Functions 2.a. _j 2.b, and 2.c must be met for the OPRM Upscale Function 2.f to be OPERABLE.

The above revision, which changes the phrase, 'must be operable

• to 'are required' is editorial in nature in that the meaning is unchanged, is consistent with the structure of the i existing Hatch TS Bases, and, therefore, is acceptable. The revision also incorporates an  :

- editorial change, which correctly identifies Function 2.f as an APRM function Instead of an

- OPRM function, and, therefore, is acceptable. To be consistent with this latter revision, the  !

licensee also changed the last sentence in this paragraph from 'OPRM Upscale Function 2.f" to 'APRM Function 2.f, OPRM Upscale.' These revisions are consistent with the exiving Hatch, Units 1 and 2 TS Bases, and, therefore, are acceptable.

An additional revision to the TS Bases on Page 3.3 7 changes (from two to one) the number

of LPRMs in a cell that must be operable for APRM Function 2.f, OPRM Upscale, to be OPERABLE. This reduction in the number of required LPRMs increases the sensitivity of the OPRM trip sensitivity and core coverage because OPRM trip sensitivity increases as LPRM failures increase. The staff concludes that increasing the OPRM trip sensitivit/ by reducing l the number of required LPRMs per cellis conservative in that power oscillations will be more i

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readily detected, and, therefore, is acceptable.

3.0 CONCLUSION

Based on the above review, the staff concludes that the licensee's proposed OPRM system

• monitoring period extension from 6 months to one complete fuel cycle is consistent with the staff's generic approval of the system and is, therefore, acceptable. Approved interim means ,

of power oscillation detection will remain in place until full activation of the OPRNM system.

The staff also concludes that the TS Bases changes for Hatch, Units 1 and 2, are editorial in nature and consistent with the existing Hatch, Units 1 and 2, TS Bases, and are conservative

= because of the increased sensitivity of the OPRM trip as a function of operable LPRMs per l

coll. The TS Bases changes, therefors, tre acceptable.

i Principal Contributor: M. Waterman i l

Date: September 12 r1997 L

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