ML20083A199

Power Operation of Hatch 1 & 2 Reactors W/O Forced Recirculation

ML20083A199
Person / Time
Site:	Hatch
Issue date:	02/28/1983
From:	Gridley R, Stoll C GENERAL ELECTRIC CO.
To:
Shared Package
ML20083A202	List: ML20083A199 ML20083A462
References
83NED016, 83NED16, NEDO-30059, TAC-53306, TAC-53307, NUDOCS 8312200208
Download: ML20083A199 (7)

Text

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NEDO-3005) 83NED016 Class I February 1983 l

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POWER OPERATION OF THE HATCH 1 AND 2 REACTORS WITHOUT FORCED RECIRCULATION C. H. Stoll Approved: A 6f/ 3 K. L. Gripey, fianager Fuel and Services Licensing C'

NUCLEAR POWER SAN JOSE, CAUFORNIA 95125 SYSTEMS DIVISION

• GENERAL ELECTRIC COMPANY GENERAL $ ELECTRIC 7-83f2200208 830228 PPDR ADOCK 05000321 PDR

NEDO-30059 k l l

DISCLAIMER OF RESPONSIBILITY TNs documes was prepared by or for me General Electric Conspany. Neither me General Elecbc Company nor any of the contributors to this document:

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Makes any warratsty or representation, express or implied, wnth respect to the accwacy, con pleteness, or usetuksess of me information containedin ttnis docu.

ment, or that the use of any information discksed in tNs document may not infringe privatey owned rights; of B.

Assumes any responsibimy for HabiHry or damage of any khd wtnich may result kom the use of anyinformahion disclosedin ins document.

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CONTENTS Za.ge

1. INTRODUCTION 1

2. SAFETY AND OPERATION 1

, 3. DISCUSSION 1 3.1 Safety Evaluation 1 3.2 Operatienal Items 2

4. CONCLUSIONS 2 DISTRIBUTION w

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NEDO-30059

( 1. INTRODUCTION Current technical specifications for Hatch 1 and 2 preclude power opera-tion with natural circulation. It is desirable to be able to operate for a short time in this mode so that in the event of a trip of both recirculation pumps, one or both of the pumps may be put back in service within a reasonable time to reestablish forced circulation operation without having to scram the i

plant.

2. SAFETY AND OPERATION The items considered for operation at natural circulation are as follows: .

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a. impact on accident analyses results;

b. impact on transient analyses results;

c. potential thermal stratification at low power and flow; and '

(- d. operational stability.

3. DISCUSSION 3.1 SAFETY EVALUATION The loss-of-coolant accident (LOCA) analyses performed and documented in j the Hatch 1 and 2 final safety analysis reports and updated for fuel reloads are limiting analyses that apply to the entire power flow map including the natural. recirculation line. Thus current Hatch LOCA analyses are consistant with power operation with natural circulation.

. For transient analyses the limiting transient events for power operation

[ using only natural circulation are less limiting than the limiting transient s

events at full power and flow. Current-reload analyses are conserv.atively.

j - applicable for power operation with natural circulation.

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3.2 OPERATIONAL ITEMS Operating at power with natural circulation is an operating region of reduced neutron flux damping characteristics and increases the probability of experiencing an increase in the. normal neutron flux noise that occurs during boiling water reactor (BWR) operation. The consequence of such a potential noise amplitude increase is not considered to be of any safety concern. Oper-ating recommendations to avoid or control postulated noise amplitude increases are given in Service Information Letter No. 380 Category 1.

A worst case analysis for a BWR has been performed by General Electric to bound the potential impact of neutron flux oscillations on fuel performance.

These evaluations postulated limit cycle oscillations of neutron flux just ,

l below the average power range monitor scram setpoint for a 30-min duration

, before any operator action to mitigate the oscillations. It was concluded that no additional plastic strain is imposed on the fuel cladding and cladding

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incremental fatigue life usage is negligible. These conclusions have been pro-vided to the Nuclear Regulatory Commission for information in a proprieta'ry document.

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At very low power and very low core flow for a sustained period of time some potential exists for thermal stratification to occur in the lower plenum that could cause undesirable thermal stresses on the reactor pressure vessel.

BWR startup test data for a late BWR plant indicate that at power levels above approximately 5 percent good mixing occurs in the lower plenum which would pre-clude thermal stratification. Similar mixing is expected in any BWR jet pump plant.

4. CONCLUSIONS i

Based on current technical data and analyses, there are no safety concerns I associated with power operation of Hatch 1 and 2 without forced recirculation.

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However, there is a likelihood of experiencing some neutron flux noise which can be easily suppressed.

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Power operation for prolonged periods of time at power levels below .cww-5 percent (without forced recirculation) is not recommended in order to avoid thermal stratification in the lower plenum. #

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DISTRIBUTION

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• B. W. Smith 881 B. Stevens (5 + 1 fiche) 126 C. H. Stoll 897 M. E. Tanner 855 A. N. Tschaeche 682 N. M. Varadarajan 855 NEB 0 Library (3) 528 VNC Library (2) V01 TIE (5) SCH ,

TPU File 305 9

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