ML20006B704

Application for Amends to Licenses DPR-57 & NPF-5, Respectively,Amending Tech Specs to Clarify Revised Method of Suppression Pool Average Temp Determination

ML20006B704
Person / Time
Site:	Hatch
Issue date:	01/26/1990
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20006B705	List: ML20006B704 ML20006B706
References
HL-911, NUDOCS 9002050272
Download: ML20006B704 (8)

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U.S. Nuclear Regulatory Commission  :

ATTN:- Document Centrol' Desk Washington, D.C. 20555 PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366

l. OPERATING LICENSES DPR-57, NPF-5 .'

L REQUEST:TO REVISE TECHNIf%L SPECIFICATIONS:

SUPPRESSION POOL TEMPERMURE MONITORING U Gentlemen: l 0 - In accordance with the provisions of 10 CFR 50.90, as required by l 10 CFR 50.59(c)(1), Georgia Power Company (GPC) hereby proposes a change to L the Plant Hatch - Units 1 and 2 Technical Specifications (TS), Appendix A L .to Operating. Licenses LPR-57 and NPF-5. i p

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Georgia Power Company (GPC) received a Notice of Deviation from the NRC '

D in Inspection Report 88-38 for failure to use a'l of.the -temperature L . ' sensors in the suppression pool to establish average-(or: bulk) pool L temperature. In response to the deviation, GPC has revised phnt' ,

L procedures to use a representative average of all suppression pool z temperattire sensors to determine average pool temperatures and, on l November;29, ~1989 submitted a revision to the Unit 1 and-Unit 2 . Mark I Containment Plant Unique Analysis Reports. This revised method.is now used l

'to show compliance'with Technical Specifications (TS) limits on suppression pool- temperature. This proposed TS change clarifies the revised method of P . suppression pool average temperature determination.

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Enclosure 1 provides a detailed description of-the proposed change and

'the-circumstances necessitating the change request.

u Enciosure 2 details the basis for our determination that the proposed p, -change does not involve significant hazards considerations.

Enclosure 3 provides page change instructions for incorporating the a . proposed change into the TS. The proposed changed pages for Unit I and '

Unit 2 follow Enclosure 3.

To -allow time for orderly incorperation into copies of the TS, GPC requests ~ the proposed amendment, once approved by the NRC, be issued with an ' effective date to be no 17."er than 60 days f' rom the date of issuance of

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Georgia Poiver A U.S. Nuclear Regulatory Commission f January 26. 1990 '

Page Two s

In' accordance to the requirements of 10 CFR 50.91, a copy of this-letter and all applicable enclosures will be sent to Mr. J. L. Ledbetter of.

the Environmental Protection Division of the Georgia Department of Natural Resources. -;

Mr. W. G. Hairston, III states that he is a Senior Vice President of l l . Georgia Power Company and is authorized to execute this oath on behalf of

., Georgia Power Company and that, to the best of his knowledge and belief, the facts set forth in this letter are true.

GEORGIA POWER ff>ANY

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• BY)$ N . G. Hairston, Ill~ (

Sworn to and subscribed before me this c .94 day of Achae ,1990.

NOTARY fBLIC

Enclosures:

MY 00MMIS$10N EXPlRES JANUARY 12,1993 l

1. Basis for Change Request l 2. 10 CFR 50.92 Evaluation

3. Page Change Instructions  :

c: Georaia Power Comoany Mr. H. -C. Nix, General Manager - Nuclear Plant t- Mr.-J. D. Heidt, Manager Engineering and Licensing - Hatch ,

G0-NORMS U.S. Nuclear Reaulatory Commission. Washinaton. D.C.

Mr. L. P. Crocker, Licensing Project Manager - Hatch U.S. Nuclear Reculatory Commission. Reaion II ,

Mr. S. D. Ebneter, Regional Administrator ,

Mr. J. E. Menning, Senior Resident Inspector - Hatch State esGeorcia Mr. J. i. Ledbetter, Commissioner - Department of Natural Resources l

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ENCLOSURE 1

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PLANT-HATCH - UNITS 1, 2 R

' NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPf REQUEST TO REVISE TECHNICAL SPECIFICATIONS:

SUPPRESSION POOL TEMPERATURE MONITORING BASIS FOR CHANGE RE0 VEST PROPOSED CHANGE:

The proposed change will modify the Technical Specification (TS) to require an average (bulk) temperature to be used- to show compliance to the TS limits on suppression pool temperature. Specifically, limiting conditions for operation (LCO) and surveillance requirements (SR) in Unit 1 TS 3.7.A.1, and 4.7.A.1,1and Unit'2 TS 3.6.2.1 b (and corresponding Action and SRs) will specify average suppression chamber water temperature. The surveillance requirements for both units will specify that the average pool >

temperature shall be determined using a weighted average of the suppression pool temperature sensors as described in the TS Bases. The Bases of both -

unit's - TS have been revised to describe the method (s) used to determine average suppression pool temperature.

BASIS FOR PROPOSED CHANGE: >

-Temperature limits on the suppression pool for BWRs with Mark I containments have been implemented to minimize the potential for high amplitude loads during transient and accident events. Because'of the importance of the suppression pool as an ' intermediate heat sink, the pool temperature must be monitored during normal operation as well as during transient / accident conditions.

The original design of the Hatch containment had four temperature sensors, T48-N009A-D (referred to as the N009 series) installed in the suppression pool lower elevation. These sensors were used to monitor pool temperatures to ensure conformance to TS limits.

' Subsequent to the initial containment design, concerns were raised about unstable steam condeas;. tion and associated high loads on the containment structure at high pooi temperatures. This resulted in the local pool temperature limits specified in NUREG-0783, and the need to have enhanced suppression pool monitoring capability. Eleven temperature elements, T48-N301 through N311 (referred to as the N300 series) were installed at higher elevations in the pool. During normal plant operation, when the suppression pool water is not being circulated, thermal stratification may cause slight differences in the temperature in the upper and lower regions

, of the pool. Placing the residual heat removal (RHR) system in the suppression pool cooling mode during normal operation produces a well mixed suppression pool.

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ENCLOSURE 1 (Continued) .

REQUESf TO REVISE TECHNICAL SPECIFICATIONS:

SUPPRESSION P0OL TEMPERATURE MONITORING BASIS FOR CHANGE RE0 VEST Although concerns over local pool temperature limits have been alleviated for BWRs with quencher devices on the safety relief valve (SRV) discharge lines, determination of the average of bulk pool temperature is important.

The bulk pool temperature is an assumed initial- condition for many safety analyses, it is also an important plant parameter which must be monitored during normal, abnormal, and emergency operations.

Procedural changes have been implemented at Plant Hatch requiring a representative average of the eleven N300 series sensers and the four N009 series- sensors be used to determine bulk pool temperature. The fou- L'009 series sensors are averaged to determine the lower pool temperatare, and the eleven N300 series sensors are averaged to determine s le upper ,

temperature. The bulk temperature is the numerical average of the average upper- and average . low:r temperatures. Previously, the method of determining TS conformance was to use the average of the N009 series sensors, which is less restrictive. The proposed change to TS will delineate that averaae temperature must be used to show conformance to TS limits and that under normal conditions all fifteen temperature sensors must be used. The proposed TS allow for use of a " pre-planned alternate method" in situations where one or more temperature sensors are inoperable.

methods are' discussed in the revised Unit I and Unit 2 TS Bases,-and toe

• ent Unique Analysis Reports, Section'7.5 (Reference 1), as summarized be e ob

..m Mark I suppression chamber is a toroidal (doughnut-shaped) structure about half filled with water. It lies below and encircles the drywell.

Sixteen cylinder-shaped bays are .onnected to form the " doughnut", and a quadrant ' is defined as a 90 degree sector of the torus (equivalent to four ,

bays). The quadrants are selected such that each has one N009 series sensor and from 2-4 N300 series sensors. One alternate method, in the case where one or more temperature elements are inoperable, is to average the remaining operable elements. The operable N009 series sensors (lower pool elevation) would be used to determine the aver s lower elevation temperature; the average of the operable N300 series sensors would determine the upper pool temperature, and the two values would be averaged to calculate the bulk pool temperature. This alternate method requires at least one operable N300 series sensor in each quadrant of the suppression '

pool. If each quadrant does not have at least one N300 sensor operable, another alternate method may be used. This method averages the operable n N009 series sensors and adds 50F. The 50F adder is equivalent to a situation where the average of the N300 series sensors is reading 100F 1 higher than the N009 series sensors. This is because the bulk pool temperature is normally represented by the numerical average of the upper Y

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ENCLOSURE 1 (Continued)

REQUEST TO REVISE TECHNICAL SPECIFICATIONS:

SUPPRESSION POOL TEMPERATURE MONITORING BASIS FOR CHANGE RE0 VEST pool temperature readings (N300 series) and the lower pool temperature readings (N009 series). Therefore if the N300 series sensors were reading

-10 degrees higher than the N009 series sensors, it would be equivalent to a  :

bulk pool temperature 5 degrees ' higher than the N009 series sensors were indicating.

In. order to determine the 50F adder, operational data on suppression pool <

temperature was reviewed for both Unit I and Unit 2. A special purpose procedure was written to record detailed temperature- data during late spring and summer of 1989. Several hundred surveillance data packages were reviewed which represented periods of normal operation without suppression pool cooling (SPC), normal operation with SPC, and testing of the high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems.

The conclusion of this review is that a 50F adder on the average of the operable N009 series sensors is sufficiently conservative to account for potential thermal stratification in the suppression pool during normal.

operation without pool cooling. The largest temperature differential observed in either unit during normal operation without pool cooling was approximately 3.50F, with the average being approximately 2 degrees.

The review also indicates that this 50F adder is not necessary when at least one RHR pump is in the suppression pool cooling mode and testing which adds heat to the suppression pool is not being performed. Thermal mixing is effective in this case, resulting in little, if any stratification. Data for both units during this operational condition indicates the temperature differential between the average of the N009 sensors and the average of all fifteen sensors (i.e., bulk temperature) to be on the order of 10F or less.

When large amounts of steam are discharged into the pool (i.e., HPCI, RCIC, or SRV operation), thermal stratification may be increased. In most cases both . upper and lower sensors wili be available to determine bulk temperature during heat additions to the pool. However, in the unlikely l event that less than one N300 per quadrant is available, the 50F adder L would be applied even if RHR was operating in the SPC mode during the heat addition. The SPC mode acts to reduce any stratification between the upper and lower elevations and reduce pool bulk temperature once the heat addition to the pool has stopped, l i L

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-ENCLOSURE 1.(Continued)

REQUEST TO REVISE TECHNICAL SPECIFICATIONS: ,

SUPPRESSION POOL TEMPERATURE MONITORING i BASIS FOR CHANGE RE0 VEST REFERENCES

1. Letter HL-801, W. G. Hairston, III to NRC, "PVAR Revision for Torus Rock Bolt Evaluations and Suppression Pool Temperature Monitors, dated November 21, 1989.

2. Letter HL-738, W. G. Hairston, III to NRC, " Technical Specifications Improvement Program, Request to Revise Technical _ Specifications" dated December 21, 1989.

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ENCLOSURE 2 PLANT HATCH - UNITS 1, 2 .

- NRC DOCKETS 50-321, 50-366 OPERATING LICENSES OPR-57, NPF-5 REQUEST TO REVISE TECHNICAL SPECIFICATIONS:

SUPPRESSION P0OL TEMPERATURE MONITORING 10 CFR 50.92 EVALVATION PROPOSED CHANGE:

The proposed change will modify the Technical Specifications (TS) to.

require an average (bulk) temperature to be used to show compliance to the TS limits on suppression pool temperature. Specifically, limiting conditions for operation (LCO) and surveillance requirements (SR) in Unit 1 TS: 3.7.A.1 and 4.7.A.1, and Unit 2 TS 3.6.2.1.b (and corresponding Action and SRs) will specify average suppression chamber water temperature. The Bases of both units TS have been revised to describe the method (s) used to determine average suppression pool temperature.

BASIS FOR' PROPOSED CHANGE:

Georgia Power Company (GPC) has reviewed this proposed change and has determined it does not involve a significant hazards consideration.

The proposed. change does not involve a significant increase in the

- probability, or consequences of an accident previously evaluated. The heat capacity of the suppression pool, the existing suppression pool . temperature limits, and the heat additions to the. suppression pool assumed in accident / transient analyses are not impacted by this change. The TS have been modified to require a more stringent method of monitoring temperature, consistent with current Plant Hatch procedural requirements.

The proposed' change does not create the possibility of a new or different type of accident- from any previously analyzed, because the new TS requirement simply increases -the amount of instrumentation required to monitor average (bulk) suppression pool temperature. No new modes of operation are introduced by this change, and the pool temperature sensors provide monitoring and alarm functions only. Also, no physical changes are being made to the pool temperature monitoring system.

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,,- . l ? i; ENCLOSURE 2 (Continued)

REQUEST TO REVISE TECHNICAL SPECIFICATIONS:

SUPPRESSION POOL TEMPERATURE MONITORING i

10 CFR 50.92 EVALUATION The proposed change does not involve a significant decrease in the margin of safety. Monitoring of the suppression pool temperature will be at least ds ' accurate as before and reflects a better method of determining conformance to TS temperature limits. This method (using all of the available pool temperature sensors) is currently being utilized in plant >

procedures.

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