2CAN108706, Application for Amend to License NPF-6,changing Tech Specs to Decrease Required Differential Pressure Produced by HPSI Pumps During Surveillance Testing.Fee Paid

Application for Amend to License NPF-6,changing Tech Specs to Decrease Required Differential Pressure Produced by HPSI Pumps During Surveillance Testing.Fee Paid

ML20236H846
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/28/1987
From:	Campbell J ARKANSAS POWER & LIGHT CO.
To:	Calvo J Office of Nuclear Reactor Regulation
Shared Package
ML20236H848	List: 2CAN108706, Application for Amend to License NPF-6,changing Tech Specs to Decrease Required Differential Pressure Produced by HPSI Pumps During Surveillance Testing.Fee Paid ML20236H853
References
2CAN108706, NUDOCS 8711050003
Download: ML20236H846 (10)

Text

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ARKANGAS POWER & LIGHT COMPANY CAPITOL TOWER BUILDING /P. 0 BOX 551/LITTLE ROCK, ARKANSAS 72203/(501) 377 3525 T, GENE CAMP 8 ELL Vice President October 28, 1987 <

I Nuclear Operations 2CAN108706 l U. S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 ATTN: Mr. Jose Calvo, Director Project Directorate IV

SUBJECT:

Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Technical Specification Change Request Surveillance Requirement for High Pressure Safety Injection Pump Differential Pressure

Dear Mr. Calvo:

The Arkansas Power & Light Company (AP&L) hereby requests an amendment to its Operating License No. NPF-6 for Arkansas Nuclear One - Unit 2 with the enclosed submittal of a proposed change to the Technical Specifications. 3 This Technical Specification change will benefit the future operation of i AN0-Unit 2. We wish to implement this improvement in conjunction with Cycle 7. Therefore, we would appreciate your review and approval of the enclosed material so that the Operating License Amendment can be issued prior to the start of our next refueling outage which is scheduled to begin on February 12, 1988. The circumstances of the proposed amendment, however, are not of an exigent or emergency nature.

The proposed Technical Specification change involves decreasing the required differential pressure produced by the high pressure safety injection pumps during surveillance testing. The proposed char.ge will increase operational flexibility without any significant decrease in the margin of safety.

AP&L has evaluated the proposed change in accordance with 10CFR50.91(a)(3) using the criteria in 10CFR50.92(c) and has determined that the change  ;

involves no significant hazards consideration. The basis for this  !

determination is included in the enclosed submittal.  !

A copy of this amendment request and enclosure has been :ent to Ms. Greta Dicus, Acting Director, Division of Environmental Health Protection, State Department of Health in accordance with 10CFR50.91(b)(1).  !

l 8711050003 871029 PDR t

ADOCK 05000368 \\

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Mr. Jose Calvo October 28, 1987 A cleck in the amount of $150.00 is included herewith as an application fee in accordance with 10CFR170.12(c)

Very truly yours,

//

T. Gene Campbell TGC/sd Attachments / Enclosures .

cc: Ms. Greta Dicus, Acting Director Division of Environmental Health Protection '

State Department of Health }

4815 West Markham Street Little Rock, AR 72201 i

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l-STATE OF ARKANEAS )

) SS COUNTY OF PULASKI )

I, T. Gene Campbell, being duly sworn, subscribe to and say that I am Vice President, Nuclear Operations for Arkansas Power & Light Company; that I have full' authority to execute this oath; that I have read the document i numbered 2CAN198706 and know the contents thereof; and that to the best of my knowledge, information and belief the statements in it are true.

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T. G. Cad 11 SUBSCRIBED AND SWORN T0 before me, a Notary Public in and for the CountyandStateabovenamed,thisOhdayof 0 bar ,

1987.

w& cA NotarhPublic

,My Commission Expires:

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i i I i l ENCLOSURE i

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PROPOSED TECHNICAL SPECIFICATION CHANGES

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AND RESPECTIVE SAFETY ANALYSES IN THE MATTER OF AMENDING i LICENSE N0. NPF-6 ARKANSAS POWER & LIGHT COMPANY-ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368.

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I PROPOSED CHANGE l

l It is proposed that surveillance requirement 4.5.2.f.1 on Page 3/4 5-5 be changed as indicated on the revised copy of this page attached to this transmittal.

DISCUSSION '!

~The surveillance requirement for verifying that the high pressure safety injection (HPSI) pumps achieve a specified differential pressure was established to assure that the HPSI pumps will develop sufficient head to .1 fulfill their safety function. The differential pressure currently specified in'the. surveillance requirement is based on an analysis which provided little, margin for variation in pump performance. Additional analyses have shown that a lower differential pressure requirement will not adversely impact the original analysis results. The proposed revision establishes a more realistic differential pressure requirement for the HPSI  !

pumps which will increase operational flexibility. The new performance I requirements established by this proposed revision would also support a I reduction of the injection leg flow rate requirements of Technical Specification 4.5.2.h. The changes in the flow requirements are very small ]

I however, no changes to this specification are proposed in this revision. ]

DETERMINATION OF SIGNIFICANT HAZARDS Arkansas Power & Light Company has performed an analysis of the proposed i change in accordance with 10CFR50.91(a)(1) regarding no significant hazards consideration, using the standards in 10CFR50.92(c). 1 l

A discussion of those standards as they relate to this amendment request follows:

Criterion __1 Does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed reduction of required differential pressure for the HPSI pump does not increase the probability or consequences of a previously evaluated accident. The potential effects of decreasing the HPSI required differential pressure have been' considered with respect to all accident analyses of Chapter 15. The effects of the change have specifically been evaluated with respect to a) loss of coolant accident (LOCA) analysis in SAR Chapter 6, b) steam line break analysis in SAR Chapter 15, and c) steam generator tube rupture analysis in SAR Chapter 15. The remaining accidents were determined to be unaffected by the proposed change.

The proposed reduction of required differential pressure for the HPSI pump 1 will not affect the peak cladding temperatures, zircaloy oxidation i fractions, or fraction of rod cladding oxidized for large break LOCAs (i.e.,

area > 5 ft2 ). The high pressure safety injection pumps are started by a l low pressurizer pressure safety injection actuation signal (SIAS) when the pressurizer pressure drnps to 1766 psia, bewever, safety injection pump flow is not credited until after the safety injection tanks (SIT) have emptied.

The SITS totally fill the reactor vessel downcomer, and thereafter, the combined HPSI/LPSI flow maintains a full downcomer with excess flow spilling from the break. The revised HPSI flow, associated with the proposed

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- reduction in differential pressure requirements,:will still be sufficient to maintain a full downcomer. The reduced differential pressure would therefore.have vi tually no impact on the HPSI pump's contribution to mitigation of larp break LOCAs.

The small break LOCA (area <.5 ft )2 analysis has also been evaluated to assess potential effects from the proposed reduction in required differential pressure. For this accident, the HPSI pumps will be started by a low pressurizer pressure SIAS at a pressure of 1766 psia. Due to the slewer depressurization of the RCS for a small break accident, the HPSI.

pumps will begin discharging water to the RCS at elevated RCS pressures.

A comparison of large and small break LOCAs is presented in Section,6.3.3.2.4-of the ANO-Unit 2 SAR. The results of the comparison demonstrate thet small break LOCAs are not limiting with respect to peak cladding temperatures, maximum individual rod cladding oxidation or total j cladding oxidation. To assure that small breaks remain non-limiting,2AP&L i has performed a new analysis of the limiting small break. The 0.1 ft LOCA analysis was repeated with a revised HPSI pump flow / head curve based on the proposed reduced differential pressure requirements. This new analysis has shown that'the peak cladding temperature changes less than 20 F from the original 0.1 f t2 break analysis, and therefore, is still much lower than the peak cladding temperatures for large break LOCAs. Similarly,.the maximum cladding oxidized for the hottest rod and the total cladding oxidation for the revised small break LOCA analysis are virtually unaffected and are bounded by calculated values for the large break LOCA. Thus, the proposed reduction in required differential pressure for the HPSI pump will not 1 adversely affect previous analysis results which demonstrated that the large break LOCA produces the limiting peak cladding temperatures.

The potential effects of the proposed reduction in required differential  !

pressure on the steam line break analysis have also been evaluated. For a steam line break, the rapid blowdown from the affected steam generator leads to significant cooling and attendant pressure decreases in the RCS. In the presence of negative moderator temperature coefficient the cooling of the RCS inserts positive reactivity. As reflected in the current FSAR analyses, for some of the steam line break cases considered, this positive reactivity insertion could lead to a brief period of criticality after scra. The HPSI system would be actuated by a low pressurizer pressure SIAS for many of the cases considered. The addition of borated water mitigates the reactivity transient and repressurizes the RCS. AP&L has submitted a ceparate '

Technical Specification amendment to increase tne boron concentration in the .

refueling water tank (RWT) which provides suction for the HPSI pumps. The  !

increased boron concentration in the RWT will partially offset the effect of the proposed reduction in the required differential pressure.

AP&L has reanalyzed the liiniting steam line break case incorporating Cycle 7 '

data, the proposed decreased HPSI differential pressure, and the increased minimum boron concentration in the RWT. Tables 1 and 2 compare the peak return to power and the post trip reactivity of the revised analysis for Cycle 7 to those of the Reference analysis. Based on the comparison, AP&L has concluded that the proposed reduction in required differential pressure will have negligible effect on the steam line break analysis when the additional effects of increasing the RWT boron concentration are considered.

The proposed reduction of required differential pressure for the HPSI pump will not affect the steam generator tube rupture analysis. For this event, the 11 PSI system is assumed to actuate and maintain reactor coolant system pressure. This transient does not result in uncovering the core or in any reactivity transients. Thus ,the accident analysis results are insensitive to the exact repressurization of the reactor coolant system. The slight decrease in RCS pressurization would slightly decrease leakage through the ruptured tube with a corresponding decrease in steam generator pressurization and calculated offsite doses. Thus the proposed decrease in the required differential pressure will have a slightly beneficial effect on the analysis results.

Criterion 2 Does not create the possibility of a new or different kind of accident from any previously evaluated.

The proposed change does not create the possibility of a new or different kind of accident from any previously evaluated since this change involves a minor reduction in a parameter already specified in the surveillance requirements. The proposed change has no effect on plant design or on operator response to transients or accidents. The proposed reduction in required differential pressure will therefore not create any potential for unanalyzed accidents.

Criterion 3 Does not involve a significant reduction in a margin of safety.

The proposed change does not significantly reduce any margin of safety for the plant. The slight reduction in required differential pressure affects the small break LOCA analysis and the steam line break analyses. AP&L has reanalyzed.these events and demonstrated that the margins of safety are not significantly reduced. The peak cladding temperatures, maximum oxidation for the limiting rod, and total oxidation f6r the revised small break LOCA analysis are completely bounded by the large break LOCA results with no substantial decrease in margins from the previous small break analysis. The effect of the reduction in required differential pressure on the steam line break analysis is partially offset by another proposed Technical Specification amendment to increase the RWT boron concentration. The revised steam line break analysis results shown in Tables 1 and 2 demonstrate that the proposed change does not significantly affect any safety margins. With respect to the steam generator tube rupture, the proposed reduction in HDSI differential pressure requirement will actually improve the margin of safety.

CONCLUSIONS The Commission has provided guidance concerning the application of the standards for determining whether a significant hazards consideration exists. This guidance includes examples (51FR7750) of types of amendments that are considered not likely to involve significant hazards considerations. The changes proposed in this amendment have been reviewed against the examples provided by the Commission. i l

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--f, Example.(vi) relates to' changes which may involv small reductions in safety margin but the results of the change are still within applicable acceptance criteria. 'This example is applicable to the proposed changes. The very small. incremental reductions ~in margin associated with the proposed change j are not significant. AP&L has completed detailed analyses of the accidents i which are affected and these analyses have demonstrated that the changes

- from the original accident analysis are inconsequential. ,

Based on these evaluations, AP&L has determined that this change involves no i significant hazards considerations.

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TABLE 1 PEAK RETURN TO POWER DURING A STEAM LINE BREAK EVENT

(% 0F FULL POWER)

Case Reference' Cycle 7 Full load, two-1oop initial .

30.8 9. O condition, nozzle break without moisture carryover, with loss of AC power.

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-TABLE 2 PEAK POST-TRIP REACTIVI'iY'0URING A STEAM LINE BREAK EVENT f

(% Ap) /

Case Reference Cycle 7 Full 1 cad, two-loop initia1 +0.023 -0.034 condition,-nozzle break without nioisture carryover,. with Joss

. of AC. power.

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