ML20245D669

Forwards Supplemental Response to ATWS rule,10CFR50.62 Re Alternate Rod Insertion.Concludes That Unit 2 in Compliance W/Atws Rule & Expects Unit 3 to Be in Compliance After Completion of Mod & Testing

ML20245D669
Person / Time
Site:	Peach Bottom
Issue date:	04/21/1989
From:	Gallagher J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-59125, TAC-59126, NUDOCS 8905010095
Download: ML20245D669 (6)

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, . . 10 CFR 50.62 PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA 19101 (215) 841 5001 JOSEPH W, G ALL AGHER April 21, 1989

,JcU".'L"c's.

Docket Nos.: 50-277 50-278 TAC Nos.: 59125 59126 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

SUBJECT:

Peach Bottom Atomic Power Station Units 2 and 3 Alternate Rod Insertion Modification Pursuant to ATWS Rule

REFERENCE:

NRC Safety Evaluation Report on PBAPS Compliance with 10 CFR 50.62 c(3) and c(5) dated-December 21, 1988

Dear Sir:

This letter supplements Philadelphia Electric Company's response to the Anticipated Transients Without Scram (ATWS) Rule, 10 CFR 50.62, relative to the Alternate Rod Insertion (ARI) requirements pertaining to Peach Bottom Atomic Power Station. Upon approving the Peach Bottom ARI design, the NRC required Philadelphia Electric Company to perform a preoperational test to confirm that the actual ARI function time is within design limits (see reference above). The expected Peach Bottom ARI function time, 24 seconds, was discussed in an April 3, 1987 letter from J. W. Gallagher (PECo) to D. R. Muller (NRC). Because Philadelphia Electric Company was aware that similar ARI systems at other nuclear power plants did not meet their function time design criterion when tested, General Electric Company was retained to perform a Peach Bottom plant specific analysis to justify a longer function time. Attached is a General Electric Company evaluation of Peach Bottom Unit 2 control rod drive ARI performance which concludes that a 35.4 second function time is acceptable. This evaluation bounds Peach Bottom Unit 3 and is discussed in more detail below.

8905010095 890421 f.0 fh PDR ADOCK 05000277 - - -.

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,U. S. Nuclear Ragulatory Commission April 21, 1989 Page 2 General Electric Topical. Report NEDC-30921, " Assessment'of ATWS Rule Compliance Alternatives", July-1985, provided design criteria for ARI. The 15 second control-rod start-of-motion and 25 second i . control rod full-insertion' criteria given in topical report NEDC-30921 are the result of generic conservative assumptions used in the calculation of the scram discharge volume fill time. Because these time criteria are generic.and bounding for BWRs, they can be

' modified on the basis of evaluations using plant-specific data. The attached General Electric evaluation is based on Peach Bottom Unit 2 data and concludes that a total function time of 35.4 seconds

. fulfills the design objectives of ARI. This function time is based on a conservative scram discharge volume in-leakage rate of five gallons per minute per control rod drive (rate consistent with NRC Generic Safety Evaluation Report, "BWR Scram Discharge Volume,"

December 1, 1980).- This evaluation bounds Peach Bottom Unit 3.

Unit 3 is equipped with a larger scram discharge volume than Unit 2 and has equivalent control rod drives.

On March 9, 1989 a preoperational test was performed on Unit 2.

The test confirmed-that the ARI function time is less than 35.4 seconds. In conclusion, the Company considers Unit 2 to be in compliance with the ATHS Rule ARI requirements and expects Unit 3 to be in compliance after completion of the modification and testing.

If you have any questions or require additional information, please do not hesitate to contact us.

Sincerely, Attachment cc: W. T. Russell, Administrator, Region I, USNRC T. P. Johnson, USNRC Senior Resident Inspector T. E. Magette, State of Maryland R. E. Martin, USNRC Peach Bottom Project Manager J. Urban, Delmarva Power J. T. Boettger, Publi" Service Electric & Gas H. C. Schwemm, Atlantic Electric T. R. Gerusky, Commonwealth of Pennsylvania i,

g;.

Docket Nos. 50-277 50-278-

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'GE Nuclear Energy-ENGINEERING SERVICES REACTOR DESIGN ENGINEERING January 27, 1989 cc: J. E. Cearley L. B. Claassen J. F. Klapproth 698-89-001

.To: G. .I. Samstad

.From: B. W. Joe

Subject:

Peach Bottom 2 CRD ARI Performance

References:

1. " Assessment Of ATWS Compliance Alternatives,"

NEDC-30921, July 1985 2.

NRC Generic Safety Evaluation' Report, BWR Scram Discharge volume, December 1, 1980

3. G. P. Budock to S. Playhar, "ARI Rod Insertion Time Ektension Information",

January 5, 1989 ,

4. A. R.-Diederich to D. W. Diefenderfer, " Peach Bottom Atomic Power Station, Unit'2 Alternate Rod Insertion Modification No. 865 P.O.

ME-275230-No," January 23, 1989

5. DRF C11-00189, Peach Bottom 2 ARI SDV Fill Evaluation, Index 12

'The purpose of this letter is to provide the results of an evaluation of the Alternate Rod Insertion. control rod start-of-motion based onand' full-insertion plant-specific time criteria'for Peach Bottom Unit 2 data.

INTRODUCTION In the' event that.the normal scram path cannot be initiated by the Reactor Protection System (RPS), the Alternate Rod Insertion 1 of 4

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(ARI) of the Control Rod Drive (CRD) System functions as an L alternative path for reactor shutdown. The signal to initiate f the ARI function comes from a reactor vessel dome high pressure i

signal, a reactor vessel low-low water level signal, or manuel l action. Following ARI initiation, ARI valves in the scram air header open and vent the header. This allows the hydraulic control unit inlet and outlet scram valves to open to initiate control rod insertion. Furthermore, the air lines to the scram discharge volume (SDV) vent and drain valves will depressurize resulting in the closure of these valves. There is no ARI requirement for the SDV vent and drain valves to close.

The criteria for the control rod start-of-motion and full-insertion time for ARI for Peach Bottom 2 were evaluated using plant specific data. The 15 second control rod start-of-motion and 25 second control rod full-insertion criteria given in topical report NEDC-30921 (Ref. 1) are the result of generic conservative assumptions used in the calculation of the scram discharge volume (SDV) fill time. Because these values are generic, they can be modified on the basis of evaluations using plant-specific data. The next limiting requirement is that full rod insertion is to be completed within 60 seconds of the ARI initiation time to maintain pressure supression pool temperature limits. Therefore for a given plant unique configuration, the 15 L and 25 second values may be capable of being exceeded as long as the 60 second value is not exceeded, and the SDV maintains its

ability to accept water until all rods have been fully inserted.

RESULTS For Peach Bottom 2, based on the limiting available SDV volume of 825 gallons (Ref. 4), a deviation from the 15 and 25 second criteria has been found to be acceptable. Becausc the SDV fill time criteria depend upon the average CRD in-leakage rate, evaluations were performed for the NRC SER-suggested SDV in-leakage of 5.0 GPM/CRD (Ref. 2) and two additional in-leakage values of 4.0 and 3.0 GPM/CRD.

The 4.0 and 3.0 GPM/CR0 leakage rates are conservatively estimated to correspond to maximum average withdraw stall flows of 2.5 and 1.6 GPM, respectively, utilizing test data which correlate withdraw stall flow rates with post-scram CRD leakage rates. The criteria based on the 4.0 or 3.0 GPM/CRD leakage rates may be utilized if drive maintenance is performed to assure that the actual average withdraw stall flow is less than the maximum average withdraw stall flow corresponding to the chosen criteria. The latest test data from Peach Bottom 2 (Ref. 3) show an average withdraw stall flow of 1.0 GPM.

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The summarized'in results of the thePeach Bottom following table.2' plant unique evaluation are 1

SDV In-Leakage Maximum Average (GPM/CRD) Withdraw Stall Start-of-Motion' Full-Insertion Time Allowable Flow (GPM) Time Allowable Limit (S.ec. ) Limit (Sec.)

e -_

5.0x ---

30.4

'35.4-4.0' 2.5 39.3 44.3-3.0 1.6 54.1 59.1-A' in the' maximum 100% insertion scram time of S.0 seconds was utilized evaluation.

The scram time-assumes a maximum 90% rod travel ~ scram time of 4.0 seconds plus the additional time required,to reach 100% insertion under ARI conditions. The

'latest Peach Bottom 2 scram test data.(Ref.

show 3), a maximum 90%

4 insertion scram time'of 3.13 seconds .

The evaluation also assumes that CRD motion and-the consequent

!. ~SDV.inleakage begins at the time of ARI: initiation. If test data L shows that the first CRD notion occurs'at.a later time,Ithen the.

start-of-motion and full- insertion time' limits may be adjusted.

}

'accordingly notion occurs. by adding to them~theitime at'which the first CRD (For example, if the first CRD motion = occurs 5 -

seconds'after ARI' initiation,-then 5 seconds may be added to'the

-start ~of-motion and full-insertion time limits.) The~ final.

full-insertion time limit must not exceed 60 seconds unless

.additional temperature. evaluations-are limits. performed for the supression pool 4

~

' ANALYSIS The following description utilizes the evaluation where the SDV in-leakage rate is assumed to be 5.0 GPN/CRD.

The occurs. SDV is assumed to be initially empty ihen'ARI initiation The in-leakage into the SDV from the closed outlet scram valves is assumeC to be negligible. To assure a conservative analysis, alliof the 185 CRD's except one are assumed to begin t

inserting at the time'of ARI initiation and leak water into the SDV limit is at~5.0 GPM/CRD from this time until the full-insertion time reached.

Each CRD also contributes approximately 1 gallon of water to the SDV due to stroking. As water enters the SDV,'the pressure in the SDV will increase since the SDV vent and drain valves are also conservatively assumed to be closed at the time:of ARI' initiation.

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The last CRD begins inserting at 30.4 seconds after ARI initiation and leaks water into-the SDV at 5.0 GPM for 5.0 seconds, which is the assumed 100% scram time, until the full-insertion scram functiontime limit of 35.4 seconds is reached and the ARI is completed.

The 35.4 second full-insertion time limit is not directly based on the total available SDV volume, but rather is based on the maximum the cRD scram pressure within the SDV which will not adversely affect performance.

o gallons of water has entered the After SDV. 35.4. seconds, a total of'722 The evaluation is contained in Design Record File Cll-00189, Index 12 (Ref. E).-

Revie

\QOAE. G.LGibo d By:

m i bolst Date' n

contr ' Rod Drive LSE ,

07WJ.

Verified By: A. C. Tsang

//27/89 ~'

.Date Reactor Pressure Vessel LSE C

Reviewed By: N. CJ Shirley l M Date Licensing and Consulting Services 6

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