ML19347F315

Application to Amend License DPR-35 to Change Tech Specs Allowing Operation W/One Recirculation Loop Out of Svc. Application Supercedes 801121 Ltr 80-295 Re Provisions for 50% Reactor Power W/One Recirculation Loop Out of Svc

ML19347F315
Person / Time
Site:	Pilgrim
Issue date:	05/12/1981
From:	Howard J BOSTON EDISON CO.
To:	Ippolito T Office of Nuclear Reactor Regulation
Shared Package
ML19347F316	List: ML19347F315 ML19347F317 ML19347F318
References
81-94, NUDOCS 8105180356
Download: ML19347F315 (5)

Text

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f BOSTON EDISON COMPANY BOO BOYLSTON STREET DOSTON. MASSACHUSETTS 02199 J. EDWARD HOWARD was peso.osmr om.e May 12,1981 BECo. Ltr. #81-94 s Proposed Change #81-02 Mr. Thomas A. Ippolito, Chief Operating Reactors Branch #2 Division of Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C. 20555 License No. DPR-35 Dociet No. 50-293 Revised Request for Technical Specification Changes Concerning Single Loop Operation Reference (a) BECo letter #80-295 (J.E. Howard) to NRC (T.A. Ippolito)

" Proposed Technical Specification Change Concerning Single Loop Operation", dated November 21, 1980

Dear Sir:

Facility Operating License No. DPR-35 for Pilgrim Nuclear Power Station Unit #1 (PNPS-1) requires that the plant be shutdown if an idle recirculation loop can-not be returned to service within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Boston Edison requests that this license provision be revised to allow operation with one recirculation loop out of service. It is also requested that this pro-BECo. letter #80-295 dated November posed change(a))which 21,1980,(ref. supercedeincluded in it's entirety, provisions for 50% reactor power with one re-circulation loop out of service.

The loss of a single recirculation pump has occurred at several operating BWR's and is not, therefore, an improbable event. While the time required to procure necessary parts and to repair the loop depends on the nature of the failure, any loss of operating capacity would have a significant economic effect. Modifying the Technical Specifications as requested will reduce this potential economic impact without reducing the safety of plant operation.

4 WO3 TON EICON COMPANY Mr. Thomas A. Ippolito, Chief May 12,1981 Page Two The evaluation of this proposed mode of operation provided to Boston Edison by GE and described in Attachment (C), supports the conclusion that this mode of oper-ation~will not reduce safety margins.

Schedule'of Change This change will be put into effect upon receipt of approval from the Comission.

Fee Consideration No fee is proposed, as this change supercedes the Reference (a) letter which included payment pursuant to 10 CFR 170.12 and is still under review by your office.

Should you have any questions on this subject, please do not hesitate to contact us.

Very truly yours, Jhk Attachments

( A) - Modified Rod Block Equation (B) - License & Technical Specification Changes (C) - Pilgrim Nuclear Power Station Single Loop Operation, NED0-24268, June 1980 with Errata and Addenda Sheet No. 1, Sept. 1980 3 signed originals and 37 copies Commonwealth of Massachusetts)

County of Suffolk )

Then personally appeared before me J. Edward Howard, who, being duly sworn, did. state that he is Vice President - Nuclear of Boston Edison Company, the applicant herein, and that he is duly authorized to execute and file the submittal contained herein in the name and on behalf of Boston Edison Company and that the statements in said submittal are true to the best of his knowledge and belief.

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My Commission expires: 70[f [,, /984 M ,1 sll No)fary PubTic /

w Attachment A Modified Rod Block Equation This attachment describes the procedure for modifying the rod block equation for one-pump operation.

a. The two-pump _ rod block equation in the existing Technical Specification is of the form:

RB = (mW + K)% (1) where .

RB = power at rod block in %

m = flow reference slope for the rod block monitor (RBM)

W = drive flow in % of rated K = power at rod block in % when W = 0.

For the case of top level rod block at 100% flow, denoted RB 100 3

RB 100

= m( 00) + K or K = RB - m(100) 100 Substituting for K in Equation (1), the two pump equation becomes:

RB = mW + (RB 100 - m( 00 (2)

b. Next, the core flow (F ) versus drive flow (W) curves are determined for the two-pump and one-pump cases. For the two-pump case the core flow and drive flow are derived by measuring the differential pressures in the jet pumps and recirculation loop, respectively. Core flow for one pump operation must be corrected for the backflow through the inactive jet pumps thus:

Actual core flow (cne pump) = Active jet pump flow - inactive jet pump flow.

Both the active and inactive flows are derived f rom the jet pump differential pressures. The drive flow is derived from the differ-ential pressure measurement in the active recirculation loop. These two curves are plotted in Figure 1. The maximum difference between the one-punp and two-pump core flow is determined graphically. This occurs at about 35% drive flow which is denoted W. J Page 1 of 3 l

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c. Next, a horizontal line is drawn from the 35% drive flow point'on the one pump curve to the two pump curve and the corresponding flow, W 2 , is determined. Thus, AW = W g -W*2.

The rod block equation corrected for one pump flow is:

~

RB = mW + - m(100) - ARB 109 where A RB = RBy - RB 2

~"w RB = mW + RB - m(100 + AW) (3) 100

d. The constants from the Technical Specification are:

m = 0.65 RB = 07 100 From Figure 2:

AW = W g -W2 = 35 - 30 = 5 Evaluating in Equation (3),the one-pump rod block equation becomes:

RB = 0.65W + 107 - 0.65(100+5) = 0.65W + 38.7 (4)

This line is depicted in Figure 1 as the corrected rod block line for one-pump operation.

-APRM TRIP SETTING The APRM trip settings are flow biased in the same manner as the rod block monitor trip setting. Therefore, the APRM rod block and scram trip settings are subject to the same procedural changes as the rod block monitor trip setting _ discussed above. ,

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