B17057, Forwards Changes to TS Bases Section 3/4.4.9, Pressure Temperature Limits. Change to TS Bases Section 3/4.4 Is to Clarify Applicability of Copps (Cold Overpressure Protection Sys) Curves,As Described in Bases of TS

Forwards Changes to TS Bases Section 3/4.4.9, Pressure Temperature Limits. Change to TS Bases Section 3/4.4 Is to Clarify Applicability of Copps (Cold Overpressure Protection Sys) Curves,As Described in Bases of TS

ML20236T525
Person / Time
Site:	Millstone
Issue date:	07/17/1998
From:	Bowling M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20236T527	List: B17057, Forwards Changes to TS Bases Section 3/4.4.9, Pressure Temperature Limits. Change to TS Bases Section 3/4.4 Is to Clarify Applicability of Copps (Cold Overpressure Protection Sys) Curves,As Described in Bases of TS ML20236T530
References
B17057, NUDOCS 9807280240
Download: ML20236T525 (6)

Text

- - - _ - - - - - - - - _- -- -- - - - - - - ---------- ------- - - - - -

IC Ndd ""P* F'"Y "d '" " 256)' '***'rora. cr 06385 4 LNudear Energy wai,too Noctear po.e, station Northeast Nuclear Energy Company e.0. Box 128

. , Waterford, CT 06385-0128 (860) 447-1791 i Fax (860) 444-4277 The Fortheast Utilities System JUL i 71998 Docket No. 50-423 B17057 i Re: 10CFR50.59 L

l U.S. Nuclear Regulatory Commission ,

l Attention: Document Control Desk 5 Washington, D.C. 20555 Millstone Nuclear Power Station, Unit No. 3 Change to Technical Specification Bases Cold Overpressure Protection System -

Isolated Looo Ooeration (TSCR 36-98)

Northeast Nuclear Energy Company (NNECO) is providing the NRC Staff with changes l' to Technical Specification (TS) Bases Section 3/4.4.9 (Pressure / Temperature Limits) l for information only.- These changes have been. reviewed and approved by the l Millstone- Unit' No. 3 Plant Operating Review Committee on June 26,1998, in l- accordance with the provisions of 10CFR50.59. l l: 1 Description of Chance

The change to Technical Specification Bases Section 3/4.4 is to clarify the applicability )

1 of the COPPS (Cold Overpressure Protection System) curves, as described in the l Basas of the Technical Specifications.' The three issues addressed are: i l

a) Clarify the fact that the power operated relief valve (PORV)'setpoint curves are only applicable when no more than one RCS loop is isolated from the remainder of the reactor coolant system (RCS);

b) When one RCS loop is isolated from the remainder of the RCS, the temperatutc )

3,- input from the isolated loop must be removed from the COPPS auctioneered

' ' 3 ): 0 _ circuitry if a reactor coolant pump (RCP) is. in operation; and c) When either one loop is isolated and the temperature input from the isolated

)l' l loop'has not been removed from the, COPPS circuitry and an RCP is.in gl operation, or if more than one loop is icolated, the PORVs must have their block {0 valves closed or COPPS must be blocked.

9907290240 990717 PDR- ADOCK 05000423 P PDR ,-g

U.S. Nucinr Regulatory Commission B17057\Pcgn 2 in addition, the case of a single loop stop valve being closed is addressed.

' Sucole' mental information Prior to Amendment 157 to the Millstone Unit No. 3 Technical Specifications (TS), the

, PORV COPPS curves were presented in the TS for four loop and three loop operation l as Figures 3 4-4a and 3.4-4b, respectively. Amendment 157 revised these figures and the corresponding titles from three and four loop operation to low and high PORV setpoint curves, but did not indicate any restrictions on their use with regard to the number of unisolated loops.

The development of the curves enveloped the results from three and four loop operation based on analyses performed by Westinghouse. However, during the preparation' of the amendmont submittal, which supported Amendment 157, the fact that the PORVs were only qualified for three or four loops unisolated was not clearly indicated in either the Limiting Conditions of Operation or in the applicable Bases of the Technical Specifications.

Prior to Amendment 157, the COPPS curves were only used to protect the Appendix G l limits. During the preparation of the amendment submittal, it was identified that valve l undershoot could challenge the integrity of the reactor coolant pumps #1- seal.

l Therefore, the Technical Specifications were wiitten so as to provide protectico for the i RCP #1 seal, as we!I as Appendix G limits.

With one loop isolated, it was noted that the temperaiu input for the PORV COPPS ,

circuitry would include one temperature input from the isolated loop. Since the COPPS ]

circuitry selects the lowest temperature, this is only a concem when the isolated loop is i l at a temperature lower than the unisolated portion of the RCS. For Appendix G l considerations, this lower temperature is conservative since the PORVs would actuate at a lower pressure. However, if an RCP was in operation, the resulting undershoot could challenge the #1 seals.

To address the above issues, the BASES of the Technical Specifications have been revised. The revision clarifies that Figures 3.4-4a and 3.4-4b apply only for three or four loops unisolated and that, with one loop isolated and an RCP in operation, the temperature input from the isolated loop is required to be removed from the COPPS circuitry. If a loop is isolated without removing its temperature input from the PORV calculated setpoint auctioneered circuit and at least one RCP is in operation, then the PORVs must have their block valves closed or COPPS must be blocked. Similarly, .

l these actions to remove COPPS from service are required if more than one loop is isolated. Under these conditions, RCS overpressure protection must be provided by the RHR suction relief valves or the RCS must be depressurized and vented.

The term " isolated" loop means that both of the RCS loop stop valves are closed. The

. possibility exists that only one loop stop valve could be closed. As noted above, he j

' concern with an isolated loop is that the RCS temperature in tha isolated portion oi me j l

' U.S. Nuciser R:gulatory Commission B17057\Pegn 3 1,oop could be lower than the unisolated portion of the RCS. This is a concern since valve undershorts at the lower pressure setting corresponding to the lower temperature could challenge the RCP #1 seal when an RCP is in operation. For an isolated loop there is no concern related to the Appendix G limits since the fluid in the isolated loop cannot reach the reactor pressure vessel. However, for a single loop stop valve closed, natural circulation could exist. In particular, if the steam generator is colder g than the RCS temperature and the hot leg loop stop valve is open, co' der fluid could I reach the reactor pressure vessel. For this case, a single failure of the hot leg temperature sensor could result in an unconservative PORV pressure setting. For this reason, the PORVs cannot be used for Cold Overpressure Protection when only one loop stop valve is closed. Thus, to eliminate the potential challenge to the intogrity of l the RCP #1 seal, it is required that the PORVs have their block valves closed or COPPS be blocked when only one loop stop valve is closed. Since it takes some time for natural circulation to significantly lower the temperature of the RCS fluid, the above restriction applies only when a single loop stop valve is closed for an extended period.

During surveillance or other evolutions when a single loop stop valve is closed for a j short period of time, the PORVs can be used for Cold Overpressure Protection and {'

RCPs can be in operation, since the RCS temperature will remain relatively stable.

The change to the Technical Specification Bases for Overpressure Protection Systems is to provide clarification that TS Figures 3.4-4a and 3.4-4b apply only for three or four loops unisolated and does not change the function or operation of any system, structure or component. ,

A copy cf the marked up Technical Specification bases pages is contained in Attachment 2. A copy of the retyped Technical Specification Bases pages is contained i in Attachment 3. )<

if you have any questions, please contact Mr. D. Smith at (860) 437-5840.

Very truly yours, l

NORTHEAST NUCLEAR ENERGY COMPANY l I

Martin L. Bowling, Jr.

$bh J Recovery Officer - Technical Services cc- H. J. Miller, Region I Administrator ,

W. D. Travers, Ph. D., Director, Special Projects Office J. W. Andersen, NRC Project Manager, Millstone Unit No. 3 A. C. Ceme, Senior Resident inspector, Millstone Unit No. 3 l- j l

(

i Docket No. 50-423 B17057 u

l Attachment 1 Millstone Nuclear Power Station, Unit No. 3 l Change to Technical Specification Bases

! Cold Overpressure Protection System -

Isolated Loop Operation (TSCR 3-6-98)

NNECO's Commitments l

l t

t f

l )

p July 1998 )

i

• L' U.S. Nuclear Regulatory Commission ,

l' B17057%ttachment 1\Page1 l

l Enclosure l List of Regulatory Commitments l

l r

The following table identifies those actions committed to by NNECO in this document. i Please notify the Manager - Regulatory Compliance at the Millstone Nuclear Power  ;

Station Unit No. 3 of any questions regarding this document or any associated I regulatory commitments.

Number Commitment Committed Date or Outage

-None l-l L

_--_ _._-.__._.-.-__.__.._.m_.m __ ____ _ _ . _-_ _ _ -

.__-_j

Docket Nos. 50-243 B17057 i

I Attachment 2 Millstone Nuclear Power Station, Unit No. 3 Change to Technical Specification Bases Cold Overpressure Protection System -

Isolated Loop Operation (TSCR 3-6-98)

Marked up Pages July 1998 l A

L_________.