ML20247M529

Application for Amend to License DPR-3,modifying Tech Spec 3.2.4,Table 3.2-1 to Substitute Limit on Operating Loop Average Temp for Current Limit on Cold Leg Temp

ML20247M529
Person / Time
Site:	Yankee Rowe
Issue date:	07/24/1989
From:	Drawbridge B YANKEE ATOMIC ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20247M533	List: ML20247M529 ML20247M632
References
BYR-89-120, PC-226, NUDOCS 8908020137
Download: ML20247M529 (5)

Text

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~ YANKEE ATOMICELECTRIC COMPANY "'C"',]g*]o"f,*g'"

I 580 Main Street, Bolton, Massachusetts 01740-1398

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YANKEE July 24 1989 PC 226 BYR 89-120 i United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

References:

(a) License No. DPR-3 (Docket No. 50-29)

(b) YAEC-1652, " Yankee Nuclear Power Station Core 20 Performance Analysis," August 1988

Subject:

Request for Change to Technical Specification 3.2.4

Dear Sir:

i Pursuant to Section 50.90 of the Commission's Rules and Regulations, the Yankee Atomic Electric Company hereby requests the authorization to make the following changes.

Proposed Change We. propose to modify Table 3.2-1 of Technical Specification 3.2.4 to substitute a limit on the operating loop average temperature for the current limit on cold leg temperature. The proposed average temperature limit will be constant between 50% and 100% power. Below 50% power the limit will decrease linearly to ensure acceptable results for low power Main Steam Line Break events. This change will allow higher Main Coolant System temperatures during part-load operation than are permissible under the current cold leg temperature limit. The design DNBR at full power remains bounding under the proposed change. Revised pages containing the proposed changes are attached.

In addition to the above change, we propose to make an editorial change as

. described on Page 4 of this letter.

Reason for Change The change will allow greater operational flexibility during part-load operation. -

Basis for Change The current limit on cold leg temperature is provided to assure steady state operating conditions consistent with the assumptions of the analysis of approach to DNB limits during transients. The analyses are typically based on l

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United States Nuclear Regulatory Commission. July 24, 1989 L Attention:, Office of Nuclear Reactor Regulation Page 2 BYR 89-120 full power operation, and the limit' is applied to the operating power range.

With the proposed change, the design full power operating conditions will remain bounding.

A DNB evaluation has demonstrated that

with the revised limit, DNB margins during part-load operation will continue to be bounded by full power conditions. For:the current cold leg temperature limit, the limiting DNBR occurs at full power operating conditions. DNB performance improves with decreasing power level. The proposed average temperature limit has been derived to maintain DNBR margins' equal to or. greater than the limiting full power condition. For the-most limiting design conditions, which incorporate the power distribution limits of Technical Specifications 3.2.2 and 3.2.3, the full power DNBR remains limiting. Thus, under the proposed average temperature limit DNB performance during part-load operation is bounded by the limiting full power condition.

The table below summarizes the results of the DNB. evaluation using the revised average temperature limit. The values given include the effect of control rod insertion to the PDIL as well as the increased cold leg temperature at the reduced power levels. The design MDNBR incorporates the powerHdistribution. limits of Technical Specifications 3.2.2 and 3.2.3 in addition to the increased cold leg temperatures.

Power (%) Nominal MDNBR Design MDNBR 100 4.16 2.93

.90 4.62 2.99 80 4.95' 3.06 70' 5.20 3.10 Transients initiated from the proposed part-load operating conditiot.s have been evaluated. The main steam line break transient is the only licensing analysis affected by the proposed change. Zero and 50% power cases have been reanalyzed for this event, assuming initial Main Coolant System temperatures consistent with the proposed change. For both the zero and 50%

power cases the available shutdown margin is adequate to preclude inadvertent criticality. Thus, the results of the main steam line break event remain acceptable.

The table below summarizes the results of the main steam line break reanalysis using the revised temperature limit. The reanalysis was based on Core 20 reactivity data and flux peaking factors consistent with the Core 20 reload analysis (Reference (b)).

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'i ' United States Nuclear' Regulatory' Commission July 24,1989 Attention: Office of Nuclear Reactor Regulatica Page 3 BYR 89-120 MSLB Analysis Using Revised Limit Minimum p Analysis Initial Subcriticality L ' Case' T-ColdOF (% Reactivity) full Power 520 0.84 50% Power 531 0.59 Zero Power 536- 0.22 Safety Considerations This changeuis. requested ~in order to enhance operational flexibility.by increasing the allowable Main Coolant System temperature during part-load

. conditions. The effect of this' change on the steady-state DNBR.and transient

! licensing analyses has been evaluated. This proposed change would not:

(1) Involve a significant increase in_the probability or consequences of an accident previously analyzed. An increase in temperature will not increase the probability of an accident. The main steam line break is the only licensing analysis affected by the change. The reanalysis of this event has shown that the consequences remain acceptable. Therefore, there is not a significant increase in the probability or consequences of a previously analyzed event.

j (2) Create the possibility of a new or different kind of accident from any previously analyzed. An increase in temperature will not result in a~new failure mechanism which could initiate an accident.

Therefore, the proposed change will not create the possibility of a i new or'different type of accident.

(3) Involve a significant reduction in a macgin of safety. The steady-state DNBR margin has been evaluated at part-load conditions with the increased cold leg temperatures allowed by this change.

The DNB performance at reduced load is bounded by the limiting full power condition. The transient licensing analyses were also evaluated, with the main steam line break being the only affected event. Reanalysis of this transient has shown that the results will remain acceptable. Therefore, this change will not result in a significant decrease in safety margins.

Based on the consideration contained herein, it is concluded that there  !

is reasonable assurance that operation of the Yankee plant consistent with the proposed Technical Specification will not endanger the health and the safety aof the public. This proposed change has been reviewed by the Nuclear Safety Audit and Review Committee.

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. United States Nuclear Regulatory Commission July 24, 1989 Attention:. Office of-Nuclear Reactor Regulation Page 4 BYR 89-120 Proposed Change In' addition to the v.verage temperature limit change, we propose to modify the last paragraph of Technica1' Specification Base 3/4.2.4 to remove the word " Exxon".

Reason for Change Since the Exxon fuel is not used in Yankee's core, the word " Exxon" is not needed.

Basis'for Change The change is editorial in nature, and the rod bow penalty for the fuel in Yankee Rowe is still applied as described.

Safety Considerations This change is editorial; this proposed change would not:

(1) Involve a significant increase in the probability or consequences of an accident previously analyzed.

(2) Create the possibility of a new or different kind of accident from any previously analyzed.

(3) Involve a significant reduction in a margin of safety.

Based on the consideration contained heroin, it is concluded that there is reasonable assurance that operation of the Yankee plant consistent with the proposed Technical Specification will not endanger the health and the safety of the public. This proposed change has been reviewed by the Nuclear Safety Audit and Review Committee.

Schedule of Change These changes to the Yankee Technical Specifications will be implemented upon Commission approval. A timely review and approval of this submittal would be appreciated.

We trust that you will find this submittal satisfactory; however, should you desire additional information, please contact us.

Very truly y rs, Y 'E'E ATOM ELECTRIC COMPANY

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B. . Draw 4 rid i Vice President and Manager of Operations BLD/0027u Attachments L

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United States Nuclear Regulatory Commission July 24,1989 Attention: Office of Nuclear Reactor Regulation Page 5 BYR 89-120 COMMONWEALTH OF MASSACHUSETTS)

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Then personally appeared before me, B. L. Drawbridge, who, being duly sworn, did state that he is Vice President and Manager of Operations of Yankee Atomic Electric Company, that he is duly authorized to execute and file the foregoing document in the name and on the behalf of Yankee Atomic Electric Company and that the statements therein are true to the best of his knowledge and belief.

U S s ,u ,r w Helen D. Sammarco Notary Public My Commission Expires November 7, 1991

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