ML20247E683

Safety Evaluation Supporting Amend 123 to License DPR-3

ML20247E683
Person / Time
Site:	Yankee Rowe
Issue date:	08/31/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20247E658	List: ML20247E653 ML20247E668 ML20247E683
References
NUDOCS 8909150354
Download: ML20247E683 (3)

Text

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/ o,, UNITED STATES 8

L- o NUCLEAR REGULATORY COMMISSION g E WASHINGTON, D. C. 20555

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.123 TO FACILITY OPERATING LICENSE NO. DPR-3 YANKEE ATOMIC ELECTRIC COMPANY YANKEE NUCLEAR POWER STATION DOCKET NO.50-029 INTRODUCTION By letter dated October. 21, 1988 and as supplemented November 22, 1988, the Yankee Atomic Electric Company (YAEC or the licensee) requested an amendment to Facility Operating License No. DPR-3 for the Yankee Nuclear Power Station (YNPS or the plant).

This amendment:

1. incorporates as a result of Amendment No. 69, overpressurization protection into the description of the bases for main coolant system high pressure (Page B2-5)

2. removes the high pressurizer water level trip instrumentation from table 3.3-1 (Page 3/4 3-2), Table 4.3-1 (Page 3/4 3-8) and the associated bases description in section 2 (Page B2-4) as a result of Amendment No. 69 crediting the overpressurization protection provided by the main coolant system high pressure trip.

DISCUSSION The High Main Coolant System Pressure trip was installed at Yankee Nuclear Power Station (YNPS) in 1981 and presently replaces the High Pressurizer Water Level trip in providing primary protection for overpressurization of the Main Coolant System. This amendment modifies Section 2, Bases descriptions and operable instrumentation requirements in two tables in the technical specifications to be consistent with the 1981 change in plant. Removing the High Pressurizer Water Level trip from the required operable instrumentation will allow greater operational flexibility during full-load operation.

EVALUATION The High Pressurizer Water Level trip instrumentation was originally provided to ensure protection against Main Coolant System overpressurization by limiting the water level to a volume sufficient to retain a steam bubble and 9

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prevent water relief through the pressurizer safety valves during an uncontrolled rod withdrawal or loss of load event. ,

However, the High Main Coolant System Pressure trip was incorporated into the Technical Specifications by Amendment No. 69, to provide additional protection against Main Coolant System overpressurization.

The High Main Coolant System Pressure trip has been credited in the loss of load and more recently in the control rod withdrawal safety analyses. The control rod withdrawal transient was analyzed using the GEMINI Code for predicting plant pressure response and the COBRA-3C Code to evaluate Departure from Nucleate Boiling Ratio (DNBR). This methodology has been previously approved in conjunction with the reload analysis for YNPS.

The reactivity addition rate in the rod withdrawal analysis was varied between a minimum value of less than 0.1E-05 delta k/k/sec and a maximum value of 20.0E-05 delta k/k/sec. All other reactivity feedback parameters were held constant. The minimum reactivity addition rate was determined such that an automatic reactor trip would not occur. The maximum reactivity addition rate is greater than the maximum reactivity insertion rate currently allowed by Technical Specification 4.1.3.1.3. This was done to bound all allowable reactivity insertion rates.

Only a narrow range of slow reactivity addition rates (between 0.1E-05 and 0.2E-05 delta k/k/sec) caused a reactor trip by high pressure. Faster reactivity addition rates caused a reactor scram by high neutron flux. In every case, the analysis has shown the response of the pressurizer water level is such that a loss of the pressurizer steam bubble or water relief through the safety valves will not occur. The DNBR calculation also yields acceptable results for this event.

The results of the analysis described above demonstrate that the High Main Coolant System Pressure trip, in conjunction with the pressurizer safety relief valves, provides adequate protection against system overpressure. The Pressurizer High Water Level trip is completely redundant and not required to provide overpressure protection when the High Pressure trip is operable.

For these reasons, the staff finds with the licensee's proposal to remove the operability requirement for the High Pressurizer Water Level trip and the associated description contained in Section 2, Bases to be acceptable.

The staff also agrees with the licensee's proposal to modify the high main coolant system description contained in Section 2, Bases. The High Coolant System Trip was incorporated into the technical specifications to provide protection against main coolant system overpressurization. The licensee's modification of the description is consistent with Amendment No. 69 and the Standard Technical Specifications (NUREG-0452).

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I SAFETY CONCLUSION Based on our review of the material submitted by YAEC we find that the modt-fications to the technical specifications do not involve a significant increase in the probability or consequences of an accident previously analyzed. The modification to the High Main Coolant System bases description and the removal of the High Pressurizer Water Level bases description in Section 2 are adminis-trative changes, and as such, would not involve a significant increase in the probability or consequences of an accident previously analyzed because the High Main Coolant System Pressure instrumentation will provide overpressurization protection for transient event.

Based on the considerations contained herein, it is concluded that the operation of the Yankee Plant with the proposed amendment will not endanger the health or the safety of the public and is acceptable.

ENVIRONMENTAL CONSIDERATION I

This amendment involves a change in the use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has deter-mined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously published a proposed finding that the amendment involves no significant hazards considera-tion and there has been no public comment on such finding. Accordingly, this  ;

amendment meets the eligibility criteria for categorical exclusion set forth in i 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact  !

statement or environmental assessment need be prepared in connection with the issuance of this amendment.

CONCLUSION The Commission made a proposed determination that the amendment involves no significant hazards consideration, which was published in the Federal Register (53 FR 50336) on December 14, 1988, and consulted with the State of Massachusetts. No public comments were received and the State of Massachusetts l' l did not have any comments.

The staff has concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safet of the public will not be endangered by operation in the proposed manner, and 2) such activities I will be conducted in compliance with the Commission's regulations, and (3) the {

issuance of this amedment will not be inimical to the common defense and j security or to the health and safety of the public. t Principal Contributor: Patrick Sears j l

Dated: August 31, 1989 I .

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