ML20207U155

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Safety Evaluation Supporting Amend 56 to License DPR-57
ML20207U155
Person / Time
Site: Hatch Southern Nuclear icon.png
Issue date: 06/16/1978
From:
Office of Nuclear Reactor Regulation
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ML20204B112 List:
References
FOIA-87-76 NUDOCS 8703240671
Download: ML20207U155 (6)
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o UNITED STATES f , NUCLEAR REGULATORY COMMISSION

{ E WASHINGTON, D. C. 20566 s...../

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0. 56 TO FACILITY OPERATING LICENSE NO. DPR-57 GEORGIA POWER COMPANY OGLETHORPE ELECTRIC MEMBERSHIP CORPORATION MUNICIPAL ELECTRIC ASSOCIATION OF GEORGIA CITY OF DALTON, GEORGIA EDWIN I. HATCH NUCLEAR PLANT UNIT NO.1 DOCKET NO. 50-321 I. INTRODUCTION By letters dated February 9, February 10, and April 26, 1978, Georgia Power Company (the licensee) requested changes to the Technical Speci-fications appended to Facility Operating License No. DPR-57 for the Edwin I. Hatch Nuclear Plant, Unit 1 (HNP-1). The proposed changes would:

(1) revise the limiting conditions for operation and surveillance require-ments associated with the Plant Service Water System to reflect the addition of an independent capability of providing cooling water to diesel generator 18, (2) revise the surveillance requirements for relief /

safety valves to reflect the replacement of three-stage topworks valves with the two stage topwork design that is identical to that to be used on Hatch Unit 2, and (3) revise the operability requirements for the Standby Gas Treatment System to reflect an extension of the HNP-1 secondary containment by the addition of that space which comprises the refueling floor of HNP-2. During the course of staff review of these requests we determined that revision of the operability requirements and addition of surveillance for the Main Control Room Environmental System should be made. The staff recommended this revision based on the Technical Specifications of HNP-2, since both Units share a common Control Room and should have consistent Technical Specifications. The changes were discussed with the licensee and he agreed with the staff recomendations.

II. EVALUATION

, a. Plant Service Water Systen I

In the arrangement of the Plant Service Water (PSW) system described in the HNP-1 FSAR, Section 10.7, cooling water to Diesel Generator 1B (designated as the " Swing" diesel generator supplying either HNP-1 or

HNP-2) is normally supplied by the Division I section of the PSW system.

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I In the event of failure of the Division I section, cooling water to Diesel Generator 1B will automatically be supplied by the Division II section of the PSW system. The modification to the PSW system of HNP-1 was accomplished by the licensee to reflect the current design bases for HNP-2 such that the cooling water to swing Diesel Generator 1B will be independently supplied by a standby service water pump (as shown in Figure 9.2-3 sheet 1 of HNP-2 FSAR). However, the cooling water intertie between Diesel Generator 1B and the existing PSW system's divisional piping has been retained for use when the standby service water pump is inoperable.

The standby service water pump motor is supplied electric power from MCC R24-S026. The design of this 600V ac motor control center is such that it is supplied by the 4160V ac bus to which Diesel Generator 1B is aligned. The circuits for swing Diesel Generator 18 automatically align it to the accident unit.

Automatic start of the standby service water pump is initiated by a start signal from Diesel Generator 1B or by a signal from the Diesel Generator 1B load sequencer, and the pump will run when power to MCC R24-S026 is available.

The licensee's application proposes the addition of operating limits associated with inoperability of various components of the PSW system which provides cooling water to the Diesel Generators. In the modified PSW system, the licensee has changed the primary source of cooling water for swing Diesel Generator 18. By providing a separate and independent standby service water pump and eliminating the automatic swing between the Division I and Division II sections of the HNP-1 PSW system, the reliability of the.HNP-1 diesel generator cooling water system is enhanced.

This is because a single failure to any one cooling supply will render only its respective diesel generator inoperable ed will not affect operation of the two remaining diesel generator . The original cooling water intertie between the two divisions of the HNP-1 PSW system, has been retained to operate as originally designed, i.e., whenever the standby service water pump is inoperable. The intertie provides additional flexibility for the cooling water supply system of Diesel Generator 18.

Since the two pairs of motor-operated valves that are provided between the HNP-1 PSW system and the standby service water pump will be closed with power to their motor operators locked out, a single failure will not compromise the independence of the standby service water pump and the HNP-1 PSW system.

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Diesel Generator 1B and its associated buses ensures that the diesel is automatically aligned to the accident unit. The motor control center that supplies power to the standby service water pump will " follow" Diesel Generator 1B. Thus, this pump does not depend on the availability of either HNP-1 or HNP-2, but is supplied directly by the swing diesel generator.-

Control,-indications and alarms associated with the standby service water pump will be located in both HNP-1 and HNP-2 main control panels.

- Alams will also be provided that monitor the status of 600V MCC R24-5026.

Based on our review of the indications and alams, we detemined that specific' indication should be provided to monitor the correct position of

-the various control switches that are associated with the automatic start of the standby service water pump. In discussions with representatives of Georgia Power, the licensee confimed that indications are currently available to the operators of both HNP-1 and HNP-2 when the various control switches are not in proper alignment to enable the automatic start of the standby service water pump.

The proposed changes to the -Technical Specifications would add Limiting Conditions of Operation, Surveillance F quirements and associated Bases for the standby service water pump. These changes are addressed in Sections 3.5.J and 4.5.J of the Technical Specifications for HNP-1. The requirements included in the revised sections are consistent with the *

%rrent Technical Specifications that govern the Plant Service Water system.

During the course of our review, we determined that certain changes to the licensee's submittal should be made: (1) the nomal availability of the PSW system should include all pumps, i.e. , 4 plant service water pumps and the standby service water pump in lieu of the licensee's proposed 3 plant service water pumps and the standby service water pump; (2) the demonstration of operability of the divisional intertie valves should be specifically included in the Surveillance Requirements associated with those conditions in which the standby service water pump is inoperable and cooling water to diesel generator 1B is intertied with the PSW divisonal piping supply. These changes were discussed with the licensee and he agreed with the staff's recommendations.

Based on the above, we find the addition of limiting conditions for opera-tion and surveillance requirements for the standby service water pump, as proposed by the licensee and amended by the staff to be acceptable.

b. Safety / Relief Valves The licensee's submittal dated February 10, 1978, indicated his intent to modify the safety / relief valves for the main steam supply system by replacing the three stage topworks with a new design consisting of a two stage topworks. The salient feature of the modification as it relates to the current Technical Specifications is the removal of the function of the spring bellows. The function of the bellows was to control the pilot valve opening _ pres _sure,_and _the current specifications require monitoring

the integrity of the bellows. By the removal of the bellows function, the associated surveillance requirement would no longer be required.

The staff has previously reviewed the new design of pilot-operated' valves manufactured by Target Rock Corporation. As part of that review, the licensee (Georgia Power Company) indicated that testing of the valves will be performed to establish satisfactory service requirements. It is further noted that the General Electric Company has agreed to work with the staff and with licensees to maintain a surveillance program once the new design safety-relief valves are installed on boiling water reactors.

The licensee has indicated his intent to participate in this program.

On the basis of the foregoing, we find the proposed elimination of the surveillance requirement of the integrity of the relief valve bellow to be acceptable. However, to' provide for the flexibility of partial replace-ment of all safety / relief valves with the newer two-stage topworks design, we have revised the licensee's submittal to retain the surveillance requirement of monitoring the integrity of the bellows, annotating that this requirement does not apply to the newer design. _This revision to the licensee's submittal was discussed with representatives of Georgia Power and they agreed.

c. Standby Gas Treatment System Changes to the SGTS technical specifications were requested by the licensee to account for the expansian of the Unit 1 secondary containment to include the Unit 2 refueling floor. This modification will expand the volume of the Hatch Unit 1 secondary containment and, thus, the volume served by the Unit 1 standby gas treatment system (SGTS). The proposed changes to the Technical Specifications include operating requirements for having both Unit 1 and Unit 2 SGTS operable. The joint operation of both Units' SGTS will provide the necessary capability to reduce and hold the expanded Unit 1 secondary containment at a negative pressure.

We have reviewed and evaluated the proposed changes to Section 3.7.B of the Hatch Unit 1 Technical Specifications. The licensee has proposed that _

three of the four SGTS trains from both units be required to be operable when the Hatch Unit 1 secondary containment is required. The staff has modified the licensee's submittal to specifically require that both trains from Unit 1 and one of two from Unit 2 be operable. This will assure the capability of the SGTS trains to draw down and maintain a negative pressure in the Unit 1 secondary containment when the Hatch Unit I secondary containment is required. Requiring both Unit 1 trains to be operable will assure that adequate suction can be drawn from below the refueling floor in the Unit 1 reactor building, assuming a single active failure causing the loss of one train. To allow operational flexi-bility, one train in Unit 1 may be inoperable for up to 7 days providing the remaining systems are demonstrated operable at an increased surveillance frequency. If the system is not made operable within the 7 days, Unit 1

reactor operations and irradiated fuel handling and/or handling of casks in the vicinity of the spent fuel pools are terminated.

The staff has added the requirement that both Unit 1 SCTS trains ani one of the two Unit 2 SGTS trains be operable before Unit 1 reactor ( xrations and irradiated fuel handling or handling of casks can begi . TP,s wil?

prevent starting operations with the plant in a degraded cv-w m This change was discussed with the licensee and he agreed.

The requirements for Unit 1 secondary containment integrity er. N amended by the staff to include requirements for sealing hatches a o < a ng access doors between the Unit 1 and Unit 2 secondary containments, ihh will assure that the Unit 2 secondary containment is isolated f n the Unit 1 secondary containment and, thus, the capability of ths SGiS to mufntain a negative pressure is not affected. There is also a requirement ;;o main- .

tain the Unit 1 secondary containment during all operational conditions of Unit 2 except cold shutdown. This is in agreement with the Unit 2 specifications.

The licensee did not object to these changes.

Based on the above considerations, the staff has concluded that the proposed specifications will provide adequate assurance that sufficient SGTS trains will be operable to mitigate the potential consequences of postulated accidents.

We further conclude that the conclusions reached in the Hatch Unit 1 Safety Evaluation (May 1973) concerning the capability of the SGTS trains to collect activity released to the secondary containment during postulated accidents remain valid and the dose consequences of postulated accidents remain unchanged. Therefore, the staff has concluded that the proposed changes to Section 3.7.B of the Technical Specifications as modified by the staff are acceptable.

d. Control Room Environmental System By Amendment No. 51 to DPR-57 the HNP-1 Technical Specifications were revised by adding a pressurization mode of operation for the main control room which is shared between the two units. By Amendment No. 44 of the HNP-2 FSAR, the licensee indicated that the control room ventilation system would be tested by verifying that on an initiation signal, the system automatically switches into the pressurization mode and maintains a pressure differential in the control room of >0.1 inch water guage relative to the

, adjacent turbine buildiiig. The test will be performed periodically.

The staff review determined that this pressure differential pro-vides adequate margin to assure that the control room will be maintained at a slightly positive pressure during pressurization and is acceptable. As a result of this review, Operating Limits and Surveillance Requirements for this mode of operation were issued for HNP-2.2 To provide consistency between the two Hatch units, especially where each unit's Technical Specifications apply to the same system, e.g. Control Room Environmental System, the staff suggested that HNP-1 specifications be revised. This revision was discussed with the licensee and he agreed.

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Environmental Consideration We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendrent involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.

Conclusion We have concluded, based on the considerations discussed above, that:

(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the )

amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendaent will not be inimical

.to the common defense and security or to the health and safety of the public.

Date: June 16, 1978 o

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