ML20003B483

Submits Addl Info for Incomplete Items Re Auxiliary Feedwater Sys in Response to NRC 791016 Ltr Advising of Addl Requirements to Be Implemented

ML20003B483
Person / Time
Site:	Prairie Island
Issue date:	02/04/1981
From:	Mayer L NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20003B484	List: ML20003B483 ML20003B488
References
NUDOCS 8102120234
Download: ML20003B483 (6)

Text

% e NSF NORTHERN STATES POWER COMPANY M I N N E A PO L.l S. Ml N N E S OTA 55409 February 4, 1981 Director of Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Auxiliary Feedwater System Information In a letter dated October 16, 1979 the NRC Staf f advised Northern States Power Company of additional requirements to be implemented for the auxiliary feedwater systems at the Prairie Island Nuclear Generating Plant. In correspondence dated November 21, 1979, December 28, 1979, December 31, 1979, and December 18, 1980 Northern States Power Company provided additional information for NRC Staff review of this subject, submitted proposed Technical Specification changes, and committed to procedural and equipment changes which address the concerns of the NRC Staf f.

In communications with our Project Manager in the Division of Licensing we have been informed that there are eight areas in which NRC Staf f review is not complete. These are :

a. Recommendation GS-1 which requires a more restrictive time limit for inoperable motor driven auxiliary feedwater pumps.

b. Additional Short Term Recommendecion 1 which requires NSP to provide information on condensate storage tank level alarms,

c. Additional Short Term Recommendation 2 which requires NSP to provide information related to auxiliary feedwater pump endurance tests.

d. Additional Snort Term Recommendation 3 which requires NSP to provide information on auxiliary feedwater flow instrumentation.

l e. Recommendation GL-3 which requires independence of the turbine-driven auxiliary feedwater pumps from all AC power.

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f. Recommendation GL-4 which requires auxiliary feedwater pumps to be protected against loss of suction,

g. Recommendation GL-5 which requires auxiliary feedwater pump actuation circuitry to meet safety-grade standards.

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h. Auxiliary feedwater system flow design basis as specified in l

Enclosure (2) to the NRC's October 16, 1979 letter.

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NORTHERN CTATED POWER COMPANY Director of NRR February 4, 1981 Page The purpose of this letter is to address each of these open items and provide sufficient information for the NRC Staff to complete their safety evaluation of the Prairie Island auxiliary feedwater system. Each of these items is addressed below and in the attached material.

Recommendations GS-1, Auxiliary Feedwater ( AFW) Technical Specifications In a License Amendment Request dated December 31, 1979 Northern States Power Company proposed revised Limiting Conditions for Operation and Surveillance Requirements for the auxiliary feedwater system. NRC Staff review of the proposed changes resulted in the conclusion that a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period of pump inoperability is the maximum that will be allowed.

Response

This subject has been discussed with the Prairie Island Licnesing Project Manager in the Division of Licensing. Northern States Power Company will accept this change.

Additional Short Tenn Recommendation (1), AFW Primary Water Supply NRC Staf f review of information provided by NSP on November 21, 1979 resulted in a request for information in five areas:

a. Information to verify that the level indicators and the high/ low level alarms are available to control room operators of both units. -

b. Verification that the instrumentation is redundant and separated all the way from the detectors at the condensate storage tanks to the readouts and alarms in the control room.

t c. Verification that the systems are powered from redundant power

' sources with one train having a back-up battery source,

d. Verification that inadvertent valve closure in a common header will not defeat the redundance of the condensate storage tank high/ low level alarms and level indicators,

e. Aside f rom short time intervals for reasons such as maintenance, verification that the valves joining the condensate t ?nks to the common header will be in the open position while the reactor is in the power operating range.

Response

a. A design change has been completed (79L566) to provide redundant low level alarms for both units. The high/ low level bistable for each unit has been converted to a dual low level bistable. Low level signals are

! provided to both Unit No. 1 and Unit No. 2 annunciator alarms from each level bistable. The bistables have been calibrated such that

NORTHERN STATED POWER COMPANY Director of NRR February 4, 1981 Page the alarm occurs when condensate storage tank level drops below 12 inches curresponding to over 9000 gallons of water per tank. This would provide operators with at least 20 minutes of reaction time to line up alternate sources of water.

b. One level transmitter is installed on No. 11 condensate storage tank and one level transmitter is installed on No. 12 condensate storage tank.

These devices are well separated physically.

No cable separation criteria was specified for these instruments during plant construction. A review of the circuit schedule for the cables, however, indicates that they are routed in separate raceways with the exception of common routing in three segments of one tray between the control room and relay-cable spreading room.

c. Both level channels are powered from instrument inverters. These inverters are supplied from the Class IE DC battery system.

d. When the manual cross-tie valve between the Unit No. I and Unit no. 2 condensate storage tanks is closed, each level transmitter responds to its associated tank (s).

e. Valves joining the condensate storage tanks to the auxiliary feedwater pump suction header, as well as the two valves cross connecting the Unit No. I and Unit No. 2 condensate storage tanks, are verified to be correctly positioned during the pre-startup valve lineup check of the condensate system.

Additional Short Term Recommendation (2), AFW Pump 48-Hour Test The NRC Staff requires completion o* 148-hour endurance test. Test criteria should include demon:trating that the pumps remain within design limits with respect to bearing and oil temperatures and vibration and that pump room ambient conditions do not exceed environmental qualification limits for safety related equipment in the room.

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Response

l j The required tests have been completed. A copy of the test re port is provided in Attachment (1).

Additional Short Term Recommendation (3), AFW Flow-Indication The NRC Staf f requires reliable indication of auxiliary feedwater flow to each steam generator in the control room. The latest requirements are provided in NUREG-0737, Item II.E.1.2 (Part 2).

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NCRTHERN CTATED POWER COMPANY Director of NRR February 4, 1981 Page - .

Response

As described in our letter dated November 21, 1979 each steam generator is provided with control grade auxiliary feedwater flow indication in the control room. This indication is powered by safeguards power supplies.

Flow channel electrical components are not located where they would be subject to a harsh accident environment.

As described in our letter dated December 18, 1980 each steam generator has four level channels (3 narrow and I wide range). Each channel is powered f rom a safeguards power supply. Wide range indication is available in both the control room and the hot shutdown panel.

We believe the instrumentation meets the clarification specified in NUREG-0737, Item II.E.1.2 (Part 2), for Westinghouse slants. Flow indication is of secondary importance for assuring the heat removal capability of plants provided with U-tube steam generators. No further modifications are believed to be required to satisfy NRC Staf f requirements in this area.

Long Term Recommendation GL-3, Independence cf AC Power The NRC Staf f specifies at least one auxiliary feedwater system pump and its associated flow path and essential instrumentation should automatically initiete AFW system flow and be capable of being operated independently of any AC power source for at least two hours.

Response

Design Change E-80Y129 has been initiated to free the turbine driven auxiliary feedwater pump from the need for AC power. This change will be completed at the first refueling outage following receipt of necessary materials.

A summary of the design change is provided in Attachment (2).

Long Term Recommendation GL-4, Suction Protection for AFW Pumps The NRC Staf f requires that procedures be available for switching to a seismic Class I water supply. Protection of the pumps in the event of loss of water supply or isolation of the pump suction must also be provided.

Response

As stated in our letter dated December 18, 1980 procedures have been modified to provide for prevention of pump damago and transfer to alternate water supplies.

Design Change 80L579 has been initiated to provide suction protection for the auxiliary feedwater pumps. This modification will protect the pumps from a loss of suction. This change will be completed at the first refueling outage following receipt of necessary materials.

A summary of the design change is provided in Acts +me (3).

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NORTHERN STA rEO POWER COMPANY Director of NRR February 4, 1981 Page t Long Term Recommendation GL-5, Safety Grade Automatic Initiation The NRC Staf f requires that safety grade automatic initiation circuity be provided for the auxiliary feedwater system. The latest requirements are provided in NUREC-0737, Item II.E.1.2 (Part 1).

Response

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Documentation of the reliability of the automatic actuation circuitry for i

the Prairie Island auxiliary feedwater system has been provided to the NRC Staff for their review in correspondence dated November 21, 1979, December 28, 1979 (including schematics), and December 18, 1980. We believe that Staff review of this material will conclude no additional modifications to the actuation circuitry for the auxiliary feedwater system are necessary.

Additional material will be submitted for NRC Staf f review on request.

Enclosure (2) to NRC Letter dated October 16, 1979, Auxiliary Feedwater System Flow Basis Enclosure (2) to the letter from D G Eisenhut dated October 16, 1979 was a generic request for additional information regarding auxiliary feedwater system flow requirements.

Response

The evaluation required by Enclosure (2) to Mr Eisenhut's letter has been

! completed by Westinghouse for the Prairie Island plant. A copy is provided

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in Attachment (4).

Please contact us if you have any questions concerning the information we have provided.

I l 0-l L 0 Mayer, P Manager of Nuclear Support Services LOM/DKM/jh I

cc J G Keppler NBC Resident Inspector G Charnof f Attachments i

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Attachments Director of NRR February 4, 1981 Attachment 1 Auxiliary Feedwater Pump Enduran:e Te<,t Attachment 2 Turbine-Driven Auxiliary Feedwater Pump AC Independence Design Change Attachment 3 Auxiliary Feedwater Pump Suction Pressure Protection Design Change ,

Attachment 4 Basis for Auxiliary Feedwater System Flow Requirements i

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