ML20247E573

Responds to 980308 RAI Re 951120 Summary Rept Submittal Addressing GL 87-02,resolution of USI A-46.No New Commitments Made within Submittal

ML20247E573
Person / Time
Site:	Prairie Island
Issue date:	05/07/1998
From:	Sorensen J NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, TAC-M69474, TAC-M69475, NUDOCS 9805180388
Download: ML20247E573 (7)

Text

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l Northern States Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. East Welch, Minnesota 55089 l

May 7,1998 Generic Letter 87-02 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT l Docket Nos.50-282 License Nos. DPR-42 l 50-306 DPR-60 l Response to Request for Additional loformation on the Prairie Island Nuclear Generating Plant, Units 1 and 2, Resolution of Unresolved Safety Issue A-46 i (TAC Nos. M69474 and M69475) l By letter dated March 8,1998, NRC staff transmitted a Request for Additional l Information related to ot'r November 20,1995 summary report submittal addressing Generic Letter 87-02, " Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety issue (USI) A-46." Our response to this request is attached to this letter.

This response contains no new NRC commitments, nor does it modify any prior commitments. Please contact Jack Leveille (612-388-1121, Ext. 4662) if you have any further questions related to the status of the outlier resolutions.

Joel P Sorensen Plant Manager l Prairie Island l

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USNRC NORTHERN STATES POWER COMPANY May 7,1998 Page 2 c: Regional Administrator- Region Ill, NRC Senior Resident inspector, NRC NRR Project Manager, NRC Kris Sanda, State of MN J E Silberg Attachments:

1. Affidavit

2. Attachment 2, Response to NRC Request for Additional Information - USl A-46, Prairie Island Nuclear Generating Plant 8702-07. DOC

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I UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET NO. 50-282 50-306 Response to Request for Additional Information on the Prairie Island Nuclear Generating Plant, Units 1 and 2, Resolution of Unresolved Safety issue A-46 Northern States Power Company, a Minnesota corporation, with this letter is submitting information requested by NRC Request for Additional Information regarding Generic Letter 87-02.

This letter contains no restricted or other defense information.

NORTHERN STATES POWER COMPANY BY ~

gfJoel P Sore'nsen Plant Manager Prairie Island Nuclear Generating Plant j i

On this y of / dM / before me, a notary public in l and for s6id County, perso'na [e) red Joel F sorensen, Plant Manager, Prairie i

j lsland Nuclear Generating Plant,pnd being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to best of his knowledge, information, and bel'ef the statements made in it E re tru n it is not interposed for delay.

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Response to NRC Request for Additional Information - USI A-46 Prairie Island Nuclear Generating Plant

a. Describe what reviews were performed to determine if any local operator actions required to safely shut down the reactor (i.e., implement the SSEL

[ safe shutdown equipment !!st]) could be affected by potentially adverse environmental conditions (such as loss of lighting, excessive heat or humidity, or in-plant barriers) resulting from the seismic event. Describe how staffing was evaluated and describe the reviews that were conducted to ensure operators had adequate time and resources to respond to such events.

Response

Potential events which must be considared in the USl A-46 program are a safe shutdown earthquake (SSE) and loss of offsite power (LOOP). The USl A-46 accident scenario (SSE + LOOP) explicitly excludes loss of coolant accidents (LOCA) and high energy line breaks (HELB). Therefore, the lighting, heat, and humidity cond;tions to be considered are equivalent to those in a loss of offsite power (LOOP) scenario.

Local operator actions and resource needs for the USl A-46 program are enveloped by existing Normal, Abnormal, and Emergency Operating Procedures to bring the plant from a normal operating mode l to a hot shutdown condition. As required by GIP-2, the safe shutdown j equipment list (SSEL) was reviewed by the p' ant Operations Department to confirm that it is compatible with these plant procedures. l The plant operating procedures used to shut down the reactor following a LOOP have previously been evaluated for local operator actions as one of the accident scenarios. The operator actions, beyond those associated with the LOOP accident scenario, which must be performed 1 to bring the plant from a normal operating mode to a hot shutdown condition, are those specifically associated with the vibratory motion of the SSE. Existing Abnormal Procedures for Earthquakes accommodate operator actions with respect to time and resources required to respond to the event. As a result of the USl A-46 review program, the Abnormal Procedure for Earthquakes was revised to include the re-starting of a Control Room Chiller if the operating chiller tripped due to relay chatter. The restarting of Control Room chillers from the Control Room has been demonstrated by occasions when the chillers have been tripped by other plant evolutions besides relay chatter.

Further verification of adequacy of existing abnormal and emergency operating procedure guidance and integration of required operator actions was accomplished by running two specifically designed simulator scenarios where the 6xpected conditions of the plant 1

I kttachment 2 Page 2 of 4 fouowing a seismic event accompanied by a LOOP were established and the operators were a!! owed to use only the equipment of the SSEL.

l Iri both cases, hot shutdown conditions were achieved without oifficuity l using normal 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> statiing levels.

Ti:o potential for in plant barriers caused by failure of plant structures and cauipment is not considered a credible obstacle to local operator actions for safely shutting down the plant. The potentiai for local failure of architectural features (such as suspended ceilings in the control room) and the potential for adverse seismic spatial interactions in the vicinity of safe shutdown equipment, where local operator actions may be required, was explicity evaluated as required in GIP-2.

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b. As part of the licensce's review, were any control room structures that could impact the operator's ability to respond to the seismic event identified? Such items might include but are not limited to: MCR [ main control room) ceiling tiles, nonbolted cabinets, and nonrestrained pieces of equipment (i.e., computer keyboards, monitors, stands, printers, etc.).

Describe how each of these potential sources of interactions has been evaluated and describe the schedule for implementation of the final resolutions.

Response

Control Room structures and equipment which could impact the operator's ability to respond to a safe shutdown earthquake include the suspended ceiling, lighting and computer equipment. These structures and components were evaluated as part of Prairie Island's A-46 review.

l The method used for evaluating these potential sources of seismic l spatial interaction is described in GIP-2. All of the above control room ,

structures and equipment passed the GIP screening criteria except for l the lighting diffusers in the ceiling grid which were designated as outliers. Resolution of these outliers were completed in December 1997 by securing the lighting diffusers to the ceiling grid.

c. Describe what reviews were performed to determine if any local operator actions were required to reposition ' bad cctor relays" . For any such act9ities describe how cdverse environmental conditiors (such as loss of lighting, excessive heat or humidity, or in-plant barriers) resulting from the seismic event were analyzed and dispositioned. Describe how staffing was evaluated and describe the reviews that were corducted to ensure operators had adequate time and resources to respond to such evente.

6702-C7. DOC s

, Attachment 2 Pag) 3 of 4

Response

Credit was taken for operator action to restart a Control Rocm Chiller from the control room if relays associated with the Control Room Chiller seal-in circuits tripped the operating chiller unit. As stated in the response to item a. above, the Abnormal Procedure for Earthquakes was revised to include the re-starting of a Control Room Chiller if the operating chiller tripped due to relay chatter. Re-start of the tripped chiller is not an immeciate concern as control room temperature will increase gradually. This allows operators sufficient time to perform this function.

d. Describe which of the operator actions associated with resetting SSEL equipment affeded by postulated relay chatter are considered to be routine and consistent with the skill of the craft. If not considered skill of the craft, what training and operational aids were developed to ensure the operators wii!

perform the actions required to reset affected equipment?

Response

Re-starting of the Control Room Chillers when tripped by relay chatter is considered to be routine and within the skill of the craft.

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e. Assume the alarms associated with " bad actor relays" are expected to annunciate during the seismic event. Do the operators have to respond to those annunciators and review the annunciator response procedures associated with them for potential action? Hcw would those additional actions impact the opetator's ability to implement the Normal, Abnormal, and Emergency Operating Procedures required to place the reactor in a safe shutdown condition?

Response

When faced with an avalanche of alarms, existing operator procedures direct the operator to respond by confirming that safe shutdown events based on their priority and importance have taken place. This includes confirming or initiating a reactor trip and monitoring of normal cascading events that follow the trip. These existing procedures include the recognition of operator capability limits end are designed to dedicate operator resources to the actions of the highest importance and priority. The desired accomplishment of functions for Reactivity Control, Pressure Control, inventory Control, Decay Heat Removal and Support System functions are no different for earthquake initiated alarms than that caused by any other scenario. Existing procedures adequately encompass these potential scenarios and there is no

., Attachment 2 Page 4 of 4 reasonable basis or evidence which would suggest that spurious alarms resulting from an earthquake require special operating procedures.

f. To the extent that Normal, Abnormal, and Emergency Operating Procedures were modified to provide plant staff with additional guidance on mitigating the A-46 Seismic Event, describe what training was required and provided to the licensed operators, nonficensed operators, and other plant staff required to respond to such events.

Response

See responses to item c. and d. above. No additional training was deemed required to re-start the Control Room Chillers when ambient control room temperatures were gradually increasing.

8702-07. DOC