ML101380525

Additional RAI for Ultimate Heat Sink License Amendment Request (ME1669-70)

ML101380525
Person / Time
Site:	Byron
Issue date:	05/18/2010
From:	David M Plant Licensing Branch III
To:	Simpson P, James Smith Exelon Corp
marshall david 415-1547
References
TAC ME1669, TAC ME1670
Download: ML101380525 (3)

Text

From: David, Marshall Sent: Tuesday, May 18, 2010 11:30 AM To: patrick.simpson@exeloncorp.com; Jean.Smith@exeloncorp.com Cc: Ken Nicely; Lisa.Schofield@exeloncorp.com; Campbell, Stephen; Casto, Greg; Purciarello, Gerard

Subject:

Byron 1&2 - Additional RAI for Ultimate Heat Sink License Amendment Request (ME1669-70)

Importance: High Pat, Jean, Below is the additional question on the subject license amendment request that we discussed on May 13, 2010. I will be placing a copy of this e-mail into ADAMS.

Thanks, Marshall David Senior Project Manager Braidwood and Byron Stations (301) 415-1547 The image cannot be display ed. Your computer may not hav e enough memory to open the image, or the image may hav e been corrupted. Restart y our computer, and then open the file again. If the red x still appears, y ou may hav e to delete the image and then insert it again.

REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNIT NOS. 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455 The Nuclear Regulatory Commission (NRC) staff is reviewing Exelon Generation Company, LLCs (the licensees) license amendment request (LAR) dated June 30, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML091831253), as supplemented by letter dated January 25, 2010 (ADAMS Accession No. ML100280553). The LAR requests to revise Technical Specification (TS) 3.7.9, "Ultimate Heat Sink (UHS)," for Byron Station, Unit Nos. 1 and 2 (Byron), to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect the results of a revised analysis for the UHS.

The NRC staff has determined that additional information is required to complete its review.

The specific information requested is addressed in the Request for Additional Information (RAI) below. The RAI was discussed with your staff on May 13, 2010, and they agreed to respond within 45 days after the date of this message.

The NRC staff considers that timely responses to requests for additional information help ensure sufficient time is available for staff review and contribute toward the NRCs goal of

efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1547.

Background:

The January 25, 2010, responses to NRC staff questions 1.a and 9.b stated that certain operator actions would be taken within the first 10 minutes from the control room including,

4) Closing the associated riser valve of any fan that does not start in high speed.

Scenarios 8A through 8D in the LAR use one set of cell flow rates, which assume 10 percent effective cooling for cells whose fans fail after loss-of-coolant accident (LOCA) initiation. The 10 percent effective cooling was based on the inability to shut the associated riser valve and still take credit for some cooling in an inactive cell with SX flow. This corresponds with the statement in the RAI response on page 16 that, Postulated breaker failures would also result in the loss of power to the motor operated riser valves for the impacted SXCT [essential service water cooling tower] fan. Apparently, the computer program does not model the closing of riser valves for cells whose fans do not start in high speed as stated in response to NRC staff questions 1.a and 9.b.

The same could be said for scenarios 10-13 in the LAR for the riser valves, although they account for local manual closing of the failed bypass valve in 30 minutes.

Question:

If the operators were able to close one or both of the riser valves for fans that do not start in high speed after LOCA initiation as your procedure calls for, please confirm and justify that the calculations and the corresponding new TS requirements for this LAR are still conservative and bounding regarding SX pump discharge temperature. In other words, please confirm and justify that the SX pump discharge temperature remains at or below 100° F for the scenarios in the LAR that form the basis of the revised TS. If not, please provide the results of additional, bounding analyses demonstrating that SX pump discharge temperature remains at or below 100° F, and list and explain any new assumptions in making the additional analyses.

E-mail Properties Mail Envelope Properties (0046140293E11F408991442DB4FE25CA06C5021747)

Subject:

Byron 1&2 - Additional RAI for Ultimate Heat Sink License Amendment Request (ME1669-70)

Sent Date: 5/18/2010 11:29:40 AM Received Date: 5/18/2010 11:29:40 AM From: David, Marshall Created By: Marshall.David@nrc.gov Recipients:

patrick.simpson@exeloncorp.com (patrick.simpson@exeloncorp.com)

Tracking Status: None Jean.Smith@exeloncorp.com (Jean.Smith@exeloncorp.com)

Tracking Status: None

ken.nicely@exeloncorp.com (Ken Nicely)

Tracking Status: None Lisa.Schofield@exeloncorp.com (Lisa.Schofield@exeloncorp.com)

Tracking Status: None Stephen.Campbell@nrc.gov (Campbell, Stephen)

Tracking Status: None Greg.Casto@nrc.gov (Casto, Greg)

Tracking Status: None Gerard.Purciarello@nrc.gov (Purciarello, Gerard)

Tracking Status: None Post Office:

HQCLSTR01.nrc.gov Files Size Date & Time MESSAGE 27916 5/18/2010 image001.gif 4173 Options Expiration Date:

Priority: olImportanceHigh ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: