2CAN070403, Clarification of a Request for Additional Information Response for Environmental Report

Clarification of a Request for Additional Information Response for Environmental Report

ML042100060
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/15/2004
From:	Mitchell T Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2CAN070403, TAC MB8405
Download: ML042100060 (7)

Text

4i

- ~-Entergy Operations, Inc.

1448 S.R.333 Entagv

{Russellville, AR 72802 Tel 501 858 5000 2CAN070403 July 15, 2004 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Clarification of a Request for Additional Information Response for Environmental Report TAC No. MB8405 Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6

Dear Sir or Madam:

By letter dated April 23, 2004 (2CAN040402), Entergy provided responses to NRC requests for additional information (RAls) on the Arkansas-Nuclear One, Unit 2 (ANO-2) License Renewal Application Environmental Report. The responses to the RAls were related to the severe accident mitigation alternatives (SAMAs). In a teleconference on June 15, 2004, the Staff requested a clarification to RAI 7. The clarification to RAI 7 is contained in the attachment.

There are no new commitments contained in this submittal. Should you have any questions concerning this submittal, please contact Ms. Natalie Mosher at (479) 858-4635.

I declare under penalty of perjury that the foregoing is true and correct. Executed on July 15, 2004.

oth G. Mitchell Director, Nuclear Safety Assurance TGM/nbm Attachment

i 2CAN070403 Page 2 cc: Dr. Bruce S. Mallett Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Drew Holland Mail Stop 0-7 D1 Washington, DC 20555-0001 U. S. Nuclear Regulatory Commission Attn: Mr. Tom Kenyon Mail Stop 0-11 F1 Washington, DC 20555-0001 Mr. Bernard R. Bevill Director, Division of Radiation Control and Emergency Management Arkansas Department of Health 4815 West Markham Street, Slot 30 Little Rock, AR 72205-3867

Attachment to 2CAN070403 RAI 7 Clarification

i Attachment to 2CAN070403 Page 1 of 4 RAI 7 Clarification: The NRC requested Entergy to further address contributions to core damage frequency (CDF) from fire events for selected SAMAs.

The Staff indicated that because the reported CDF for fires is much larger than the internal events CDF, estimated benefits (which are based on internal events) should be increased by a factor of five for some SAMAs. When this adjustment is performed, a number of SAMAs appear cost beneficial and several additional SAMAs are within a factor of two of being cost beneficial. With the higher benefit estimates, SAMAs may appear cost beneficial because of the way benefits and costs were calculated. Also, certain SAMAs may not reduce risk in fire events (in which case a multiplier of five would not be appropriate).

Response: Entergy is providing refined cost/benefit estimates for selected SAMAs. The following table provides results of the refined cost/benefit estimates.

SAMAs for which NRC Requested Refined Benefit/Cost Estimates SAMA Benefit x1 Cost Benefit Refinements Cost Estimate

$) Estimate Refinements AC/DC-10 14,254 155,456 Evaluated benefit of Adjusted 1998 Calvert eliminating failure to align Cliffs estimate to account the 125VDC buses to for inflation alternate power sources AC/DC-16 15,252 35,000 Evaluated benefit of None reducing probability of failure to recover from loss of offsite power AC/DC-24 9,742 131,094 Evaluated benefit of Used 1998 Calvert Cliffs eliminating failure to align estimate adjusted to 2D01 to an alternate power account for inflation source AT-02 39,778 412,225 Evaluated benefit of Adjusted 1993 eliminating failure of NUREG-1462 estimate to borated water injection account for inflation and following an anticipated backfit costs transient without scram CB-10 428 35,000 Evaluated benefit of None eliminating failure to properly handle a ruptured steam generator

Attachment to 2CAN070403 Page 2 of 4 SAMA Benefit xi Cost Benefit Refinements Cost Estimate

($) Estimate Refinements CB-26 13,357 70,000 Evaluated benefit of None eliminating inter-system loss-of-coolant accident (ISLOCA) contribution from failure of the low pressure safety injection lines and halving ISLOCA contribution from reactor coolant pump seal cooler tube rupture CC-07 12,389 1,308,651 Evaluated benefit using Adjusted 1993 analysis case steam NUREG-1462 estimate to generator tube rupture account for inflation (SGTR)

CC-19 14,608 1,000,000 None Performed cost estimate CC-20 52,044 424,783 Evaluated benefit of Performed cost estimate removing common cause failure of sump suction valve operators and reduced excess conservatism in failure to recover sump suction valves CC-21 10,918 424,783 None Performed cost estimate CW-01 55,837 826,670 None Performed cost estimate CW-06 9,174 35,000 Evaluated benefit of None reducing failure to trip reactor coolant pumps upon loss of component cooling water (CCW)

CW-09 100,967 1,158,000 None Performed cost estimate CW-21 2,144 35,000 Evaluated benefit of None reducing individual support system human failure events CW-23 3,037 35,000 Evaluated benefit of None eliminating failure to recover failed service water equipment CW-24 9,174 100,000 Evaluated benefit of Performed cost estimate reducing failure to trip reactor coolant pumps upon loss of CCW

Attachment to 2CAN070403 Page 3 of 4 SAMA Benefit x1 Cost Benefit Refinements Cost Estimate

($) Estimate Refinements CW-27 44,981 247,000 Evaluated benefit of Performed cost estimate reducing common cause failure of service water pump discharge strainers EV-02 89,000 934,566 None Performed cost estimate EV-22 14,399 565,000 Evaluated benefit of None eliminating failure to provide water to containment spray EV-30 18,901 424,783 None Performed cost estimate FW-13 5,228 314,393 Evaluated benefit of Adjusted 1998 Calvert eliminating failure to align Cliffs estimate to account to the alternate for inflation condensate storage tank HV-03 87,101 1,200,000 None Performed cost estimate HV-05 51,896 628,000 None Performed cost estimate OT-06 3,046 1,100,000 Evaluated benefit of None eliminating main steam line breaks (MSLBs)

The following four SAMAs from the above table are within a factor of two of being cost beneficial when the Staff-recommended factor of five is used to account for external events (factor of two if SAMA affects SGTR, ISLOCA, or MSLB).

1. AC/DC-16, Emphasize steps in plant recovery following a station blackout event:

More in-depth review of the proposed SAMA reveals that steps in plant recovery are emphasized within the current operations training cycle. Standard post-trip actions direct operators to assess plant conditions and enter the station blackout emergency operating procedure (EOP) if at least one 4160V vital bus is not energized. The station blackout EOP delineates steps in plant recovery following a station blackout event. As part of the standard post-trip actions, the instructions are repeatedly addressed during classroom training and simulator exercises in accordance with 10CFR Part 55. Since this SAMA does not relate to adequately managing the effects of aging during the period of extended operation, and is adequately addressed within the current operations training cycle, no further action is necessary as part of license renewal pursuant to 10CFR Part 54.

2. CC-20. Replace either containment sump valve 2CV-5649-1 or 2CV-5650-2 with an air-operated valve: This modification is only slightly within a factor of two of being cost beneficial when the Staff-recommended factor of five is used to account for external events. Although the refined benefit estimates remove bounding modeling assumptions and the refined cost estimates are less conservative than the original cost estimates, other conservatisms listed in response to RAI 8b in correspondence dated April 23, 2004 (2CAN040402), still exist. Thus, the analysis adequately accounts for external events and uncertainty and the SAMA is not cost-beneficial.

Attachment to 2CAN070403 Page 4 of 4

3. CW-06. Proceduralize shedding CCW loads to extend CCW heat-up time: While adding steps to accomplish during an accident scenario may address one particular human failure probability, the additional required actions may adversely impact the probability of successful completion of other steps critical to event mitigation. The benefit of this SAMA is small enough that its implementation is not warranted in light of the potential detrimental impact to operator performance of other event mitigation actions. Since this SAMA does not relate to adequately managing the effects of aging during the period of extended operation, no further action is necessary as part of license renewal pursuant to 10CFR Part 54.

4. CW-27. Replace current service water pump discharge strainers with backwash filters to reduce probability of common cause failure: Although this SAMA does not relate to adequately managing the effects of aging during the period of extended operation, it is currently undergoing evaluation as a potential future modification for reasons unrelated to license renewal.