ML032820506

Questions Regarding SX AOT Extension Request

ML032820506
Person / Time
Site:	Byron, Braidwood
Issue date:	10/07/2003
From:	Dick G NRC/NRR/DLPM/LPD3
To:	Bauer J Exelon Corp
Dick G F, NRR/DLPM, 415-3019
References
Download: ML032820506 (5)

Text

From: George Dick To: INTERNET:Joseph.Bauer@exeloncorp.com Date: 10/07/2003 9:21AM

Subject:

Questions Regarding SX AOT Extension Request

Joe, We will try again. If this doesnt work I will FAX them.

Please review the attachment and let me know if there is a need to clarify any of the questions.

Thanks, George

1. In Attachment 1, Section 4.1 (1st paragraph) of the June 11, 2003, submittal, the licensee states that, ".....However, the actual plant design and supporting analyses demonstrate that the plant has additional capability to prevent and mitigate a loss of SX to a unit than credited in the current plant licensing basis, (e.g., the backup fire protection system the cooling to the Chemical and Volume Control (CV) centrifugal charging pumps which is not credited in the licensing basis)." Discuss fully the additional capabilities that exist, and to what extent these capabilities satisfy licensing basis requirements for safety-related applications (e.g.,

Seismic Category I, QA-1, EQ). Also, discuss the compensatory measures that will be taken to assure that these additional capabilities will be available.

2. In Attachment 1, Table -2, the licensee indicated that the defenses against human errors are preserved. However, the staff notes that the licensees compensatory measures credit additional operator actions. This would suggest that the potential for human error has increased. Please explain.

3. Describe the compensatory measures that will be taken to preserve the SX function against the adverse affects of inclement weather conditions that might arise, and to preserve on-site and off-site electrical sources during the period of allowed outage time (AOT) extension.

5 In its application the licensee has stated, Credit for the dedicated operator to maintain and respond to SX-related problems is recognized as a key compensatory measure. In the six bullets that follow this statement the term dedicated operator occurs three times and designated operator appears twice. The staff position on dedicated does not necessarily mean that operator has no other duties as long as the other duties do not interfere with performing the required tasks. A dedicated operator is located in the immediate vicinity of where the task is to be performed and is capable of performing the task on demand. Therefore, no decision time, preparation time, or travel time is involved. A designated operator is available to perform the specific task when required, but may have other responsibilities that require him/her to be away from the immediate vicinity of where the required task is to be performed. Implied in both dedicated and designated is that the individual is qualified to do the task. Please clarify whether the operators are dedicated or designated in each of the five instances in this case. If these are designated operators, what tasks take precedence and how does the operator know when and what tasks to perform?

6 The submittal further indicates, These personnel represent additional operators (i.e., one senior reactor operator (SRO) in the control room, one

reactor operator (RO), and one equipment operator) assigned to monitor SX performance and take these actions as a back up to the normal shift staff;(.)

a. Please describe the command, control, and communication arrangement and protocol these additional operators have with the normal control room crew.

b. What are the tasks anticipated to be required in this case and what is the level of complexity/difficulty of each? What are the consequences of not successfully accomplishing the tasks?

c. How much time is available to accomplish the above tasks and how much time have the tasks been demonstrated to take? If these are designated operators how has travel time been accounted for?

Please describe the demonstration.

d. What are the communication requirements and how have they been demonstrated acceptable?

e. Please describe the environmental conditions at each task location.

Please describe the access to required equipment.

7 Section 9.2.1.2.2 of the Byron and Braidwood (B/B) UFSAR states that the essential service water pumps are located at the lowest level of the auxiliary building to ensure net positive suction head. Section 9.2.1.2.7 of the B/B-UFSAR states that Pumps 1A and 2A are located in one compartment, and that Pumps 1B and 2B are located in a separate adjacent compartment. Each compartment has a watertight door. During replacement of the SX pump suction isolation valves, a postulated flood originating in one of the SX pump rooms (caused, for example, by spurious opening of the common upstream suction isolation valve) could propagate to other areas of the auxiliary building since the watertight door would be opened to allow personnel and equipment access.

Please describe how internal floods that may originate in one of the SX pump rooms during replacement of the SX pump suction isolation valves have been addressed in the risk evaluation. Provide relevant flood initiating event frequencies, sequence descriptions, core damage frequency estimates, and large early release frequency estimates.

8 Section 4.3.1.2 (Page 16 of 52) in Attachment 1 of Exelons request states that The risk evaluation of internal events incorporates a number of compensatory measures that the plant will take to assure the risk impacts are acceptably low. In order to: (a) ensure that the proposed

compensatory measures are not being relied upon to compensate for weaknesses in plant design, and (b) clearly understand which compensatory measures should be referenced the staffs safety evaluation supporting the license amendment. Please provide the results of a sensitivity study that shows how the incremental conditional core damage probability and the incremental conditional large early release probability change if none of the compensatory measures are implemented.

9 Provide the details of any significant findings and observations from the probabilistic risk assessment (PSA) peer review certification conducted for the Byron Station. Include in the discussion any improvements or corrections that were made in the plant as a result of the findings. Note that it is not necessary to provide this information for the Braidwood Station since it was previously sent to the NRC staff on July 7, 2000 as a response to a request for additional information issued in conjunction with Exelons request to extent allowable completion times and change surveillance requirements for emergency diesel generators.

10 Attachment 4, Table 2-1 of Exelons request summarizes the major changes made to the Braidwood and Byron PRA models since Exelons request to extent allowable completion times and change surveillance requirements for emergency diesel generators was submitted (January 20, 2000). Please provide the following information:

a. Describe the quality process used to control how the PRA model changes were reviewed and approved. Discuss internal, external, and peer reviews as applicable.

b. What is the current freeze date of the Braidwood and Byron PRA models? List all PRA model changes that have been identified/planned but not yet implemented, indicating their anticipated impacts (if any) on the risk results and conclusions concerning the extension of the SX train completion time request that is currently under consideration.

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Questions Regarding SX AOT Extension Request Creation Date: 10/07/2003 9:21AM From: George Dick Created By: GFD@nrc.gov Recipients Joseph Bauer (INTERNET:Joseph.Bauer@exeloncorp.c Post Office Route Joseph INTERNET:exeloncorp.com Files Size Date & Time RAI.SX.AOT.Questions.wpd 13123 10/07/03 06:50AM MESSAGE 925 10/07/03 09:21AM Options Expiration Date: None Priority: Standard Reply Requested: No Return Notification: None Concealed

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