ML23257A158

NRC Staff Feedback Draft TSTF-601, Extend Shield Building Completion Time After Refueling for Pre-submittal Meeting on 9/18/23

ML23257A158
Person / Time
Site:	Technical Specifications Task Force
Issue date:	09/18/2023
From:	NRC/NRR/DSS/STSB
To:	Technical Specifications Task Force
References
Download: ML23257A158 (2)

Text

NRC staff feedback RE: draft TSTF-601, Extend Shield Building Completion Time After Refueling for pre-submittal meeting on 9/18/23 The TSTF submitted draft traveler TSTF-601 to support a pre-submittal meeting. The NRC staff has the following initial comments/questions for discussion during the pre-submittal meeting.

Note: Page numbers below refer to the pdf page in the document in ADAMS (ML23205A234).

1) Pages 6, 9, 11 - Are the potential dose consequences in Mode 3 following a refueling outage (RFO) significantly reduced from Mode 1 (and 2)?

a. Note: NRC staff may have additional questions regarding the reduced potential for dose consequences in Modes 3 and 4 vs. Mode 1. STS currently allow 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore the shield building in Mode 1.

b. The traveler could be revised to only allow entry to Mode 4, not 3 and 4 because the primary containment pressure would be lower in Mode 4 and the driving force into the shield building lower.

c. The STS Bases state that 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (in Modes 1-4) is a reasonable completion time because of the low leakage design of the containment building and the low probability of an event. The proposed Bases for Action A.1 for the shield building TS do not maintain the premise that the containment building has a low leakage design. There is no discussion of why the low leakage aspect is no longer important, especially considering that the primary containment pressure is likely to be relatively high following a loss of coolant accident (LOCA) in Mode 3.

Alternately, the Bases should recognize the low leakage design of the primary containment for Action A.1.

2) Based on statements on page 9 and related to the above, how much reduction in primary containment pressure occurs between a large break that occurs in Mode 3 and one that occurs at power? What is a substantial reduction in pressure? It seems that the reduction in radionuclides and decay heat would not have a large effect on the primary containment pressure. However, the paragraph implies that the driving force within the primary containment is reduced.

3) Pages 8 and 9 -It doesnt seem necessary to include the filter systems in the traveler.

All the actions that need to be performed to get the shield building leak tight are specific to the shield building. There is a surveillance requirement (SR) for the shield building that requires verification that the filter systems will draw a vacuum, but that does not prevent the filter systems from being operable at any time. The filter system SRs can be done separately from the shield building and before the shield building is operable. In addition, the filter system trains are only required to be tested for flow during alternating refueling outages.

4) What is the basis for the allowing a loss of function for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> per proposed Condition B of the shield building air filtration system1? Having these systems operable in Mode 3 provides a safety benefit. Eliminating all proposed changes to the filter system TSs from the proposal would eliminate the allowance for a loss of function, simplify the change, and provide the safety benefit.

1 The shield building air filtration system is called the Shield Building Air Cleanup System (SBACS) in the Westinghouse STS (NUREG-1431, TS 3.6.13) and the Shield Building Exhaust Air Cleanup System (SBEACS) in the Combustion Engineering STS (NUREG-1432, TS 3.6.8).

5) Page 17 - Response to question 1 seems OK if you answer the probability and consequences questions separately, but there is some increase in the probability of the consequences that could occur if an accident occurred with the shield building inoperable, which it is for a longer time period.

6) Page 18 - Response to question 3 does not appear to answer the question. There is a small reduction in margins because the shield building (and filter systems) are allowed to be inoperable at higher pressures and for longer periods of time.

7) Page 4 - near the bottom calls the filter systems cooling systems is this right?

8) Page 11, the second paragraph refers to low-energy condition. Does this expression apply to all Mode 3 pressure and temperature conditions?

9) Page 10. Discuss how the limiting condition for operation (LCO) 3.0.6 applies to the shield building air filtration and the shield building, when the shield building is inoperable.

10) Page 16. Explain the last variation - ... the proposed Actions are modified by a note stating that the provisions of Specification 3.0.4 are not applicable, which is the equivalent allowance for a non-STS plant TS. This difference does not affect the applicability if TSTF-601 "