ML20329A343

Slides - DC Cook Unit 2 Pre-Application ILRT 11/30/2020 Meeting Slides (Epids: L-2020-LRM-108)

ML20329A343
Person / Time
Site:	Cook
Issue date:	11/24/2020
From:	Scott Wall Plant Licensing Branch III
To:	Gebbie J Indiana Michigan Power Co
Wall S
References
EPID: L-2020-LRM-108
Download: ML20329A343 (3)

Text

Quantitative Result Comparison Metric Unit 1 Unit 2 Duration of Extension 6 months 18 months Internal Events LERF 8.35E-9 2.96E-8 External Events LERF 3.05E-8 9.54E-8 Total LERF 3.88E-8 1.25E-7

• Difference in results primarily from difference in duration

• Ratio of Duration = 1:3

• Ratio of Risk = 1:3.2

• Key difference between the Units is that the longer duration causes Unit 2 to pass the 1E-7 threshold for LERF discussed in RG 1.174 acceptance guidelines

Consideration of Total Risk

• RG 1.174 provides the following guidance:

When the calculated increase in LERF is in the range of 10-7 per reactor year to 10-6 per reactor year (i.e., the increase in LERF falls within Region II of Figure 5),

applications are considered only if it can be reasonably shown that the total LERF is less than 10-5 per reactor year.

• For DC Cook Unit 2, the simple sum of its 3 models (FPIE, FPRA, SPRA) shows a LERF higher than 1E-5 per reactor year

• Sufficient conservatisms exist in these models to conclude that a realistic estimate of total site LERF would remain below 1E-5 per reactor year

Additions to Unit 2 Submittal

• Because of the guidance to consider Total Risk, Unit 2 contains the following information, in addition to everything contained for the Unit 1 Submittal:

• A quantitative sensitivity for the credit of FLEX in the Unit 2 FPRA

• A qualitative discussion on sources of conservatism within the PRAs

• For each identified conservatism, the submittal provides a discussion including the impacted models, and how significant we estimate the conservatism to be

• This additional information will demonstrate that total LERF for DC Cook Unit 2 can reasonably be shown to be below 1E-5