ML24043A117
| ML24043A117 | |
| Person / Time | |
|---|---|
| Issue date: | 02/13/2024 |
| From: | Broadbent G, Pimentel F, Sarikaya B NRC/NRR/DRA/ARCB |
| To: | David Garmon-Candelaria NRC/NRR/DRA/ARCB |
| References | |
| Download: ML24043A117 (7) | |
Text
©2024 Nuclear Energy Institute Greg Broadbent Industry Consultant, Entergy (Retired)
Baris Sarikaya Constellation Energy Group Frankie Pimentel, Sr. Project Manager -
Engineering & Risk, NEI February 13, 2024 Best-Estimate Plus Uncertainty Approaches to Dose Analysis
©2024 Nuclear Energy Institute 2 Many safety analyses are applying a best-estimate plus uncertainty (BEPU)
Currently approved for 50.46 LOCA calculations for Peak Clad Temperature NEDE-33005P-A GNF TRACG LOCA PCT Application NEDE-32906P-A GNF TRACG AOO Calculations Radiological analysis is a good candidate for applying BEPU approaches Many independent inputs that are defined by probability distributions Very similar approach to that assessed by NRC in 1996 in ML003702950 Suggested by ACRS Applied to PWR MSLB and SGTR
Background
©2024 Nuclear Energy Institute 3 Current Regulatory Guidance Section 5.1.3 of Reg Guide 1.183 Rev. 1 The licensee should select the numerical values to be used as inputs to the dose analyses with the objective of determining a conservative postulated dose.
For input parameters subject to a probability distribution, the selection of the worst-case (e.g., 10th percentile) for all inputs can lead to overly-conservative dose results.
©2024 Nuclear Energy Institute 4 Inputs Subject to Probability Distribution Dose Inputs Subject to a Potential Probability Distribution (Not All Inclusive) 5% X/Q Worst 2-Hour X/Q Occurs at Time of Peak Release 10% Powers Aerosol Removal Rate Worst Case Core Source Terms 10% Containment/Drywell Spray Removal Rate Concurrent Independent LOOP SG Tube Failure is at Worst-Case Location (i.e., top of tube bundle)
Dropped Bundle in High Peaking Bundle and Impacts Other High Peaking Bundles Worst-Case Single Active Failure Control Room Breathing Rates
©2024 Nuclear Energy Institute 5 Approach Overview
©2024 Nuclear Energy Institute 6 EAB Short-Term Probability Distribution 0
10 20 30 40 50 60 70 80 90 100 1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 Cumulative Probability (%)
EAB Dispersion Coefficient (s/m3)
EAB Short-Term Overall Site Limit X/Q Distribution Data PAVAN Data Fit Added Data 5%
6.18E-4 Annual X/Q 1.93E-5 50%
8.71E-5 Direct from PAVAN Output
©2024 Nuclear Energy Institute 7
- Consistent with current regulations
- Continues to provide reasonable assurance of meeting the 50.67 regulatory limits
- Consistent with other approved methodologies (e.g., PCT)
- Consistent with current regulatory guidance
- Meets the objective of determining a conservative postulated dose per Section 5.13 of RG 1.183 Rev. 1 For additional clarity, does Section 5.1.3 need a statement to the effect of:
Best-Estimate Plus Uncertainty approaches that develop conservative doses based on sampling input distributions are acceptable and will be evaluated on a case-by-case basis.
Conclusions