ML17032A343

NEI-EPRI Slides. DG-1327 NRC Meeting

ML17032A343
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Site:	Nuclear Energy Institute
Issue date:	02/02/2017
From:	Eichenberg T Nuclear Energy Institute
To:	Office of Nuclear Regulatory Research
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DG-1327 Clarification Reactivity Initiated Accident Guidance T. W. Eichenberg EPRI Fuel Reliability Program, Reg-TAC Chair Sr. Specialist Reactor Safety Analysis, TVA January 25, 2017

• White Flint, Rockville MD 1

Overview

• Categories for Discussion

- Methods & Assumptions

- Failure Thresholds

- Release Fractions

- Miscellaneous 2

PWR vs BWR Perspective

• While Rod Eject / Blade Drop are Reactivity Initiated Accidents

- These different events dont share an identical topology

• Analytical space is different

- Every assumption isnt automatically meaningful to both PWRs and BWRs

- Example from item 2.2.5

• (a) is PWR speak

• (b) is BWR speak

- Example item 2.2.10

• Muddy regarding BWR 3

Methods & Assumptions

• Approved Models

- What does account for calculational uncertainties mean?

- Realistic / Risk Informed methods to be allowed?

- Expecting a full RG 1.203 process?

4

Methods & Assumptions

• 5% power DNB/CPR threshold?

- Value is below TS monitoring power level.

• Correlation range of applicability may not extend that low

- DNB/CPR may not be appropriate metric relative to very fast transient condition 5

Methods & Assumptions

• Misc. Assumptions

- Are sensitivity studies going to be plant and cycle specific?

- What is NOT a major reactivity feedback?

• Direct Moderator Heating Non-Eq. T-H

- What is meant by manufacturing tolerances?

• Plant , fuel type, and/or cycle specific.

As-built vs bounding tolerance

- Accounting for something vs.

sensitivity/parametric evaluation.

6

Methods & Assumptions

• Misc. Assumptions

- What is meant by wider operating conditions?

- Effectively, youre saying the determination of limiting conditions is non-linear.

• When does the search stop? To survey a larger population implies a realistic assessment.

- What is sufficient parametric study?

7

Methods & Assumptions

• Misc. Assumptions

- Why do advanced methods need to implement artificial conservatism to compare against failure criteria?

- Extensive focus on bounding assumptions

• Seems incompatible with implications of 2.2.4 (limiting scenario tied to non-linear effects, not artificial conservatisms) 8

Methods & Assumptions

• Misc. Assumptions

- Approved hydrogen pickup model is explicit

- Need for an approved hydride orientation model is not as obvious. Need to validate the failure curve utilized.

- Is the use of RG 1.224 account for hydride orientation issue?

9

Failure Thresholds

• EPRI Test Program

- Why Revision 1

• MBT Data / NSRR corrections

- Temperature Effects

- Pulse Effects

- Power History Effects

- Hydrogen > 300ppm

- Elongation

- Failure Limits http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002005540 10

Failure Thresholds

• Best Estimate?

- Yes, in the sense that curve fits are relative to nominal data.

- No, in the sense that the shape of curve fits displays negative impact in areas without failures

• Low Hydrogen region

- No, in the sense that correlation coefficients are in some cases substantially less than 1 11

Release Fractions

• Appropriate Location

- Keep information in one place; remove from DG-1327

- Locate to 1.183, 1.195, etc. (sign of a bigger problem)

• Example: Changing dose method constitutes an AST/TID backfit?

12

Release Fractions

• Transient Fission Gas Release

- Database doesnt represent low burnup 13

Miscellaneous

• Logistical Issue

- Approved Analytical Methods must Exist

• Method reviews in a timely manner?

• Potential New Method Elements

- Transient Fission Gas Release / Mechanical aspect

- Corrosion/Hydrogen Uptake/Crud

- Hydride Characterization

- FCI Impact if Centerline Melt Allowed

- Contribution of Fission Gas Release to Pressure Surge 14

Questions?? / Discussion 15