AREVA Comments on Combustible Gas Control Regulations for New Plants

1. AREVA Comments on Combustible Gas Control Regulations for New Plants 

2. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego

3. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego 10 CFR 50.44 Requirements Complete rewrite of 10 CFR 50.44 in 2003 Prior to 2003, 10 CFR 50.44 required design-basis H2 analysis Assume oxidation of 5% (active) fuel cladding Based on five times the 1% core-wide oxidation required by 10 CFR 50.46 Currently, key CGCS issues for design and licensing resolution H2 loads resulting from 100% clad-water reaction H2 distributed in the containment and removed for load minimization Global H2 concentration in containment atmosphere does not exceed 10% by volume Demonstrate no risk of flame acceleration or deflagration-to-detonation transition Demonstrate equipment survivability from a deflagration Provide monitoring of oxygen and hydrogen concentrations Containment structurally withstands severe accident loads Most requirements addressed in Chapter 19 Severe Accidents However, SRP and RG 1.206 retain expectation of beyond-design-basis evaluations in Chapters 3 (Structural) and 6 (Containment)

4. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Credited Experimental DatabaseHydrogen Dynamics Hydrogen Production Behavior of overheated fuel Effects of water/steam injection Hydrogen source term Hydrogen Distribution Use of similarity arguments addressing Vapor and aerosol distribution Pressurization/depressurization Global convection (mixing) Local heat transfer Distribution of energy Hydrogen Combustion Hydrogen generated during MCCI will autoignite Potential combustion mode based on gas distribution and temperature OECD Report on Flame Acceleration and DDT Hydrogen Recombiners Development of correlations Performance in harsh environments Efficiency

5. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Issue Resolution Experience- EPR™ Design Elements Hydrogen Distribution Short-term: Containment flow paths encouraging natural convection Long-term: Non-safety sprays Hydrogen Combustion Large containment volume dilutes potential for detonation Compartmentalization (detonation requires space for flame acceleration) Pressure loads relieved via dedicated severe accident heat removal system Hydrogen Recombination 47 Passive Autocatalytic Recombiners (PARs)

6. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Issue Resolution Experience- Inspection/Testing Elements Equipment Survivability (ES) of PARs and CONVECT system for atmospheric mixing Functional requirements defined through performance testing (re: experimental database) GDC requires that these systems be regularly inspected and tested GDC 42 - The containment atmosphere cleanup systems shall be designed to permit appropriate periodic inspection GDC 43 - The containment atmosphere cleanup systems shall be designed to permit appropriate periodic pressure and functional testing 10 CFR 50.44 requires ES evaluation considering H2 production from 100% clad oxidation Demonstration under the most adverse condition for equipment qualification, not ES This requirement appears to be contrary to statements appearing in SECY-90-016 and SECY-93-087

7. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Issue Resolution Experience- Analysis Elements Successful application of evaluation methods Modeled after RG 1.203 “Transient and Accident Analysis” (2005) for DBAs Topical report ANP-10268(PA) approved in 2007 Explanation of methodology well received by NRC and ACRS Results in EPR™ FSAR show that for the “more likely” severe accident scenarios: H2 loads consistent with 10CFR50.44 (100% clad-water reaction) H2 well-mixed in the containment The global H2 concentration in the containment atmosphere does not exceed 10% by volume The H2 concentration reduced to levels below 4% by volume 12 hours after the onset of a severe accident There is no risk of flame acceleration or deflagration-to-detonation transition AREVA’s original containment combustion loads analysis applying RG 1.7 not accepted by NRC staff Have insisted that DG-1203 be applied (requires more rigorous approach) Revised combustion loads analysis evaluated deterministically considering a suite of “more likely” severe accident scenarios

8. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Lessons Learned/Concerns 2003 update to 10 CFR 50.44 incomplete Counterpart changes to linked documents including 10 CFR 50.46, NUREG-0800, and RG 1.206 were not updated 10 CFR 50.46 assumptions for design-basis core-wide hydrogen release should have also been eliminated Resolution of issues in FSAR considering severe accidents belong in one place: Chapter 19 (consider revision of NUREG-0800 and RG 1.206) Equipment survivability expectations blur the line between equipment qualification and survivability H2 generation from 100% oxidation of fuel cladding assumption (i.e., most adverse condition) is very conservative for equipment survivability criteria AND is contrary to the position appearing SECY-93-087 This is an example of how expectations for beyond-design-basis is creeping into the design-basis domain

9. AREVA Comments on CGCS Regulations – 2010 ANS Annual Meeting – San Diego Lessons Learned/Concerns 2003 update to 10 CFR 50.44 incomplete Structural analysis requirement is “a moving target” and confusing Analysis applying RG 1.7 being supplanted by unapproved DG-1203 Appearance in FSAR Chapter 3 confuses both regulator and applicants about design, analysis, and inspection requirements (i.e., EQ vs. survivability; safety vs. non-safety) Industry and NRC should reconcile these remaining issues