ML20178A249

Public Watchdogs - 10 CFR 2.206 Meeting with NRC - Petition Review Board, June 23, 2020

ML20178A249
Person / Time
Site:	San Onofre
Issue date:	06/24/2020
From:	Public Watchdogs
To:	Office of Nuclear Material Safety and Safeguards
CSBajwa NMSS/DFM/CTCF 415.5341
Shared Package
ML20178A247	List: ML20178A248 ML20178A249
References
2.206
Download: ML20178A249 (15)

Text

PublicWatchdogs 10 CFR 2.206 Meeting with NRC Common Mode Flooding of ISFSI San Onofre June 24, 2020 June 24, 2020 Charles Langley and Paul Blanch PE 1

Introduction

• Participant introduction

• Professional Background

• SES Participation

• Conducted IAW Management Directive 8.11

• Holtec FSAR UMAX 2018 Revision 5 (ML18192B094) and NUREG 1536 June 24, 2020 Charles Langley and Paul Blanch PE 2

Flooding = DISASTER When water enters above the vents at San Onofre, each of the 72 Vertical Ventilated Modules that store the nuclear waste will be flooded.

Once this flooding occurs, there is no known means discussed in the Final Safety Analysis Report, NRC or Holtec documents, to recover from this event and restore cooling.

June 24, 2020 Charles Langley and Paul Blanch PE 3

Brief Summary of Original Petition

• Design Base Event (DBE) Flooding not analyzed

• Damage to Vertical Ventilated Modules (VVM) may be unrecoverable June 24, 2020 Charles Langley and Paul Blanch PE 4

New Information

• Flooding is Design Basis Event (DBE)

• Water will be above UMAX inlet and outlet vents

• Most water will flash to steam and be expelled

• May be repetitive with waves and surges

• Once water recedes, subcooled water will remain in VVM blocking all cooling

• All passive cooling flow will terminate in all 72/73 VVMs

• MPC structural integrity not analyzed June 24, 2020 Charles Langley and Paul Blanch PE 5

New Information

• Fuel and VVM temperatures and pressures not analyzed beyond 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />

• Recovery discussed and includes removal of MPC from VVM

• Remove obstructions by washing and vacuuming if required

• Process must be repeated 72/73 times

• Radiation levels may prohibit recovery June 24, 2020 Charles Langley and Paul Blanch PE 6

Flooding considerations from NUREG 1536

• The NRC staff has generally considered that the following events should be evaluated as design-basis accidents in the SAR:

• The SAR should establish a design-basis flood condition. If the SAR establishes parameters for a design-basis flood, all of the potential effects of flood water and ravine flood byproducts should be recognized. Serious flood consequences can involve effects such as blockage of ventilation ports by water and silting of air passages.

Other potential effects include scouring below foundations and severe temperature gradients resulting from rapid cooling from immersion.

June 24, 2020 Charles Langley and Paul Blanch PE 7

Unanalyzed condition unless addressed in FSAR TEXT REDACTED BY NRC/HOLTEC June 24, 2020 Charles Langley and Paul Blanch PE 8

Rapid cooldown could potentially result in uncontrolled thermal stresses and failure in the structural members.

• If not controlled, the extremely rapid cooldown rates to which the hot MPC internals and fuel cladding could be subjected during reflooding of the MPC cavity could potentially result in uncontrolled thermal stresses and failure in the structural members. (page 81 -- OOE Staff Evaluation of Trojan ISFSI)

June 24, 2020 Charles Langley and Paul Blanch PE 9

Typical Temperature Profile of Holtec MPC June 24, 2020 Charles Langley and Paul Blanch PE 10

Outlet Typical Cask Installation Temp Not Max 32 Hour Temps analyzed MPC Lid 631 F 631 F Fuel Cladding Divider Shell 964 F 694 F <475 F MPC Basket MPC Shell 936 F 732 F 475 F Insulation 693 F Containment Shell 732 F 475 F June 24, 2020 Charles Langley and Paul Blanch PE 11

Maximum Teperatures (sic) reached after 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> of complete duct blockage June 24, 2020 Charles Langley and Paul Blanch PE 12

Maximum Teperatures (sic) reached after 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> of complete duct blockage

• Short term operations include but are not limited to MPC drying and onsite transport. The 1058°F temperature limit applies to MPCs containing all moderate burnup fuel. The limit for MPCs containing one or more high burnup fuel assemblies is 752°F.*

• See ML18192B094 June 24, 2020 Charles Langley and Paul Blanch PE 13

Summary/Issues/Conclusions/Questions

• Flooding of ISFSI has not been analyzed

• Flood analysis, if existing, withheld from public

• Flooding above VVM vents will halt all cooling for all VVMs

• Steam will be produced

• Subcooled seawater will block all cooling with no possible recovery

• Flow blockage has only been analyzed for 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> June 24, 2020 Charles Langley and Paul Blanch PE 14

Summary/Issues/Conclusions/Questions (continued)

• Structural impact of multiple rapid temperature changes not analyzed

• Impact of residual salts and flood byproducts not analyzed

• Common mode failure has not been considered or discussed

• Radiological impact has not been addressed

• All of the potential effects of flood water and ravine flood byproducts should be recognized. (NUREG 1536)

• No Emergency Plans for recovery from 72 flooded VVMs June 24, 2020 Charles Langley and Paul Blanch PE 15