ML20178A249
| 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: |
| 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
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 June 24, 2020 Charles Langley and Paul Blanch PE 8
TEXT REDACTED BY NRC/HOLTEC
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
Typical Cask Installation Max 32 Hour Temps June 24, 2020 Charles Langley and Paul Blanch PE Outlet Temp Not analyzed Fuel Cladding 964 F MPC Basket 936 F MPC Shell 732 F MPC Lid 631 F Divider Shell 694 F Containment Shell 475 F 631 F 732 F Insulation 693 F 475 F
<475 F 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