ML24268A276

Email from Connie Kline with Questions on Perry CBS Exemptions

ML24268A276
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Site:	Perry
Issue date:	06/23/2024
From:	Kline C Public Citizen
To:	Bernie White Storage and Transportation Licensing Branch
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ML24268A275	List: ML24268A276 ML24268A277 ML24268A279
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Download: ML24268A276 (1)

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Hi Mr. White,

[External_Sender] Holtec CBS Variant Basket Exemption Perry NPP Sunday, June 23, 2024 10:51:49 PM Holtec CBS basket varjants.pdf Thank you so much for taking the time to speak with me on 5/10/24 regarding the Holtec CBS variant HI-STORM Flood and Wind (FW) MPC-89 for which the NRC granted an exemption in May to load two of these dry cask systems in August 2024 at the Perry nuclear power plant.

I'm sorry it's taken me so long to get back to you with some additional questions, concerns etc. which are attached to this email. My excuse is that the dog ate my homework. I researched pertinent documents and crafted questions/comments, and then the document disappeared from my computer, so I had to start all over again.

Some unexpected things came up which delayed locating and reviewing the pertinent documents again.

Thank you so much for your consideration, patience and for indulging my questions. I look forward to replies.

Connie Kline

I reviewed these documents pertaining to the Holtec HI STORM dry cask systems with the Continuous Fuel Basket Shim (CBS) variants. Portions of two ot them are highlighted below.

1) Holtec 2 page fact sheet with diagram https://holtecinternational. com/wp-content/uploads/2019/1 0/HTB-007-H I-STORM-FW-Rev-13. pdf

2) 9/12/2023 NRC Holtec Report of Apparent Violations Being Considered for Escalated Enforcement https://adamswebsearch2. nrc.gov/webSearch2/main.jsp? AccessionNumber=ML23145A175

3) 10/25/23 Holtec Slides & Viewgraphs https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML23297A261

4) 1/31/24 NRC Memo - Safety Determination of a Potential Structural Failure of the Fuel Basket During Accident Conditions for the HI STORM 100 and HI STORM FW Dry Cask Storage Systems https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24018A085

5) 2/8/24 NRC Public Meeting Holtec & User Slides https://adamswebsearch2. nrc. gov/webSea rch2/main.j sp? Accession Number= ML24036A281

6) 2/27/24 Energy Harbor request for exemption to load basket canister Holtec MPC-89 system baskets/canisters in question in Aug. 2024 https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24058A180

7) 3/6/24 meeting slides https://adamswebsearch2. nrc.gov/webSearch2/main.jsp? AccessionNumber=ML24065A118

8) 3/6/24 rneeting summary https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24067A301

9) 3/26/24 EA & FONS! granting exemption for Holtec dry cask system(s) in question at Dresden https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24066A034

10) 5/3/24 EA/FONS! granting exemption for Holtec dry cask system(s) in question at Perry https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24103A110 9/12/2023 NRC Holtec Report of Apparent Violations Being Considered for Escalated Enforcement https://adamswebsearch2. nrc.gov/webSearch2/main.jsp? Accession Number= ML23145A175 These were some key points I gleaned from this document. Page numbers refer to PDF.

,,, - NRC conducted a routine onsite fabrication inspection December 12-15, 2022 at Holtec's Advanced Manufacturing Division in New Jersey.

, - from November 6, 2020, to July 19, 2021, Holtec made design changes to four multi-purpose canister (MPC) fuel baskets.

The basket's primary function is to prevent criticality under a tip over event.

The violations consisted of:

• Holtec failed to obtain a Certificate of Compliance (CoC) Amendment

• Holtec failed to maintain records Holtec failed to subject design variants to original design control measurements - no analyses of load transfer, various stresses etc.

, "The design change was from the standard nonwelded Metamic-HT co-planar slotted plate basket design held together only by welded outside cell corners, to a completely non-welded Metamic-HT co-planar slotted plate basket design, held together by continuous shims running the total outside length of the basket and bolted to top and bottom basket plate extensions.

Hereafter, 'the standard non-welded Metamic-HT co-planar slotted plate basket design' is generally referred to as the 'original design.' In addition, as part of the basket design change, several continuous shims, that are smaller in size, are bolted to plate extensions at a standard spacing along the total length of the basket to also help hold the basket assembly together. This basket design change was designated as the CBS variant and has been applied to four different multi-purpose canisters. For the HI-STORM FW system, Holtec has designed the MPC-37-CBS and MPC-89-CBS variants, and. for the HI-STORM 100 system, the MPC-68M-CBS, and MPC-32M-CBS variants" p 1, "Improper basket tip over analysis (failure to meet design bases requirements) of the CBS basket variants *could result in a critically event or the inability to remove a spent fuel assembly from a basket cell that has permanent deformation after the design basis accident condition occurred.'...

Kline 1

"Previously, for the standard basket designs the basket corner welds were modeled as elastic elements. In the CBS design change, the welds have been eliminated and bolts are now used to hold the baskets together "Elimination of the original design 'elastic' corner welds and replacement with bolts to hold the baskets together' show large local strains in the fuel basket, reaching the rupture strain for the MPC 89-CBS basket...

1,C "For the MPC 89-CBS and MPC 37-CBS tip-over analysis, the results show large local strains. These results do not support Holtec's conclusion that there was no permanent deformation in the active fuel region and there is no effect on the fuel assembly spacing. The tip-over stress results for the bolts and shims for the CBS baskets were not reported or evaluated in the calculations...

"For all four CBS baskets. there is no analysis of the differential thermal expansion between the basket panels and the MPC shell to ensure the gaps are sufficient to prevent stresses from thermal expansion. Also. none of the analysis results address the design criteria for the fuel basket, which requires the maximum total deflection of the basket be less than the allowable values in the FSARs."

1/31/24 Safety Determination of a Potential Structural Failure of the Fuel Basket During Accident Conditions for the HI STORM 100 and HI STORM FW Dry Cask Storage Systems https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24018A085 My questions and comments follow below. Page numbers refer to PDF.

p

'1 THERMAL EVALUATION "Holtec has not thermally analyzed a postulated non-mechanistic accident (i.e., cask tip-over) resulting in a horizontal cask orientation.

" Although a thermal analysis of the horizontal configuration has not been performed, the "average" MPC gas temperature will remain much the same as the conditions of normal storage, due to no change in decay heat. Therefore, the MPC internal pressure... will remain the same and will not breach the MPC and the associated confinement welds. While the fuel rods might not be retrievable based on the unanalyzed fuel temperatures, the MPC confinement system will remain intact and will not be degraded...

"Therefore, the staff concludes, per its thermal evaluation, that the containment will remain intact and therefore the non-mechanistic tip-over accident condition does not result in significant safety consequences for the HI-STORM FW and HI-STORM 100 storage systems."

p b CRITICALITY EVALUATION "The staff assessed the potential for an inadvertent criticality in the case of an unanalyzed geometry (e.g.,

complete structural failure of a fuel basket). A failure of the basket eould result in the basket material and fuel debris rubblizing at the bottom or side of the MPC due to a postulated cask accident (e.g. tip-over).

Nonetheless, as explained below, the staff does not expect any significant change to the prior criticality evaluation, where the basket geometry was known and included in a bounding criticality evaluation."

(Assuming that) "... even when fresh, the contents were enriched to less than 5 wt.% 235U."

."Given those conservative considerations and that the degradation of the CBS basket will not impact the MPC confinement boundary during a non-mechanistic tip-over accident event; staff has determined water in-leakage to be highly unlikely, and staff finds reasonable assurance that a post-accident configuration will remain subcritical. Therefore, there is no criticality safety concern for the CBS basket variants for both the HI-STORM 100 and FW casks under the assumption of fuel basket failure."

p 5 6 SHIELDING EVALUATION "As the damage is localized and the vast majority of the shielding material remains intact, the effect on the dose at the site boundary is negligible...

"A non-mechanistic tip-over accident condition is considered a hypothetical accident scenario and may affect the HI-STORM FW overpack by resulting in limited and localized damage to the outer shell and radial concrete shield...

Kline "However, the adjacent and one meter dose rates may be increased, which should be considered in any post-accident activities near the affected cask.

"In terms of damaged fuel, and the potential change in dose rate as a result of fuel debris or a damaged fuel assembly collapse, the dose rate is not very significant for the storage of damaged fuel and/or fuel debris.

"Any potential damage to the fuel cladding resulting from the fuel basket failure would remain within the MPC and would not result in any safety consequences that affects the shielding capability.

"Further, in the event of a tip-over, NRC staff anticipates that licensee's corrective actions would include a radiological and visual inspection to determine the extent of the damage to the overpack and the contained MPC and that special handling procedures, including the use of temporary shielding, would be implemented by the general licensee."

1 6 STRUCTURAL EVALUATION

" Thus, the staff concludes that the MPC confinement boundary maintains its structural integrity and no water is able to enter the interior of the MPC during accident conditions...

"However, the non-mechanistic tip-over analysis did not reasonably assure that the CBS baskets maintain their deflection and stress requirements. The stress contour results for several of the basket analyses indicated localized stresses in the active fuel region that exceed the primary stress limits as well as the true fracture strength of the basket material.

"These results indicate that some areas will experience complete failure of the material for several of the HI-STORM FW fuel basl<ets currently submitted for Amendment 7...

"Nonetheless, should the fuel basket fail to maintain its structural integrity, and, in a worst-case scenario, allow the fuel assemblies and cladding to fail, the fuel will be maintained in a subcritical condition... Therefore, the staff concludes that the non-mechanistic tip-over accident condition does not result in significant safety consequences... "

CLADDING INTEGRITY

"... fuel rod cladding is not considered in the design criteria for confinement of radioactive material under normal, off-normal, or accident conditions. Since fuel cladding is not relied on for demonstrating safety, there is no requirement to demonstrate structural integrity of the cladding. Since the MPC maintains structural integrity, the staff concludes that any potentially damaged fuel resulting from the fuel basket failure would remain within the MPC."

1) 1 RETRIEVABILITY AND RECOVERY

" As discussed in NUREG-2215, retrievability is applicable only during normal and off-normal conditions and does not apply to accident conditions.... Therefore, the staff concludes that the retrievability requirement for the systems with CBS fuel basket designs is satisfied... Also as discussed in NUREG-2215, recovery is the capability of returning the stored radioactive materials from an accident condition to a safe condition without endangering public health and safety or causing significant or unnecessary exposure to workers... The staff's review did not identify issues with the overpack or MPC in the tip-over analysis.

"Should the basket fail, and some fuel be rubblized, the fuel may not be easily recovered at the fuel assembly level. However, recoverability of the MPC with the encapsulated fuel is still possible."

I' d 9 HANDLING OPERATIONS

"... dry cask handling outside of the Fuel Handling Building require either the use of single-failure-proof lifting devices or the imposition of a lift height limit, which is supported by a drop analysis...

" Therefore, a similar conclusion to that for the non-mechanistic tip-over can be made for dry cask handling accident conditions. The MPC confinement boundary maintains its structural integrity and no water can enter the interior of the MPC. Should the fuel basket fail to maintain its structural integrity during stack-up the fuel will be maintained in a subcritical condition...

"It should be noted that the tech specs (TSs) do not address the loading and handling operations inside the licensee's Fuel Handling building, which are site-sr;>ecific. Therefore, operations occurring inside the Fuel Handling Building, that involve loading and handling of the MPC and transfer cask in a wet condition are not covered by the dry cask non-mechanistic tip-over accident analysis. These wet loading operations require the Kline fuel basket to maintain its geometry and structural integrity in order to prevent fuel criticality. The magnitude of load demands on the fuel basket during these wet loading/handling operations are not significant and not expected to challenge the geometry and structural integrity of the fuel baskets. Site-specific loading and handling configurations inside the Fuel Handling Building are addressed by licensees under 10 CFR Part 50, typically with the goal of demonstrating through analysis that the analyzed configuration will remain stable and that a tip-over, or any load challenging the fuel basket structure, will not occur under accident conditions.

QUESl IONS/COMMENTS The following are general questions.

1. According to the NRC, as of March 2024, there were 21 licensees who had loaded 200 CBS basket variant dry cask systems.

A. Please provide a list of the 21 licensees, the nuclear plants at which the 200 CBS basket variant dry casks are located, and the number of loaded variant dry cask systems at each plant.

B. How many exemption requests have been received and granted to date?

C. How many additional basket variant dry cask systems have been loaded since March 2024?

D. Are dry casks (ISFSI) monitored continuously for radiation?

E. If not, what is the monitoring schedule?

F. What radionuclides are monitored?

G. Is ISFSI reporting separate from the reactor effluent/environmental reports and if so, where is it available at NRC.gov?

The following questions/comments refer to the 1/31/24 Safety Determination above.

2. My general impression of this document is that within a three month period from September 2023 to January 2024, the NRC staff did a 180° minimizing, and dismissing the concerns raised in the 9/12/23 document above and making a number of assumptions.

• The thin-walled multi purpose canister (MPC) is assumed to maintain its structural integrity during a tip over event so no water can enter the interior of the MPC and any damaged fuel would remain within the MPC.

• Subcriticality is also assumed. "Nonetheless, should the fuel basket fail to maintain its structural integrity, and, in a worst-case scenario, allow the fuel assemblies and cladding to fail, the fuel will be maintained in a subcritical condition."

It is also assumed that while radiation released due to a basket tip over accident might exceed the one meter dose rate (p 5-6 "Shielding Evaluation"), site boundary dose rates would not be exceeded.

3. According to 1..; "Criticality Evaluation", assumptions are based on fresh fuel enriched to less than 5 wt.% 235U. The NRC has approved enrichment up to 8% wt. 235U (see links below).

A. If the CBS baskets in question continue to be used, will increased enrichment above 5% wt. 235U (and use of higher burnup fuel) be analyzed for a tip over accident?

Global Nuclear Fuel Coe etc.

https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML23191A147 Louisiana Energy Services has also applied to increase enrichment above 5.5% wt. 235U but less than 10%.

https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24052A385

4. Could you please briefly describe the accident scenario(s) that were considered under which a potential basket tip over could occur and the locations at a reactor site?

5. p. 7 "Fuel cladding is not relied upon for demonstrating safety and there is no requirement to demonstrate structural integrity of the cladding."

A. Why is there no requirement to demonstrate structural cladd ing integrity?

B. Why is cladding not relied upon as an additional redundant safety layer C. Doesn't "rubblized", irretrievable fuel indicate cladding failure?

Kline

6. While the NRC considers "rubblized" fuel an unlikely, hypothetical worse case scenario, the NRC acknowledges that a subcritical accident where fuel is "rubblized" would require additional shielding and worker protection. (p 5 b)

7. According top. 4 "Thermal Evaluation", since Holtec did not perform thermal analysis, the NRC apparently performed its own thermal analysis or is relying on past thermal analyses.

8. p 6 "Structural Evaluation" indicates that stress limits could still be exceeded but assumes that the fuel will remain subcritical.

A. Have any additional stress/strain, elasticity, load transfer analyses been done?

The following questions pertain to these documents (page #s are PDF):

2/27/24 Energy Harbor exemption request to load two Holtec MPC-89 system baskets/canisters variants at the Perry reactor in Aug. 2024 https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24058A180 3/26/24 EA/FONSI granting exemption for Holtec dry cask system(s) in question at Dresden https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24066A034 5/3/24 EA/FONSI granting exemption for Holtec dry cask system(s) in question at Perry https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML24103A110

9. p 1 of Energy Harbor exemption request states, "Currently, EHNC plans to load MPC-89CBS systems during the summer 2024 dry cask campaign and during future campaigns."

"Future campaigns" appear to indicate that in February Energy Harbor expected that these variant basket designs would continue to be manufactured.

10. According to i' 17 J ::i of the Perry License Renewal Application, Energy Harbor has already loaded two Holtec MPC-89 casks. "Currently the ISFSI has 25 MPC-68 and two MPC-89 systems on the pad."

https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML23184A081 A. When were the two existing MPC-89 systems loaded?

8. Are they the CBS variant baskets?

11. p 6 1 of the Dresden EA/FONSI states, 'The staff considered the no-action alternative. The no-action alternative (denial of the exemption request) would require Constellation to unload spent fuel from the MPC68M-CBS in the HI-STORM 100 Cask System to bring it in compliance with the CoC. Unloading the cask would subject station personnel to additional radiation exposure, generate additional contaminated waste, increase the risk of a possible fuel handling accident, and increase the risk of a possible heavy load handling accident. Furthermore, the removed spent fuel would need to be placed in the spent fuel pool, where it would remain until it could be loaded into an approved storage cask."

I don't see the precise language that is in the Dresden EA/FONSI about unloading and returning fuel to the pool in the 5/3/24 Perry EA/FONSI.

A. Does this mean that none of the basket variants have been loaded at Perry?

8. Has a dry cask system (Holtec or another manufacturer) ever been unloaded and the fuel returned to the spent fuel pool?

12. p !) of the Energy Harbor exemption request states, "Improvements implemented through the new variant pertain to the external shims, which are between the basket periphery and the MPC shell, and the elimination of the difficult to manufacture friction-stir-weld (FSW) seams joining the raw edges of the basket panels."

A. For how many years were the "original design" baskets manufactured?

B. Did Holtec ever indicate to the NRC that they were difficult to manufacture?

C. Does "difficult" mean more "expensive" to manufacture, i.e. are the variants cheaper to manufacture?

Kline The following questions pertain to Holtec.

1. Other than the Notice of Violations, what, if any, enforcement action has the NRC undertaken?

2. In response to the violations, what corrective actions has Holtec undertaken?

3. What procedures have been implemented to prevent recurrence of a similar situation?

4. Does NRC consider that compliance has been or still needs to be restored?

5. Could the NRC have ordered a recall of already delivered dry cask systems with the CBS basket variants and require Holtec to issue a licensee refund?

6. Instead of issuing exemptions to load the CBS basket design variant dry cask systems, could the NRC have required temporary re-racking of the SFPs. which while not ideal, has been done for years?

7. Can the NRC issue monetary penalties?

8. Can the NRC order Holtec to stop manufacturing the CBS basket design variants and return to manufacturing the "original design"?

9. I cannot find an accession number for Amendment No. 7 to CoC No. 1032 for the HI-STORM FW system that Holtec submitted.

10. Has Holtec submitted an additional amendment? If so, what is its accession number?