ML20330A238
| ML20330A238 | |
| Person / Time | |
|---|---|
| Site: | 07201015 |
| Issue date: | 10/20/2020 |
| From: | Office of Nuclear Material Safety and Safeguards |
| To: | |
| Terry T | |
| Shared Package | |
| ML20330A237 | List: |
| References | |
| NRC-1160 | |
| Download: ML20330A238 (98) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
NAC International Pre-Decisional Enforcement Conference Docket Number:
72-1015 Location:
teleconference Date:
Tuesday, October 20, 2020 Work Order No.:
NRC-1160 Pages 1-96 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005 (202) 234-4433
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION PREDECISIONAL ENFORCEMENT CONFERENCE IN THE MATTER OF NAC International Tuesday, October 20, 2020 Via Video Teleconference The above-entitled matter was convened at 1:00 p.m., Christopher Regan, NRC, presiding.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 From the Nuclear Regulatory Commission:
CHRISTOPHER REGAN, Deputy Director, Division of Fuel Management, Office of Nuclear Material Safety and Safeguards LEIRA CUADRADO, Chief, Inspection and Oversight Branch ROBERT SUN, Enforcement Coordinator, NMSS DAVID JONES, OE/EB LORRAINE BAER, OGC/GCHA/AGCMLE TOM BOYCE, NMSS/DFM/MS. BAYONA:
JON WOODFIELD, NMSS/DFM/IOB MARLONE DAVIS, NMSS/DFM/IOB TOMEKA TERRY, NMSS/DFM/IOB YONG KIM, NMSS/DFM/IOB ANTONIO RIGATO, NMSS/DFM/MS. BAYONA:
From NAC International:
KENT COLE, President & CEO GEORGE CARVER, Vice President, Engineering and Licensing WREN FOWLER, Director of Licensing MARC GRISWOLD, Senior Project Engineer RYAN BAILEY, Senior Project Engineer ROBERT HELFRICH, General Counsel DANIEL F. STENGER, Hogan Lovells
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 P R O C E E D I N G S 1:01 p.m.
MR. REGAN: Good afternoon. My name is Christopher Regan. I am the Deputy Director of the Division of Fuel Management for the Nuclear Regulatory Commission's Office of Nuclear Materials Safety and Safeguards.
Today, we will conduct a Pre-decisional Enforcement Conference (PEC) between the NRC and NAC International to discuss two apparent violations (AVs) of NRC requirements. The apparent violations were described in an inspection report (IR) issues to NAC International on September 3, 2020. The inspection report can be found in our electronic document system, ADAMS, at Accession Number ML20225A032.
The letter that transmitted the inspection report offered NAC International the opportunity to either request a Pre-decisional Enforcement Conference or to request alternative dispute resolution with the NRC to address the apparent violation. Subsequently, on September 11, 2020, NAC International requested a Pre-decisional Enforcement Conference with the NRC.
The date of today's conference was selected based on the mutual agreement of both parties.
Ordinarily, the NRC would have hosted this
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 conference in person with NAC International, but these are not ordinary times. As a result, this conference is being conducted remotely using video teleconferencing technology. Audio for this meeting is through the moderated telephone line. Please note that only the presenters at this conference have video capability and can mute and unmute their lines as needed to support the discussions.
The WebEx audio and video features are disabled for the rest of the participants and members of the public. I would also note that this meeting is being transcribed. The meeting today is a Category One public meeting between the Nuclear Regulatory Commission and NAC International. A Category One public meeting is one where the public is invited to observe the meeting, and will be provided an opportunity to communicate with the NRC after the business portions of the conference are completed.
At the end of the business portion of this meeting, the operator will provide instructions on how to solicit your line to be opened so that you may ask questions to the NRC on the topics to be discussed today. For the benefit of those listening by phone today, we ask that you please speak clearly and state your name and affiliation before continuing. Next
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 slide, please.
Before I go any further, I would like to introduce the NRC staff representatives. Then I will give NAC International an opportunity to introduce its representatives. Again, my name is Christopher Regan.
I'm Deputy Director of the Division of Fuel Management. With me here today are Leira Cuadrado, Chief of the Inspection and Oversight Branch in the Division of Fuel Management, Robert
- Sun, our Enforcement Coordinator in the Office of Nuclear Materials Safety and Safeguards, David
- Jones, Enforcement Specialist in the Office of Enforcement, Lorraine Baer, attorney in our Office of General Counsel, Tom Boyce, Chief of the Materials and Structural Branch in the Division of Fuel Management, and Jon Woodfield, the Lead Inspector for the NAC International inspection, the subject of today's meeting.
I would also like to note that additionally, we have NRC staff representation from Leira and Tom's group, including Marlone Davis, Tomeka Terry, Yong Kim and Tony Rigato. So next I'll ask NAC International representatives to introduce themselves.
MR. COLE: Yeah, thanks, Chris. This is Kent Cole, President and CEO of NAC International. I
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 have with me Wren Fowler, who is Director of Licensing. Also, I have George Carver, who is our Vice President of Engineering, Licensing and Support.
I have Marc Griswold, who is a Senior Project Engineer for NAC International. I have Robert Helfrich, who is NAC's general counsel. I also have Ryan Bailey, who is NAC's Senior Project Manager for our Palo Verde implementation.
MR. HELFRICH: And also joining us on our behalf remotely by audio, is Mr. Dan Stenger, a partner with the Hogan and Lovells law firm in Washington, DC, on our behalf. Thank you.
MR. COLE: Thanks, Chris. That's it here for the NAC participants.
MR. REGAN: Very good. Thanks, Kent.
Thank you and welcome. I want to emphasize that the fact we are conducting this conference today does not mean that the NRC has made a final determination that violations occurred or that enforcement action will be taken. This is in part why the issues were described in the inspection report as apparent violations.
The conference is an important step in our deliberative process. The main purpose of this conference is to afford NAC International the opportunity to provide the NRC with additional
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 information that can be used to make an informed decision on the final enforcement action. However, no decisions will be reached or discussed during this conference.
I encourage you to be candid in providing your perspectives on the apparent violations, their safety significance, the circumstances surrounding the apparent violations, any corrective actions taken and planned, and any other information that you believe bears on the NRC's enforcement decision. A copy of the agenda for today's conference was included in the public meeting notice posted on the NRC's web page.
Concluding my remarks, Leira will provide some brief remarks. After this, Robert will discuss the Agency's enforcement policy and process just to make sure there's a good understanding, followed again by Leira, who will discuss the apparent violations that are at issue today. NAC will then be given an opportunity to provide opening remarks and present your perspectives on the apparent violations.
I note that the agenda provides for a break or a caucus prior to the conclusion of the conference. This break will allow the NRC staff to briefly review what we heard and determine if we have any follow-up questions for you. We encourage you to
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 also use that time to determine if you have any additional information you would like to present.
Following those final discussions, we will then proceed to closing remarks.
At this time, if there are not any questions, I will turn it over to Leira. Are there any questions before I turn it over to Leira?
MR. COLE: None from us.
MR. REGAN: All right, very good. Leira, I turn it over to you.
MS. CUADRADO: Thank you, Chris. Good afternoon. I am Leira Cuadrado, Chief of the Inspection and Oversight Branch in the Division of Fuel Management. The Inspection and Oversight Branch in the Division of Fuel Management is responsible for conducting inspections of transportation, package, and spent fuel storage system vendors to assess compliance with the regulations and their license or certificate of compliance.
In accordance with our normal processes, the documents associated with this conference, including any material provided by NAC International today, are already or will be available for public inspection in the Agency-wide Documents Access and Management System electronic records management
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 system, commonly known as ADAMS. The NRC is interested in feedback from participants and observers about how we conduct meetings.
Any persons listening on the teleconference bridge who would like to provide feedback to the NRC on this meeting may obtain a feedback form by downloading the form from ADAMS with Accession Number ML011160173. This form is also available at the public meeting notice on the NRC website, NRC.gov.
Before I present the apparent violations identified by the NRC, Robert Sun will take this opportunity to discuss the Agency's enforcement policy and process. The floor is yours, Robert.
MR. SUN: Good afternoon. My name is Robert Sun. I'm an Enforcement Coordinator for the Office of Nuclear Material Safety and Safeguards.
Next slide, please. Similar to Chris' opening remarks, I would like to emphasize that the NRC has not reached any final enforcement decision on the matter communicated on our September 3,
2020 inspection report. This conference is part of our information-gathering process used to help the NRC make an informed regulatory decision.
The inspection report you received in
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 September provided our perspectives on the apparent violations of NRC requirements that we believe occurred. This conference is your opportunity to provide your perspectives on the apparent violations and any additional information that you feel is pertinent to the NRC's enforcement decisions. Next slide, please.
There are four possible outcomes which meet the Agency's enforcement policy objectives.
These outcomes include 1) No enforcement action taken;
- 2) A notice of violation (NOV). An NOV is simply a written notice that a violation has occurred and how the requirement was violated. A written response from a licensee or CoC holder may be required for a notice of violation; 3) A notice of violation with a civil penalty. The purpose of a civil penalty is to emphasize compliance in a way that prevents future violations and focuses your attention on significant violations; and 4) Finally, in rare cases, the NRC can issue orders, which can be used to modify, suspend or revoke a license. Next slide, please.
When determining what sanctions should be employed, the NRC first works to determine what level violation or violations have occurred. If we determine that a violation has occurred, we use three
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 levels to classify violations according to their significance. The NRC uses four significance levels, I through IV, for violations at SL-I being the most significant and those at SL-IV the least significant.
SL-I, II and III violations are considered escalated enforcement actions that are candidates for monetary civil penalties or fines. Next slide please.
We take four factors into consideration in determining the severity level. First, we consider if there were any actual consequences, which would include things like overexposures or unintended releases of radioactive material. Next, we consider if there were any potential consequences. Third, we consider if the violation impacted the NRC's ability to perform its regulatory oversight function.
Finally, we consider if there were any willful aspects of the violation. Next slide, please.
After we have determined significance, the NRC has a systematic process used to determine if a civil penalty is warranted, and if so what should be the amount. Again, each violation classified at SL-III or above is a candidate for a monetary civil penalty. The civil penalty assessment process considers three elements. First, we consider your enforcement history and the severity level of the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 underlying violation.
Next, we consider how the violation was identified, whether it be licensee-identified or revealed by some other means, like through an NRC inspection or self-revealed through an event.
Finally, we look at corrective actions. For the NRC to assign corrective action credit, we typically look for actions that are prompt and comprehensive such that they would prevent future violations from occurring.
The NRC can exercise discretion depending on the circumstances to either increase or decrease the amount of a civil penalty. Although each case is different, absent the use of discretion, there are three possible outcomes for most cases. No civil penalty, a base civil penalty, or a civil penalty at twice the base value. Following this conference, we will make a decision based on the information we obtained during our inspection activities and considering any new information you provide during this meeting.
When we issue our decision, we will notify you by phone and by letter. This process can take up to several weeks. Next slide, please. NRC licensees and certificate of compliance holders have appeal
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 rights and may challenge any NRC action. Instructions for challenging an enforcement action will be either in the action itself or in the transmittal letter.
When civil penalties are issued, the particular action provides hearing
- rights, as well as another opportunity to request alternative dispute resolution.
Next slide, please.
If a civil penalty is imposed or an order is issued, normally our Office of Public Affairs will issue a press release within a day or so of the final action being issued and received. I'd like to close by just reminding you that everything I just discussed regarding sanctions, civil penalties and the overall process used to reach a final enforcement decision is publicly available and discussed in detail in our enforcement policy, which can be found at www.nrc.gov.
Next slide, please, and I'll now turn the conference back over to Leira, who will present the apparent violations.
MS. CUADRADO: Thank you, Robert. The apparent violations that are the subject of this conference were described in the NRC's inspection report issued on September 3, 2020. Next slide, please. In brief, on February 24th through February 27th, 2020, the NRC conducted an announced inspection
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 with NAC International at their corporate office in Norcross, Georgia.
Based on the information developed during the inspection, two apparent violations were identified and are being considered for escalated enforcement action in accordance with the NRC enforcement policy. Next slide, please. With regards to the first apparent violation, the Title 10 of the Code of Federal Regulations, commonly referred to as 10 CFR 72.146(c), titled Design Control, requires in part, that a certificate holder shall subject design changes, including field changes, to design control measures commensurate with those applied to the original design.
Changes in the conditions specified in the license or the CoC require prior NRC approval.
Contrary to the above, prior to December 30, 2016, the certificate holder (NAC) implemented a design change for the MAGNASTOR spent fuel cask without ensuring that design control measures were commensurate with those applied to the original design.
Specifically, NAC failed to use the nonlinear LS-DYNA computer model (identified in the MAGANASTOR Final Safety Analysis Report (FSAR)
Sections 3.7.3.7 and 3.10.4.4 as the method of
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 evaluation for concrete cask tip-over analysis applied to the original design) for the assessment of acceleration values for a design basis tip-over accident of the MAGNASTOR CC5 spent fuel cask. Next slide, please.
With regard to the second apparent violation, 10 CFR 72.48(c)(2)(viii), titled Changes, Tests, and Experiments, requires, in part, that a certificate holder shall obtain a CoC amendment pursuant to 10 CFR 72.244, prior to implementing a proposed change that would result in a departure from a method of evaluation described in the Final Safety Analysis Report (as updated) used in establishing the design bases or in the safety analyses.
MAGNASTOR Final Safety Analysis Report Section 3.7.3.7, titled Concrete Cask Tip-Over, states, in part, that the concrete cask tip-over analyses are performed using LS-DYNA. Contrary to the above, on December 30, 2016, the certificate holder (NAC) failed to obtain a CoC amendment from the NRC pursuant to 10 CFR 72.244 prior to implementing a design change for the MAGNASTOR CC5 spent fuel cask that resulted in a departure from a method of evaluation (MOE) described in the MAGNASTOR Final Safety Analysis Report.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 More specifically, NAC failed to utilize LS-DYNA, a non-linear analysis methodology that was described in the MAGASTOR Final Safety Analysis Report Section 3.7.3.7, when implementing a design change for the MAGNASTOR CC5 spent fuel storage cask. The purpose of this conference is to offer NAC the opportunity to provide your perspective and any additional information regarding these apparent violations in order to allow us to reach an informed final decision for this enforcement action.
This concludes my presentation of the apparent violations identified in the NRC inspection of NAC International. I will now turn it over to Chris.
MR. REGAN: So unless there are any questions at this time from NAC representatives about the apparent violations or how the conference will be conducted, I'd like to turn the conference over to NAC International to provide the certificate-holder's perspectives on the circumstances associated with the apparent violations. NAC's presentation is also attached to the public meeting notice if members of the public that are not using WebEx would like to follow along.
The NAC presentation material can also be
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 found at ADAMS Accession Number ML20293A289. I'd now like to turn it over to Kent for their presentation.
MR. COLE: Thank you, Chris, Robert and Leira for your opening remarks. Good afternoon. I'm Kent Cole, President and CEO of NAC International. We thank you for arranging the PEC, and we look forward to this discussion. If I may say, this PEC will be the first time for NAC to fully explain the details of our position and address the inspection issues of concern to the NRC.
We requested this conference after we saw the formal inspection report findings, and have devoted much effort to try to understand the areas of confusion. I sincerely hope that our presentation will provide you with a mutually constructive opportunity to better understand NAC's approach, rationale and results.
I'm confident we can narrow the areas of disagreement. There are enough details, and I don't want to delay the presentation with opening remarks.
But the key takeaways that I would like to respectfully offer for your consideration as we begin are as follows. The 72.48 evaluation performed for CC5 FSAR non-mechanistic tip-over did not result in a departure from the existing MOE and the licensing
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 basis that required prior NRC approval.
The CC1/CC2 FSAR LS-DYNA licensing basis was reasonably determined to be applicable to CC5, and neither a 72.48 nor a design control violation has occurred. However, NAC acknowledges that there is an opportunity to strengthen its documentation of 72.48 evaluations, particularly as it relates to changes in MOE that are not a departure.
NAC takes safety and regulatory compliance seriously, and hopes this presentation helps clarify any misunderstandings the NRC may have with the 72.48 evaluation performed for CC5. Now, I will turn it over to Wren Fowler, NAC's Director of Licensing.
MR. FOWLER: Thanks, Kent, and good afternoon, everyone. Again, my name is Wren Fowler.
I'm the Director of Licensing at NAC International.
Thanks again to the NRC for being flexible with NAC in scheduling this meeting today. NAC has taken a look at the information the NRC provided, and their choice letter and their inspection report, and decided it would be in everyone's best interests to conduct this meeting today.
So before I get into the meat of the presentation, I would like to bring to the forefront the purpose of this presentation. I'd like to also
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 confirm real quick with Chris, y'all can see our slides, correct?
MR. REGAN: Yep, we got them, thanks.
MR. FOWLER: All right, good. So the purpose of this presentation is to demonstrate two things. One, that NAC did indeed use the design control measures in the FSAR for incorporating our fifth concrete cask design, known as CC5, into the MAGNASTOR FSAR, specifically with regards to the tip-over evaluation. Two, demonstrate that the method of evaluation used by NAC to incorporate it was not, and I quote, "a departure" per the regulations.
These two items are directly related to the NRC's assertion that NAC violated two regulations when incorporating CC5 into the FSAR. NAC is confident that the
- NRC, after hearing this presentation, will have a better understanding of what NAC did and what NAC did not do when we incorporated CC5 into our FSAR and will come to the conclusion that no violations have occurred. Next slide, Ryan.
Now that you know the purpose of this presentation, I'd like to go ahead and give you the road map for how we will present today. This presentation is broken down into two parts. Part 1 will focus on giving you several overviews and will
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 take primarily a regulatory approach to addressing the NRC's assertion that NAC violated two regulations.
We will start off by summarizing the two apparent violations that are in the NRC inspection report. Next, we will give you an overview of what is a non-mechanistic tip-over event. Then we will go over what the licensing basis is for the event as presented in our FSAR. This will include the design control measures that were discussed for evaluating the event.
That information will be the foundation to explain how we incorporated CC5 into the FSAR, which was done via the 72.48 process. In order to present that, we will need to go over that regulation and what specific parts of it that apply to the violations.
After that, we will share with you the 72.48 determination process and licensing basis design control measures NAC implemented in order to show CC5 did not require prior NRC approval for us to incorporate into our FSAR. Next slide.
The second part of this presentation has a slightly different focus, and includes items we feel are important that the NRC is fully aware of. First is MAGNASTOR Amendment 9. This amendment incorporated a new concrete cask design known as CC6. The way it
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 was evaluated and approved by the NRC has significant relevance to the two violations. Second, we'd like to address several foundational statements presented in the NRC inspection report that we feel are either not accurate or not presented correctly.
Third, we would like to discuss an issue that occurred at Palo Verde earlier this year with their implementation of the MAGNASTOR system, as we feel several matters relevant to that situation have been incorrectly commingled with our licensing basis and the violations the NRC says we committed. Fourth, NAC took several corrective actions from the situation at Palo Verde, and we would like to share those with you. We would also like to share with you several actions we took after receiving the NRC's inspection report stating we violated two of their regulations.
Then lastly, we'll conclude the presentation.
Next slide. The NRC inspection report that NAC received several weeks ago included two violations, both of which are related to the same topic. That is, we did not use the computer program LS-DYNA to evaluate CC5 for tip-over. The first violation asserts NAC did not follow the licensing basis design control measures that were commensurate with those applied in the original design. I'd like
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 to reiterate purpose number one of this presentation, which is today we will demonstrate that NAC did indeed use the licensing basis FSAR design control measures when incorporating CC5 into the FSAR.
The second violation asserts that NAC departed from using a method of evaluation described in the FSAR when incorporating CC5. Specifically, NAC did not use the computer program LS-DYNA to evaluate CC5 for tip-over. I'd like to reiterate purpose number two of this presentation, which is NAC did not depart from the method of evaluation used in the FSAR for verifying the licensing basis LS-DYNA model.
Thus, NAC did not need to obtain CoC amendment from the NRC per the regulations.
In summary, NAC followed the licensing basis design control measures in the FSAR for incorporating CC5, and NAC appropriately applied the 72.48 regulation when determining if prior NRC approval was needed when incorporating CC5 into the FSAR. Next slide.
With all that said, let's now talk about what a non-mechanistic tip-over event is. This is a hypothetical event where a loaded concrete cask tips over and falls on an ISFSI storage pad. This is a hypothetical because the design and regulatory
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 approval, the system cannot tip over, but it is evaluated for it anyway.
The result of this event is a loaded cask tipping its center of gravity over the lowest cask corner. In doing this, the cask develops some amount of potential energy. As the center of gravity goes over the lowest corner, this potential energy is converted into kinetic energy and is represented by an angular velocity about the cask's lowest corner up until the cask impacts the storage pad, where the kinetic energy is then transferred to the pad.
This results in a rapid deceleration, which is measured in g-loads of the cask and loaded canister, and requires the canister and fuel basket to be structurally evaluated to confirm stress levels are below limits. Next slide. Now everyone loves a good figure in addition to a verbal description, so here we're providing a very detailed illustration of the event. Let's not focus right now on the equations at the bottom of the figure, but rather the figure itself, going from left to right.
Position A shows the cask in its normal upright storage condition. As you can see, the cask has some physical height and the center of gravity is located somewhere in the middle. In Position B, you
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 can see we have non-mechanistically tipped the cask over so that the center of gravity is now directly over the lowest corner of the cask. At this point, the cask has developed its maximum potential energy for the event, because the center of gravity has been lifted vertically as high as it will physically go.
In Position C, the cask is now horizontal, just before impact on the pad. It was moved there by the potential energy being converted into kinetic energy. It is represented by the angular velocity about the lowest corner. We have represented that here by the arrow and Omega term about the lowest corner. As you see, the center of gravity is now some height above the pad.
The relative height difference of the center of gravity from Position B to C is the amount of potential energy converted to kinetic energy. That energy has to go somewhere, and Position D represents that kinetic energy being transferred to the storage pad. In order to do that, the cask has to decelerate.
This deceleration, again, is measures in g-loads, which the canister and fuel basket will experience.
On the bottom left we provided a detailed ledger for you, and would also like you to now focus your attention on Equation 1 in the bottom middle of
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the slide. This is the conservation of energy equation for the event, and we will discuss this equation next in the presentation, as it is part of the licensing basis design control measures for the cask tip-over event. Next slide.
Now that we got a
fundamental understanding of the tip-over event, let's discuss the licensing basis evaluation for it in the FSAR. The licensing basis evaluation has several parts, and it is not just limited to LS-DYNA. After reviewing the NRC inspection report, we noticed that it omitted several of these areas, so hopefully this discussion will help the NRC have a better understanding of what the licensing basis contained.
First, there is a licensing basis LS-DYNA model in the FSAR. This computer model formed the original licensing basis g-loads for the tip-over events. It accomplished this by simulating the tip-over events. The simulation doesn't start with the cask in its normal vertical storage condition, but rather it starts the simulation with the cask horizontal, on its side and on the generic storage pad.
The model run is then initiated with the angular velocity about the lowest cask corner. This
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 simulates the impact load on the pad. The method of evaluation for determining this initial angular velocity is show in FSAR Section 3.10.4.4, and this same method of evaluation is used to check the final results of the simulation, again, as shown in FSAR Section 3.10.4.4. This equation is at the bottom of this slide.
It equates the potential energy developed during the tip-over to the kinetic energy of the cask upon pad impact. This equation ensures the LS-DYNA results are acceptable. There are two terms in this equation I want you to focus your attention on, as they will be discussed later in this presentation.
That is the moment of inertia term, which is represented here by a capital I, and the angular velocity term, which is represented by the Greek symbol Omega.
As you can see, there is more to this than just LS-DYNA, and it is all part of the design control process outlined in the FSAR. Next slide. As I stated on the previous slide, the NRC inspection report omitted several areas related to tip-over.
Another key area is the actual structural evaluations for the canister and fuel basket. LS-DYNA is not the licensing basis program used to structurally evaluate
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 cask systems. That is done in another computer program known as ANSYS.
Those calculations can be found in FSAR Sections 3.71, 3.72 and 12.2.12.4. What LS-DYNA is really used for is to determine if the g-loads used in the AMPs evaluation are bounding. LS-DYNA itself does not do any structural evaluations in our licensing basis. To illustrate this design control process, let's go to the next slide.
Now you may think the slide is busy, and yes, you are right, it is. But that is the graphical representation of the design control process in our FSAR and approved by the NRC. Starting on the left, we have our cask design attributes. These are then fed into the licensing basis LS-DYNA model. The model is initiated and checked using the licensing basis method of evaluation for verifying the conservation of energy. This is the equation we previously discussed.
Next, the resulting model g-loads are compared to our licensing basis ANSYS model to ensure those models structurally bound the loads seen during the tip-over event.
As you can see, this involves much more than just LS-DYNA. And speaking of LS-DYNA, what exactly is that model? Well, a picture says a
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 thousand words, and here it is. It's pretty basic, too. Not a lot of detailed component modeling going on. Pretty much a bunch of blocks and cylinders.
There are all homogenized regions used to simplistically represent a detailed cask.
Remember, all we want to know are the resulting g-loads at the top of the canister and fuel basket to ensure the ANSYS structural models are acceptable. Here the cask is modeled as two concentric cylinders. One is for concrete, the other is for the metal liner. The finer details are not explicitly modeled, such as the rebar, the vents, the pedestals, the lids and the canister itself, much less the fuel basket.
The cylinder we use to represent the liner is modeled as a rigid body, as well. In the model, it will not flex. The loaded canister is just represented by a strip of finite elements on the inner diameter of the cask liner, as well. Next slide. So far you have heard me refer to the licensing basis design control measures while going over the licensing basis tip-over evaluation, so let me summarize it real quick.
First, there is a simplistic LS-DYNA model of a cask, and it is evaluated on a generic pad and
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 soil. Second, there is a licensing basis method of evaluation used to determine the initial angular velocity of the cask, which is used to initiate the LS-DYNA simulation. That same method of evaluation is the licensing basis method of evaluation used to ensure the conservation of energy is preserved in LS-DYNA. In other words, it's used to check the model results.
Lastly is the verification that the g-loads used in ANSYS bound the tip-over event. Next we get into the 72.48 process, which is how NAC incorporated CC5 into the FSAR. But before we get into the details, let's go over the pertinent parts of the regulation. Next slide.
What is 10 CFR 72.48? Well, this is a change control process, and it allows cask designers the ability to make changes to their designs without obtaining prior NRC approval, provided certain conditions are met. The condition pertinent to this presentation and the violation the NRC cited in their inspection report is criterion 8. This criterion states the certificate holder, like NAC, must obtain prior NRC approval if there would be a departure from a method of evaluation described in the FSAR, used in establishing the design bases or in the safety
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 analyses.
The key word here is departure. The regulation does define this, but it also gives two instances where a certificate-holder can make a change yet it would not be considered a departure. Let's take a closer look at these two exceptions. Next slide. These regulatory exceptions and discussions on them can be found in the NRC's Regulatory Guide 3.72, Rev. 1. One, a certificate-holder can make a change to an element of a method of evaluation provided the results of the analysis are conservative or essentially the same.
Two, changing from a method described in the FSAR to another method is acceptable provided it has been previously approved by the NRC for the intended application. Now I'd further like to add, Regulatory Guide 3.72 Rev. 1 endorsed NEI 12-04, Rev.
- 2. That document, as well, provides further guidance on these two exceptions. Next slide.
Now that we have an understanding on the pertinent areas of the 72.48 process, let's talk about how NAC used that process and the licensing basis design control measures to incorporate CC5 into the FSAR without needing prior NRC approval. First, NAC identified the licensing basis methods of evaluations
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 in its FSAR. This included the licensing basis LS-DYNA model and the licensing basis method of evaluation for determining the angular velocity input for LS-DYNA, and the licensing basis method of evaluation for checking the LS-DYNA output kinetic energy.
For determining the angular velocity NAC used the licensing basis method of evaluation presented in FSAR Section 3.10.4.4. This is the same equation you have seen several times so far in this presentation. Before I go to the next slide, I want you to picture in your mind the terms of this equation rearranged to solve for the angular velocity term, which is omega. This would give the equation the square root of 2 mgh divided by I, which is the moment of inertia term. Next slide.
Now in the NRC inspection report, there is a discussion that NAC ratioed some results or used something called linear scaling. Well, this is probably where the confusion is partially coming from.
NAC didn't ratio any results or use linear scaling.
We did a comparison of CC5 angular velocity to CC1, which is the simplistic cask in the licensing basis LS-DYNA model. We did that by taking the previously discussed licensing basis method of evaluation for
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 determining the initial angular velocity for LS-DYNA and solved for Omega.
We did that for both CC5 and CC1 and then took the ratio of them so we could see how different they were. There are other ways we could do this comparison, but this was the one we chose. Below is the equation for that comparison. At its core, it is the same equation in the FSAR we've been discussing.
Now you may be asking yourself, where did all these new terms come from? This has to do with the moment of inertia term in the core equation, and I'll explain why that is the case when we go to the next slide.
The end result was a relative difference of less than one percent for the angular velocities between CC1 and CC5, not that different. So that was one piece of the puzzle solved for us. That is the angular velocity used in the licensing basis LS-DYNA model was applicable to CC5. But NAC continued on, following the rest of the design control measures as presented in the FSAR. Next slide.
Next is the LS-DYNA model itself. First, the simplistic cask model was verified to be applicable to CC5. And as you previously saw, there is not a lot of detail in that model. CC5 is also similar in design and materials used when compared to
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 CC1, so nothing substantially different there. Next, the generic FSAR pad and soil remained the same, so no difference there either. Thus, in the end the biggest parameter to verify is the angular velocity input into LS-DYNA. If that had changed substantially, we would have had to build a new model and run it to see the final results in order to ensure the licensing basis and the structural evaluations were bounding.
Now I made the claim that the angular velocity term is the most important term, and I'd like you to keep that thought in the back of your mind. We will revisit that when we get to the second part of this presentation. Next slide. Now there is something very specific I would now like to talk about, and I alluded to it earlier. That is, per the72.48 regulation, there are two exceptions to a departure. As I have pretty much worn out so far, we used the licensing basis method of evaluation for determining the angular velocity input into LS-DYNA.
NAC didn't change that method of evaluation, but it is important to recognize that a method of evaluation can have input parameters and what are referred to as elements. These elements themselves may have a method of evaluation associated with them, too. A while back I asked you to remember
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the moment of inertia and angular velocity terms used in the conservation of energy equation.
NAC didn't change those elements per se, but we did change how the moment of inertia term was derived. The moment of inertia term itself has a method of evaluation tied to it, and the FSAR makes that clear. LS-DYNA was used to derive that value.
However, NAC elected to use another method in deriving the moment of inertia term for CC5 and CC1 when doing the angular velocity comparison that I showed you earlier. That is, a classical derivation versus a numerical one out of LS-DYNA -- in engineering vernacular, a hand calculation.
Now at this point, you probably know where I'm going with this. NAC is allowed to do this per the 72.48 regulation because it is not a departure, and it meets one of the two exceptions I have already outlined. Next slide. NAC recognizes this is a new method relative to the MAGNASTOR FSAR, but it's not a departure. The regulation allows a certificate holder the ability to change methods, provided it has been previously approved by the NRC for the intended application.
NAC holds two other certificates with the NRC. One is the NAC-MPC system, and the other is the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 NAC-UMS system. Both of these systems were approved by the NRC for the tip-over evaluation to have their moments of inertia be derived via the hand calculation. The regulations and NRC endorsed-guidance allows NAC to use a previously approved method in another one of our licensed cask systems provided it's being used for the same intended application, in this case, the tip-over evaluation.
Thus, no departure has occurred by using a hand calculation for the CC5 moment of inertia.
At the time, hopefully we've cleared up a lot of misunderstandings. NAC indeed used the licensing basis design control measures presented in the FSAR. NAC also used the licensing basis methods of evaluations in the FSAR, but did change how the moment of inertia for CC5 and CC1 was derived when comparing the two angular velocities. However, this was not a departure and is allowed under the current regulations and NRC endorsed industry guidance.
That concludes the first part of this presentation, which was focused more on the regulatory aspect of the issues at hand. Next is Part 2 of this presentation. Here we will focus on other items of importance, and I've listed those topics here from the earlier presentation introduction. Earlier, I alluded
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 to some upcoming information about MAGNASTOR Amendment 9, and a new concrete cask known as CC6. I'd like now to share those details.
First, the NRC inspection report states the NRC technical staff would likely not approve via an amendment how we incorporated CC5 into the FSAR.
For MAGNASTOR Amendment 9, we added a new cask design known as CC6. This new cask design was evaluated in the same manner as we had done for CC5, but we chose to put it in the amendment submittal for various site-specific project reasons. It was because of these reasons we did not do it via the 72.48 process.
However, we could have done so if it wasn't for those reasons.
Contrary to the NRC inspection report, the NRC technical staff approved our approach and even documented its acceptance in their safety evaluation report. The technical staff even went to great detail to explain why it is acceptable. Next slide. So here is an excerpt from the safety evaluation report, and I'd like to give you just a few moments to briefly read through it before I go on.
There are several items here I want to point your attention to. One, the NRC staff didn't believe NAC needed to perform any more analysis than
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 what we provided to justify the new cask design. Two, the NRC staff had reasonable assurance the system would perform its intended safety function during tip-over. Third, the NRC staff recognized that CC6 was similar to all prior cask designs, which included CC5.
There were conservatisms built into the successor evaluations to LS-DYNA.
This included the much higher ANSYS accelerations used, the FSAR generic pad and soil remained unchanged, CC6 and CC1 were of similar construction, and lastly, the initial angular velocity of CC6 is within two percent of CC1. The NRC staff, by issuance of this safety evaluation report, has concluded a two percent difference is acceptable to the NRC. If the cask is essentially the same and the angular velocity is within two percent of CC1, then there is reasonable assurance the system will perform its safety function. That is the case for CC5.
Remember, the angular velocity of CC5 is less than one percent different from CC1, well within this two percent acceptance value. Next slide.
For my last slide, I'd like to summarize a few facts about CC6 and Amendment 9. First, NAC did not build or run a new LS-DYNA model for CC6, nor was one provided. Second, the tip-over approach for CC6
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 is the same used for CC3, CC4 and CC5. Third, as stated in the safety evaluation report, CC6 is similar in construction to all prior casks, which includes CC3, 4 and 5. Fourth, there remains significant design margin relative to CC1. The generic FSAR pad and soil remain unchanged, construction and materials for the cask are similar.
While CC5 is not shorter than CC1, like CC6 is, CC5 is essentially the same height. And as the NRC staff concluded, the very important angular velocity term is within two percent of CC1. CC5 is well within this acceptance value for the staff.
Lastly, by issuance of the Amendment 9 safety evaluation report, the NRC staff has approved the approach NAC used for incorporating CC5 into the FSAR without re-performing a new LS-DYNA model and run.
With that said, thank you for your time.
That concludes my portion of the presentation. I will now pass the presentation along to Senior Project Engineer, Mark Griswold.
MR. GRISWOLD: Thank you, Wren, good afternoon. As Wren stated, my name is Mark Griswold.
I'm a Senior Project Engineer here at NAC. I am going to discuss a few specific comments that NAC has on the NRC inspection report, many of which Wren
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 touched upon earlier in his presentation. I will summarize a number of comments and provide additional details regarding NAC's perspective and position (audio interference).
I will start with the observation that the inspection report presents LS-DYNA as the MOE for tip-over evaluation. However, as we have discussed, the MOE for tip-over also includes the predecessor calculation of potential energy and angular velocity prior to impact. These are inputs to the LS-DYNA model that can be developed from classical formulas through application of the conservation of energy and the basis cask physical parameters, and are elements of the MOE and in NAC's licensing basis.
LS-DYNA is used to perform dynamic analysis of structures, but it does not calculate initial potential energy or angular velocities resulting from a tip-over. Our next comment, the IR did not acknowledge significant conservatism in g-load input into the subsequent ANSYS stress evaluations for determining whether the canister and basket stresses resulting from the tip-over g-loads are within applicable stress limits.
G-loads resulting from a
tip-over calculated by LS-DYNA are not subject to specified
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 regulatory limits or criteria. In other words, there are no regulatory g-load limits, only stress limits applied in subsequent analyses. NAC utilized bounding acceleration values of 35g for the basket and 40g for the canister in its downstream ANSYS structural evaluation.
Next, the NRC staff assert that NAC changed its MOE for tip-over from LS-DYNA to linear scaling. However, NAC's 72.48 evaluation and supporting calculations do not estimate any g-loads for CC5. NAC would like to point out that any MOE that replaces LS-DYNA for dynamic analysis of tip-over events would, at the very least, need to produce g-load outputs like LS-DYNA, which the CC5 72.48 did not do. Next slide.
Our next comment is that the inspection report presented concerns in the non-linear behavior of the tip-over model parameters and
- inputs, specifically with respect to variations and interdependence of the pad and soil properties considered. This implies that there would be uncertainty in results due to changing pad and soil properties. However, the generic pad and soil properties considered in the licensing basis analysis, which has not changed in the FSAR since the initial
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 issuance, are the only properties pertinent to the 72.48 evaluation of CC5 tip-over.
Next, the inspection report also indicated that a scaling method resulted in an errant determination that each cask had a uniform density cylinder. NAC believes that this statement is referring to the mass moment of inertia approximation in the angular velocity comparison, which uses an equation based on a solid cylinder with uniform density.
NAC is confident that the use of this representation of the cask's moment of inertia is appropriate for the evaluation of the cask's relative angular velocities, and I will provide additional detail on that position on a later slide.
Finally, the inspection report focuses on minor differences in the cask design and does not acknowledge the more important fact that CC5 has substantial similarities to the licensing basis cask design, especially with respect to parameters that are key to the analysis of the non-mechanistic tip-over or that would have a significant impact on the simplified cask geometry represented in the licensing basis LS-DYNA model.
In general, geometry, materials and design
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 of both casks are very similar. CC5 is a CC1 cask with shielding enhancements, which include a more dense outer rebar cage, a thicker lid, a thicker liner, and shield bars in the vent. These shielding enhancements result in an increase in cask weight of less than six percent, which all else being equal, would have the general effect of a reduction in decelerations experienced during an impact.
The weight increase is relatively uniformly distributed and results in a comparable increase in the mass moment of inertia. This slide will provide more detail on the substantial similarities between CC5 and the licensing basis cask design. On the right of the slide are scale drawings of the CC1 and CC5 cask assemblies and the table of select parameters. Visually, the casks appear to have significant similarities. Both are right circular cylinders of reinforced concrete with steel inner liner.
The main structure of the pedestal at the bottom of the cask is the same in both designs. The outer and inner diameters of the cask are the same.
All materials of cask construction are the same. The height is essentially the same. CC5 is 0.6 inches taller than CC1. This is a difference of only 0.3
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 percent in cask height. The casks' center of gravity (CG) is essentially the same. CC5's CG is approximately 2.1 inches higher than CC1. This is a difference of less than two percent.
As I mentioned on the previous slide, the shielding enhancements resulted in an increase in weight of less than six percent or approximately 17,500 pounds. The weight is largely comprised of distributed masses as follows. The rebar spacing of the outer cage is slightly more dense, but amounts to an increase of only 900 pounds or approximately 0.3 percent of the total weight. It is also widely distributed in the circumferential and axial directions.
An inch and a quarter increase in cask liner thickness is the most significant contributor to the weight increase, accounting for approximately 14,900 pounds or about four percent of the total weight. Like the rebar, this additional weight is evenly distributed along the axis of the cask and has very little net impact on the CG height. Cask lid thickness increase which amounts to approximately 1,600 pounds, and the inlet vent shield bars, which amount to 580 pounds, are more local masses, with the cask lid being at the very top and the inlet shield
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 bars at the very bottom.
However, together these contribute a very small amount to the total mass of the system, about 0.7 percent. Further, the impacts of all of these minor changes are accounted for in the system's weight and CG calculation, which is an input into the angular velocity comparison. Next slide.
On this slide, I will provide additional detail on the validity of the uniform density cylinder approximation for the mass moment of inertia. Before I go into depth on that, I would like to explain a little about mass moment of inertia for those who are unfamiliar. Mass moment of inertia is a physical parameter which is equivalent to mass for rotational systems. It relates to an object's resistance and changes in angular velocity at the point of rotation and depends solely on the distribution of mass relative to that point of rotation.
Closed form classical representations for mass moment of inertia, like the one used in the CC5 72.48 evaluation, are commonly used in engineering practice. As was discussed earlier, the FSAR states that LS-DYNA is used to calculate the mass moment of inertia used for the calculation of Omega. LS-DYNA calculates mass moment of inertia, mass, CG, and other
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 physical parameters of the model based on the classical definition of those parameters and the representation of the geometry and materials in the model.
It is important to not lose perspective if the mass moments of inertia in LS-DYNA are the result of the simplified model built to conservatively simulate the impact of deceleration loads. In other words, there is nothing special about the method used by LS-DYNA to calculate mass moments of inertia and is itself an approximation based on simplified geometry.
Now looking at the differences between CC5 and CC1 outlined on the previous slide, one would expect the approximate six percent increase in mass to produce a
comparable increase in the (audio interference) are not concentrated, close to, or far from the point of rotation. They are relatively uniformly distributed.
Moving back to the first bullet on the slide, it is important to understand that NAC's CC5 72.48 evaluation, the mass moment of inertia approximation is only used in calculating the relative difference of the cask system's response to motion in the determination of a relative angular velocity. For reference, as used in the CC5 72.48 evaluation, the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 uniform density cylinder approximation for mass moment of inertia results in a CC5 to CC1 ratio of 1.073.
In order to demonstrate the suitability of this simplified uniform density representation, which the inspection report described as errant, NAC subsequently developed highly detailed 3D design models of the CC5 and CC1 casks, which are shown on the right of this slide. These models include all features of the cask, canister and basket discreetly modeled, as well as a representative fuel mass in each of the basket filters.
Corresponding densities are applied to all components based on their material, and as such, these models represent as close to a realistic distribution of mass as possible and can produce values for mass moment of inertia at a high-level of accuracy. The 3D models result in a CC5 to CC1 mass moment of inertia ratio of 1.062, which is very close to the 1.073 from the approximation.
The similarity in the relative difference in the reported values from the drastically different approaches demonstrates the suitability of the simplified mass moment of inertia representation with capturing the relative difference between two casks' mass moment of inertia. Also, note that the relative
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 increase in mass moment of inertia is only slightly greater than the relative increase in loaded system weight (audio interference).
That is the conclusion of my portion. Now I will pass to NAC Senior Project Manager Ryan Bailey, who will touch on the implementation of CC5 at Palo Verde and how that relates to the NRC inspection report.
MR. BAILEY: Thank you, Mark. Good afternoon. My name is Ryan Bailey and I am the NAC Project Manager for AAPS Palo Verde. The NAC team and I supported Palo Verde during their recent transition from the older NAC-UMS dry cask storage system to the higher capacity MAGNASTOR system. NAC provided support throughout the design, fabrication, delivery, 72.212 development, dry runs and cask loading phases of the project.
This support included assisting Palo Verde during their Region IV dry cask storage inspection, which took place from August 2019 to March 2020. APS Palo Verde became NAC's first customer to select the CC5 concrete design. The NRC inspection at Palo Verde, which began in August 2019, was still ongoing during the NAC's scheduled triennial inspection.
NRC Region IV inspectors had previously
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 raised concerns regarding scaling or ratioing of g-load accelerations for the Palo Verde site-specific condition. During the February 2020 NAC inspection, NAC was in the process of working with Palo Verde to resolve the Region IV inspectors' questions. Those questions were ultimately resolved when NAC and Palo Verde decided prior to the first MAGNASTOR cask loading to perform a site-specific LS-DYNA evaluation for tip-over.
Completion of the model run and issuance of the calculation resolved the inspectors' concerns with cask tip-over. It's important to note that the Palo Verde LS-DYNA model run and calculations were in progress prior to NAC's inspection entrance meeting.
Results of the run were in line with NAC's previous calculation results. Palo Verde subsequently moved forward with their first MAGNASTOR cask loading in early March 2020.
Why is it important to discuss the Palo Verde inspection in today's conference? Although unrelated to the NAC proposed AV's, NAC believes that the Palo Verde Region IV inspection is relevant because the NRC inspection report appeared to commingle several facts between the two inspections.
Next slide. For example, the inspection report states
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 that prior to December 30, 2016, the certificate-holder, NAC, implemented a design change for the MAGNASTOR spent fuel cask system. This is an accurate timeline.
However, the inspection report goes on in the same paragraph to discuss hand calculated acceleration results. As discussed throughout today's conference, NAC did not ratio or scale any acceleration results to incorporate CC5 into our FSAR in 2016. In 2019, to support the Palo Verde site's specific application, however, NAC did, in fact, ratio acceleration results. Again, this was not part of the CC5 incorporation into the FSAR, and is unrelated to the AV's being considered today.
Also in the inspection report, the NRC discussed concrete and soil material properties and pad and soil configuration. I've noted several times in today's conference, the CC5 concrete cask was incorporated into the FSAR using the generic FSAR pad, in other words, the same pad that was used for CC1 and CC2. However, pad and soil configurations did, in fact, change to evaluate the tip-over on the Palo Verde pad to support their site-specific application.
To summarize, NAC's Palo Verde 72.212 support activities were separate from and three years
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 after NAC's licensing efforts which incorporated CC5 into our FSAR. Next slide. This slide provides a timeline summary of the significant events from both the NAC triennial NRC inspection and the Palo Verde Region IV inspection discussed on the previous slide.
NAC's incorporation of CC5 into the FSAR and NAC's inspection events are shown in blue. Palo Verde site specific support activities and Region IV inspection events are shown in red.
There are a couple of important takeaways from this slide. First, as you can see on the left side of the timeline, the 72.48 which incorporated CC5 into our FSAR was complete long before NAC ever contracted with Palo Verde to provide MAGNASTOR systems. Next, note the yellow box on the timeline.
This was the point in time when Region IV was reviewing the Palo Verde responses while in parallel NAC's triennial audit entrance meeting was taking place in Norcross, Georgia. Based on the language in the inspection report, this was the point in time when facts between the NAC inspection regarding CC5 incorporation into the FSAR and the Palo Verde site-specific inspection began to (audio interference).
The remaining points on the timeline simply provide key dates of both NAC's and Palo
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Verde's inspection proceedings for reference. Next slide. This slide is just a summary. It describes first the process in which NAC incorporated CC5 into the FSAR, which Wren described in detail earlier in today's conference, and second, to describe the process in which Palo Verde accepted CC5 concrete cask tip-over on the Palo Verde ISFSI pad.
I won't read each bullet, since this information was previously discussed. However, we thought it might be helpful to consolidate both processes on one slide for convenience. The key takeaway from this slide is located on the final bullet beneath the Palo Verde process. Through subsequent open dialogue with Palo Verde, Region IV and NRC headquarters, NAC understands and agrees with the NRC's position that the site-specific LS-DYNA model and calculation was the appropriate choice of analysis rather than NAC's initial approach of ratio of g-loads. Next slide.
As a result, following the Palo Verde inspection, NAC promptly entered the issue into our corrective action program as Corrective Action Report (CAR) No. CAR 20-01. Corrective actions as a result of this CAR are the following. An evaluation of the ability to perform their intended safety function, an
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 extent of condition review on 1) design control methods, and 2) all other customer site-specific tip-over analyses. NAC performed a root cause analysis to determine the cause and corrective actions to prevent recurrence.
NAC reviewed our calculation process and procedures for weakness related to this specific issue. NAC reviewed our project management planning procedures for weakness related to design deliverables. NAC conducted employee training on this CAR, the corrective actions associated with it and lessons learned. In addition to performing our own corrective actions listed here, NAC participated in Palo Verde's root cause analysis and multiple other extent of condition reviews and corrective actions as part of the Palo Verde team.
As a side note, NAC is in the process of updating our 72.48 training program to include Regulatory Guide 3.72 Rev. 1, now that NEI 12-04 has been endorsed by the NRC. This concludes the portion of the presentation regarding the Palo Verde inspection. I'll now turn it over to George Carver to discuss the NAC actions taken as a result of today's proposed AV's.
MR. CARVER: Thank you, Ryan. Again, my
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 name is George Carver. I'm the VP of Engineering and Support Services at NAC. In continuation, I'd like to highlight some actions NAC has taken in response to receiving the apparent violations and actions to provide the information requested by the inspection team on their exit. First, NAC has issued a self-identification report for potential escalation within NAC's corrective action program pending the outcome of this PEC.
At a minimum, NAC will use this report to further improve the descriptions associated with the 72.48 approved changes, particularly with respect to changes in MOE that are not departures. NAC has also performed LS-DYNA analysis for all MAGNASTOR cask designs, CC3, CC4, CC5 and CC6. These analyses have shown consistency with the FSAR CC1 and CC2 license basis results, and remain bounded by the licensing design basis accelerations used in the FSAR ANSYS calculations.
NAC has verified LS-DYNA was used for all subcontracted site-specific implementations of CC3, CC4, CC5 and in the future, CC6. NAC has reviewed our earlier cask designs, the MPC and UMS systems, and have found the tip-over analyses to be consistent with the current NAC MAGNASTOR licensing basis. And NAC
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 has performed an inspection of our 72.48 activities with respect to linear scaling and ratioing dispositions and found no indications of a departure from the FSAR MOE. Next slide, please.
I'd like to present further information on NAC's CC5 cask design. In preparation for this conference, NAC prepared an LS-DYNA model to explicitly evaluate the CC5 cask for the non-mechanistic tip-over impact onto the FSAR pad and soil. The cask was modeled in LS-DYNA using an approach consistent with the licensing basis analysis in CC1 and CC2. The CC5 model incorporates the physical differences of the CC5 cask design.
The CC5 LS-DYNA model is shown in the images on the right. Note that the cask model does not appear significantly different than licensing basis LS-DYNA model presented earlier in this presentation. To be specific about the differences, the cask model is slightly taller. The thicker lid is represented by a slight increase in the density in the cask lid section of the model. The inlet bars are represented by a slight increase in the density in the pedestal section of the model.
The thicker liner is explicitly modeled and still modeled as a rigid body. The increased
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 density of the outer rebar cage is represented by a slight increase in the density of the concrete section of the model. The FSAR pad and underlying soil are represented by the same material models utilized in the CC1 and CC2 licensing basis analysis. The results which are shown in the table below show that the LS-DYNA run produced peak accelerations for CC5 that are essentially the same as the licensing basis analysis.
Another output from this model and an important point is the relative difference in the CC5 and CC1 model moment of inertia, which in this case is 1.064 and is consistent with the uniform density cylinder approximation made on Slide 31. This further demonstrates that it's an MOE change that is not a departure because the results are essentially the same.
This further supports the conclusion NAC made in the CC5 72.48 determination that no additional tip-over analysis was required as the existing licensing basis analysis (audio interference) the CC5 cask design. Next slide, please.
I believe NAC has put forth a compelling presentation regarding our purpose, which is to demonstrate NAC used the existing FSAR design control measures and demonstrate that the method of evaluation
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 used was not a departure. This presentation also provided some supplemental information for your consideration of NAC's position. Therefore, in conclusion, the 72.48 evaluation performed for CC5 FSAR non-mechanistic tip-over did not result in a departure from the existing MOE in the licensing basis.
CC1, CC2 FSAR LS-DYNA licensing basis was reasonably determined to be applicable to CC5. All of NAC's cask designs are essentially variations in the CC1, CC2 license design. CC5 meets the same criteria the NRC used to approve CC6 in the Amendment 9 SER.
There is low regulatory significant and low safety significance associated with these AV's based on NRC's acceptance of Amendment 9 and margin relative to existing ANSYS inputs.
Since NAC has performed for this PEC supplementary LS-DYNA calculations for CC3, 4, 5 and 6 with a generic pad and soil and have shown them to be consistent with the CC1, CC2 design, NAC has further supported that there is no safety significance. Based on the foregoing, NAC believes that neither a 72.48 nor design control violation has occurred.
Finally, NAC takes nuclear safety and regulatory compliance seriously as reflected in our
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 past inspection results and the bulk of the results from this inspection. I hope this presentation has helped clarify any misunderstandings the NRC may have had with regards to the underlying facts associated with the identified apparent violations. Thank you for your attention, and I'll return this presentation over to Mr. Cole to provide his closing comments.
MR. COLE: Thanks, George. I'd like to briefly summarize and tie together what you've heard from us today. First, the MOE for non-mechanistic tip-over events is more than just LS-DYNA run to determine impact deceleration g-loads. It includes classical calculations used in the (audio interference). It includes subsequent downstream structural evaluations with ANSYS. Clearly it is an over-simplification to say that NAC's 72.48 evaluation for CC5 failed to use LS-DYNA.
Second, NAC appropriately exercised design control measures commensurate with the original licensing basis tip-over evaluations to confirm their applicability to CC5. We appropriately executed the 72.48 process by using the conservation of energy equations to compared impact angular velocities. As defined in the regulations, this did not involve a departure from the licensing basis MOE. We determined
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the existing licensing basis LS-DYNA and ANSYS evaluations were applicable to CC5.
This is what we did. We acknowledged that the method of calculating the moment of inertia was a change. However, such a change is not a departure because the method we used was previously approved by the NRC for the intended application. Given the differences in CC1 and CC5, one would expect an approximate six percent increase in mass to produce an approximate six percent increase in the moment of inertia. And that's what we have shown today using three different methods of calculating the moment of inertia.
This further supports that the change in MOE for the moment of inertia was not a departure, because the calculated ratio shows the moment of inertia for CC5 to CC1 are essentially the same results upon comparison of the 72.48, with the LS-DYNA runs. Third, NRC accepted the 72.48 evaluation method that we used for CC5 when it recently approved the SER for CC6 in MAGNASTOR Amendment 9. As noted in the presentation, we confirmed the same circumstances and criteria that the NRC noted as their basis of acceptance of CC6 are also applicable to CC5.
Now I
understand the complexities,
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 including the Region IV inspection at Palo Verde and COVID-related work and travel restrictions, I
sincerely question why NAC was not afforded an opportunity to better understand and respond to the NRC preliminary findings prior to issuance of a choice letter with apparent violations, implying potential safety significance. We are committed to a robust safety culture based on continuous improvement and learning.
We sincerely take the opportunity to self-assess and improve in the issues that both APF and these AV's are no different. As we hope you recognize from today's presentation, we have applied significant resources to assess the IR findings and to perform extensive condition reviews. We have implemented and continue implementing multiple corrective actions, including notably improving the 72.48 documentation for changes in MOE.
Thank you for your attention today, all of you. This summarizes our response to the inspection report and AV's and we sincerely appreciate the opportunity to provide these clarifications. We hope the NRC will reconsider these two AV's. That's the conclusion for us, Chris, I turn it back to you.
Thank you.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. REGAN: Thank you, Kent. Thank you, gentlemen for the very, very informative presentation.
I think now we will now take our recess for approximately 20 minutes for the NRC to discuss the information that has been presented by you today, determine if we have any questions or clarifications from myself and the NRC staff regarding what you've presented. I'd like to suggest that -- I currently have a time of about 2:25. Let's reconvene at 2:45, please, 2:45 or quarter to 3:00.
For Trent on the bridge line, if you can mute all the lines and then I will let you know, we'll come back at 2:45 when you can open up the lines again for those on the participants list or the speakers list. So we will reconvene at 2:45. Thank you, everybody.
(Whereupon, the above-entitled matter went off the record at 2:25 p.m. and resumed at 2:45 p.m.)
MR. REGAN: All right. Hopefully, everyone can hear me. Welcome back. Thank you, Haile. Welcome back. NRC staff have a few questions and some clarifications for NAC, and I'll ask the NRC staff to identify themselves before asking their questions, and I'll lead off with questions -- Leira, can you go back up to the top of our list, please?
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 Thank you. All right. So Jon Woodfield, our lead inspector, has a few questions for clarification for NAC International. Jon, you have the floor.
MR. WOODFIELD: Can you hear me okay?
MR. COLE: Yes, Jon, we can hear you.
MR. WOODFIELD: Okay. The first question is on slide 36. It is stated that NAC has performed LS-DYNA analyses recently for CC3, CC4, CC5, and CC6, and the resulting accelerations are essentially the same as for FSAR CC1 and CC2. So the question is were there any non-conservative results based on those analyses and also, was this done for the standard in oversized pads?
MR. FOWLER: Hey, Jon, this is Wren. I think Marc --
MR. GRISWOLD: Yes.
MR. FOWLER: -- you can address this. So I'm going to let -- pass it over to Marc Griswold, and I believe he can provide some clarification on those two bullets in our slide.
MR. GRISWOLD: So this is Marc Griswold.
So to answer your question, all of the new analyses that were performed for CC3, 4, 5, and 6 were done on the long pad because as shown in the FSAR, that pad produced slightly higher g-loads than the short pad.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. WOODFIELD: So you did have non-conservative results with respect to CC1 and CC2 results? You had higher g values?
MR. FOWLER: Give us just one second, Jon.
MR. WOODFIELD: Sure.
MR. GRISWOLD: Okay. So with respect to non-conservative results, we do have some data that relative to CC1 were a little higher, and then we had some that were lower. So I have specifically CC5 demonstrated slightly non-conservative results.
MR. WOODFIELD: Would you have the relative size of those non-conservative results as far as a percentage maybe?
MR. FOWLER: So Jon, just to make sure we understand what you're asking here when it comes to conservative versus non-conservative, are you wanting to know whether these g-loads went up or these g-loads went down?
MR. WOODFIELD: If they went up.
MR. FOWLER: Okay. You all understand?
MR. GRISWOLD: Yes. I can get an actual number. Let's see, the -- for CC5, the basket peak acceleration went up 1.8 g's,.66 -- oh,.8 --.8 g's, and then the TSC peak acceleration actually went down
.4 g's.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. FOWLER: Do you -- did you hear that, Jon?
MR. WOODFIELD: Yes. So one value went up higher and one value went lower than for CC1?
MR. FOWLER: Right. Both values are less than 1 g. And one thing I'd like to add, too, is well, since we're already getting into some of the --
some technical-related questions, if there's further information and stuff you would like us to send over, that's something that we can talk about as well instead of getting into a lot of technical detail that, as we already discussed, we did, for the sake of this conference, do a lot of engineering associated with all this stuff. So I just wanted to put that out there as well that we're open to sharing that information as well.
MR. GRISWOLD: All calculations are available.
MR. WOODFIELD: Thank you, Wren. Wren, as far as the process goes, yes, if there is any information that you have that you can't necessarily articulate in a full manner here during the conference, that's certainly something that we can arrange or at least we'll agree upon that you will supplement after the PEC. Obviously, it would be
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 publicly available, but you can obviously supplement that after the PEC if that's information you can't provide right now during the conference.
MR. WOODFIELD: Okay. Sure. That -- I think that would be very helpful. We'll answer as much as we can on the fly here, but there may be some stuff that it might be better discussed, you know, after providing you the details.
MR. WOODFIELD: Okay. Thank you very much.
MR. REGAN: All right. Jon, you didn't have any more questions, did you?
MR. FOWLER: No. I was only assigned the one.
MR. REGAN: Okay. Thanks, Jon. Next, let's go to Tony Rigato. Tony, you want to go ahead and ask your questions?
MR. RIGATO: Sure. Can you hear me okay?
MR. FOWLER: Yes. We got you.
MR. RIGATO: All right. Just making sure because (audio interference) a speaker off a phone and just making sure. So, with respect to slide 10, LS-DYNA was noted as the MOE in the FSAR. Why wasn't it used to actually determine g-load in the first place since angular velocity alone cannot produce g-loads?
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. FOWLER: Sure. So that was kind of the key point of the slide I was talking about, our design control process. The process and the SAR both had input into LS-DYNA and also an output verification that's done for the LS-DYNA model. So we followed that design process, and that design process resulted in validating the existing LS-DYNA model into SAR, and the results for CC5 were applicable from CC1 to 5. So that was one of the key things we wanted to make sure everybody understood. Yes, at the time, there wasn't an explicit model for CC5 and LS-DYNA, but we saw the design control process for inputs and validations as described in the FSAR.
MR. RIGATO: You guys ready for the next question or should I wait? Chris, do you have any --
is there anything else I should be waiting for? Or I understand the answer that you provided. I don't know if I should continue forward.
MR. REGAN: No. That's fine, Tony. You know, just recall this is being transcribed so we do have the ability to go back and review. If you're satisfied that you got an answer to the question, you feel free to move to your next question.
MR. RIGATO: All right. Thanks. What would constitute a significant difference in angular
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 velocity that would then prompt you to go ahead and use LS-DYNA, difference in percentage-wise, if they're 1 percent, 2 percent, 10 percent?
MR. FOWLER: Sure, Tony --
(Simultaneous speaking.)
MR. RIGATO: Go ahead.
MR. FOWLER: Sure, Tony, we understand the question. I think -- give me just a second, put you on mute. I think we have somebody here that's already prepared to answer that question. So give us just a moment so I can make sure I know the right person.
MR. RIGATO: Sure.
(Pause.)
MR. FOWLER: Okay. Tony, thanks for waiting for us. I just wanted to make sure that we had the right people ready to speak to that question.
First thing that I want to say to that is we do each one of these changes and look at each one of these on a case-by-case basis. So we don't throw a hard number out there. When we do a design change, we look at each one individually on its own, and each one of these changes that we've done for these casks haven't prompted us to think that it's a significant change.
However, I will say this. After preparing for this conference, we have looked at going up to a 3
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 percent difference seems to be a point of threshold where you start to notice some significant differences. But we haven't had any to date that have gone that high. We look at those on a case-by-case basis, so I would answer your question that way the first way. And then the second way is that we've done some sensitivity runs and 3 percent is when we start to see some small but different changes.
MR. CARVER: The lower acceleration.
MR. FOWLER: Okay.
MR. CARVER: There's not much change in the peak accelerations.
MR. FOWLER: Did you hear what George said? He had a little bit more clarification on the 3 percent.
MR. RIGATO: Not quite.
MR. CARVER: Yeah, the changes Wren's talking about, when we see higher changes in Omega, it starts to -- it seems like the lower accelerations start to pick up, but the higher accelerations don't seem to change.
MR. REGAN: Just a quick note for the transcriber. Can -- when you're speaking -- this is Chris Regan -- can you please identify yourself before you speak. Thanks.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. FOWLER: So the first part was me, Wren Fowler, and then the second part was George Carver.
MR. DAVIS: This is Marlone. I want to ask a question on -- specific on when you say the 3 percent threshold, is that the threshold that you would need to run LS-DYNA, or do a more detailed calculation?
MR. FOWLER: So, Marlone, what we did was
-- is for preparation for this conference, we did run these numbers up to start to see what the effects are.
And all we're noting is that we do see some effects when you get to about 3 percent. So we're not drawing a hard line in the sand one way or the other. We're just telling you what our experience has been when we did a sensitivity run on this in preparation for this conference.
MR. DAVIS: And for those -- that's what I'm trying to understand a little bit more. At that -
- when you start to see some variations, so what's that, an increase, a decrease in g-loads, what's the resulting of that?
MR. FOWLER: Oh, George, do you want to explain that again?
MR. GRISWOLD: Yes. The changes --
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 PARTICIPANT: Let me pause for a minute.
MR. FOWLER: Yes. Hold on just a second.
(Pause.)
MR. FOWLER: So Marlone, we've done one of these runs just a sensitivity to see what happened by increasing the acceleration 3 percent or decreasing it 3 percent to see the effects. Marc has some familiarity with that, and he can share a little bit of the details associated with it.
MR. GRISWOLD: Yes. So this is Marc Griswold. Basically, what Wren's talking about is we did a little bit of sensitivity studies, and we varied the initial angular velocity of a -- you know, keeping the model the same and looked at how that impacted the results. And our conclusions were at about 3 percent, we saw a comparable increase or decrease in the g-load. And so that's what we've kind of drawn our basis of that would be the threshold, at least based on our experience at this point.
MR. FOWLER: So in other words, it was pretty small relative to the margins, Marlone. Again, this is some of the technical stuff that we've prepared for this conference that might -- you know, if you're -- you all are wanting it, we're willing to share it, and we can talk about it later as well.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. DAVIS: Okay. Thank you. Yes, but --
yes, I think just to get some perspective on the sensitivity run that was -- what was done just to look at the results because as you know, from a regulatory perspective of it, when you're making some of these changes and you're just looking at the -- using the same methodology, you're looking at essentially the same for non-conservative or conservative, it kind of boasts to whether or not you need to come in for prior NRC review and approval or not. I just wanted to put that while we're asking that particular question in perspective.
MR. FOWLER: Sure. We -- I understand what you're talking about.
MR. RIGATO: I had one last question.
MR. REGAN: Yes. Go ahead, Tony.
MR. RIGATO: So in the -- the original FSAR stated that the mass moment of inertia were calculated using our DYNA, but in the presentation, you make reference to hand calculations and calculating the mass moment of inertia. Could you explain when you actually did use hand calculations?
Actually, you know, like calculating out in Excel or physically by hand, or did you actually -- or it used LS-DYNA to calculate mass moment of inertia been
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 placed into the mass energy equation that you put on like slide 9 or 10?
MR. FOWLER: Let me try to paraphrase what you're asking to make sure I understand. This is relative to just MAGNASTOR, or are you referring to hand calculations used for the moment of inertia from UMS and MPC?
MR. RIGATO: Well, I guess it could be --
I mean it could be for any of those systems, but MAGNASTOR seems -- says very clearly that LS-DYNA was used to calculate the mass moment of inertia. But you make --
MR. FOWLER: Right.
MR. RIGATO: -- reference to hand calculations, so I don't know if LS-DYNA was used consistently to calculate the mass moment of inertia or not for any of CC1, CC2 to CC5.
MR. FOWLER: So for LS-DYNA for CC1, in the FSAR, there's a table that has all the variables listed out. I mean it has a note by the inertia that says it was derived from LS-DYNA. Obviously, it's very convenient to, if you already have a model built, to use that to extract a known variable out versus going and trying to do a hand calc. But a hand calc is literally done by hand, a calculator, or the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 formula is used in Excel. So that is the note that we were referring to in our slides that makes it clear that LS-DYNA was used to derive the moment of inertia, because we have a note by that variable in the FSAR.
What we were saying for the hand calculation is that that is an acceptable method that's alternative to LS-DYNA, because we viewed that for tip-over evaluations in our UMS and MPC systems as licensed by the NRC.
MR. RIGATO: So the UMS does not use LS-DYNA to calculate mass moment of inertia?
MR. FOWLER: Correct.
MR. RIGATO: Okay. For CC1 through CC5 and 6, for the MAGNASTOR, it does?
MR. FOWLER: Say that one more time?
MR. RIGATO: So for CC1 through CC6, is the mass moment of inertia calculated using LS-DYNA?
MR. FOWLER: George, you want to answer --
MR. CARVER: No. Only the FSAR bases CC1 and CC2 used the LS-DYNA moment of inertia. The rest of the systems have a hand-calculated moment of inertia associated with their disposition.
MR. RIGATO: Okay. Thank you.
MR. CARVER: I'm sorry. That was George Carver speaking.
MR. COLE: This is Kent Cole. But I would
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 like to note that the presentation does present that we went back and we ran the supplemental LS-DYNA calculation for CC5, and we compared the CC1 to CC5 in LS-DYNA to the CC1 to CC5 with the uniform density assumption and further compared it to those very detailed models that Marc showed that the ratio or the relative difference between those two were very compatible. And since NAC was attempting with our calculation of angular velocity to determine if there was a significant departure in Omega for these new casks that we were bringing in, that was an appropriate comparison. And in all cases, those --
you know, those differences in the moment of inertia are very comparable and they supported the conclusion that the angular velocities were comparable. I mean very simply, we're starting with a CC1 cask, and all of these casks add a little bit of weight and approximately increase the moment of inertia by the same amount. So if you're looking at the angular velocity equation, those factors almost cancel each other out, and you're really left with the height difference which is, in all of these cases, fairly small. And then of course, it's the square root of that factor, so it further reduces any small differences that are produced there.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. RIGATO: Do you have a table that actually shows what the mass moment of inertia is for all those systems, for the CC1, CC2, 3, 4, 5, and 6 somewhere just to be able to compare them?
MR. COLE: Yes. We can provide that.
MR. RIGATO: That can be provided?
MR. COLE: I think the thing to note in particular is that, you know, different methods can produce a different mass moment of inertia. But what we're trying to do is determine the relative difference. So whatever method you do, if you apply it both to CC1 and to whatever cask design that you're analyzing, that's what we would do (audio interference) but the angular velocities were comparable. But we can provide more specific information.
MR. FOWLER: Yes. And this is Wren. On slide 18, this is where we were trying to illustrate that it's the relative comparison between the two. So in that case, you use LS-DYNA. If you used a hand calc, what matters is the consistency between the two for CC1 and CC5, because you're looking at the relative ratio and comparison between the two, not necessarily the magnitude differences between the different methods.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. RIGATO: Yeah. A table would be great to actually compare what the differences are, because I can't tell from looking from CC2 onwards relative to CC5 what the actual difference is. So it would be helpful to have that.
MR. FOWLER: Sure. I'm taking some notes here on some of these things that you all are wanting.
MR. RIGATO: Thank you.
MR. FOWLER: We'll probably need to follow up afterwards to make sure that we got out lists matched, but I have that written down here.
MR. REGAN: Yes. Wren, this is Chris Regan. Maybe at the end before we close the business portion, we'll just do a quick review of what supplemental information you might provide to the NRC after we've completed out questions; okay?
MR. FOWLER: Okay. That sounds good.
MR. REGAN: All right. Tony, did you have any additional -- any follow-up questions to the three that you were interested in asking?
MR. RIGATO: No. That's fine. I would --
I guess something that George had mentioned was that different methods can produce different moments of inertia. When you provide that table, it will be difficult perhaps then with what you've said to really
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 compare, because if CC1 was done only with LS-DYNA, maybe you should also include a hand calculation of CC1 to determine the differences between the two because otherwise, we might be comparing apples to oranges. So maybe it be best to compare CC1's mass moment of inertia with a hand calculation versus CC5, 6, 2, 3, 4 and so on, just as a note if they're that different, which they may very well be, but I would imagine they shouldn't be all that different. But that's up to you.
MR. REGAN: Okay. Thanks, Tony.
MR. RIGATO: Thank you.
MR. REGAN: All right. Let's move on.
Now Tom, you had a question that you wanted to ask.
MR. BOYCE: Yes. Good afternoon. I'm Tom Boyce. I'm the Chief of the Materials and Structural Branch, Division of Fuel Management. I work for Chris. Tony works for me. And I've been following with great interest all the questions, and I believe I understand them. There are some people on the call that may not have a full understanding of the engineering that we're talking about, so may I request that we go to slide 11? And I think NAC, you're in charge of the slides. There's a picture and I think it would be great if you could show on that picture
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 what you're calling the method of evaluation and what would be an element of the method of evaluation.
Specifically, LS-DYNA is probably one of the elements, but the hand calculation doesn't show up on the picture. So I'm hoping you can walk us through that kind of thing.
MR. REGAN: Yes. So to minimize the logistics here, Haile, can you just pull up the NAC presentation and take us to slide 11. We'll have to just do a little bit of maneuvering here. Hopefully, Haile can get us there efficiently. Haile Lindsay is our Webex master for today.
MR. BOYCE: And failing that, if we aren't successful, I think many of us have the slides here at NRC, but I think we'd still enjoy the explanation if possible.
(Off record comments.)
PARTICIPANT: Outstanding, Haile. Thank you very much, sir.
MR. FOWLER: Okay. This is Wren. I'll take the first cut at this and then I'll let anybody else were that wants to jump in. First of all, this illustration shows everything associated with tip-over. You have input parameters and other stuff that go into the mode. You have stuff that's associated
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 with the model and checking it. And you have stuff that are downstream associated with it for evaluating the structural integrity of the system. All of that -
- all these methods that are embedded in here have to do with the tip-over evaluation. You have a method of evaluation known as LS-DYNA. You have a method of evaluation known as the conservation of energy, which is used for producing the initial angular velocity into LS-DYNA and checking the output kinetic energy.
You also have the design attributes which would --
mostly would refer to as input parameters into the model. Then you also on the right-hand side have all the methods of evaluations for the structural evaluation associated with the basket and canister.
So the point that we were trying to make is that for one topic, which is the tip-over, there are multiple MOEs used to look at that event, got LS-DYNA, you got conservation of energy, you got ANSYS.
All of these fit the big picture, and that was one of the things that we wanted to really point out in the presentation, that while the inspection report is really solely focused on LS-DYNA, there's a whole lot more to this than just one MOE, which is LS-DYNA.
There are other MOEs. They're saying hey, you validate what goes into the model, you validate stuff
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 that goes out of the model. There's methods of evaluation associated with the structural evaluations themselves. The --
MR. BOYCE: If I could follow-up? What we're looking for is perhaps where does the hand calculation fit into this drawing?
MR. FOWLER: So you see the conservation of energy box that has a very simple classical mechanics equation in it?
MR. BOYCE: Yes.
MR. FOWLER: That is the MOE explicitly called out in FSAR for how we figure out what angular velocity goes into LS-DYNA, and that's explicitly the equation that's used to validate the output kinetic energy of the model.
MR. BOYCE: Okay.
MR. FOWLER: So that equation, at its core, is what we're using to verify that CC5 is okay to come into the FSAR because we're looking at that impact on the LS-DYNA model itself that's already there.
MR. BOYCE: Right. And making an assessment without running LS-DYNA that changes are not significant?
MR. FOWLER: Right. That is an assessment
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 but also, we wanted to make it very clear that's part of the design control process that's in our FSAR. So it's not like it's something that we're -- it's not an assessment that we're just making up on our own. It's an assessment that's outlined in the FSAR itself.
MR. BOYCE: I understand. Thank you.
That's all I had, Christ.
MR. REGAN: Okay. Thanks, Tom. This is Chris Regan again. Okay. Marlone, you had a follow-up question that you are seeking clarification on.
MR. DAVIS: Yes. And this is again related to the regulatory process and the corrective action. In looking at what you've performed, during your review, your 72.48s that were performed for CC3, CC4, and CC5, what were the results of those reviews, and what did you identify? Did you identify issues in the screening area? Did you identify issues in assessing the evaluation questions? What were your results?
MR. FOWLER: Marlone, this is Wren. Could you do me a favor? Could you elaborate a little bit more on the context of your question? We're trying to get a better understanding of where you're coming from, what exactly you're looking for. Honestly, we can come back at 72.48, so what about it are you
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 interested in?
MR. DAVIS: I just wanted to know your results. I mean what was your findings, because you mentioned that you performed some corrective actions to better inform your 72.48 process. So I just wanted to understand what did you identify when you went back and actually looked at the one that put those into effect within the design process that there was not a departure; what did -- what improvements are you making?
MR. FOWLER: So I'll give you an example for CC5. First of all, going back and looking at what we documented, important -- very important question is whether or not we got the evaluation question correct, yes or no whether it required regulatory approval.
We've gone back and looked at those, and we believe that those are adequate. We have taken a look internally at the level of detail that we write into these justifications. It's very important from a regulatory standpoint to get the question right, yes or no, but it's also important that, you know, we provide enough detail in there that we can independently assess the adequacy of that decision.
We do believe there's plenty of room for improvement. Going back and looking at stuff,
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 remember CC5 goes all the way back to 2016, so we're talking about perspectives that were five years ago.
We've come a long way with NEI 12-04 dealing with method of evaluations, etcetera. So we believe, after going back and looking at this stuff, that there's plenty of room for improvement that our staff can make when it comes to the level of detail we write into those questions, whether it's explicitly listed in the question or it provides a clean reference that another person can go pick up that reference and pick right up from the 72.48. Those are the two big things that pop into my head when you asked that question. Anybody else here have anything?
MR. COLE: This is Kent Cole. I would just reiterate what Wren said in particular with respect to, you know, any even small changes in methods that are not departures, that one of the key learnings here is we need to do a better job of documenting that and the rationale that supported that. But the -- you know, the approach that brought in CC3 and 4 is the same as CC5, so the learnings are the same from those three 72.48s.
MR. DAVIS: But no specific examples or examples when answering the screening question that you check the box for MOE being changed from the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 conservation of energy?
MR. FOWLER: So, for right now, we've been really focusing upon the regulatory piece of the process, which is the evaluation section itself. As part of our continuing reviews, we will look at how to improve the screening and applicability sections.
MR. DAVIS: Yes, Wren, I understand that but again, my question is the screening is a part of that, so if you don't get the screening right, you can't -- you won't evaluate the evaluation right. You don't mark MOE, then you won't even look at the criterion 8. You would just look at 1 through 7, so that's what --
MR. FOWLER: Right.
MR. DAVIS: -- I'm trying to understand.
What are specific examples that you guys identified when you went back and looked at those 72.48 evaluations or the whole process?
MR. FOWLER: Sure. Well, again, we're still in the process of going back and looking at those. I will tell you for CC5, we did recognize that there was an adverse effect associated with that change, which is what trips us into the evaluation section. So we did meet the regulatory requirement, which is perform the evaluation when it's supposed to
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 be done. And we also believe we got the question right and the answer is "no" from a departure from an MOE.
But I understand where you're coming from about the level of detail and getting the screening questions right themselves. Whether you get the right one right or you get another one that does trip you into evaluation, you want to make sure that you answer each question correctly. That's something that we're continuing to go back and look at.
MR. DAVIS: All right. Thank you.
MR. REGAN: All right. Thanks, Marlone.
This is Chris Regan. I had one question I'd like a little bit of clarification on, and then maybe one quick follow-up if we have time. So -- and this goes back to the information you talked about on slide 36 just for your reference. You talked about performing an inspection yourselves of your 72.48 activities relative to the use of what we called linear scaling or ratioing dispositions. Could you share and elaborate a little bit on the results of those quote, unquote, "inspections?" What did you find? Talk a little bit more about what you identified.
MR. CARVER: Okay. This is George Carver.
We took a look across all platforms UMS NAC and MAG.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 We went through an initial screen and picked out of 2,000 -- probably 2,300 72.48's examples that had descriptions relative to scaling or ratio or -- and stuff, and we got down to about 25 that actually, you know, had any real effect -- not real effect -- that actually said I'm using linear scaling to do something. And each one of those instances were minor changes in -- with respect to ratioing of the margins associated with that particular component. So it was a pretty small number. Even out of the 25 we got down to, maybe only 7 -- 8 or -- 8 -- less than 10 actually said we did linear scaling associated with some change, nonconformance, and we ratio'd the results.
MR. COLE: Chris, this is Kent. Just -- I think just to add to that, look, that was a large look to go look at over 2,000 of these and get in kind of screened down to 25. I think our initial assessment is that there is no departure here. These look like, you know, places where there is lots of margin and we didn't really change the method, at least from an initial perspective. But we've got to look at that with a little bit more rigor to give you a definitive response on whether there was a change in method and confirm that there was a departure. We just haven't finished that as we've walked through these and taken
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 a deliberate approach to trying to look at all these and get them down to a handful for further investigation.
MR. REGAN: Okay. Thanks, Kent. Thanks, George. All right. I had just one more question, and I apologize to my own staff because I'm going a little off script here, and there was one more question that I thought of after we had concluded our caucus.
On slide -- I think its slide 34 you talked about, you know, the relationship to the 72.212 evaluation done for Palo Verde, acknowledged the use that linear scaling was not necessarily conservative in that case given all the changes to pad parameters.
Can you talk a little bit why this would also not be appropriate for a potential use of 72.212 evaluations, you know, as a required analysis for any other potential future applicant if you're asserting that the current process, the current approach that you have is acceptable but yet for Palo Verde, with the number of changes to the pad parameters, there was a decision that an LS-DYNA analysis was appropriate? So could you talk a little bit through about your logic about why perhaps Palo Verde was unique and that this same scenario wouldn't require an LS-DYNA analysis for any other potential site use and require a 72.212
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 evaluation?
MR. FOWLER: So Chris, this is Wren. I'll take the first stab at this. When it comes to comparisons at its site between their pad design, which may have a different thicker pad, different mud mats, subsoil, it may be bedrock, may be any number of things that are different from our generic, that's to say, our pad and soil, which is really just a simple site pad and subsoil. So as far as the 72.212 evaluation, the licensee has to take a look at, you know, am I going to build a new pad or do I have an existing pad and either way, how does that compare to the pad that's in the generic FSAR. If that's different, which it may or may not be, if it is different, then the tip-over needs to be evaluated for that pad.
And that's what we recognize we didn't do necessarily correctly at Palo Verde. We assumed that we could ratio or linearly scale the results from a generic FSAR for that. In reality, that pad is different than the pad in our FSAR. Thus, it needed to do an LS-DYNA run on it, because there was no way to validate the LS-DYNA model in the FSAR as being applicable. So that's a different situation than what we were describing here, which is in our FSAR, if
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 we're bringing in a new concrete cask, we are looking at the same pad, same subsoil. The question is, is there something different about the cask and the rotation of the cask. But for a site, they got to look at, hey, you know, what is the difference between our ISFSI pad and subsoil compared to the subsoil compared to the generic FSAR. It was a long-winded answer but hopefully I made some sense.
MR. REGAN: Yes. So, basically, you would acknowledge that there may be other cases where the --
if the parameters are sufficiently different from your generic pad, that an LS-DYNA analysis might be necessary for the purposes of satisfying 72.212 bounding analysis -- bounding 72.212 requirement?
MR. FOWLER: That's correct -- that's correct.
MR. REGAN: Okay. Thank you. And then maybe I just pull the thread a little bit more. You indicated there was -- you discussed a little bit about the rationale or the logic of why you included in Amendment 6 this approach but hadn't in the other ones, but yet you say, Well, we could have done it by 72.48, but we elected to include it in the amendments
-- I'm sorry, Amendment 9 application for CC6. Can --
just -- could you just repeat what you said is the
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 logic of why you included that in Amendment 9 versus just doing it by 72.48?
MR. FOWLER: Sure. So in the slide, I briefly say it's for site-specific project reasons.
So for this particular project, you have to look at what would we have to do scope-wise to include it in the FSAR before we do an amendment for the specific payload and loading patterns for that site. And that would require us, for instance, having to do shielding evaluations for all the different payloads that could fit into that cask. That takes time. That takes money. That may not support the project's schedule.
So when you go and look at the tech specs for Amendment 9 in CC6, you will notice that that cask is locked per se, for lack of a better word, to only being applicable to BMW 15 by 15 fuel. That means we only had to do one set of shielding evaluations for one fuel type. So it's a time scale thing. We needed
-- we wanted to get it put together fast to support the project without having to evaluate all these other payloads that at the time aren't applicable to that cask's use in the future.
MR. REGAN: Okay. Thank you, Wren.
That's helpful. Thank you.
MS. CUADRADO: I do have a follow-up.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. REGAN: Okay. I was just going to ask for any -- so that's kind of our formal questions.
I'd ask are there any additional questions from the staff that we want to ask? Go ahead, Leira.
MS. CUADRADO: It was just a follow-up question to what you just asked, and that is when NAC says that they verified that LS-DYNA was used for all the subcontracted site-specific MAGNASTOR implementation, and it made me think about your question about in the case of Palo Verde, it was kind of not used. Did you find -- with Palo Verde, like the question or the LS-DYNA was just wrong for your other sites in due process, or was it for preparing for this particular Pre-decisional Enforcement Conference?
MR. FOWLER: So for all the subcontracted sites minus Palo Verde that we've been subcontracted for, we have used LS-DYNA for evaluating tip-over on their site-specific pad and soil. Palo Verde was the only exception. Obviously, for them prior to loading their first canister, we did a site-specific LS-DYNA run for them to close out the Region 4 inspection so that they could go ahead and proceed with their first system.
MS. CUADRADO: Okay. Thank you.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. REGAN: Okay. At this point, hearing no further questions form the NRC staff, Wren, could I ask you to just review what you had in the way of any takeaways of information you would like to provide to us in the way of supplemental information after the close of the PEC?
MR. FOWLER: Sure. So I had one item down. There was a request for a table showing the magnitude of the moments of inertia for the different casks as well as their relative ratios and also the method used for each one of them so the NRC person could get a
comparison between the different magnitudes and different methods and their ratios.
MR. REGAN: Okay. That was one. I thought I had heard there was a second one. Could I just verify with the NRC staff that that was the only supplemental information that we were interested in receiving from NAC?
MR. DAVIS: This is Marlone. This is in regards to the sensitivity run, about the 3 percent threshold.
MR. WOODFIELD: This is Jon Woodfield. We were supposed to get something about the -- all the runs you did for the different canisters or casks, about where you went higher g's in CC1.
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 MR. DAVIS: Yes. I think, Jon, it should be higher or lower because if it's lower, it could be a non-conservative change in that case also, so it just depends based on the runs and the parameters.
MR. REGAN: All right. Is that clear for NAC International, and do you commit to provide that information to us?
MR. FOWLER: Sure -- make sure I got this right. Wants the sensitivity run that shows the 3 percent up, 3 percent down effects on the basket and canister, the g-load, and the LS-DYNA run for CC3, 4, 5, and 6 that we did as preparation for this conference? I think I got -- I think that's what I heard.
MR. REGAN: Yes, where you show the final g-values that you came up with.
MR. FOWLER: Sure.
MR. REGAN: Well, that you -- what you had for CC1.
MR. FOWLER: Got you. Okay. Yes, I have it down here. So those are the three things and yes, Chris, we'll provide that to you all.
MR. REGAN: And you can work with Leira to let us know what kind of timeframe you might provide that information to us, you know, after the close of
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 the PEC.
Okay. All right. With that, hearing no further questions from the NRC staff, I'd like to ask NAC International if you have any closing remarks.
MR. COLE: Yes, Chris. Thank you very much. Look, I sincerely hope that the presentation that we provided today was constructive and I hope it narrowed the areas of, you know, any confusion of misunderstanding about what we did and the level of, you know, disagreement between us on this matter.
Look, we take, you know, nuclear safety very, very seriously. We want to be the very best we can be as a nuclear supplier and desire to learn and improve. And as I mentioned earlier, we certainly -- as I, you know, identified issues both with APS that we've already partially addressed and some supplementary issues here in particular with the way we document any changes in MOEs that aren't departures. But we're taking a good hard look and, you know, intend to improve based on what we've learned here. So again, hope the information was useful to you and, you know, hope that you'll reconsider the two ABs based on the information that we provided to you today. Thanks.
MR. REGAN: All right. Thanks, Ken. So in closing this Pre-decisional Enforcement Conference,
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 I remind everyone present and listening that the apparent violations discussed today are subject to further review. Based on the information presented today, they may be revised prior to taking any enforcement actions. Statements or expressions of opinion made by the NRC staff or the lack thereof do not represent final agency positions or determinations. The NRC will consider the information provided today and as supplemented in making appropriate enforcement decisions, and we will notify NAC International by telephone and in writing when we are ready to announce our decision. With that, the business portion of this conference is closed, and I'll now turn it over to Leira for any questions or comments from the public. Leira?
MS. CUADRADO: Thanks, Chris. Now that the business portion of the conference is over, I would like to offer those listening in today the opportunity to comment or ask questions on the contents of this meeting. We will afford 20 minutes for questions and answers. When you ask a question or make a comment, please clearly state your name and affiliation. I'll now ask the operator to provide the instructions for asking questions of the NRC staff.
Operator, could you please let us know if there are
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 any questions or comments in the queue.
OPERATOR: Thank you. At this time, we'll begin the question and answer session of the conference. To ask a question, press "star," then "1" and record your name clearly for question introduction. You must record your name clearly for your question to be introduced. Again, to ask a question, press "star 1" and clearly record your name.
One moment to see if we have any questions.
(Pause.)
OPERATOR:
There are no questions currently in the queue at this time.
MS. CUADRADO: Thank you. I'll just --
again, I'll remind participants that this is your opportunity to ask comments or questions to NRC staff about the discussions we just had today with NAC International regarding apparent violations. If you have any question of comment you would like to make, the operator has shared instructions on how to prompt the operator to open your line.
(Pause.)
MS. CUADRADO: I also note that the slide showing in the Webex also provides the instruction on how to prompt the operator.
(Pause.)
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(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433 OPERATOR: And currently there's no questions in the queue at this time.
MS. CUADRADO: All right. So Chris, with no comments or questions from the public or anyone participating, I'll turn it over to you to adjourn the meeting.
MR. REGAN: Okay. Thank you. There are apparently no further questions or comments from the public. If there are folks on the bridge line from the public that would like to offer feedback, I'd like to remind you that there is a meeting feedback and comment form, and the feedback form accession number included in the public meeting notice for this meeting as well as in the reference slide for this presentation as you can see on the current slide.
Hopefully you can see that. And with that, I would like to thank you all for your participation. This conference is now adjourned. Thank you, all.
(Whereupon, the above-entitled matter went off the record at 3:53 p.m.)
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