ML24361A082
| ML24361A082 | |
| Person / Time | |
|---|---|
| Issue date: | 12/19/2024 |
| From: | Charles Brown Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-0150 | |
| Download: ML24361A082 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Fuels, Materials, and Structures Subcommittee Docket Number:
(n/a)
Location:
teleconference Date:
Thursday, December 19, 2024 Work Order No.:
NRC-0150 Pages 1-91 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
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1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 4
(ACRS) 5
+ + + + +
6 FUELS, MATERIALS, AND STRUCTURES SUBCOMMITTEE 7
+ + + + +
8 THURSDAY 9
DECEMBER 19, 2024 10
+ + + + +
11 The Subcommittee met via videoconference, 12 at 1:00 p.m. EST, Ron Ballinger, Chairman, presiding.
13 SUBCOMMITTEE MEMBERS:
14 RONALD G. BALLINGER, Chairman 15 VICKI M. BIER, Member 16 VESNA B. DIMITRIJEVIC, Member 17 GREGORY H. HALNON, Member 18 CRAIG D. HARRINGTON, Member 19 WALTER L. KIRCHNER, Member 20 ROBERT P. MARTIN, Member 21 SCOTT P. PALMTAG, Member 22 THOMAS E. ROBERTS, Member 23 MATTHEW W. SUNSERI, Member 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
2 ACRS CONSULTANT:
1 DENNIS BLEY 2
3 DESIGNATED FEDERAL OFFICIAL:
4 CHRIS BROWN 5
6 ALSO PRESENT:
7 THOMAS BOYCE, NMSS 8
DARRELL DUNN, NMSS 9
JOE FALDOWSKI, EPRI 10 MARK RICHTER, NEI 11 DAN RUBY, NMSS 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
3 CONTENTS 1
2 Opening Remarks and Objectives 4
3 Ron Ballinger, ACRS Subcommittee Chair 4
Staff Opening Remarks..............
8 5
Tom Boyce, NMSS 6
Regulatory Guide 3.78.............. 10 7
Darrell Dunn, NMSS 8
EPRI Susceptibility Rankings and Relevant 9
Experience
................... 47 10 Joe Faldowski, EPRI 11 NEI Perspective
............. 74 12 Mark Richter, NEI 13 Public Comments (None)
............. 89 14 Adjourn the Public Session
........... 92 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
4 P-R-O-C-E-E-D-I-N-G-S 1
1:00 p.m.
2 CHAIR BALLINGER: Good afternoon. This is 3
a meeting of the Fuels, Materials, and Structures 4
Subcommittee of the Advisory Committee on Reactor 5
Safeguards.
6 I'm Ron Ballinger, Chair of today's 7
Subcommittee meeting. ACRS members in person: Craig 8
Harrington who, due to conflict of interest issues, 9
may recuse himself for some topic. Tom Roberts, 10 myself, Bob Martin, and Scott Palmtag. Members 11 virtually attending -- I know who could be virtually 12 attending, but it's hard for me to tell.
13 MR. BURKHART: We've got Greg.
14 CHAIR BALLINGER: I think we have Greg for 15 sure --
16 MR. BURKHART: Matt.
17 CHAIR BALLINGER: -- Matt Sunseri. I 18 don't know about Vesna. Walt I don't see.
19 MR. BURKHART: Yes, yes, Vesna, Vicki, 20 Walt, all are on.
21 CHAIR BALLINGER: Oh, you got them all?
22 Okay. Good. Okay.
23 Chris Brown of the ACRS staff is the 24 Designated Federal Officer for this meeting.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
5 We have a quorum.
1 During today's meeting, the Subcommittee 2
will receive a briefing on DG-3058, otherwise known as 3
Reg Guide 3.78; acceptable ASME Section XI Inservice 4
Inspection Code Cases for 10 CFR Part 72.
5 The proposed Reg Guide provides acceptable 6
methods and procedures that would be acceptable for 7
inservice inspection of spent fuel storage 8
installations and other licensees/CoC holders related 9
to 10 CFR 72.
10 The proposed Reg Guide specifies 11 particular Section XI Code Cases that would be 12 acceptable. In particular, the proposed Reg Guide 13 endorses the use of ASME Code Case N-860, Inspection 14 Requirements and Evaluation Standards for Spent 15 Nuclear Fuel Storage and Transportation Containment 16 Systems;Section XI, Division 1, and Section XI, 17 Division 2.
18 For this reason, the Subcommittee decided 19 to review this document.
20 The ACRS was established by statute and is 21 governed by the Federal Advisory Act, or FACA. The 22 NRC implements FACA in accordance with its 23 regulations.
24 Per these regulations and the Committee's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
6 Bylaws, the ACRS speaks only through its published 1
Letter Reports. All member comments should be 2
regarded as only an individual opinion of that member, 3
not a Committee position.
4 All relevant information related to ACRS 5
activities, such as letters, rules for meeting 6
participation, and transcripts, are located on the NRC 7
public website and can be easily found by typing about 8
us ACRS in the search field on the NRC's home page.
9 The ACRS, consisting of the agency's value 10 of public transparency and regulation of nuclear 11 facilities, provides opportunity for public input and 12 comment during our proceedings. We have received no 13 written statements or requests to make an oral 14 statement from the public, but we also have set aside 15 time at the end of this meeting for public comments.
16 The Subcommittee will gather information, 17 analyze relevant issues and facts, and formulate 18 proposed conclusions and recommendations, as 19 appropriate, for deliberation by the full Committee.
20 A transcript of the meeting is being kept 21 and will be posted on our website.
22 When addressing the Subcommittee, the 23 participants should first identify themselves and 24 speak with sufficient clarity and volume, so that they 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
7 may be readily heard. If you are not speaking, please 1
mute your computer on Teams or by pressing *6 if 2
you're on the phone.
3 Please do not use the Teams chat feature 4
to conduct sidebar discussions related to 5
presentations, but, rather, limit use of the meeting 6
chat function to report IT problems.
7 For everyone in the room, which we have 8
nobody in the room, but put everything, all your 9
electronic devices in silent mode -- I guess that 10 includes the members -- and mute your laptops.
11 For presenters, your table microphones, as 12 you probably realize, are extremely unidirectional.
13 You almost have to have it directly in front of you.
14 Otherwise, we can't hear, and certainly the court 15 reporter can't.
16 Finally, if you have any feedback for the 17 ACRS about today's meeting, we encourage you to fill 18 out the public meeting feedback form on the NRC's 19 website.
20 We will now proceed with the meeting and 21 we'll call on Tom Boyce for any opening remarks.
22 Tom?
23 MR. BOYCE: Yes. I'm assuming you can 24 hear me and see my screen.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
8 CHAIR BALLINGER: Barely.
1 MR. BOYCE: Better?
2 CHAIR BALLINGER: Better. Better.
3 MR. BOYCE: All right. So I'm Tom Boyce.
4 I'm a Branch Chief for Materials and Structural 5
Engineering in the Division of Fuel Management and the 6
Office of NMSS.
7 Joining me, to my right is Shana Helton, 8
the Director of the Division of Fuel Management, and 9
on my left, Laura Howards, a Materials Engineer in the 10 Materials and Structural Branch.
11 At the table is:
12 Darrell Dunn, a Senior Materials Engineer, 13 who will be giving the NRC's presentation right after 14 I conclude my remarks.
15 Joe Faldowski of EPRI, he's a Senior 16 Program Manager for Used Fuel and High Level Waste.
17 And Mark Richter of NEI, who is a 18 Technical Advisor at NEI.
19 First, a very brief history of this issue.
20 We observed chloride-induced stress 21 corrosion cracking manifesting itself at several new 22 plants and one international plant and issued an 23 Information Notice in 2012, IN-2012-20, and we advised 24 the spent fuel community that they needed to manage 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
9 chloride-induced stress corrosion cracking.
1 In parallel, we sent a letter requesting 2
that ASME develop a Code Case for inspection of CISCC.
3 ASME has worked since then and issued ASME Code Case 4
N-860. Today's Reg Guide 3.78 endorses N-860. So 5
we're here today to tell you about that.
6 We think this Reg Guide development is 7
entirely consistent with the mission of the Division 8
of Fuel Management and will result in more effective 9
and efficient regulation. The staff used a risk-10 informed approach in developing this guidance that has 11 considerable value to industry. You'll hear from 12 Darrell that we did a reg analysis and we came up with 13
$25 million savings to industry over a 40-year period.
14 We believe this Reg Guide is aligned with 15 the goals of the ADVANCE ACT. We are seeking approval 16 of the ACRS to publish the Reg Guide as soon as 17 possible, consistent with the normal Reg Guide 18 publication process. And that concludes my remarks.
19 CHAIR BALLINGER: Thank you. So I believe 20 on our agenda, Darrell, you have the floor.
21 MR. DUNN: Okay. Thank you very much. I 22 appreciate the introduction. I'm just going to jump 23 into it here. I've got an outline of topics that I'm 24 going to cover today to understand the purpose and 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 applicability of the Reg Guide, but I have a slide on 1
that.
2 I do have a number of slides that describe 3
the ASME Code Case and give some background 4
information on that; why it came into development, 5
which I think we've heard from Tom, but also how the 6
Code Case works.
7 I have a number of slides that cover our 8
regulatory approach for endorsing this Code Case. We 9
went beyond what the Code Case does for very low 10 susceptibility sites. And I'll describe how we 11 developed that and the information that we used to 12 support that.
13 We did issue the Reg Guide for public 14 comment in July of this year. We did receive some 15 public comments from NEI. And so I'll describe those 16 comments and what kind of changes we made to our 17 Regulatory Guide associated with those comments.
18 I have one slide on a regulatory analysis.
19 It describes the conclusions from that. And then I 20 have a slide on the timeline and the next steps in 21 terms of what we need to do to complete this process 22 and issue the final Reg Guide. And I'll end with some 23 acknowledgments of staff that provided significant 24 contributions to both the development of the ASME Code 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
11 Case and the Regulatory Guide 3.78.
1 So again, the purpose here is to identify 2
acceptable ASME Section XI Inservice Inspection Code 3
Cases that can be used by our independent spent fuel 4
storage installation specific licensees, general 5
licensees, and Certificate of Compliance, or CoC, 6
holders under our regulations for storage in 10 CFR 7
Part 72.
8 This provides guidance on inservice 9
inspections of these spent fuel storage systems, and 10 then, that's a key aspect of what needs to happen when 11 these systems or licensees go through renewal. We 12 have regulatory requirements that they have to have 13 aging management programs. And we've identified 14 chloride-induced stress corrosion cracking as the only 15 credible aging mechanisms that could potentially 16 affect most of our dry storage systems that are 17 currently in use.
18 Again, in this particular initial issuance 19 of Reg Guide 3.78, we have one Code Case that's being 20 endorsed, the ASME Code Case N-860. In the future, 21 revisions of this Reg Guide may include additional 22 Code Cases. So it will be somewhat similar to Reg 23 Guide 1.147, although we don't anticipate the huge 24 number of Code Cases for 10 CFR Part 72 inservice 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
12 inspections. So a few additional Code Cases are 1
likely. There's currently one in development, but, in 2
concept, similar to Reg Guide 1.147.
3 So a little bit of background information 4
on the ASME Code Case. This was developed over a 5
five-year period from 2015 to 2020. As Tom mentioned, 6
this was initiated with an NRC request. And so I have 7
the ADAMS Accession Numbers of this request and ASME's 8
response on this slide.
9 The Code Case developed applies only to 10 welded austenitic stainless steel canisters that are 11 exposed to ambient air by passive ventilation. And I 12 have a schematic on my following slide that gives you 13 a diagram of what these systems look like and how that 14 works.
15 These types of systems are the majority of 16 the dry storage systems that we currently have in use 17 in the U.S., and more than 90 percent of our dry 18 storage systems are of this design. And it's 19 currently used at 71 operating independent spent fuel 20 storage installations.
21 The Code Case assumes that chloride-22 induced stress corrosion cracking is the most credible 23 and bounding aging degradation mechanism. That is 24 consistent with our guidance in our NUREG-2214, our 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
13 Managing Aging Processes in Storage report. And 1
again, as Tom has mentioned, we've seen this 2
degradation phenomena in our operating reactor 3
components, operating power reactor components, but 4
not in any ISFSI inspection.
5 I will say that, for the 71 ISFSIs that 6
currently use these systems, about a third of those 7
are now in the period of extended operation. They 8
have gone through a renewal process, either a license 9
renewal or a CoC renewal. They have aging management 10 programs that address this degradation phenomena.
11 They've conducted inspections. Some of 12 those sites have conducted multiple inspections.
13 Calvert Cliffs has conducted three at five-year 14 intervals, starting in 2012, and there has never been 15 an identified instance of localized corrosion or 16 stress corrosion cracking at any of the ISFSI sites to 17 date.
18 So the slide here just has a schematic, a 19 couple schematics of the types of dry storage systems 20 that we're talking about. We've got several different 21 vendors that produce vertically-oriented systems.
22 And I didn't change my pointer to a laser.
23 So hopefully you can see my cursor here.
24 But there's a welded stainless steel 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
14 canister inside of a very thick ventilated overpack 1
here. The canister has an internal structure for 2
supporting and keeping spent fuel assemblies in a 3
known orientation and geometry. That canister with 4
spent fuel has some amount of decay heat. That decay 5
heat is removed because this overpack has an inlet 6
vent at the bottom and an outlet vent at the top. And 7
so air passes over this canister and takes away the 8
decay heat.
9 Similarly, we have horizontal storage 10 systems produced by one of our CoC holders. You know, 11 the same type of concept. Here you see the canister 12 inside of this horizontal storage module. There is a 13 vent at the bottom that takes in air. Air flows 14 around the sides of the canister and exits through the 15 roof of this particular system to remove the decay 16 heat.
17 So all these systems are in what we call 18 a sheltered environment. They're not directly exposed 19 to rain, but they are exposed to ambient air via this 20 ventilation process, and these vertical casks and HSMs 21 provide shielding protection for workers and members 22 of the public and also physical protection for things 23 like tornado-driven missiles.
24 MEMBER ROBERTS: Tom Roberts. What do you 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
15 have to do to gain access for inspection?
1 MR. DUNN: So I have a slide on that.
2 There have been inspections that have been conducted 3
on both of these types of systems. They are typically 4
done with fiber optic systems, usually with a remote 5
crawler. And I have a picture of one of those. And 6
they typically will go through the vents, either the 7
inlet vent for some of the horizontal systems or the 8
outlet vents for some of the vertical systems.
9 MEMBER ROBERTS: Thank you.
10 MR. DUNN: Okay. So as Tom mentioned, we 11 have seen CISCC of power reactor components. The 12 schematic over here on the left side of this slide is 13 something that was developed by the Central Research 14 Institute of the Electric Power Industry in Japan, 15 CRIEPI. And so it has a schematic of what happens in 16 this process.
17 And so if we have stainless steel in an 18 environment that's maybe close to a
marine 19 environment, a marine shoreline -- which is typically 20 the case in Japan, and that's why they have so much 21 interest in this -- you can have deposition of sea 22 salt particles on the stainless steel surface.
23 The relative humidity of the canister, if 24 the component surface gets high enough, we can have 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
16 deliquescence of those sea salt particulates and that 1
forms a saturated solution on the stainless steel 2
surface. That saturated solution can induce pitting 3
or localized corrosion, crevice corrosion, of the 4
stainless steel. And if that occurs in a region where 5
we have a weld, you have potential residual stresses.
6 That pit or corrosion spot can act as a stress riser 7
and we can get stress corrosion cracking initiated.
8 So the Information Notice that we 9
published -- this is Information Notice 2012-20 --
10 identified four different sites. And I have a couple 11 of pictures here of some of the CISCC events of these 12 power reactor components.
13 The Koeberg event was a refueling water 14 storage tank. What you see there is the weld has been 15 cleaned off, and then, examined using a penetrant 16 test. The pinkish-colored dye is the actual 17 penetrant, and the little streaks coming off of that 18 weld are cracks that are emanating from that weld 19 because of the residual stresses in that component.
20 And at the bottom of the list, a useful 21 picture, I would say, but it's the San Onofre 22 emergency core cooling system, again, where you see 23 indications emanating from the weld of that particular 24 piping system.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
17 So the Code Case, taking this knowledge 1
into consideration, is focused on examinations of 2
welded regions of the canisters because that's the 3
location where, if you get localized corrosion, hidden 4
corrosion, or crevice corrosion, there's enough 5
residual stress to initiate stress corrosion cracking.
6 The Code Case uses a
progressive 7
inspection methodology to identify and characterize 8
corrosion. There's a visual screening inspection 9
that's done initially. And many of the inspections 10 that would be performed will indicate that there's no 11 additional indications that need any followup and 12 that's where the inspection will end.
13 If there is something that is identified, 14 there is a higher resolution visual inspection that 15
- occurs, and
- then, there can be supplemental 16 inspections, either service or volumetric inspections.
17 And we have seen the development of eddy current 18 systems that can be used on some of these remote 19 crawlers or systems to do inspections that are at a 20 technology readiness level that are basically ready to 21 deploy. There's still some work that's going on for 22 doing, like, a UT inspection, if you wanted to do 23 depth characterization of any types of indications.
24 And then, the Code Case has provisions to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
18 adjust the number of canisters that get inspected or 1
the inspection frequency based on the initial 2
examination results.
3 So the pictures on the right side here 4
show some of the vertical systems. The first, 5
basically, just shows the scaffolding and things that 6
have to be in place in order for staff to get to the 7
outlet vents of these vertical systems.
8 And then, the lower picture there, this 9
was actually a test. The lid of that overpack was 10 removed. And this is not an actual loaded system. So 11 we could look at the way the crawler goes through the 12 outlet vent. But you see the crawler there. It has 13 magnetic wheels on it. It sticks to the side of the 14 ferritic steel liner of the concrete overpack and it 15 has a fiber optic probe on it with camera that allows 16 the visual inspection to be conducted.
17 So the Code Case uses a report that was 18 generated by EPRI as a result of an NEI and NRC 19 regulatory issue resolution protocol that took place 20 between 2010 and 2016. That EPRI report describes the 21 susceptibility assessment criteria for CISCC. Joe is 22 going to have some additional slides on that. So I'm 23 just going to give a very high-level description of it 24 here.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
19 There is a ranking system that is set up 1
in that document, a CISCC ranking, termed ZISFSI. And 2
there's three terms there.
3 A chloride starting composition, and 4
that's, basically, dictated by the distance that the 5
ISFSI is located from an ocean or marine shoreline.
6 So the closer you are, the higher that number gets.
7 And that's the biggest factor that drives these 8
ranking criteria.
9 The chloride adjustment factor --
10 MEMBER MARTIN: A quick question.
11 MR. DUNN: Uh-hum.
12 MEMBER MARTIN: What does that metric look 13 like? I mean, is it somewhat subjective? A ranking, 14 like 1, 2, 3, 4, 5, based on 1, 2, 3, 4 miles, or 15 something? Or what does that look like.
16 MR. DUNN: Yes. So I actually have a 17 screenshot of that in a subsequent slide. And it 18 tells you distances and chloride starting values. It 19 basically goes from 1 to 9. Okay? So if you're more 20 than 20 kilometers from the shoreline, it's 1. It 21 doesn't matter if you're 50 kilometers or 500 22 kilometers; it's 1. If you're less than 90 meters 23 from the shoreline, it's 9. Okay?
24 MEMBER MARTIN: All right.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
20 MR. DUNN: But I have a table that has all 1
those values.
2 MEMBER MARTIN: Okay. Thank you.
3 MR. DUNN: And then, there's a chloride 4
adjustment factor. This takes into consideration 5
distance from a salted road or within 200 meters of a 6
salted road, or within 1,000 meters of a cooling tower 7
and the salinity of that cooling tower.
8 And then, there's an absolute humidity 9
adjustment factor that considers the average absolute 10 humidity for the site.
11 And the way the Code Case works is it 12 defines a high-ranked site as having a ZISFSI ranking 13 of 8 or above and a low susceptibility as an ZISFSI 14 having a rank of 7 or below.
15 The Code Case does have a CISCC growth 16 rate equation that only considers canister surface 17 temperature, which is often measured during these 18 inspections. That growth rate equation is not 19 intended to predict whether CISCC can occur. It's 20 only used to determine what that next inspection 21 interval should be if CISCC is determined to be 22 present or is likely to be present.
23 And then, the Code Case has provisions for 24 increasing the maximum inspection interval for what 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
21 they term low-ranked sites, ZISFSI rankings of 7 or 1
below, from 10 to 20 years, if there are multiple 2
inspections that are conducted with no indications of 3
chloride-induced stress corrosion cracking.
4 MEMBER MARTIN: Do you consider it meant 5
for kind of your implementation of risk-informed 6
approach in this sort of thing? Or is it just 7
something that's always been there, and because it 8
looks like risk-informed, right, how far you're away 9
10 MR.
DUNN:
So are you
- asking, 11 specifically, about the susceptibility ranking or?
12 MEMBER MARTIN: Yes, the susceptibility 13 ranking.
14 MR. DUNN: Sure. Yes, and that's 15 consistent with what we've seen for operating 16 experience at power reactor sites. The only time 17 we've ever seen those types of events were ones that 18 are located very close to the shoreline. And I'll 19 have a subsequent slide that talks about that.
20 In terms of risk-informing, you know, the 21 lower-ranked sites, going from an increased inspection 22 interval, if there's no indication of localized 23 corrosion, is a way to risk-inform these inspections.
24 We've done something beyond that in this particular 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
22 Code Case to look at those very low susceptibility 1
sites, those sites that are generally greater than 20 2
kilometers from the coast. And I'll describe that.
3 Okay. So our regulatory approach here for 4
endorsement, we consider the methodology that was in 5
the Code Case, which I've described in the previous 6
slides. But, then, we also considered some additional 7
technical information that either wasn't available 8
when the Code Case was written or wasn't considered 9
because the information that was available wasn't 10 complete.
11 And so we did consider the power reactor 12 operating experience with CISCC, where we have ISFSIs 13 located in the U.S., and the inspection results that 14 have been generated from those inspections.
15 And really very importantly -- and I'll 16 have several slides on this -- is the composition of 17 the deposits that are actually on those canister 18 surfaces and what that really means for 19 susceptibility, which really wasn't considered in the 20 Code Case at all.
21 So again, we have this Information Notice.
22 We have referenced this Information Notice in our 23 Regulatory Guide Information Notice 2012-20. Again, 24 this identified CISCC events for power reactor 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
23 components, including stainless steel piping and 1
tanks. And these instances have occurred at three 2
places in the U.S.: San Onofre in California, and 3
then, St. Lucie and Turkey Point in Florida, and then, 4
there is another plant in South Africa, the Koeberg 5
station, where this type of an event was also 6
observed, which I showed pictures of in an earlier 7
slide.
8 Again, we perform inspections at ISFSI 9
sites. There is no indication of localized corrosion 10 or stress corrosion cracking on any of the canisters 11 that have been inspected to date. But we utilize this 12 information that's in our Information Notice.
13 So the plot here at the bottom on the left 14 side is a map of the U.S. with ISFSI locations 15 identified. And the green points are generally 16 licensed ISFSIs. So these are ISFSIs that are, 17 basically, co-located with a power plant and they're 18 generally licensed through 10 CFR 72.210 for operating 19 reactor licensees and the license to operate an ISFSI.
20 And the purple stars there indicate where those CISCC 21 events have occurred at operating reactors. So again, 22 San Onofre, St. Lucie, and Turkey Point.
23 Up on the right is a picture of the 24 African continent and a detailed image of South Africa 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
24 and the location of the Koeberg plant here on the 1
southwest coast of Africa, and a picture of what that 2
plant looks like and its proximity to the coast --
3 very obviously a coastally-located plant.
4 So for all of these CISCC events, if we 5
took the same methodology that we've used in the 6
susceptibility assessment, all of these events would 7
have, our locations where CISCC has occurred, would 8
have a susceptibility ranking greater than or equal to 9
7.
10 We've also referenced in our Regulatory 11 Guide some reports that were generated by Sandia 12 National Laboratories after the Code Case was 13 developed. And what's done in these reports is there 14 was sampling of deposits that's actually on some of 15 these canisters when inspections were conducted. Two 16 of those reports were generated for inland sites, and 17 then, the third one was what was called a near-marine 18 East Coast site. It's actually a fair distance from 19 the open ocean, but it is next to an estuary.
20 And the conclusion of all these reports is 21 that the risk of canister CISCC at all of these sites 22 is low. And the reason for that is there's a low or 23 very low surface chloride concentration -- very low 24 being less than 5 milligrams of chloride per square 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
25 meter; low being up to maybe 45 milligrams of chloride 1
per square meter.
2 There's also evidence in these 3
examinations of these salts that were removed from 4
these canisters that there's other things besides 5
chloride present. And the other things include, among 6
other things, nitrate salts and sulfate salts --
7 nitrate being, particularly, the good inhibitor of low 8
chloride corrosion and stress corrosion cracking. The 9
amount of nitrate that's present, as described in the 10 analysis of these reports, is equal to or greater than 11 the amount of chloride that is present on these 12 surfaces.
13 So we've referenced some more detailed 14 studies that looked at the effect of inhibitors and 15 how these typical marine salt aerosols evolve over 16 time. We've referenced work in 2015 by Chi, et al.,
17 which shows that what happens with these marine salt 18 aerosols is they generally transform over time from a 19 chloride-rich salt to a salt that has sulfate and 20 nitrate. And that occurs because we have nitrogen-21 containing and sulfur-containing emissions that are 22 generated from the combustion of hydrocarbon fuels.
23 Those nitrogen-and sulfur-containing oxides mix with 24 water in the atmosphere. They form an acid, and that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
26 acid reacts with the chloride salts to form nitrate 1
and sulfate salt deposits. And the chloride generally 2
gets carried away as an acid gas.
3 So over time, we don't necessarily really 4
experience an accumulation of chloride on the surface, 5
and we expect that we'll get an accumulation of 6
nitrate-and sulfate-containing salts, and that's 7
consistent with what we've seen in the analysis from 8
the Sandia National Laboratories' reports.
9 We've referenced some information that 10 shows that nitrate and sulfate are known localized 11 corrosion inhibitors for stainless steels, and we've 12 also had some references to show that nitrate is an 13 effective inhibitor of chloride-induced stress 14 corrosion cracking.
15 The image at the bottom is another one of 16 our references in the Reg Guide. What's done here is 17 an interesting way to show that nitrate is an 18 effective inhibitor. What's done here is that there's 19 droplets, for replicate tests, of droplets a solution 20 that contains chloride. And as you go from left to 21 right, that droplet contains either zero nitrate left, 22 and at the righthand, the nitrate concentration, the 23 molar ratio of nitrate to chloride is, basically, one-24 to-one.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
27 So when you get to a molar ratio of about 1
one nitrate to two chlorides, you, basically, get 2
inhibition of localized corrosion and you see that 3
there's no longer a rusty spot on the stainless steel 4
because localized corrosion in the form of pitting is 5
no longer happening in this system.
6 So our Regulatory Guide, we have a table 7
in our Reg Guide, Table 1, Acceptable Section XI Code 8
Cases. Right now, that only identifies Code Case N-9 860.
10 And just kind of as a review, the link to 11 Code Case N-860 as written, a maximum inspection 12 interval for a low-ranked site, something with a CISCC 13 susceptibility ranking of 7 or below, can be increased 14 from 10 years to 20 years if there's multiple 15 inspections conducted and there's no indication of 16 CISCC.
17 Our Reg Guide takes an alternative 18 approach. And I'll have some more details on the 19 following slide. We have determined that, for inland 20 ISFSI sites, sites that are generally 20 kilometers or 21 more away from a marine shoreline, they generally have 22 a ZISFSI ranking of 3 or below. We think we can 23 accept an inspection interval that goes up to 40 24 years, simply because the susceptibility of these 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
28 systems to chloride-induced stress corrosion cracking 1
is low. Even if you could get chloride-induced stress 2
corrosion cracking to occur, it's going to be a very 3
long-term process to get that to propagate to any 4
significant depth through the container thickness.
5 CHAIR BALLINGER: This is Ron Ballinger.
6 The CoC period is 40 years, correct?
7 MR. DUNN: That's correct.
8 CHAIR BALLINGER: So you're effectively 9
eliminating inspection?
10 MR. DUNN: So the inspection would 11 coincide with, effectively, renewals, yes.
12 And again, this is based on technical 13 information that was either not available at the time 14 that the Code Case was written or not considered 15 because the information that we had at the time was 16 really not complete.
17 And again, we expect that we will update 18 this regulatory guidance and include additional future 19 acceptable ASME Section XI Code Cases that can be used 20 by our 10 CFR Part 72 licensees and certificate 21 holders.
22 So what does this actually look like?
23 Well, we've got 71 operating sites, as I mentioned.
24 We've got over 3800, almost 3900, welded austenitic 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
29 stainless steel canisters in use as of October of 1
2024.
2 We know that the composition of salts on 3
these canisters at these low-ranked sites are not 4
likely to promote stress corrosion cracking at all or 5
localized corrosion. There's just not enough chloride 6
and there's more than adequate inhibiting species on 7
the surfaces to prevent that from happening. But 8
again, even if it could occur, the time for initiation 9
would be lengthy and the propagation rates would be 10 very slow.
11 So if we take here in this table, again, 12 the way the ASME Code Case works, the dividing point 13 is between 7 and 8. We've subdivided that low 14 susceptibility ranking, broken out in three different 15 bins -- 1 to 3, 4 to 7, and 8 to 10 -- in terms of the 16 susceptibility ranking.
17 There are 60 sites, approximately 60 18 sites, that fall into this low susceptibility ranking 19 because, generally, they're more than 20 kilometers 20 from the coastline. And so there's just no way that 21 they have a high susceptibility ranking. And so for 22 those sites, we would have a maximum inspection 23 interval of 40 years.
24 The Code Case has provisions to adjust the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
30 inspection interval for sites that are 7 and below.
1 We've retained that. We haven't changed that at all.
2 And so the maximum inspection interval for those sites 3
would be 20 years. And currently, the Code Case does 4
not allow revision of the inspection interval for 5
high-ranked sites. Those are 8 to 10 and that would 6
be still be a maximum inspection interval of 10 years, 7
consistent with the Code Case.
8 MEMBER MARTIN: Question. Part of the 9
justification, of course, is the presence of the 10 inhibiting species, the nitrate. Does it not have a 11 degradation potential over this trend?
12 MR. DUNN: Yes, you can now guess nitrate.
13 Yes, you can go through a transformation reaction and 14 you can lose nitrate from the surface, but you're also 15 16 MEMBER MARTIN: I mean, how do you ensure 17 that the inhibiting species is still doing its job?
18 MR. DUNN: So there is a whole lot of 19 there right now. And so we expect that, as we 20 actually do inspections, that would be something that 21 gets periodically monitored --
22 MEMBER MARTIN: Right.
23 MR. DUNN: -- in the course of doing those 24 inspections. But again, even if don't have that, even 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
31 if don't rely on that, we don't have a highly 1
deliquescent salts present at those inland sites.
2 They are too far away from the ocean. So we don't 3
have really aggressive species like magnesium 4
chloride, which can deliquescent at really low 5
relative humidity values, higher temperatures, and 6
give us fast propagation rates.
7 So again, even if we assume that CISCC 8
does occur, it's going to take a long time for that to 9
happen because getting enough salts on the surface, 10 you would have to lose the nitrate. You would have to 11 get the canister temperature low enough to get 12 deliquescence of those salts, and it's, typically, 13 going to be something like sodium chloride, which 14 needs a much higher relative humidity to get 15 deliquescence to occur. And because you're at a lower 16 temperature, crack growth rate is just much slower.
17 So even without the presence of nitrate, 18 we believe we can justify a 40-year inspection 19 interval simply because the timeline for CISCC to 20 initiate and propagate to any meaningful depth, it's 21 going to be a very long-term process, much greater 22 than 40 years.
23 MEMBER MARTIN: So has nitrate always been 24 used on these canisters?
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32 MR. DUNN: No.
1 MEMBER MARTIN: Is that relatively new or?
2 MR. DUNN: So it's not an intentional 3
addition to the canisters. It's just something that 4
happens as a result of a natural process. Again, 5
basically, these chloride salts are good getters of 6
atmospheric pollutants, either in transit to the 7
canister or after being deposited on the canister. So 8
we're not intentionally adding this or promoting that.
9 We're just saying here's what we actually have.
10 We don't have pure chlorides on the 11 canister surface. We've got something that's much 12 more benign than that.
13 MEMBER MARTIN: Okay.
14 MR. DUNN: And I think you mentioned 15 earlier, you were asking about the table, the values 16 of the chloride, the starting values as a function of 17 distance. This is where that is on the slide. You 18 can see how that works out.
19 So we did get some public comments from 20 NEI and NEI members on this Regulatory Guide. They 21 included questions about, you know, the process for 22 accrediting previous inspections to establish a 40-23 year inspection interval, and how a licensee that 24 either didn't have the Code Case in use at the time or 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
33 didn't fully adopt the Code Case could also go to a 1
40-year inspection interval.
2 So we did make some changes to our Staff 3
Regulatory Guidance, which is in Section C of our Reg 4
Guide. We enhanced the references to different parts 5
of the ASME N-860 Code Case, in particular, the parts 6
that address inservice inspection and how the 7
inspection is conducted and the inspection results, 8
and also, you know, the records of reporting that need 9
to take place, documentation of the inspection 10 results, and how one justifies and documents revisions 11 to the inspection interval.
12 We did not specifically address or make 13 changes to address cases where the licensee has not 14 fully adopted the Code Case N-860. There's variations 15 in approved aging management programs from one 16 licensee to another. And we believe that a licensee 17 could do a reconciliation and compare what their aging 18 management program does versus what the requirements 19 are in N-860, but we declined to provide generic 20 guidance on what that would look like.
21 And we did do a regulatory analysis that 22 supports this Code Case.
23 Is that an ACRS member? I think Vicki --
24 CHAIR BALLINGER: Oh, I'm sorry.
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34 MEMBER BIER: Yes.
1 CHAIR BALLINGER: Vicki?
2 MEMBER BIER: Yes. Just a quick question.
3 Was any thought given to doing, say, a 30-year 4
inspection interval rather than 40 years, both from a 5
kind of defense-in-depth perspective -- what if there 6
is something, you know, we missed in this analysis? --
7 but also kind of from a public confidence perspective?
8 Because if there were to be any significant problems, 9
I think there's a different public perception to say 10
- well, we had an inspection scheduled, and 11 unfortunately, this happened just a year or two before 12 our inspection, versus well, we really didn't think we 13 needed to inspect for this.
14 So anyway, that's just a question. I'm 15 not arguing that you should have done it, but I'm 16 curious whether that was considered.
17 MR. DUNN: So the answer to your question 18 is, you know, we didn't specifically consider a 30-19 year inspection interval. Again, our basis for going 20 from 20 to 40 years was that we limited the number of 21 sites that could do that to these very low 22 susceptibility sites, where we know that the present 23 condition of those sites is there is really a very low 24 probability that we'll ever see chloride-induced 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
35 stress corrosion cracking, pitting, or crevice 1
corrosion on any of these systems at these sites.
2 And again, if we ever did have an 3
evolution of that environment where that was possible, 4
that propagation rate would be very slow and it would 5
take a long time for those conditions to develop. So 6
we think we're very comfortable with the 40-year 7
inspection interval simply because of the timeframe 8
that it would take for this to initiate and the amount 9
of time it would take for any meaningful propagation 10 through the canister, all of the canister.
11 I will also point out that we did not 12 change the inspection interval for higher 13 susceptibility sites. Those are consistent with what 14 we have in the ASME Code Case.
15 MEMBER BIER: Okay. Thank you. That 16 explanation makes sense.
17 CHAIR BALLINGER: Hi. This is Ron again.
18 NUREG-2214 allows you to inspect a 19 fraction of the canisters, am I correct?
20 MR. DUNN: That's correct.
21 CHAIR BALLINGER: So this Code Case also 22 allows that?
23 MR. DUNN: Yes. So the way the Code Case 24 works is that, if you're what's termed a low 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
36 susceptibility site, 7 or below, you're looking at one 1
canister at a site. If you're 8 and above, you're 2
looking at two canisters for a given site. And then, 3
there's provisions in that to increase the number of 4
canisters if you have, you know, occurrences of 5
localized corrosion or stress corrosion cracking. So 6
it's basically consistent with an extended condition 7
evaluation that would be in an aging management 8
program.
9 However, if we increase the number to an 10 additional canister, then, thereafter, the Code Case 11 says this is something that the Corrective Action 12 Program for the site has to handle. It needs to be 13 turned over to them to deal with.
14 CHAIR BALLINGER: I'm not answering, but 15 I don't know -- we're multitasking here.
16 What would happen if some event occurs 17 where we end up with an interim storage facility where 18 you have thousands of canisters? Now what happens?
19 MR. DUNN: Okay.
20 CHAIR BALLINGER: Code Case N-860-2, or 21 something?
22 MR. DUNN: So would the --
23 CHAIR BALLINGER: Because the NRC has 24 licensed in theory one of these sites.
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37 MR. DUNN: We've licensed actually four.
1 CHAIR BALLINGER: Four?
2 MR. DUNN: So, well, let's call it three, 3
and none of them have any canisters.
4 CHAIR BALLINGER: Yes.
5 MR. DUNN: So there is an interesting 6
history here and it probably goes beyond what you're 7
asking. For the Waste Control Specialists' Interim 8
Storage Partners Facility in Andrews County, Texas, 9
what that licensee did was to, basically, adopt 10 approved aging management programs of systems that 11 they're planning to locate to their site.
12 So there's a number of those systems that 13 have already gone through renewal. They already have 14 aging management programs. And so that's what they've 15 done.
16 They could so adopt the Code Case, but the 17 way their license works right now is that, you know, 18 they're basically doing inspections that are 19 consistent with the renewed license or renewed CoC.
20 So you have a whole bunch of different 21 systems, right? So you've got things from different 22 locations. And so they might actually be doing quite 23 a bit more than just one canister per site, consistent 24 with what was done before.
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38 We have gotten guidance from OGC that 1
says, well, you know, really, if you're going to go to 2
a 40-year license, if you're going to license an 3
interim storage facility, then, really, what they have 4
to have is a maintenance plan that addresses potential 5
aging effects. Now, they could incorporate an 6
approved aging management program or they could use an 7
approved Code
- Case, but they don't have to 8
specifically adopt an approved aging management 9
program.
10 So I think that that's about the extent 11 that I could answer your question.
12 CHAIR BALLINGER: All of these canisters 13 in this case would already have been in an inspection 14 program before they were transported to this --
15 MR. DUNN: Correct.
16 CHAIR BALLINGER: -- to this facility?
17 MR. DUNN: Right.
18 CHAIR BALLINGER: But it's a lot longer 19 than 40 years. They would be at this facility for a 20 lot longer than 40 years.
21 MR. DUNN: Correct. Correct. And the 22 susceptibility ranking of those sites that we have 23 licensed is going to be low.
24 CHAIR BALLINGER: Yes.
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39 MR. DUNN: It's going to be 1 to 3.
1 CHAIR BALLINGER: Yes.
2 MR. DUNN: Probably 1.
3 CHAIR BALLINGER: Thank you.
4 MR. DUNN: Okay. So for the regulatory 5
analysis, we, basically, determined that, as Tom 6
mentioned, there's a value in issuing this Regulatory 7
Guide. There is some cost to the industry to 8
implement this Regulatory Guide, the guidance in this 9
Regulatory
- Guide, adopting the Code Case and 10 potentially looking at some type of amendment 11 application.
12 There is a cost to the NRC, a relatively 13 minor cost to the NRC in terms of developing this 14 Regulatory Guide and actually implementing it, if we 15 have to review some amendment applications. But, 16 overall, there's a net savings to the industry from 17 inspections that would not need to occur at those low 18 susceptibility sites.
19 We also determined that the Reg Guide is 20 justified from a quantitative standpoint because, you 21
- know, there's benefit to having a
consistent 22 inspection methodology for these systems. There is a 23 way that the inspection results are collected, 24 collated, and then, can be compared and shared with 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
40 different system users.
1 And then, there is also value in having an 2
approved Code Case and a methodology for some of the 3
future storage system renewal applications that we 4
expect in the coming years. And there's a number of 5
those that still have not come in for renewals.
6 All of our specifically licensees, except 7
for the very recently licensed facilities, the HI-8 STORE facility and the WCS ISP facility, all of those 9
other specifically licensees that are in operation 10 have already gone through renewal, but there still are 11 some CoCs that have not.
12 So our timeline and next steps. We 13 started the development of this Regulatory Guide in 14 February, issued it for public comment in July.
15 Addressed the comment responses and made revisions to 16 our Reg Guide in November. It's December now. We're 17 here at the ACRS Subcommittee meeting.
18 Yesterday, we received notification from 19 OGC that they have determined they have no legal 20 objections to our Regulatory Guide. So we've passed 21 that.
22 We would like to publish the Reg Guide as 23 soon as we can, but we will wait for the ACRS decision 24 before we go forward.
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41 Finally, some acknowledgments to staff 1
that made some very significant contributions to this 2
effort, going back a long time, both in terms of 3
development of the Code Case and also the development 4
of the Regulatory Guide and the regulatory analysis.
5 And that's my last slide.
6 MEMBER MARTIN: A couple of questions.
7 And I have no background in this, to be perfectly 8
honest, but I do have a curiosity.
9 You identified three plants -- SONGS, 10 Turkey Point, St. Lucie. Presumably, they all have 11 your susceptibility criteria, Z greater than 7, right, 12 or greater than or equal to 7? Are there other plants 13 that are in that range?
14 MR. DUNN: Yes. There are five.
15 MEMBER MARTIN: Oh, okay. And who are 16 those other two sites?
17 MR. DUNN: It's --
18 CHAIR BALLINGER: Pilgrim, Millstone.
19 MR. DUNN: I'm not going to pull that off 20 the top of my head.
21 CHAIR BALLINGER: Millstone. I think it's 22 Pilgrim and Millstone.
23 MR. DUNN: I believe so. Maybe.
24 CHAIR BALLINGER: What about Seabrook?
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42 MR. DUNN: I'd have to look it up. I'd 1
have to look it up.
2 MEMBER MARTIN: The stress corrosion 3
cracking that's been observed in the three plants, 4
when were they first observed? I mean, are we talking 5
after --
6 MR. DUNN: Yes, so that --
7 MEMBER MARTIN: Ten years? Twenty years?
8 I mean, just kind of get --
9 MR. DUNN: In terms of operation?
10 MEMBER MARTIN: Uh-hum.
11 MR. DUNN: Yes, I actually presented this 12 a long time ago and I don't remember. That's a good 13 question. I should have looked this up.
14 MR. BOYCE: This is Tom Boyce.
15 If you look at the IN 2012-20, it does 16 provide the timeframes. And I think for Turkey Point, 17 and it might be St. Lucie, it was 25 years before it 18 was manifested and detected.
19 MEMBER MARTIN: Okay.
20 MR. BOYCE: And then, the shortest 21 timeframe is 16 years. I'm not sure which plant that 22 was.
23 MEMBER MARTIN:
Obviously, good 24 methodology with high uncertainties, you want to be 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
43 deterministic in it. So 10 years would be consistent 1
with that sort of thing.
2 CHAIR BALLINGER: You had more than one 3
question?
4 MEMBER MARTIN: I think I asked them both.
5 CHAIR BALLINGER: Oh.
6 MEMBER MARTIN: But don't ask me what my 7
first one was.
8 Oh, right, that's right. That's right.
9 The number of plants.
10 (Laughter.)
11 CHAIR BALLINGER: Okay. Other members, 12 questions?
13 MEMBER SUNSERI: This is Matt.
14 MR. DUNN: Oh, Walt? Oh, Matt?
15 CHAIR BALLINGER: It's Matt.
16 MEMBER KIRCHNER: No, Matt's first.
17 MEMBER SUNSERI: Just a quick question.
18 In light of the rigor of the analysis and everything, 19 are there any efforts or a plan to just incorporate 20 this guidance into the ASME Code and not to take the 21 exception through the Code Case?
22 MR. DUNN: So that has been discussed. I 23 think that it's now a working group that developed the 24 Code Case. That working group has continued to meet.
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44 I think they're looking at this with a lot of interest 1
to see what happens and whether or not we're going to 2
be able to issue this Reg Guide.
3 There is talk of revising this Code Case 4
to do exactly that, to incorporate this information 5
into the Code Case and revise this Code Case to be, 6
basically, N-860-1.
7 MEMBER SUNSERI: Thank you.
8 CHAIR BALLINGER: Did I hear Walt?
9 MEMBER KIRCHNER: Yes. Thank you, Ron.
10 Where does Palo Verde fit into this 11 ranking?
12 MR. DUNN: I think Palo Verde is one of 13 those plants that actually scores zero, but it might 14 wind up being a 1 because you can't be a zero.
15 (Laughter.)
16 MEMBER KIRCHNER: Oh, okay.
17 MR. DUNN: And the way you score a zero, 18 by the way, is you're more than 20 kilometers from a 19 coast. You're not in close proximity to a cooling 20 tower, although Palo Verde is. So, yes, they're 21 probably not a zero.
22 But there are plants that, basically, sum 23 to zero. So you can be more than 20 kilometers from 24 a coast --
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45 MEMBER KIRCHNER: Right.
1 MR. DUNN: -- a thousand meters from a 2
cooling tower, and basically, low humidity.
3 MEMBER KIRCHNER: Okay. And then, Rancho 4
Seco, where does that come in?
5 MR. DUNN: Hang on. You know what? You 6
know what? We're making a list.
7 MR. RUBY: Hey, this is Dan Ruby.
8 I've got it's a 2.
9 MR. DUNN: Yes. So actually I think that 10 what I'll refer you to is our Regulatory Guide. We've 11 listed all of those 60 plants that --
12 MEMBER KIRCHNER: Okay. I'll go back and 13 check.
14 MR. DUNN: -- that rank 1 to 3. And we 15 actually provide what we think is our estimated 16 ranking of that. And so, wait. Did somebody say 2?
17 MR. RUBY: Yes. That was Dan Ruby. It's 18 a 2.
19 MR. DUNN: Yes, Palo Verde is a 1. You 20 said Rancho Seco?
21 MEMBER KIRCHNER: Okay. Yes. Thank you.
22 Yes.
So on
- deposits, especially in marine 23 environments, do you have any problems at these sites?
24 Have you observed any problems with birds?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
46 MR. DUNN: Any problems with birds?
1 MEMBER KIRCHNER: Are the canisters 2
running too hot for the birds to use them as a 3
repository?
4 (Laughter.)
5 MEMBER KIRCHNER: A depository?
6 CHAIR BALLINGER: At least we could get 7
something licensed.
8 MR. DUNN: Okay. Well, our image here, my 9
image here is not very good.
10 But in the top right here of this 11 vertically-oriented system, there's a conduit that, 12 basically, has a thermocouple in it that goes into the 13 outlet vent of this system.
14 MEMBER KIRCHNER: Right.
15 MR. DUNN: And the rest of that outlet 16 vent is covered with what they call a bird screen.
17 MEMBER KIRCHNER: Right.
18 MR. DUNN: So there are specific measures 19 taken to prevent small animals from using this as a 20 site.
21 MEMBER KIRCHNER: Right.
22 MR. DUNN: So those are universally used 23 in the dry storage systems that we've licensed.
24 MEMBER KIRCHNER: Okay. Thank you.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
47 Would the bird poop add nitrates?
1 MR. DUNN: I have no idea.
2 (Laughter.)
3 CHAIR BALLINGER: It may be an argument 4
for continuing to use fossil fuels, however.
5 (Laughter.)
6 CHAIR BALLINGER: Okay. Well, thank you 7
very much. Let's see, we're way ahead of schedule, 8
which is good.
9 So, Joe, I don't think we need to take a 10 break. Do you want to give us your presentation?
11 MR. FALDOWSKI: Yes. I'm ready to go.
12 Next slide. Thank you. So good 13 afternoon. My name is Joe Faldowski. I'm a Senior 14 Program Manager for the Used Fuel High Level Waste 15 Program at EPRI.
16 And so I'm pleased to be here this 17 afternoon to make a presentation for you that will 18 mostly parallel what you just heard from Darrell, but 19 take a little bit of a different approach in terms of 20 describing the research and the data that has been 21 generated from EPRI and others around this Code Case.
22 So if we could go to the next slide?
23 The brief outline of what I will talk 24 about is a brief background and history of the issue, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
48 and really focus on the high-level milestones 1
associated with that.
2 I'm going to go into a little bit more 3
detail about the site rankings that Darrell has 4
alluded to many times in his presentation.
5 And I'm also going to talk to you about 6
the canister ranking methodology that's associated 7
with that, that helps with the selection of the 8
canister that would be inspected on a particular 9
10 A little bit about the latest research 11 that has been
- done, mainly by the National 12 Laboratories, on this issue of CISCC, and then, what 13 EPRI sees as the next steps and the path forward, 14 along with a couple of conclusions, and then, whatever 15 discussion we need to have.
16 So moving to the background and a brief 17 history, you can just go to the next slide.
18 As has been already noted, I think most of 19 these milestones have been discussed.
20 The Information Notice in 2012-20 21 highlighted CISCC as an issue. Darrell provided a 22 picture of the Koeberg site.
23 The three small pictures that I've 24 provided in the righthand upper portion of this slide 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
49 are actually all four sites that were noted in the 1
original Information Notice. What you can see 2
commonly among those pictures is that there is a lot 3
of blue. These sites are right on the ocean with the 4
marine environment and breaking waves. So that's 5
where we started.
6 In 2015, EPRI issued its Technical Report 7
on the Susceptibility Assessment Criteria for CISCC, 8
and this is where the ranking methodology comes from 9
for these canisters and for the sites. This takes 10 into account a number of factors that can be 11 diagramed, as shown. I know you can't read it, but 12 they're on the bottom right, and we'll talk about what 13 those factors entail and how they're scored in a few 14 minutes.
15 In 2020, five years after that guidance, 16 Code Case N-860 was approved by ASME, and then, 17 earlier this year, the Draft Guide 3058 was published 18 in The Federal Register for public comment.
19 It's important to note -- and may be hard 20 to read on the lefthand side -- we had one Technical 21 Report from EPRI that was issued in 2017 which 22 provided guidance for aging management programs. And 23 part of that guidance was advocating for applying a 24 learning approach to the problem as more information 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
50 becomes available.
1 And so it's important, as we go through, 2
that we focus on what we've been learning since 2012.
3 And I'll also note that multiple organizations 4
continue to do research and collect data 5
experimentally, analytically, and operationally 6
through inservice inspections on these systems. To 7
date, no inspections resulted in additional actions 8
beyond trending, but I will speak to you more about 9
the ongoing research and what can be done going 10 forward, and what we recommend being done going 11 forward.
12 Before I do that, let me continue with a 13 little bit of background on the technical basis and 14 where the research is focused.
15 The central issue that we're talking about 16 is chloride-induced stress corrosion cracking. That 17 happens under three specific conditions and the 18 convergence of those conditions. Two of those 19 conditions are really not under question.
20 The first of susceptible material, we know 21 that austenitic stainless steels are susceptible to 22 CISCC. In that material, there must be adequate 23 tensile stress to create an environment for CISCC. We 24 also know that that tensile stress exists in these 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
51 canisters, particularly in the heat-affected zones 1
near the welds. And all of these systems have welds.
2 And so that leaves us with the main 3
research questions around the canister environment.
4 And those questions can be summarized as: what is the 5
proximity to sea spray, cooling tower spray, and road 6
salt -- effectively asking the question, what is in 7
the atmosphere to begin with? And then, the questions 8
of high humidity, rain, dust accumulation, time, and 9
declining surface temperature, which, basically, 10 centers around the question of, what is in the 11 atmosphere, how much of that can be deposited on the 12 canister surface in a deleterious way?
13 And so this is where the main research 14 questions have centered. Those research questions 15 have been answered in a research framework which 16 guides the work. Mainly today --
17 MEMBER MARTIN: Excuse. I just had a 18 question on the previous slide.
19 MR. FALDOWSKI: Sure.
20 MEMBER MARTIN: The previous slide. Yes.
21 The crevices, surface roughness, and pits.
22 So if you apply the weld, and then, maybe do some 23 finishing to kind of smooth this -- I mean, looking at 24 the pictures that Darrell had, it looked like maybe 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
52 there was some finishing on those welds, maybe to 1
reduce/minimize the presence of crevices. I mean, 2
would you expect that to improve the situation of 3
susceptibility?
4 MR. FALDOWSKI: And so a couple of things 5
there. First, the pictures that Darrell showed were 6
surface prepared for penetrant testing. So they 7
weren't the as-fabricated condition. Those were post-8 prepared for that penetrant examination.
9 But, in general, the welds may be ground 10 flush on these systems or they may not be. The issue 11 is not so much the grinding of the weld being flush.
12 It's the stress that's induced by the welding and the 13 cooling of the weld puddle. So you get a 1-inch area 14 on either side of the weld that has adequate stress to 15 produce an environment --
16 MEMBER MARTIN: So maybe a surface 17 finishing of such would have a minimal effect on this 18 or benefit?
19 MR. FALDOWSKI: Right. So then in terms 20 of the framework under which the research has been 21 conducted, there are four pillars to this framework.
22 The one we're talking about primarily 23 today is the first pillar, which is the probability, 24 which is the likelihood that CISCC will occur and 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
53 cause a confinement breach.
1 The second pillar is around consequence, 2
which is the magnitude and timing of consequences of 3
that confinement breach.
4 These two pillars taken together, we may 5
say, are about improving our understanding of the 6
phenomena. They inform the next two pillars, which 7
are the actions we may take in response to something.
8 The third pillar is an inspection program 9
which covers the robustness of the inspection program 10 to detect significant corrosion. And this is what 11 we're talking about in terms of the visual inspections 12 that have been done to date on the inservice 13 canisters.
14 And then, finally, a mitigation and repair 15 pillar, which asks the question, if we detect 16 significant corrosion, do we have the tools available 17 to address that corrosion and correct it?
18 These four pillars taken together are the 19 definition of what an effective aging management 20 program would look like. Again, we're talking mainly 21 about the probability pillar today, although I will 22 come back and have a few words for you at the end 23 about the other three pillars as well.
24 Let me give you another sort of milestone 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
54 view of some of the published results that have been 1
helping our learning along the way. There are four 2
reports, in particular, that I would like to call to 3
your attention and I'm going to provide a couple of 4
quotes from each of these reports that illustrate the 5
learning that we've been gaining over the years.
6 The first one, after the Information 7
Notice was issued in 2012, EPRI published an FMEA on 8
Welded Stainless Steel Canisters for Dry Cask Storage 9
Systems. In that FMEA, is started to set the 10 groundwork for what we've seen in terms of 11 susceptibility.
12 It said, at least in part, ISFSIs without 13 a significant source of chlorides are expected to have 14 a much lower overall susceptibility to degradation 15 when compared to marine sites with significant 16 chloride deposits on canister shells. It further said 17 non-marine ISFSIs are expected to be much less 18 susceptible to material degradation than marine sites, 19 So that was the conclusion of the FMEA in 2013.
20 In 2014, EPRI published the results of the 21 very first dry canister inspection. That was done at 22 Calvert Cliffs. And that report noted that both 23 canisters that were inspected during that inspection 24 campaign had substantial amounts of dust, particularly 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
55 on the top surface, and a few small rust blooms were 1
observed on the lead canister; however, the general 2
condition of both canisters was good, with no signs of 3
gross degradation.
4 It further noted from the analysis of the 5
accumulated dust, that chemical analysis results 6
confirmed very low chloride concentrations, less than 7
0.1 grams per square meter and that the sample 8
compositions resembled inland rainwater rather than 9
seawater, indicating that the environment is more 10 inland than marine.
11 I will note that Calvert Cliffs is located 12 on the Chesapeake Bay. So it is in a bay with 13 saltwater, but no breaking waves in that location.
14 In 2016, EPRI published its second report 15 on canister inspections, this time from the Diablo 16 Canyon site. This site, as you know, is on the 17 California coast at an elevated location above the 18 coast.
19 This report noted that the chemical 20 analysis confirmed very low chloride concentrations, 21 less than 5 milligrams per square meter, despite being 22 located close to the ocean. It further noted sea salt 23 aerosols were identified in some of the dust samples, 24 indicating that the chlorides from the ocean are being 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
56 transported inside the overpack to the canister 1
surface, although very slowly, as indicated by the low 2
concentration.
3 In parallel with that report, Sandia 4
National Lab was also working on a report, which is 5
the fourth one that's highlighted there, where they 6
compared the Diablo Canyon to the Hope Creek 7
compositions. Just to note, Hope Creek is on the 8
Delaware River, just upstream of the Delaware Bay.
9 Part of that report says soluble salt 10 phases were minor component of the Hope Creek dusts, 11 and were compositionally similar to inland salt 12 aerosols at Diablo Canyon. Sea-salt aerosols, 13 occurring as aggregates of sodium chloride and 14 magnesium sulfate, were a major component of the dust 15 samples. The differences in salt composition and 16 abundance for the two sites are attributed to 17 differences in proximity to the open ocean and wave 18 action.
19 So that was the early work that confirmed 20 what was generally stated earlier in the FMEA.
21 This led us to the next report -- yes, we 22 can move on -- the next report, which is the 23 Susceptibility Rankings Report. And here, I will 24 discuss a little bit more detail, although I think 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
57 Darrell has done a very good job describing how this 1
works.
2 The site susceptibility,
- first, is 3
quantified by calculating a ranking factor called 4
ZISFSI. ZISFSI is composed of three component 5
factors: an initial ranking based on the marine 6
aerosol, and then, an adjustment factor for local 7
sources of chloride, like salted roads or saline 8
cooling towers, and then, an adjustment factor for the 9
absolute humidity where the site is.
10 The site ranking can range from 1 to 10.
11 The main chloride starting factor ranges from 1 to 9.
12 The adjustment factor for local sources of chloride 13 can range from minus-1 to 5, and the absolute humidity 14 adjustment factor can range from minus-1 to plus-2.
15 And those are calculated based on a number of factors.
16 So ZISFSI, as it's calculated, is a 17 measure of chloride content potentially available to 18 accumulate on the canister without regard to the type 19 of chloride molecule or the conditions inside the 20 overpack. This ranking, then, is a stable ranking 21 over time.
22 MEMBER MARTIN: Just a nit, based on what 23 you said about the three terms. If you took the 24 maximum of the three, you would be above 10?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
58 MR. FALDOWSKI: That is correct. And so 1
the ranking --
2 MEMBER MARTIN: Do you cap it? Or, I 3
mean, is it just --
4 MR. FALDOWSKI: Yes, so the ranking 5
methodology in that report says that, if you arrive 6
above 10, you truncate the ranking at 10. That's well 7
observed.
8 So if you look at these factors -- and I 9
put this table here not so that you can read it, 10 obviously, but to show that you can put each factor in 11 a column; do a simple calculation, and come up with 12 the ZISFSI ranking for all the sites, as, again, this 13 is stable over time, and these numbers are exactly 14 what Darrell presented to you a few minutes ago.
15 The ZISFSIs between 1 and 3 are 60. The 16 ones between 4 and 7 are six. And the ones between 8 17 and 10 are five. And I ask you to excuse my typo on 18 the range indicators there.
19 The last column is just an indication of 20 the age, how long the systems have been on the ISFSI 21 pad. So that's the site susceptibility ranking.
22 Beyond the site susceptibility ranking, 23 the document also has a methodology for calculating a 24 canister susceptibility. This is on the particular 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
59 ISFSI pad. You can calculate the susceptibility of 1
individual canisters by calculating a ranking factor, 2
again, that ranges from 1 to 10 and is different 3
depending on the configuration of the canister.
4 So there's a horizontal canister ranking 5
and a vertical canister ranking. The components of 6
those are the same. You have a deposition factor, a 7
material factor, and a heat factor that depends on the 8
heat load of the system when it was originally loaded.
9 So this susceptibility ranking can range 10 from 1 to 10. The deposition factor, which is based 11 on the decay heat, the airflow, the deposition 12 velocity, and other factors, can range from 1 to 5.
13 The material, which is a range of materials of 14 construction of these systems, either 304 stainless 15 steel, 304L, 316, or 316L, can range from a factor of 16 zero to 3. And then, the heat load can range from 17 zero to 2 -- to aggregate these into your total 18 canister susceptibility ranking.
19 Because the decay heat changes with time, 20 the canister susceptibility also changes with time.
21 So this one is not stable in time. And on the next 22 slide, I show you how this can vary.
23 This chart, for horizontal systems on the 24 left and vertical systems on the right, shows you, for 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
60 a constant heat load and constant material, how the 1
canister susceptibility may evolve.
2 On the top left, you have a horizontal 3
canister susceptibility ranking with a ZISFSI rating 4
of 8, and on the bottom, with a ZISFSI rating of 5.
5 So you can see that, for lower site susceptibility, 6
your canister susceptibility is also lower and takes 7
longer to reach its maximum susceptibility.
8 CHAIR BALLINGER: This is Ron Ballinger.
9 I think San Onofre were shot peened. So 10 the material thing, if you have some weld mitigation 11 that's applied at the construction stage, does that 12 take these pretty much out of the area?
13 MR. FALDOWSKI: I would say you would have 14 to go back to the Venn diagram. And what you're doing 15 by shot peening is relieving the stress. So you're 16 removing one circle of that Venn diagram. So you 17 would be outside of the realm of where CISCC can 18 happen.
19 CHAIR BALLINGER: So that canister would 20 be a zero?
21 MR. FALDOWSKI: Well, I --
22 CHAIR BALLINGER: Because I think newer 23 ones are going to be shot peened or --
24 MR. FALDOWSKI: Right.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
61 CHAIR BALLINGER: -- some kind of --
1 MR. FALDOWSKI: Because the rankings don't 2
take into account stress relieving during fabrication, 3
it can't be a zero. So that was not considered in 4
2015, when these rankings were developed.
5 MR. DUNN: This is Darrell Dunn, NRC.
6 So the canister is the Holtec UMAX system 7
at San Onofre and it has been laser-peened.
8 CHAIR BALLINGER: Or laser-peened? Okay.
9 MR. DUNN: Those are the canisters that 10 have undergone stress mitigation. The licensee at 11 that site did that for, basically, asset management 12 and they did not intend to take credit for that in any 13 aging management program. They did it because they 14 wanted to have the best system that they could, to not 15 have issues with chloride-induced stress corrosion 16 cracking. So that's what they did.
17 So in the Code Case itself, the Code Case, 18 again, is limited and I believe there's something in 19 the Code Case that, basically, talks about, you know, 20 it doesn't consider, it doesn't include things that 21 are either not exposed to an ambient air environment 22 in a sheltered environment. So there are some systems 23 like that. There are systems that don't use stainless 24 steel. And I believe it also addresses the mitigation 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
62 issue. It doesn't address canisters that have 1
undergone residual stress mitigation.
2 MR. FALDOWSKI: Thanks. So we go on to 3
look at some of the latest research and this is 4
generated by the National Labs at PNNL and Sandia, who 5
have done substantial work on accelerated corrosion of 6
stainless steels in the presence of chlorides. This 7
represents some of the newest information that we have 8
on chloride composition information.
9 What this really indicates is that, for 10 the environmental factors, there are several things 11 that are very important: the chloride molecule, the 12 stainless steel type, and the presence of nitrate as 13 well in that material.
14 Looking at this chart, if you have 304 15 material, it is susceptible to chloride-induced stress 16 corrosion cracking, according to this laboratory work.
17 However, when you move to 304L or 316L, you do not 18 have susceptibility or they have not found 19 susceptibility in a sodium chloride environment, nor 20 have they found susceptibility to stress corrosion 21 cracking in a magnesium chloride environment with 22 small amounts of nitrate added. This puts the vast 23 majority of inservice canisters into one of these 24 green boxes, where the laboratory test confirmed that 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
63 CISCC susceptibility is low.
1 So moving on to next steps, in July, the 2
last week of July/the first week of August, EPRI 3
hosted a working meeting to look at the current state 4
of aging management research; what has been done to 5
date, and what can be concluded from the results, 6
keeping in mind that this research has been going on 7
for more than 10 years.
8 The outcome of this meeting was intended 9
to be a roadmap for what could be done in the next two 10 years to close out on some of the issues.
11 Participation was by invitation only, but the list of 12 invited guests was developed by the ESCP Subcommittee 13 and task group needs, and ended up being 35 attendees 14 from utilities, vendors, the NRC, DOE, National 15 Laboratories, NEI, universities, EPRI, and a few other 16 contracting organizations that have knowledge in this 17 area.
18 And that outcome will be the documentation 19 of what has been done and the roadmaps. I'm going to 20 show you some examples of that. It will be published 21 in the coming months.
22 But before I show you that information, 23 some general consensus arose from this working meeting 24 that I thought was worth sharing as well. There 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
64 points of general consensus:
1 That all of the guidance documentation 2
from EPRI, regulatory information from the NRC, and 3
the ASME documentation on dry storage system aging 4
management documents created a conservative approach, 5
based on the available information at the time that 6
they were issued. So there was no risk to identify 7
that would make anything in the current realm non-8 conservative.
9 There was general consensus that the risk 10 of CISCC at inland sites is low.
11 And there was general consensus that there 12 is still room for improvements that could be made on 13 specific topics, based on a learning approach, as 14 recommended in the 2017 EPRI guidance document.
15 And these results will be published, as I 16 said, in the coming months.
17 In terms of aging mechanisms, which really 18 is the probability pillar from what I showed you at 19 the beginning of the presentation, these are the areas 20 where the working meeting felt like progress could 21 still be made.
22 One is the inspection data review. There 23 are many inspections that have been done now, and that 24 data is being collected in a database. The meeting 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
65 felt like it was a good time to step back and look at 1
all of this data that's been collected to date, and 2
then also apply the learning that we've gained over 3
the 10 years of research to look at updated material, 4
environmental susceptibilities. For example, taking 5
into account the increased susceptibility due to 6
magnesium chloride over sodium chloride, which was not 7
taken into account in the early days when this work 8
was begun.
9 That may result in a review of the 10 susceptibility rankings that we talked about just a 11 few minutes ago, looking at a number of factors that 12 might be improved that I think I've already mentioned.
13 And so that may result in a difference or change of 14 those susceptibility rankings.
15 And then, the other thing is to look at 16 crack propagation models and potentially site-specific 17 crack propagation models. Because the current 18 equations that are used to look at crack propagation 19 to set inspection intervals are based on temperature 20 only. And now, we have better information that could 21 take into account other factors to improve those 22 models and the time, the rate of cracking, should it 23 occur. So these are areas where we think we could 24 improve.
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66 On the next slide, I show just an example 1
to say that the working meeting also considered the 2
other pillars of aging management and noted that there 3
was work that could be done and beneficial work in the 4
area of consequence and also in the area of inspection 5
and mitigation.
6 I will note that significant progress has 7
been made in the inspection and mitigation areas.
8 Visual inspection equipment is, I'll say, routinely 9
deployed now in installed systems to look at the 10 surface of the canister. Eddy current and UT 11 technology for enhanced inspections is nearing 12 deployable stage, should it be needed. It would be 13 able to be deployed into the canister overpack to look 14 at the surface, to either confirm the presence of 15 cracking or to size cracks, if they are found.
16 Also, we believe that there is some 17 benefit to collecting additional data, especially at 18 those near-marine sites and marine sites to look at 19 the composition of the environment that's on those 20 canisters.
21
- Finally, mitigation.
The leading 22 candidate for that is cold spray, and there is an ASME 23 Code Case, N-927, that is currently in develop to 24 cover mitigation, should it be needed. And it's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
67 likely that that Code Case will be also tied at some 1
point to Code Case N-860 as a following step.
2 Okay. So that's the research that's 3
happening. Let me give you just a couple of 4
conclusions to summarize what I've said.
5 MEMBER DIMITRIJEVIC: I have a question 6
about the previous slide.
7 MR. FALDOWSKI: Sure.
8 MEMBER DIMITRIJEVIC: I'm sort of curious, 9
do you -- because this is a risk-informed approach, so 10 you're doing risk ranking. And you know, I was 11 wondering, are you planning to make consequences as 12 part of that ranking and have different consequences 13 among the canisters?
14 MR. FALDOWSKI: Consequence does not feed 15 directly into the ranking. Consequence can be used to 16 inform decisionmaking, if it's needed. So I don't 17 think there was any proposal that consequence would be 18 fed into the ranking methodology.
19 MEMBER DIMITRIJEVIC: You know, in 20 general, risk for my site, the risk is a combination 21 between consequence and the degradation mechanisms.
22 So like for the typical site, that's a combination of 23 both. That's why I was curious.
24 So you are just going to use the 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
68 degradation mechanism as a base for it?
1 MR. FALDOWSKI: That's the current 2
methodology, yes, and we're not proposing a different 3
way to --
4 MEMBER DIMITRIJEVIC: Okay. Okay. All 5
right. Thanks.
6 MR. FALDOWSKI: Okay. So conclusions.
7 The initial concern for stainless steel aging 8
management was targeted at marine sites. Subsequent 9
research and operating experience has validated that 10 inland sites have a much lower potential to be 11 impacted by CISCC.
12 Greater understanding of the chloride 13 molecules, materials, and inhibitors has been 14 developing over the past several years. These reports 15 also support the conclusion that inland sites are less 16 susceptibility to CISCC.
17 We believe that, as learning continues, 18 there may be data to support further reductions in 19 inspection frequency at near-marine sites, as I 20 highlighted the results from early inspections at 21 places like Hope Creek and Calvert Cliffs.
22 And significant progress has been made in 23 the areas of inspection and mitigation with the 24 primary research expected to wrap up within the next 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
69 two years.
1 And that concludes my remarks today.
2 MEMBER MARTIN: A couple of questions.
3 One, curiosity again. If you know, in the history of 4
these canisters, for any reason, has there been a 5
situation where a canister had to be replaced and the 6
fuel removed?
7 MR. FALDOWSKI: No. No, no.
8 MEMBER MARTIN: Okay. The second question 9
-- and maybe this goes back to Darrell -- the license 10 term on these canisters is what?
11 MR. DUNN: Darrell Dunn, NRC. So 12 initially as part of our regulations in 10 CFR Part 13 72, a specific license and a Certificate of Compliance 14 that was used by a general licensee was 20 years.
15 That was changed in around, I think, the 2011 16 timeframe to be 40 years. So the initial license 17 period can now be up to 40 years; the same for 18 specifically the licensed ISFSI and a CoC. Renewals, 19 even with the initial 20-year license period, can be 20 up to 40 years.
21 So a lot of the systems that we have now 22 where we're talking about they're in the period of 23 extended operation, they've gone through renewal, they 24 had an initial 20-year license or an initial 20-year 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
70 CoC, and they've been renewed for a period up to 40 1
years.
2 MEMBER MARTIN: Okay. But where I was 3
going with this, of course, is, if you have a 40-year 4
schedule, but if someone is coming in for renewal, you 5
would have them do this inspection?
6 MR.
DUNN:
So we have regulatory 7
requirements for both specifically licensed ISFSI or 8
a CoC that uses 10 CFR 72.42 and for CoCs in 10 CFR 9
72.240, that they have to have aging management 10 programs to address any credible aging effects that's 11 not able to be addressed in a time-limited aging 12 analysis.
13 And so every renewal that's come in for 14 either a specifically licensed ISFSI or a CoC that 15 uses welded austenitic stainless steel canisters has 16 come in with an inspection. Basically, it is, 17 essentially, an inspection program for that welded 18 stainless steel canister type looking for chloride-19 induced stress corrosion cracking or localized 20 corrosion.
21 MEMBER MARTIN: And just to understand 22 what you said there, the question really is, when does 23 the clock start, right?
24 MR. DUNN: For?
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
71 MEMBER MARTIN: Yes, for the inspection 1
period. And if sites have had just 20 years and now 2
they're going for 40 years, wouldn't you want to have 3
that inspection, and then, 40 years? You wouldn't go 4
and say all right, well, now it's 40 and you're not 5
high-risk. We're just not going to look at it until 6
20 years from now.
7 MR. DUNN: It's part of the renewal. So 8
when they go through renewal at 20 years for anything 9
that we have right now is going through renewal, 10 they're doing that inspection when they're crossing 11 over into the period of extended operation.
12 MEMBER MARTIN: Okay. So the clock starts 13 with that renewal?
14 MR. DUNN: Right. Now, each site has its 15 own timeline, right? So when we have a CoC that's 16 issued in, let's say, 2000, now that CoC went through 17 renewal in 2020, 20 years later. But if there is a 18 licensee that didn't start using that system until 19 2010, their 20-year clock is 23. So they don't 20 actually have to do -- they're not in that period of 21 extended operation until they hit that 20-year mark 22 for their site.
23 MEMBER MARTIN: Sure.
24 MR. DUNN: Right?
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72 MEMBER MARTIN: Sure. Understood. All 1
right. Thanks.
2 MR. DUNN: And with respect to the 3
canisters, no, we have never had a canister that had 4
to be removed and reopened. There have been bolted 5
lid systems that have had had seal issues, where they 6
have the ring seals, metallic ring seals. They are 7
monitored and there have been a number of those that 8
have, basically, had corrosion-related issues of the 9
sealed ends and they had to be pulled out of service, 10 reflooded, and fuel removed, the canister repaired.
11 The solution to that was to change the seal material.
12 But, you know, unrelated to your initial 13 question --
14 MEMBER MARTIN: Sure.
15 MR. DUNN: -- but just to point out that 16 there have been systems and we've had to go through 17 this process. They're just not the welded austenitic 18 stainless steel canisters.
19 CHAIR BALLINGER: So in one sense, that 20 actually good news, that you had some that you had to 21 put back in the pool, de-fuel, fix, and put back 22 together. Because that means that it's possible to 23 take a canister off the pad that leaks, put it back in 24 the pool, de-fuel it, and fix it -- in theory.
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73 MR. DUNN: In theory.
1 (Laughter.)
2 CHAIR BALLINGER: In theory. It's been 3
done, right?
4 MR. DUNN: Not for a canister, but it's 5
the concept of reflooding and removing the fuel from 6
the canister has certainly been done multiple times.
7 CHAIR BALLINGER: I'm sure there's been a 8
lot of angst, but --
9 MR. DUNN: It's fairly good (audio 10 interference).
11 CHAIR BALLINGER: Is that the last -- oh, 12 I'm sorry.
13 MR. FALDOWSKI: Yes, that concludes my 14 remarks.
15 CHAIR BALLINGER: Okay. Okay. So again, 16 I would propose that we just keep going because, then, 17 we can finish a bit early.
18 So, Mark?
19 MR. RICHTER: Okay. Thank you very much.
20 And I will proceed. I think my 21 presentation is relatively short compared to the 22 others, but I don't want to get too far ahead of 23 myself. We haven't got to questions yet.
24 But, in any case, I'm Mark Richter. I'm 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
74 a Technical Advisor at NEI, Nuclear Energy Institute, 1
working in the Decommissioning and Used Fuel Section.
2 And as this slide, my title slide, 3
indicates, I'm going to be talking about NEI's and 4
industry's perspective on the Code Case and the 5
pending implementation in the Reg Guide.
6 I'm not going to dwell or restate a lot of 7
the technical background or some of the historical and 8
engineering information that both Darrell and Joe have 9
gone through. I think they did an outstanding job 10 providing the sort of technical basis supporting where 11 we hope to go with the Code Case and the Reg Guide, 12 but really want to, as the title would suggest, offer 13 our perspective on the benefits and impacts and just 14 how industry views the possibility of this Reg Guide 15 being available for us to use.
16 Before I go beyond this slide, I just want 17 to take a moment and let you know that Brian 18 Gutherman, a long-time consultant both to NEI and 19 industry on spent fuel dry storage issues, and as it 20 relates to today, in particular, aging management 21 programs, has joined virtually. There may be times 22 during my presentation where he might wish to add some 23 additional commentary at certain points. And I just 24 wanted to make you aware that he may be jumping in to 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
75 add something, but that will be determined as we go.
1 So next slide. Okay. One of the things 2
that I think we need to consider, at least again from 3
industry's perspective, and in order to move forward 4
with confidence with the Reg Guide, you know, we want 5
to look back and recognize what the historical context 6
is of spent fuel dry storage.
7 We had nearly four decades, something 8
approaching 40
- years, of safe operation, and 9
inspections to date have really not revealed any 10 evidence of a level of corrosion that would look like 11 cracking or anything that would compromise the 12 confinement. If anything, it's evidence of minor 13 oxidation or staining that might be associated with 14 ambient moisture.
15 And it's this sort of long and safe 16 operating history, inspection observations to date, 17 along with this technical basis that you've heard 18 about earlier, that really bolsters confidence from 19 our perspective in the ability to use the Reg Guide.
20 And the other thing from industry's 21 perspective that we find very appealing about this, we 22 have an aging management, a learning-based aging 23 management program that's defined in our guidance 24 document, NEI 14-03. And it was subsequently endorsed 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
76 by NRC in Reg Guide 3.76.
1 Philosophically and programmatically, this 2
Reg Guide falls right in line with that learning aging 3
management philosophy. So it's very consistent with 4
what industry has developed and implemented to date, 5
and this falls right in line with that.
6 And assuming that we do get to 7
implementation space with the Reg Guide, one of the 8
big benefits, potentially, to licensees -- and I know 9
Joe and Darrell have alluded to this earlier -- is the 10 flexibility that it may offer to a licensee in 11 development or even potentially modifying an aging 12 management program, recognizing, again, safe operation 13 and the risk-informed aspect of what we've learned in 14 the ISFSI operations.
15 Next slide. So just to kind of level-set 16 here with current status of the ISFSI licenses and the 17 storage technology, there are currently 12 Part 18 specific ISFSI licenses that have been renewed. One 19 is in the process of being finalized. There are 10 20 dry storage system CoCs that have been renewed to the 21 Part 72 general license.
22 Again, this was noted earlier. Most of 23 these renewed licenses or CoCs represent austenitic 24 stainless steel canisters. That's about 90 percent, 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
77 give or take, of the inservice systems. And there are 1
about now 3800 or so canisters in service, many of 2
them beyond 30 years. And in the very near future, we 3
will cross the 4,000-canister threshold for systems 4
inservice.
5 MEMBER HALNON: Yes, this is Greg Halnon.
6 Do those numbers include the DOE sites?
7 MR. RICHTER: No. These are the industry 8
sites, I believe.
9 MEMBER HALNON: Just the industry? Okay.
10 Thanks.
11 MR. RICHTER: And then, just to wrap up 12 kind of where we are with a forward look, there are 13 five more dry storage system CoCs that would be 14 renewed in 2027 through 2037.
15 Next slide.
16 Okay. And again, as noted earlier, the 17 age management plans for chloride-induced stress 18 corrosion cracking, they are unique and specific for 19 each system and each license or CoC renewal.
20 One of the things that is worth noting, I 21 think, in terms of the technical content of the 22 license, where it's appropriate in terms of the 23 inspection regime, if there's applicable regulatory or 24 code reference for, say, an NDE technique that's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
78
- applied, like a
visual inspection, those are 1
referenced and applied accordingly.
2 And one of the things that preceded the 3
development of the Code Case and subsequent Reg Guide, 4
you know, at times, there were not any NRC or Code 5
requirements that sort of defined what was to be 6
inspected in terms of how many, how often, and so 7
forth.
8 So we needed to establish what that 9
program would look like. And I think what you see in 10 those three sub-bullets, those are what provided, 11 those needs are what provided the impetus, at least 12 from an industry standpoint, to develop the Code Case 13 and the actions that followed.
14 Next slide.
15 So again, just to touch on some of the 16 work that has been done in terms of developing the 17 Code Case, and the basis to support that, you know, 18 Joe reviewed the EPRI site susceptibility report and 19 how that works.
20 Renewed licenses and CoCs, they establish 21 requirements for the inspections, the techniques, the 22 frequencies, what the criteria are, et cetera. That 23 is all laid out in the license or the Certificate of 24 Compliance.
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79 Then, in 2015, again, historically, this 1
milestone, NRC requested ASME to develop some standard 2
for these inspections. And that gave rise to Code 3
Case N-860, which, of course, was approved in 2020.
4 Next slide. So a couple of things that 5
are worth noting here. The approved Code Case, as a 6
matter of fact, has no effect on renewed licenses and 7
CoCs. The licenses that have an aging management 8
program in place are bound to follow that in their 9
renewed license and Certificate of Compliance.
10 So the Reg Guide that was developed and 11 would implement Code Case N-860, that is a method 12 where a licensee could adopt that voluntarily. And 13 that may be based on a number of different factors.
14 A lot of those you could boil down and call them, you 15 know, business decisions based on cost, convenience, 16 schedule, et cetera. For licensees that are 17 implementing a new aging management plan, it's 18 certainly available for them to utilize.
19 And again, that's something that a 20 licensee, along with the CoC holder, they could work 21 together to evaluate, you know, what are the benefits; 22 what are the costs for updating the aging management 23 plan to adopt the Reg Guide.
24 Changing the aging management plan can be 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
80 done via Part 72, 72.48. That process is in place and 1
fairly well-recognized.
2 But we would also suggest, too, that any 3
future renewals, again, looking at the flexibility 4
this offers, give consideration to using the Code 5
Case, such that the real process itself could be 6
potentially more efficient.
7 Next slide. So a couple of comments from 8
industry's view on the Reg Guide itself. We believe 9
it's succinct and well-written. It's very easy to 10 read and understand. We're pleased that it adopted 11 the Code Case with no exceptions or clarifications 12 noted.
13 A couple of things that are also worth 14 noting, and I think Darrell mentioned this earlier, is 15 the additional alternative to extend the canister 16 inspection interval for sites that have low 17 susceptibility. That is a feature that some sites may 18 want to be able to take advantage of. Being able to 19 do that, again, the storage conditions are a key 20 element in that. It's an important aspect of a risk-21 informed approach to any of these inspection programs 22 that are site-specific.
23 And so overall the industry supports the 24 Reg Guide. We see it as a final piece of a framework 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
81 that allows the consensus standard and the Code Case 1
to be used under ISFSI licenses. So we are very 2
supportive of its development and its use.
3 So in conclusion, there's a couple of 4
things that NEI would like to do. First, we want to 5
commend the staff for developing the Reg Guide. We 6
appreciate the fact that utilizing 72.48 to adopt it 7
without amendment is a good approach.
8 We're also very pleased, too, with the 9
fact that it recognizes the non-chloride salts and 10 their ability to mitigate initiation of stress 11 corrosion cracking is very positive thing that we want 12 to acknowledge.
13 And then also, too, it recognizes the 14 reality, the fact in history, that demonstrates that 15 stress corrosion cracking of these austenitic 16 stainless steel canisters welds is a very low 17 probability. It is very unlikely at the low 18 susceptibility sites.
19 So we also wanted to point out, too, that 20 we recognize and agree with the staff's rationale in 21 the reg analysis, where the benefits of implementing 22 this would far exceed the cost of doing that, and 23 again, want to recognize staff's work here. This is 24 really a very positive example of, again, from our 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
82 view, applying risk insights to improve the regulatory 1
framework. So we commend the staff for that.
2 So those are the extent of my remarks. If 3
there are questions for me or the group, Ron, I'll 4
turn it back to you.
5 CHAIR BALLINGER: Thank you.
6 Questions from members?
7 MEMBER DIMITRIJEVIC: Well, I want to be 8
a wise guy once again.
9 (Laughter.)
10 MEMBER DIMITRIJEVIC: I just want to say 11 you cannot really call this stress risk ranking. You 12 are ranking based on probability of failure. A risk 13 is a combination of probability of failure and 14 consequences. So therefore, you're just looking at 15 one side of the risk. And that could be perfectly 16 fine in that.
17 You make exception, I mean, and it is an 18 assumption that most of the canisters will have 19 similar consequences. So the risk is attenuated by 20 the probability of failure.
21 But, otherwise, if you have a canister 22 which may have a very high susceptibility to the 23 degradation mechanism, but if it fails, it will not 24 have consequences; you don't really want to inspect 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
83 that one. So that's my point, just being a wise guy.
1 This is not the risk; it is just probability of 2
failure.
3 MR. RICHTER: You're not being a wise guy 4
at all. I appreciate that comment.
5 And I think, you know, when you look at 6
risk, I think as a matter of definition in the purest 7
sense, I think you're right; if you look at the 8
probability of failure, that and the product of the 9
consequence, you know, that sort of defines risk. But 10 I think in the context of these inspection programs, 11 you know, we look at risk in the sense of, what is the 12 likelihood that we might see something of consequence 13 or concern? And I think, you know, if that were ever 14 to be the case, certainly there is work underway, work 15 that's been done in terms of mitigation that would 16 address that.
17 But in the context of these presentations, 18 you know, risk, you're right, to your point, it's not 19 necessarily considering, at least in a quantitative or 20 dollars-and-cents sense, what that consequence would 21 be. Only the likelihood of it appearing or occurring.
22 So I appreciate that comment.
23 MEMBER DIMITRIJEVIC: Got it. And I hope 24 you made a point about that in the Reg Guide 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
84 somewhere, you know, just a little note on that.
1 MEMBER MARTIN: One of the difficulties 2
with consequence at the moment is that there's general 3
consensus that consequence would be low in terms of 4
dose at the boundary or dose to the public.
5 What we lack is the data to back up that 6
theory. And so I believe that there's some good work 7
proposed to improve the defensibility of our 8
consequence assessment in the next couple of years and 9
to put the data behind what is generally believed to 10 be a very low consequence situation.
11 CHAIR BALLINGER: I would add that this 12 Committee has followed this for a number of years. We 13 have continuously suggested that the consequences are 14 near zero from a dose point of view.
15 And the agency now has done analysis and 16 run models, and the like, to demonstrate that, in 17 fact, the consequences, the dose consequences, are 18 just nonexistent. But it has nothing to do with the 19 Code Case, right?
20 MEMBER DIMITRIJEVIC: So then why are we 21 doing inspections?
22 CHAIR BALLINGER: I mean, it's just one of 23 those things.
24 MEMBER DIMITRIJEVIC: Yes, but, then, I'm 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
85 questioning, if the consequences are meaningless, you 1
know, then, why are we doing inspections at all? I 2
mean, what's the point?
3 MR. DUNN: So this is Darrell Dunn, NRC.
4 MEMBER DIMITRIJEVIC: And I knew you.
5 (Laughter.)
6 MR.
DUNN:
We do understand the 7
Committee's comments and desire to do a consequence 8
analysis. And that's something that we --
9 MEMBER DIMITRIJEVIC: If it's zero, I have 10 a zero desire. I don't think you need to do it. I 11 think they are very small. Sorry, it wasn't designed, 12 just like a definition.
13 MR. DUNN: But we have gotten that message 14 from the Subcommittee that they desire a consequence 15 analysis. And that's something that we do, you know, 16 we have done an initial consequence analysis. Yes, we 17 showed that the consequence is generally low with a 18 fair amount of variability because those are based on 19 our assumptions. And so we would like to further that 20 work and really have a better and defensible 21 consequence analysis and publish that.
22 But with respect to this Code Case, this 23 Code Case doesn't consider consequences at all. It's 24 simply based on a methodology of, where are you likely 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
86 to have the chloride-induced stress corrosion 1
cracking? How do these different sites rank? So 2
there's no role of consequence here in the development 3
of that Code Case, and I think that's generally true 4
of a lot of things that are done in ASME space.
5 I'm not saying that it's right or wrong or 6
that I disagree with the comment. I certainly agree 7
with the comment that, you know, the overall 8
consequences of CISCC are likely very low, and we're 9
hoping that we can carry on this work, and then, show 10 11 CHAIR BALLINGER: That's why I've kept my 12 mouth shut during all these presentations.
13 MEMBER MARTIN: I'm surprised.
14 (Laughter.)
15 MEMBER DIMITRIJEVIC: I would just like to 16 point out that my comment wasn't directed to analyze 17 some consequences. My point was that I think that 18 somewhere it should just say: the risk in this case 19 is represented just by susceptibility.
20 And somebody said that in an answer very 21 well. It analyzes that and that's why you use 22 occasionally risk-informed, even if it's not all risk.
23 That was my only comment, sort of like, 24 you know, basically, that recognizing the situations.
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87 MR. DUNN: Understood and I thank you for 1
the comment.
2 CHAIR BALLINGER: Okay. Other questions 3
from the members?
4 Or Dennis may be out there. Or a 5
consultant?
6 MEMBER KIRCHNER: Ron, this is Walt.
7 CHAIR BALLINGER: Oh.
8 MEMBER KIRCHNER: I misspoke earlier. I 9
was really interested in Diablo Canyon.
10 (Laughter.)
11 MEMBER KIRCHNER: And so when I go to --
12 sorry, it must be the high desert air out here; it's 13 drying out my brain cells.
14 But, more seriously, the table that was in 15 the EPRI presentation, does that identify the sites or 16 it's just a tabulation? I was going through the Reg 17 Guide and elsewhere in the material provided. Where 18 is the table that identifies the ranking of the sites 19 by name?
20 MR. DUNN: This is Darrell Dunn from the 21 NRC.
22 The only place that we have specifically 23 identified that is only limited to the sites that have 24 a susceptibility ranking of 1 to 3, and that's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
88 included in the regulatory analysis.
1 MEMBER KIRCHNER: Oh, it's in the 2
regulatory analysis, not the Reg Guide? Okay.
3 MR. DUNN: That's correct.
4 MEMBER KIRCHNER: I couldn't find it in 5
the Reg Guide.
6 MR. DUNN: That's correct. But it's only 7
limited to those very low susceptibility sites.
8 You had asked earlier about Rancho Seco.
9 I know that you weren't really interested in that, but 10 that's 2, by the way. Palo Verde is 1.
11 MEMBER KIRCHNER: And Diablo Canyon is 12 what?
13 MR. DUNN: Seven.
14 MEMBER KIRCHNER: Seven? Uh-hum. Okay.
15 Thank you.
16 MR. DUNN: Uh-hum.
17 CHAIR BALLINGER: Other questions?
18 Okay. Hearing none, we need to go out for 19 public comment.
20 All right. If there are members of the 21 public that would like to make a comment, please 22 identify yourself and make your comment.
23 Oops, wait a minute. BG? Who's BG?
24 MR. RICHTER: It's Brian Gutherman.
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89 CHAIR BALLINGER: Oh, sorry. Okay.
1 Brian?
2 MR. GUTHERMAN: Yes, thank you. Can you 3
hear me okay?
4 CHAIR BALLINGER: Yes, I think so.
5 MR. GUTHERMAN: Okay. Thank you.
6 Just a couple of points I would like to 7
make.
8 One goes back to Greg Halnon's remark.
9 There is one commercial spent fuel storage facility at 10 a DOE site, and I'm sure he knows it quite well. It's 11 up at INL. It's got the TMI-2 fuel there and fuel 12 debris. That is subject to this Reg Guide if DOE so 13 chooses to adopt this Reg Guide. But there's no DOE 14 fuel, by and large, at any of these NRC-regulated 15 sites.
16 The second remarks pertains to endorsement 17 or bringing the Code Case into the main Code. And I'm 18 sorry, I can't remember the member's name who had that 19 question.
20 This Code Case is unique inasmuch as 21 Section XI does not apply to Part 72 facilities. So 22 there is no such thing as an inservice inspection 23 program under Section XI. So it's kind of going to 24 hang out there by itself, as I understand it. And 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
90 Darrell can maybe clarify that.
1 Thanks. That's all I had.
2 MR. DUNN: Okay. So let me comment on the 3
TMI-2 ISFSI that's at INL. That system uses, I think, 4
a welded ferritic steel canister system that's 5
painted. So it's not an austenitic stainless steel.
6 So it's not a system that's actually covered by this 7
Code Case.
8 MR. GUTHERMAN: Thanks, Darrell.
9 MR. DUNN: Okay. And with respect to your 10 comment on the integration of the Code Case into ASME, 11 yes, you are correct, you know, there has been a long 12 process here, even in Section III, Division 3, which 13 would be the storage and transportation theme. That's 14 been an ongoing effort for 30 years, to develop that 15 Code and get it to be something where the NRC can 16 endorse it. I expect it will take at least that long 17 to develop a Section XI equivalent for those types of 18 systems.
19 So right now, there is no part of the ASME 20 Code where this could be incorporated. And maybe it 21 makes the case, you know, for why we should have a Reg 22 Guide that collates these Section XI Code Cases for 10 23 CFR Part 72 licensees and CoC holders.
24 CHAIR BALLINGER: I wouldn't consider him 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
91 a member of the public. He was part of your 1
presentation.
2 So are there any other people out there 3
that would like to make a comment? If so, please 4
state your name and make your comment.
5 Hearing
- none, that concludes the 6
presentation and the comments.
7 And we can release the court reporter.
8 Okay? Thank you.
9 (Whereupon, the above-entitled matter went 10 off the record at 2:58 p.m.)
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
NRC Regulatory Guide 3.78 Acceptable ASME Section XI Inservice Inspection Code Cases for 10 CFR Part 72 Darrell Dunn Sr. Materials Engineer NRC/NMSS/DFM/MSB
Topics Purpose and applicability of Regulatory Guide (RG) 3.78 American Society of Mechanical Engineers (ASME) Code Case N-860 Regulatory approach for ASME Code Case N-860 endorsement Public comments and revisions to RG 3.78 Regulatory Analysis for RG 3.78 Next steps Acknowledgements ACRS Fuels, Materials, & Structures Subcommittee 2
12/19/2024
Regulatory Guide 3.78 Purpose and Applicability Identify acceptable ASME Boiler and Pressure Vessel Code (ASME Code),Section XI, Inservice Inspection Code Cases for use by ISFSI specific licensees, general licensees, and certificate of compliance (CoC) holders licensed under Title 10 of the Code of Federal Regulations (10 CFR) Part 72.
ASME Code Case Endorsement ASME Code Case N-860, Inspection Requirements and Evaluation Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems ACRS Fuels, Materials, & Structures Subcommittee 3
12/19/2024
- Developed over a 5-year period from 2015-2020 per NRC request (ML15083A020); ASME response (ML15224B452)
- Applies only to welded austenitic stainless steel canisters exposed to ambient air by passive ventilation
- Majority (>90 percent) of dry storage systems in use
- Currently used at 71 independent spent fuel storage installation (ISFSI) sites
- Assumes that chloride-induced stress corrosion cracking (CISCC) is the most credible and bounding degradation mechanism
- Consistent with NUREG-2214, Managing Aging Processes In Storage,
- Inspections of welded austenitic stainless steel canisters conducted to date have not identified instances of localized corrosion or CISCC ACRS Fuels, Materials, & Structures Subcommittee 4
12/19/2024
Canister Based Dry Storage Systems ACRS Fuels, Materials, & Structures Subcommittee 5
12/19/2024 X. He et al., 2014, ML14323A067 B. Tripathi et al., 2015, SMiRT-23, Paper #185
CISCC of Power Reactor Components ACRS Fuels, Materials, & Structures Subcommittee 6
12/19/2024 Shirai et al. 2011 Philip Doubell, 2010 Fontevraud 7 A108T03 San Onofre emergency core cooling system Koeberg Barry M. Gordon 2013 NACE International Corrosion Conference Paper No. 2539
- Examinations on welded regions of canisters oIndications of localized corrosion (e.g., pitting corrosion) that can be a precursor to, or an initiation point for CISCC
- Progressive inspection methodology to identify and characterize corrosion oVisual screening examination oVisual assessment examination oSupplemental examination (surface or volumetric)
- Adjustment of number of canisters inspected and inspection frequency based on examination results ACRS Fuels, Materials, & Structures Subcommittee 7
12/19/2024 ASME Code Case N-860
- Uses EPRI-3002005371, Susceptibility Assessment Criteria for CISCC to set initial inspection population oCISCC ranking: ZISFSI = Clstarting + Cladj + AHadj oHigh rank site: ZISFSI 8 oLow rank site: ZISFSI 7
- CISCC growth rate equation only considers canister surface temperature oUsed to determine inspection interval if CISCC is identified (or likely) oNot intended to predict whether CISCC could occur
- Maximum inspection interval can be increased from 10 to 20 years for low rank sites (ZISFSI 7) with no indications of CISCC ACRS Fuels, Materials, & Structures Subcommittee 8
12/19/2024
Regulatory Approach for N-860 Endorsement
- Methodology in ASME Code Case N-860 oCISCC susceptibility assessment oInspection intervals
- Additional technical information oPower reactor operational experience with CISCC oISFSI locations and inspection results oComposition of deposits on canister surfaces 12/19/2024 ACRS Fuels, Materials, & Structures Subcommittee 9
Power Reactor CISCC Operating Experience
- NRC Information Notice 2012-20, Potential Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel and Maintenance of Dry Cask Storage System Canisters, 11/14/2012 (ML12319A400) - RG 3.78 Ref. 17
- CISCC of power reactor components, including stainless steel piping and tanks, has only occurred at locations near a marine shoreline oSan Onofre Nuclear Generating Station (SONGS) oSt. Lucie Nuclear Power Plant oTurkey Point Nuclear Generating Station oKoeberg Nuclear Power Station ACRS Fuels, Materials, & Structures Subcommittee 10 12/19/2024
ISFSI Inspection Results ACRS Fuels, Materials, & Structures Subcommittee 11 No instances of localized corrosion or CISCC on stainless steel canisters for ISFSI inspections conducted to date NRC Information Notice 201220, (ML12319A440) Atmospheric CISCC of stainless steel, power reactor components has occurred at locations that are less than 1 km from a marine shoreline ZISFSI 7 12/19/2024
Atmospheric Deposits on Canisters ACRS Fuels, Materials, & Structures Subcommittee 12 Risk of canister CISCC at these sites is low
- Low, or very low, surface chloride concentrations
- Low chloride load, combined with relatively high concentrations of nitrate RG 3.78 Ref. 14-16 12/19/2024
Effects of Inhibiting Species ACRS Fuels, Materials, & Structures Subcommittee 13
- Chi, et al. (2015) (Ref. 18) chemical transformation of sea salt aerosols chloride-rich => sulfate and nitrate
- NOx and SOx emissions generated from combustion of hydrocarbon fuels (e.g., coal, diesel, and natural gas)
- Nitrate and sulfate are known to inhibit localized corrosion of stainless steels in chloride environments (Refs. 19-22)
- Nitrate is an effective inhibitor for CISCC of stainless steels (Refs. 23-25)
Cook et al, 2017 RG 3.78 Ref. 22 Chi, et al., 2015 RG 3.78 Ref. 18 12/19/2024
Staff Regulatory Guidance
- ASME Code Case N-860 is included in RG 3.78, Table 1, Acceptable Section XI Code Cases for 10 CFR Part 72 Licensees and CoC holders.
- Code Case N-860: maximum inspection interval can be increased from 10 to 20 years for low rank sites (ZISFSI 7) with no indications of CISCC
- Alternate inspection interval allowed for inland ISFSI sites (ZISFSI 3) oAllows inspection intervals of up to 40 years sites oBased on referenced technical information that was either not available or not considered during the development of ASME Code Case N-860
- Future acceptable ASME Section XI Code Cases applicable to 10 CFR Part 72 licensees and CoC holders ACRS Fuels, Materials, & Structures Subcommittee 14 12/19/2024
ISFSI Locations and ZISFSI Values
- 71 operating ISFSI sites with 3881 welded austenitic stainless steel dry storage system canisters in use as of October 2024
- The compositions of salt deposits on spent fuel storage canisters at ISFSI sites where ZISFSI 3 are not expected to promote CISCC
- Assuming CISCC could occur, initiation time could be lengthy and the CISCC propagation rates would be much slower compared to rates that may be possible at marine sites ZISFSI Number of ISFSI sites (estimated)
Number of canisters (estimated)
Maximum inspection interval (yr) 1-3 60 3,259 40 4-7 6
307 20 8-10 5
315 10 ACRS Fuels, Materials, & Structures Subcommittee 15 12/19/2024 EPRI-3002005371
Public Comments
- Comments provided by the Nuclear Energy Institute (NEI) oProcess for crediting previous inspections for N-860 to establish a 40-year inspection interval (instead of the 20-year interval allowed by N-860) oConsider going to a 40-year inspection interval for the following cases:
a licensee did not use Code Case N-860 when inspections were conducted a licensee that follows an AMP that does not adopt the code case entirely (AMPs and code case adoption determined by the CoC holder)
- Additions to Regulatory Guide 3.78, Section C. Staff Regulatory Guidance oLicensees should follow ASME Code Case N-860
-2000 Inservice Inspection: how the inspection was conducted and the inspection results
-3000 Records and Reports: documentation of the inspection results and revisions to the inspection interval ACRS Fuels, Materials, & Structures Subcommittee 16 12/19/2024
Regulatory Analysis for RG 3.78 Action Analysis: Issuing the RG recommended would result in costs and benefits shown in Table ES 1.
Nonquantified Benefits: RG would provide improvements in knowledge and benefits to regulatory efficiency by standardizing several components of licensee ISFSI AMPs that choose to adopt the guidance Decision Rationale: NRC concludes that the RG is justified from a quantitative standpoint because o Benefits to licensees from the averted cost of ISFSI canister inspections outweigh the relatively minor cost to licensees and the NRC to issue and implement the RG o RG is also justified when considering nonquantified costs and benefits because the increase in regulatory efficiency ACRS Fuels, Materials, & Structures Subcommittee 17 12/19/2024
Timeline and Next Steps ACRS Fuels, Materials, & Structures Subcommittee 18 12/19/2024 Feb. 2024 Initiated development of Regulatory Guide (RG) 3.78 July 2024 Federal Register Notice: 89 FR 58080 issued Draft Regulatory Guide 3.78 Acceptable ASME Section XI Inservice Inspection Code Cases for 10 CFR Part 72, (ML24093A010)
Regulatory Analysis for the Draft Regulatory Guide3.78, June 2024 (ML24093A012)
Nov. 2024 Comment responses and revisions to RG 3.78 Dec. 2024 Advisory Committee for Reactor Safety (ACRS) Fuels, Materials, and Structures Subcommittee Meeting Dec. 2024 Review by NRC Office of General Council (OGC)
Jan. 2025 RG 3.78 Final Publication (pending ACRS decision)
March 2025 ACRS Full Committee Meeting - Letter on RG 3.78 TBD
Acknowledgements
- Ryan Meyer (ORNL)
- Dan Ruby
- Tom Boyce
- Meraj Rahimi 12/19/2024 ACRS Fuels, Materials, & Structures Subcommittee 19 The contributions of the following staff are gratefully acknowledged
© 2024 Electric Power Research Institute, Inc. All rights reserved.
w w w. e p r i. c o m Joe Faldowski Senior Program Manager EPRI Used Fuel & High-Level Waste Program ACRS Meeting December 19, 2024 Dry Fuel Storage System Aging Management EPRI Susceptibility Rankings and Relevant Experience Date: December 19, 2024
© 2024 Electric Power Research Institute, Inc. All rights reserved.
2 Outline
Background
Site and Canister Ranking Methodology Latest Research Next Steps Conclusion and discussion
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3 Background
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4 Brief History of Milestones 2012 - NRC Information Notice 2012-20 Several incidents of CISCC observed in in austenitic stainless steel components that were exposed to atmospheric conditions near salt-water bodies. - Songs, St. Lucie, Turkey Point, and Koeberg Letter states no immediate safety concern has been identified with currently approved licenses 2015 - EPRI issued Technical Report 3002005371 - Susceptibility Assessment Criteria for CISCC of Welded Stainless Steel Canisters for Dry Cask Storage Systems 2020 - Code Case N-860 approved by ASME 2024 - NRC DG-3058 (RG 3.78) published in the Federal Register Multiple organizations continue to evaluate CISCC in DFSs experimentally, analytically, and operationally (inspections of in-service systems)
To date, no inspections have resulted in additional actions beyond trending Learning as recommended in 3002008193 Google Maps. Retrieved 12/6/2024 from https://www.google.com/maps
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5 The Central Aging Issue for SS Canisters: CISCC*
Tensile Stress Welds, heat affected zones, gouges, scrapes Proximity to sea spray, cooling tower spray, road salt (MgCl2)
Time, declining surface temperature High humidity, rain, dust accumulation
- Chloride Induced Stress Corrosion Cracking Crevices, surface roughness, pits Stainless steel, iron/carbon steel surface transfer CISCC Main Research Questions
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6 Probability Likelihood that CISCC will occur and cause confinement breach Consequence Magnitude and timing of consequences if a confinement breach occurs Inspection Program Robustness of inspection program to detect significant corrosion Mitigation and Repair Tools to address concerns with significant corrosion, if observed 01 02 03 04 Research Framework A guide to coordinated, collaborative research leading to an end-point Effective Aging Management Program
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7 Confirmatory Early Technical Evaluations and Inspection Results Early work confirmed CISCC as leading potential degradation phenomenon and lower potential susceptibility at inland sites
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8 Susceptibility Rankings EPRI Technical Report 3002005371, 2015
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9 Site Susceptibility Ranking Site susceptibility quantified by calculating a Z ISFSI ranking factor that can range from 1 to 10:
where:
ZISFSI = relative CISCC susceptibility ranking Clstarting = initial ranking based on marine aerosol Cladj = adjustment factor for local sources of chloride AHadj = adjustment factor to account for differences in susceptibility due to climate ZISFSI is a measure of Cl content potentially available to accumulate on the canister without regard to Cl molecule type or conditions inside the overpack ZISFSI = Clstarting +Cladj + AHadj EPRI Report 3002005371
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10 Application of Ranking Methodology US ISFSI Sites with ZISFSI >3 = 11 1 ZISFSI 3 (60 ISFSIs) 4 ZISFSI 7 (6 ISFSIs) 8 ZISFSI 10 (5 ISFSIs)
Absolute Humidity Elevation (m)
Dist. to Marine Shore (km)
< 1km to Cooling Tower Tower Saline?
(0=No, 1=Low, 2=High)
Salted Road within 200m?
Cooling Tower Rank Ocean Rank Salted Road Elevation AH SUM Z_ISFSI Age (yr) 7.9 220 500 Y
Y 0
N 1.
1
-1 1
1 9
6.9 190 1000 N
N 1
-1 0
1 22 8.2 185 1000 N
N 1
0 1
1 13 7.5 270 1000 Y
Y 0
N 1.
1
-1 1
1 14 9.5 35 125 N
N 1
0 1
1 32 8.5 220 1000 N
N 1
0 1
1 8
6.7 135 330 Y
Y 0
N 1.
1
-1 1
1 22 10.8 250 420 N
N 1
0 1
1 12 7.7 190 1000 N
N 1
-1 0
1 12 8.7 280 1000 N
N 1
0 1
1 14 7.6 180 700 Y
Y 0
N 1.
1
-1 1
1 29 7.8 180 700 Y
Y 0
N 1.
1
-1 1
1 10 7.2 80 360 N
N 1
-1 0
1 22 7.8 310 1000 N
N 1
-1 0
1 18 7.3 85 390 N
N 1
-1 0
1 14 8
16 23 N
N 1
0 1
1 20 5.2 1500 210 N
N 1
-1 0
1 25 7.8 30 40 N
N 1
-1 0
1 16 7
185 1000 N
N 1
-1 0
1 15 7
185 1000 N
N 1
-1 0
1 7
7.2 200 1000 N
N 1
-1 0
1 12 8.2 220 1000 N
N 1
0 1
1 14 7
10 10 N
N 2
-1 1
1 22 9.6 230 270 N
N 1
0 1
1 20 9.6 230 270 N
N 1
0 1
1 11 7.5 290 1000 Y
Y 0
N 1.
1
-1 1
1 16 7.2 80 350 Y
Y 0
N 1.
1
-1 1
1 12 9.5 95 160 N
N 1
0 1
1 16 10.2 250 340 N
N 1
0 1
1 34 10.2 250 340 N
N 1
0 1
1 24 7.8 190 1000 Y
Y 0
N 1.
1
-1 1
1 31 7.8 190 1000 Y
Y 0
N 1.
1
-1 1
1 8
7.1 290 210 Y
Y 0
N 1.
1
-1 1
1 21 7.6 190 600 Y
Y 0
N 1.
1
-1 1
1 12 7
190 1000 N
N 1
-1 0
1 20 7.7 185 1000 N
N 1
-1 0
1 19 10.8 70 140 N
N 1
0 1
1 35 10.8 70 140 N
N 1
0 1
1 20 11.1 130 210 N
N 1
0 1
1 8
11.4 10 35 N
N 1
0 1
1 17 7.3 220 170 Y
Y 0
N 1.
1
-1 1
1 25 7.3 220 170 Y
Y 0
N 1.
1
-1 1
1 25 8
15 80 N - (was before ISFSI)
N 1
0 1
1 22 6.3 77 135 N - (was before ISFSI)
N 1
-1 0
1 16 8.9 331 950 N
N 1
0 1
1 Future 7
350 160 N
N 1
-1 0
1 22 7.3 180 1000 N
N 1
-1 0
1 10 10.8 110 600 Y
Y 0
N 1.
1 0
2 2
21 11 180 470 Y
Y 0
N 1.
1 0
2 2
19 11 180 470 Y
Y 0
N 1.
1 0
2 2
9 9
250 1000 Y
Y 0
N 1.
1 0
2 2
9 10.5 185 250 Y
Y 0
N 1.
1 0
2 2
17 10.5 185 250 Y
Y 0
N 1.
1 0
2 2
11 8.2 160 1000 Y
Y 0
N 1.
1 0
2 2
23 8
250 1000 Y
Y 0
N 1.
1 0
2 2
21 8.3 65 120 Y
Y 0
N 1.
1 0
2 2
16 8.3 65 120 Y
Y 0
N 1.
1 0
2 2
11 8.6 55 115 Y (co-located fossil)
Y 0
N 1.
1 0
2 2
23 10.5 220 500 Y
Y 0
N 1.
1 0
2 2
20 10.5 220 500 Y
Y 0
N 1.
1 0
2 2
8 11 80 180 Y
Y 0
N 1.
1 0
2 2
Future 8.3 90 170 Y
Y 0
N 1.
1 0
2 2
Future 11.6 70 130 Y
Y 0
N 1.
1 0
2 2
11 13.9 4
80 Y (co-located fossil)
N 0
N 1
1 2
2 13 9.4 220 500 Y
Y 0
N 1.
1 0
2 2
8 13.8 45 130 Y
Y 0
N 1.
1 1
3 3
19 12.3 50 250 Y
Y 0
N 1.
1 1
3 3
18 12.9 40 110 Y
Y 0
N 1.
1 1
3 3
23 8.8 3
50 Y
Y 1
N 2.
1 0
3 3
18 13.4 30 115 Y
Y 0
N 1.
1 1
3 3
19 8.8 3
50 Y
Y 1
N 2.
1 0
3 3
14 7.3 8
3.7 N
N 5
-1 4
4 16 15.5 9
15 N
N 2
2 4
4 Future 12.7 6
2.5 N
N 5
1 6
6 14 8.3 6
3 N
Y 5
1.
0 6
6 22 9
95 0.5 N
N 8
-1.
0 7
7 15 7.9 7
0.25 N
N 8
-1 7
7 9
8.4 7
0.12 N
N 8
0 8
8 19 9.7 6
0.12 N
N 8
0 8
8 21 14.6 3
1.5 Y (co-located coal)
Y 2
N 3.
5 1
9 9
7 9.7 6
0.07 N
N 9
0 9
9 6
16.4 5
0.4 N
N 8
2 10 10 16 17.4 2
0.4 Y (co-located gas)
Y 1
N 2.
8 2
12 10 13 Column Items Absolute Humidity Elevation Dist. to Marine Shore Cooling Tower Salted Road within 200m?
Age
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11 Canister Susceptibility Canister susceptibility quantified by calculating a ranking factor that can range from 1 to 10:
Canister Susceptibility makes use of best available data to predict specific susceptibility of a canister(s) on an ISFSI pad accounting for expected deposition rate, material of construction, heat load, and other factors.
HCAN = Deposition +Material + Heathoriz where HCAN = current relative CISCC susceptibility ranking of the canister Deposition = factor accounting for accumulated deposits Material = factor based on canister shell material Heathoriz = factor accounting for deliquescent area VCAN = Deposition +Material + Heatvert where VCAN = current relative CISCC susceptibility ranking of the canister Deposition = factor accounting for accumulated deposits Material = factor based on canister shell material Heatvert = factor accounting for deliquescent area EPRI Report 3002005371
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12 Canister Susceptibility Examples Canister ranking changes with Storage Duration and depends on Deposition which depends on ZISFSI EPRI Report 3002005371
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13 Latest Research
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14 US National Laboratory Research PNNL and SNL have done substantial work on accelerated corrosion of Stainless Steels in the presence of Chlorides. Results can be summarized as follows.
The Cl molecule, SS type, and the presence of NO3 are important factors Environment Material NaCl MgCl2 1
MgCl2 + NO3 3042 304L3 316L
- 1. Realistically, NO3 will be present wherever MgCl2 is present
- 2. No 304 canisters identified in service at marine sites
- 3. Represents vast majority of in-service canisters More typical of Inland site More typical of Marine site
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15 Next Steps
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16 EPRI ESCP Aging Management Working Group Meeting Objectives:
- 1. Evaluation of the current status of the aging management research - what has been done to date and what can be concluded from the results.
- 2. Development of a roadmap for the next 2 years to conclude key items.
Working Group Meeting:
- 1. Participation by invitation only. List of invited guests developed with input from Subcommittee and Task group leads. Number of registered attendees: 35
- 2. Attendees include participants from utilities (5), vendors (3), regulator (4), DOE (2), National laboratories (7), NEI (1), university (2), EPRI (5), and others.
Documentation of what has been done in the past >10 years and development of roadmap for closure of key items within the next 2 years were the key objectives
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17 General Consensus from the Working Meeting on Aging Management EPRI, NRC, and ASME Dry Storage System aging management documents create a conservative approach based on available information at the time they were issued.
Risk of CISCC at inland sites is low.
Improvements can be made on specific topics based on a learning approach as recommended in 2017 EPRI Technical Report 3002008193.
- EPRI will publish a roadmap to describe the recommended next steps based on the outcome of the working meeting Understanding of Dry Storage Canister Aging Management is Improving
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18 Aging Mechanisms - Recommended Two Year Plan 0
1 2
Year from start Continuous improvement as part of a learning aging management program Topic Recommended Research Path AH vs. RH, MgCl2 vs. NaCl, DH refinements, Matl Based on data to date Lab Experiments Fracture Mechanics Models Capture and make use of existing data
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19 2-Year Roadmaps for All Aging Management Pillars Consequence Inspection Mitigation
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20 Conclusions & Discussion
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21 Data Driven Conclusions Initial concern for stainless steel aging management was targeted at marine sites.
- Subsequent research and operating experience is validating that inland sites have much lower potential to be impacted by CISCC.
Greater understanding of the Cl molecules, materials, and inhibitors has been developing over the past several years.
- These results also support the conclusion that inland sites are less susceptible to CISCC.
As learning continues, there may be data to support further reductions in inspection frequency at near marine sites.
Significant progress has been made in the areas of inspection and mitigation with research expected to wrap-up in ~2yrs
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22 DISCUSSION
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23
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w w w. e p r i. c o m TOGETHERSHAPING THE FUTURE OF ENERGY
©2024 Nuclear Energy Institute 1 ASME Code Case N-860 and Reg Guide 3.78 NEI/Industry Perspective ACRS Fuels, Materials, and Structures Subcommittee Meeting Mark Richter Technical Advisor Nuclear Energy Institute December 19, 2024
©2024 Nuclear Energy Institute 2 Approaching 40 years of safe operation AMP inspections of inservice storage canisters to date have revealed no indications of corrosion indicative of confinement degradation Minor evidence of oxidation associated with ambient moisture noted The Code Case and endorsing Regulatory Guide align with the concept of learning aging management in NEI 14-03, as endorsed by the NRC in Regulatory Guide 3.76 Licensees could benefit from the flexibility offered by the CC and draft Regulatory Guide 3.78 while maintaining safe, risk-informed ISFSI operations Status of Spent Fuel Dry Storage
©2024 Nuclear Energy Institute 3 12 Part 72 specific ISFSI licenses renewed, one being finalized 10 Dry Storage System CoCs Renewed for Part 72 general licenses Most renewed licenses/CoCs include austenitic stainless steel canisters comprising 90+% of in-service DSSs About 3,800 such canisters in service, some for 30+ years Five more DSS CoCs to be renewed beginning in 2027 through 2037 Status of ISFSI Licenses & Technology
©2024 Nuclear Energy Institute 4 Canister AMPs for CISCC developed and approved uniquely for each license/CoC renewal Refer to Code where appropriate (e.g., visual NDE inspection technique)
No NRC or Code requirements existed for choosing which canister(s) to inspect, what to inspect, or how often Needed differentiators for different site service environments Needed actions to be taken if indications are found Need guidance for using inspection results to appropriately modify AMPs Dry Storage Canister AMPs
©2024 Nuclear Energy Institute 5 EPRI developed processes for relative site CISCC susceptibility and how to choose which canister(s) to inspect Renewed licenses and CoCs established the requirements for canister inspections - technique, frequency, acceptance criteria, corrective actions, etc.
In 2015, NRC requested ASME to develop a standard for canister inspections during the period of extended operations ASME, ISFSI owners, national laboratories, vendors, and NRC developed Code Case N-860, approved by ASME in 2020 Dry Storage Canister AMPs
©2024 Nuclear Energy Institute 6 The approved Code Case had no effect on renewed licenses and CoCs Licensees are bound to the AMPs in the renewed licenses and CoCs NRC developed draft Regulatory Guide 3.78 proposing a method for licensees and CoC to voluntarily adopt CC N-860 Licensees (in collaboration with CoC holders) need to evaluate the potential benefits of updating their canister AMPs to adopt the CC and RG Requires canister AMP revision via 10 CFR 72.48, program and procedure changes Future CoC renewals should seriously consider adopting the CC to enable a more efficient renewal review process Dry Storage Canister AMPs
©2024 Nuclear Energy Institute 7 Draft RG 3.78 is succinct and well-written Adopts the CC with no exceptions or clarifications Offers one additional alternative to extend canister inspection interval for sites with low CISCC relative susceptibility ranking This is important for establishing site-specific risk-informed inspection programs Storage service conditions are a key element of the aging management review process for license and CoC renewal Industry supports the RG as the final piece of the framework to allow the consensus standard CC to be used under ISFSI licenses Regulatory Guide 3.78
©2024 Nuclear Energy Institute 8 NEI commends the NRC staff for:
Using ISFSI service environment and material performance data in the development of DG-3058, including enabling modification of inspection intervals based on susceptibility criteria Recommending the use of 72.48 to adopt the Code Case without an amendment Recognizing the transformation of non-chloride salts into sodium sulfate and nitrite which act as CICSS inhibitors Recognizing testing results that demonstrate that CISCC of austenitic stainless steel welds at low-susceptibility sites is very unlikely NEI agrees with the staff decision rationale and implementation conclusion reflected in the associated draft regulatory analysis:
This guidance will result in total quantified benefits that exceed the relatively small costs of implementation. DG-3058 is a noteworthy example of applying risk insights to improve the regulatory framework Concluding Remarks
©2024 Nuclear Energy Institute 9 Questions?
mar@nei.org