ML24242A288
| ML24242A288 | |
| Person / Time | |
|---|---|
| Issue date: | 07/09/2024 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-2935 | |
| Download: ML24242A288 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Natrium Reactor Design-Center Subcommittee Docket Number:
(n/a)
Location:
teleconference Date:
Tuesday, July 9, 2024 Work Order No.:
NRC-2935 Pages 1-80 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com 1
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 NATRIUM REACTOR DESIGN-CENTERED SUBCOMMITTEE 7
+ + + + +
8 TUESDAY 9
JULY 9, 2024 10
+ + + + +
11 The Subcommittee met via Teleconference, 12 at 1:00 p.m. EDT, Thomas Roberts, Chair, presiding.
13 14 COMMITTEE MEMBERS:
15 THOMAS ROBERTS, Chair 16 RONALD G. BALLINGER, Member 17 VESNA B. DIMITRIJEVIC, Member 18 GREGORY H. HALNON, Member 19 CRAIG A. HARRINGTON, Member 20 WALTER L. KIRCHNER, Member 21 ROBERT MARTIN, Member 22 DAVID A. PETTI, Member 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
2 ACRS CONSULTANTS:
1 DENNIS BLEY 2
4 5
DESIGNATED FEDERAL OFFICIAL:
6 KENT HOWARD 7
8 9
10 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
3 CONTENTS 1
Opening Remarks and Objectives 4
2 NRC Opening Remarks...............
8 3
TerraPower Topical Report "An Analysis 9
4 of Potential Volcanic Hazards at 5
the Proposed Natrium Site Near 6
Kemmerer, Wyoming" 7
NRC Review of the TerraPower Topical
...... 42 8
Report 9
Public Comments................. 77 10 Adjourn..................... 80 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
4 P-R-O-C-E-E-D-I-N-G-S 1
1:01 p.m.
2 CHAIR ROBERTS: Okay. This meeting will 3
now come to order. I want to confirm the court 4
reporter can hear me. Thank you very much.
5 This is a meeting of the Advisory 6
Committee on Reactor Safeguards, Natrium Reactor 7
Design-Center Subcommittee. I'm Tom Roberts, chair of 8
this meeting. The attendants today are members Ron 9
Ballinger, Craig Harrington, Walt Kirchner, Dave 10 Petti, Greg Halnon, and Robert Martin; and online have 11
-- is Vesna Dimitrijevic online?
12 MEMBER DIMITRIJEVIC: Yes, I'm here.
13 CHAIR ROBERTS: Thank you, Vesna. And we 14 also have our consultant, Steve Schultz, online. Kent 15 Howard is the designated federal officer for the 16 meeting.
17 Today, TerraPower and the NRC staff will 18 present their work on a Natrium topical report 19 entitled An Analysis of Potential Volcanic Hazards at 20 the Proposed Natrium Site Near Kemmerer, Wyoming. The 21 topical report is incorporated by reference in the 22 construction permit application that the staff 23 recently accepted for review. This meeting gives us 24 an opportunity for an early review of this important 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 part of the safety analysis.
1 Additionally, this report describes the 2
first volcanic hazard analysis completed per Reg Guide 3
4.26, which was issued in 2021. It's entitled 4
Volcanic Hazards Assessment for Proposed Nuclear Power 5
Reactor Sites. We reviewed this reg guide in 2021.
6 One of our recommendations observed a trial use of the 7
guide was needed and timely revisions should be made, 8
as needed, based on that experience. So, in addition, 9
it counts as a topical report and assists in a safety 10 evaluation. This meeting gives the opportunity to 11 hear feedback on the reg guide and understand the 12 staff's plans to revise it.
13 The ACRS was established by statute and is 14 governed by the Federal Advisory Committee Act (FACA).
15 The NRC implements FACA in accordance with its 16 regulations found in Title 10 of the Code of Federal 17 Regulations, Part 7. Per these regulations, the 18 committee can only speak through its published letter 19 reports. We hold meetings to gather information and 20 perform preparatory work and will support our 21 deliberations at a full committee meeting. All member 22 comments should be required as the opinion of that 23 member, not a committee position.
24 The rules for participation in all ACRS 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 meetings was previously announced in the Federal 1
Register. The ACRS section of the U.S. NRC public 2
website provides our charter, bylaws, agendas, letter 3
reports, and full transcripts of all full and 4
subcommittee meetings, including slides presented 5
there. The agenda for this meeting was posted there.
6 We and the staff do not expect to discuss 7
any proprietary or export controlled information 8
today, so the entire meeting will be open to the 9
public.
10 As stated in the Federal Register notice 11 and the public meeting notice posted to the website, 12 members of the public who desire to provide written or 13 oral input to the subcommittee may do so. We have not 14 received any written input or advanced requests to 15 make oral statements from members of the public 16 regarding today's session. There will be an 17 opportunity for public comment, and we have set aside 18 time in the agenda for comments from members of the 19 public listening to this meeting.
20 Today's meeting is being conducted as a 21 hybrid meeting with participants both remote and in 22 our meeting room. A transcript of the meeting is 23 being kept and will be made available on our website.
24 We, therefore, request that participants in this 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 meeting identify themselves and speak with sufficient 1
clarity and volume, so they may be readily heard. All 2
presenters please pause from time to time to allow 3
members to ask questions. Please also indicate the 4
slide number you are on when moving to the next slide.
5 We'll take a short break after each 6
presentation to allow time to adjust screen sharing.
7 We'll take breaks during longer presentations at my 8
discretion.
9 Based on our experience from previous 10 virtual and hybrid meetings, please do not use any 11 virtual meeting features to conduct sidebar 12 discussions related to the presentations. Rather, 13 limit the use of meeting chat to report IT problems, 14 such as inability to hear or see the presentations.
15 Also, everybody on the MS Teams link or 16 phone line should mute themselves when not speaking.
17 Everybody in the room, please make sure your 18 electronic devices are on silent mode.
19 With that, we'll now proceed with the 20 meeting, and I'll call upon Dr. Barbara Hayes, who is 21 the branch chief of external hazards in the Division 22 of Engineering and External Hazards from the office of 23 NRR, to make introductory remarks to begin today's 24 presentation. Dr. Hayes.
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 DR. HAYES: Good afternoon, all. My name 1
is Barbara Hayes. I'm the chief of the Eternal 2
Hazards Branch. And as Member Roberts described, the 3
purpose of this subcommittee meeting is to discuss 4
TerraPower's topical report characterizing the 5
volcanic hazards at the proposed Natrium site near 6
Kemmerer, Wyoming.
7 This topical report is used and referenced 8
in the construction permit application for the Natrium 9
reactor design called Kemmerer Power Station Unit 1.
10 The construction permit was received in March of this 11 year, and the NRC staff accepted the application for 12 review on May 21st.
13 The topical report provides TerraPower's 14 characterization of volcanic hazards in accordance 15 with NRC's Regulatory Guide 4.26. As Member Roberts 16 pointed out, this is the first use of the regulatory 17 guide. And just as a little further background, the 18 guide came before the ACRS in February 2020 and again 19 in 2021. And in September 2023, the staff presented 20 an overview of the approach to reviewing information 21 that followed this regulatory guidance.
22 I would like to take a moment to thank 23 both the staff and TerraPower for their efforts in 24 developing and preparing the materials for this 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 meeting. I'd like to express the staff's appreciation 1
to ACRS for their time previously reviewing the 2
regulatory guide and their time today reviewing the 3
topical report.
4 We look forward to the conversation today.
5 If there are no other questions, I'll turn things over 6
to TerraPower. Thank you very much.
7 MR. KELLENBERGER: Good afternoon. My 8
name is Nick Kellenberger. I'm a licensing manager 9
with TerraPower, and with me today are Lindsay Martin, 10 who is our lead on the TerraPower licensing team, and 11 Britt Hill, who is the primary author of our topical 12 report.
13 I'll turn it over to Britt to walk us 14 through the presentation today.
15 MR. HILL: Good afternoon. My name is 16 Brittain Hill, and for the past several works I have 17 been working as a consultant for TerraPower on 18 evaluating the potential volcanic hazards of the 19 proposed Natrium site at Kemmerer, Wyoming.
20 Next slide, please. This afternoon, I'll 21 be presenting some of the key points from TerraPower's 22 topical report on the analysis of potential volcanic 23 hazards. The whole reason for doing this topical 24 report is that, within 100 to 320 kilometers from 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
10 proposed Unit 1 site, there are about 575 volcanoes 1
that formed during the last 2.6 million years.
2 Consequently, a volcanic hazard analysis appears 3
warranted for the proposed site using the criteria in 4
5 The goal of this hazard assessment is to 6
quantify volcanic hazards at the proposed site 7
probabilistically so that they can be used in 8
subsequent analyses, if those analyses are needed.
9 The analyses that we're going to talk about today 10 follow the guidance in Reg Guide 4.26.
11 Slide 3, please. Really simply put, 12 volcanic hazards can be characterized as either 13 materials that flow across the ground surface or 14 airborne particles that fall out from eruption plumes.
15 This overview map, I'm afraid I don't have a pointer, 16 but it shows this part of -- I'll point physically.
17 The proposed site is right here with a 40-kilometer 18 circle around it.
The 320-kilometer circle 19 encompasses the region of interest for the volcanic 20 hazard investigation, and the black dots represents 21 volcanoes that are younger than 2.6 million years old 22 in the proposed site or in the region of interest.
23 One thing to notice is that there are no 24 black dots within about 100 kilometers of the proposed 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 site. This is important because volcanic flow 1
phenomena, things like lava flows, pyroclastic density 2
currents, and debris flows rarely travel more than 100 3
kilometers from any erupting volcano. The few that do 4
travel a little bit farther than that also are 5
strongly affected by topography, and you'll notice 6
around the proposed site we've got a number of 7
mountain ranges, the Wind River Range to the 8
northeast, along with the Tetons and the Wyoming Range 9
out to the west. So any sort of flow phenomena, say 10 from a large eruption at the Yellowstone volcano, any 11 of those flow phenomena that might go more than 100 12 kilometers are going to be, effectively, trapped by 13 these topographic areas. They will not be able to 14 overcome them.
15 So the proposed site is located in an 16 enclosed basin that structurally, topographically, 17 physically isolates it from any potential flow 18 phenomena from a
future volcanic eruption.
19 Consequently, we can screen out surface flow phenomena 20 from the hazards analysis and don't have to do 21 anything more about them.
22 Next slide, please. So the only hazard 23 that was left is tephra fallout. And to analyze the 24 potential hazards from tephra fallout, we took two 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 different approaches. The first one covers most of 1
the volcanoes in the region because we use a similar 2
methodology for those volcanoes. The only exception 3
to this approach is how we treat the Yellowstone super 4
volcano eruption, and super volcano is kind of a loose 5
term but, here, it generally means a huge eruption 6
that involves more than 100 cubic kilometers of molten 7
rock. The reason for the separate approach is the 8
physics, the dynamics, the characteristics, and 9
modeling approaches for this kind of a super volcano 10 eruption are very different from the approaches that 11 we would use for the smaller, more typical volcanoes 12 in the region.
13 So to analyze most of the hazards from 14 570-odd volcanoes, we developed this approach where we 15 first have to estimate what were the eruption volumes 16 of tephra from these past eruptions. It's a lot 17 harder than it sounds because most of the tephra 18 deposits have been removed by erosion or buried, so we 19 have to estimate those volumes based on the 20 characteristics of the remnant volcanoes, and we use 21 a strong reliance on analogs to compare similar 22 volcanoes that are well preserved with the volcanoes 23 in the region that are not well preserved. So we come 24 up with a fairly large range of uncertainty about 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 these volumes, but we accommodate that uncertainty in 1
the analysis.
2 We also have to develop recurrence rates 3
for tephra eruptions from these volcanic fields. Not 4
every volcanic eruption is going to produce tephra, so 5
we have to estimate how many of those past eruptions 6
were likely to produce tephra and then what is the 7
recurrence rate for those tephra-formed eruptions that 8
could be used to estimate probability of a future 9
eruption.
10 Finally, once we have this and some other 11 critical information together, just detailed, of 12 course, in the topical report, we then analyze a range 13 of tephra thicknesses at the proposed site using an 14 accepted advection-diffusion sedimentation model that 15 is designed for evaluating tephra fallout away from 16 volcanoes.
17 Next slide, please. The result is that we 18 developed the tephra hazard curves, the probability of 19 exceedance for a certain thickness just on the X axis, 20 even its annual probability of exceedance on the Y 21 axis. So this is a full-probabilistic exceedance 22 curve that accounts for the likelihood of tephra-23 forming eruption, the likelihood that the wind will be 24 blowing towards the proposed site within a certain 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 sector, as well as the range of potential tephra 1
thicknesses that can occur at the site based on these 2
numerical models.
3 Now, if you look in the legend, you can 4
see that we have the abbreviations for different 5
volcanic fields followed by an S or an M. M means 6
mafic, very low-silica magma, and S means silicic, a 7
very high-silica magma. We analyze these different 8
scenario classes differently because the volumes, the 9
rates, the heights, the eruption dynamics are 10 different between mafic and silicic volcanoes.
11 So I think the curve that you're most 12 interested in is the outer black curve which is the 13 cumulative exceedance for all volcanoes at the 14 proposed site. The first thing to notice is that, on 15 the far left-hand side, you can see that the 16 probability of exceedance is less than 10 to the minus 17 5 per year for any tephra fallout site, and note that 18 the deposit thickness for that likelihood is ten to 19 the minus 6 centimeters, so we're talking about not 20 even discernable.
21 This is clearly a beyond design basis 22 external event, so everything we're going to talk 23 about falls within that beyond design basis realm for 24 potential event sequences or external event subsequent 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 analysis.
1 CHAIR ROBERTS: Yes, Britt, just to 2
clarify. The total hazard curve does not include 3
super volcano, right?
4 MR. HILL: It does not include a super 5
volcano. This is the first part. To jump to the 6
- chase, we don't have enough information to 7
probabilistically characterize the super volcano 8
eruption, but we do have enough to gain some 9
statistical insights. I'll come to that in the next 10 slide.
11 So for most of these volcanoes, the 12 average thickness is about 1 millimeter with a 10 to 13 the minus six probability of exceedance at the 14 proposed site. And more importantly, our 95th 15 percentile thickness which has, coincidentally, a 5 16 times 10 to the minus 7 probability of exceedance, is 17 about 17 centimeters. So that is one first part of 18 the risk assessment.
19 Next slide.
As I
mentioned, the 20 Yellowstone super volcano is a very different dynamic 21 sort of eruption, and we can't use that same model 22 that we used for the other volcanoes to calculate 23 deposit thickness from this really large eruption. We 24 relied on analyses that are published by the U.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
16 Geological Survey that did some very detailed 1
numerical simulations using a very advanced super 2
computer type model to look at how a tephra deposit 3
might form throughout the western United States from 4
potential Yellowstone super volcano eruptions.
5 So the USGS didn't do a fully stochastic 6
assessment of this hazard just because it's very 7
difficult to run that model stochastically. So we're 8
left with a series of scenarios that still give us 9
appropriate insights for these extremely large 10 Yellowstone eruptions, so I would view -- there's a 11 little bit of uncertainty on the precise value that 12 we're talking about for the statistics, but it's 13 pretty darn close and I do not expect, if you did a 14 fully stochastic simulation, that, even at the 95th 15 percentile, you can come up with a significantly 16 different number than what we're talking about.
17 So from these analyses, we can determine 18 that average deposit thickness would be about 84 19 centimeters in southwestern Wyoming near our Kemmerer 20 site, and that would also have a 5 times to 10 to the 21 minus 7 annual probability of exceedance. If we come 22 out to the 95th percentile thickness of, roughly, a 23 meter, 113 centimeters, it would have less than a 7 24 times 10 to the minus 8 probability of exceedance.
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17 I forgot to mention that the likelihood of 1
any super volcano eruption is very difficult to 2
estimate, but the USGS, when pushed into a corner, 3
will say it's less than one in a million per year. So 4
we're using that as our starting point as any kind of 5
eruption from the Yellowstone super volcano, i.e.
6 greater than 100 cubic kilometers, would be less than 7
one in a million.
8 DR. BLEY: I'm Dennis Bley, and if I just 9
do a little arithmetic in my head that might be wrong, 10 it looks like about half of those 10 to the minus 6 11 per year super volcano eruptions would get you to this 12 84 centimeters. So if you get it, you've got a good 13 chance of getting a lot of tephra to come out.
14 MR. HILL: Yes, that is correct. It's a 15 fairly steep curve. So the probability of exceedance 16 from any super volcano eruption, we don't have that 17 number, but I would say it's probably on the order of 18 30 or 40-plus centimeters just for any because these 19 are such large eruptions and we're only about 300 20 kilometers away from the source.
21 DR. BLEY: That's what I was guessing, so 22 I'm glad you confirmed that.
23 MR. HILL: So those are the two numbers 24 that we have to work with. Again, we can't fully 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 integrate that into the hazard curve, but this is 1
sufficient for our purposes that, even at the 95th 2
percentile, we're dealing with potentially a meter to 3
maybe a little less than a meter worth of tephra if a 4
this super volcano eruption.
5 Next slide. So if we have that kind of 6
deposit at the proposed site, there also might be some 7
potential that infrequent floods could remobilize that 8
tephra, bulk up the flood, and, with no suspended 9
solids, and go from a normal dilute flood flow into a 10 much more concentrated and potentially destructive 11 debris flow regime.
12 So we did some bounding analysis to try to 13 look at what would happen if we had a very infrequent 14 flood within this small basin that encompasses the 15 proposed site, the flood scoured up, incorporated all 16 the tephra instantaneously in the channel, and how 17 much bulking would that do to the flood, how much full 18 suspended solid would we have, compared to a normal 19 flood that has less than 10 percent total suspended 20 solid. Well, the answer is, even for the largest 21 volume eruption scenario we considered, 113 22 centimeters, conservatively bounding it with 23 essentially a 1-D model, instantaneous bulking of the 24 flow, we find that the channels that currently exist 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 in the upper branch of the north fork of the Little 1
Muddy Creek, those channels are deep enough and wide 2
enough that that bulk flow would stay wholly within 3
the existing channel banks, would not overtop the 4
banks, and would not impact the proposed site. So we 5
can screen localized regional hazards also out from 6
the hazard analysis.
7 Next slide, please.
8 DR. BLEY: I'm sorry. Do any of those 9
channels go down near enough the site that they'd be 10 used as a source of cooling water if the site --
11 MR. HILL: No. They flow maybe once every 12 couple of years, so they're not gauged. We don't know 13 the exact frequency, but they behave like other dry 14 land channels in the region. They only have flow 15 during very large, very infrequent or not very --
16 infrequently.
17 DR. BLEY: Yes, I'm familiar with those 18 kind of places.
19 MR. HILL: There's no water source 20 provided for the surface water.
21 So I know you've all had a chance to look 22 at the report. I didn't go into all the geology 23 because I know there's so many geologists in the 24 audience that are really dying to know about 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
20 advection-diffusion sedimentation models. But to 1
really wrap it up, the takeaway messages are the only 2
potential volcanic hazard at the proposed site is the 3
deposition of tephra fallout from volcano eruptions 4
that occur 100 to 320 kilometers away. Those tephra 5
fallout hazards from all the volcanic sources has a 6
95th percentile thickness of 130 centimeters, which 7
would have a less than 5.7 times 10 to the minus 7 per 8
year probability of exceedance. Most of that hazard 9
is driven from a potential Yellowstone super volcano 10 event. Finally, the potential debris flows from 11 remobilized tephra deposits should be contained within 12 existing stream channels and would not affect the 13 proposed site.
14 So with that, I've gone quick, but we're 15 here to present a summary, not the details.
16 DR. BLEY: My question might belong to 17 somebody else, but I know the staff, in their SE, said 18 they have not reviewed in any way the likelihood of 19 damage or impairment of plant equipment from the 20 tephra, so the implication is that needs to be looked 21 at later. But there's a sentence early on in your 22 report that says enhanced maintenance and inspection 23 procedures for mechanical and electrical systems also 24 appear, that word, capable of mitigating potentially 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 adverse effects of prolonged exposure to volcanic 1
tephra. My question is appear to whom and what's the 2
basis for that? It sounds like you're kind of jumping 3
the gun and saying, even if it's there, it won't do 4
any damage.
5 MR. HILL: Well, it appeared to me, the 6
author of the report, and that is why we have a 7
chapter in there about considerations for mitigation 8
and considerations for design, if warranted. I know 9
TerraPower has the option of considering all that 10 later on. But, operationally, as I go through, and I 11 think it's Chapter 9 or 10, consider that tephra 12 fallout is not an instantaneous event. It's a slow, 13 evolving hazard that allows plenty of time. Between 14 the onset of an eruption, it will be hours before a 15 tephra plume reaches a proposed site or any site. And 16 then there will be slow accumulation rates of the 17 tephra, so it doesn't all come down in one meter 18 instantaneously. It's not like a massive earthquake 19 or something. So you have time to implement 20 operational measures, closing off air circulation if 21 needed, tephra removal, tephra mitigation efforts.
22 They appear practicable without knowing the details of 23 what they may be. So that's the point that I'm trying 24 to emphasize is that there's a practicability aspect 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 of it that would allow for enhanced maintenance or 1
enhanced operations to mitigate the potentially 2
adverse effects if those adverse effects are found.
3 DR. BLEY: Okay. I understand what you 4
did and the basis for your judgment. This committee 5
and this letter to the staff had said that was one 6
area that really needed to be looked at closely, and 7
I think the applicant eventually will have to deal 8
with this a little more substantively.
9 I quickly, before this meeting, went out 10 searching to see if anything had been done in the last 11 few years, and I found a few papers out there that 12 have tracked some of the problems with tephra, 13 especially with electric power plants. And some of 14 the damage that -- this is kind of interesting to me.
15 Systems that have water flow, if this gets in it, it's 16 much more, I'll just say sharp edged. It can do a lot 17 more damage than other things and very elevated rates 18 of damage to equipment, like in a few months you saw 19 damage similar to what you'd see in 15 years or so of 20 normal operations.
21 So I think it deserves a pretty good look 22 eventually. I know it's not the subject of what we're 23 doing today, but I wanted to get you all thinking 24 about it. And there has been more work. I wish 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
23 were more, but there's more than I had seen five years 1
ago or whenever we looked at this, four years ago.
2 MR. HILL: That's correct. There are a 3
range of potentially deleterious effects on different 4
kinds of structure systems or components that we based 5
on analogous systems and other areas, like some of the 6
hydroelectric things from New Zealand. That's Tom 7
Wilson's group has been instrumental in seeing that.
8 But I think the only purpose of including 9
that information in this original report was that it's 10 very difficult to collate that sort of information in 11 any one place. There is no sensitivity guide or 12 engineering guide for how do you deal with tephra at 13 nuclear installations. IAEA is working on one but is 14 still well behind the production curve.
15 So I did assemble some of the most 16 relevant information that I was aware of so that the 17 considerations for things like mechanical abrasion 18 could be thoughtfully looked at, if warranted, to see 19 if any enhanced maintenance or design or operational 20 issues would need to be done. The need for those is 21 completely beyond the scope of this topical report on 22 volcanic hazards.
23 DR. BLEY: I like what the staff had to 24 say in this area, and I was just hoping TerraPower 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 wasn't figuring this covered it. We'll eventually see 1
that.
2 CHAIR ROBERTS: Let me follow up on what 3
Dennis was asking. One of the goals is to get a sense 4
of how useful Reg Guide 4.26 was to you. That reg 5
guide has a seven-step process, and the last couple of 6
steps in that process are basically develop what the 7
plant hazards are and then what mitigations you might 8
do to deal with whatever SSCs are adversely affected 9
by the ash fall.
10 You did some of that, I wouldn't call it 11 hand waving, but at a very high level. It is the kind 12 of things we could do, and here's kind of one 13 person's look at what the risks might be. But the 14 staff kind of said, well, okay, thank you very much, 15 we don't really think that's going to fit the bill.
16 So I'm just wondering what you plan to do.
17 MR. HILL: I first just want to make a 18 small correction to your statement that I did not look 19 at the risk. I looked at, to use the John Garret 20 terminology, what might go wrong in the sense of this 21 is the physical demand, the abrasiveness, the 22 hardness, the thermal conductivity that would be the 23 engineering inputs to answer the question of could 24 this or would this not be a potentially deleterious 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 effect on SSC performance. So, again, there is a 1
dearth of information collated from the existing 2
literature, and having that information assembled 3
provides useful guidance to both staff and TerraPower 4
on what would be some considerations if you eventually 5
had to think about these adverse effects, but it was 6
not a risk-informed decision to put Chapters 9 and 10 7
into the original report.
8 MR. KELLENBERGER: So this is Nick 9
Kellenberger again. As Britt said at the beginning of 10 the presentation, the initiating event, the eternal 11 hazard, it falls in with a beyond design basis event.
12 So based on the phases of construction permit 13 operating license, the question of what will we do as 14 we go towards operating license as we develop our 15 beyond design basis event response, we'll go through 16 and determine kind of what those responses should be.
17 And then the other thing we'll do is the external 18 hazards PRA scoping, and we have folks that go in more 19 on this, but the external hazards PRA scoping activity 20 is another -- so we've characterized our design basis 21 hazard levels for external events, so those are 22 included in our construction permit. And then the 23 beyond design basis sequences for external hazards is 24 another step in the PRA that will come between 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 construction permit and operating license.
1 CHAIR ROBERTS: So the intent for this VP 2
is it was sufficient to determine that the hazard was 3
beyond design basis?
4 MR. KELLENBERGER: That's correct.
5 CHAIR ROBERTS: Okay.
6 MEMBER DIMITRIJEVIC: Hi. This is Vesna.
7 There was a little simple question here. You know, 8
you are in the staff, too, here, basically, in the 9
looking and screening or counting hazards. But if 10 you're going to go back and look at the risk insights, 11 then you will need a little more information on the 12 hazard, not on the, you know, even this is beyond 13 design basis events. If you want to, you know, if you 14 want to estimate how efficient prevention or 15 mitigation can be, you know, you sort of need the 16 speed of accumulation of tephra or how long it will 17 take before you get warning of the hazard, you know, 18 things like that.
19 So is that something, when you were 20 looking and analyzing these hazards to get this type 21 of information, the information which would influence 22 your, you know, analysis of prevention or mitigation?
23 MR. HILL: This is Brittain Hill. Yes, 24 all that information is in Chapters 9 and 10. We did 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 not apply or develop risk insights --
1 MEMBER DIMITRIJEVIC:
No, no.
I 2
understand that you discussed this information, but do 3
you actually have a way to know in what speed, you 4
know, in what speed would, like, tephra accumulate on 5
the roofs or things like that or how long it will take 6
for the warning from eruption to get there. That's 7
what I'm asking. Is there some way that, you know, 8
you say here, I think, you know, it takes an hour or 9
something.
10 But my question is do you have way from 11 the data which you were looking to estimate those? I 12 mean, to really get some -- this is so much 13 uncertainties in this data, and I'm sure there is no 14 way, you know, to estimate that. But I'm just 15 wondering how would you analyze those preventive 16 actions?
17 MR. HILL: We use experience from around 18 the world on analogous volcanic eruptions. So we know 19 the mass flow rate, we know the transport rate, we 20 know the duration of those eruptions. In our models, 21 we know what our mass flow rate, transport rates, are, 22 so we can make a very reasonable bound about what 23 accumulation rates would be for these kind of volcanic 24 eruptions, so that's what we used to constrain 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
28 range of eruption notification times. We look at the 1
wind speeds that occur out there and say, well, if the 2
volcano is 300 kilometers away and the ash plumes 3
travel at 10 kilometer per hour, we know what the 4
arrival time is going to be and we look at the 5
accumulation rates. All that information was provided 6
just to provide that sort of perspective. It's never 7
meant to be a precise analysis of something that we 8
can't know because we don't know what the future 9
eruption duration would be. Will it be episodic?
10 Will it be continuous? I don't know. Nobody knows.
11 We can't tell that from the past eruptions either, 12 only the ones that have been observed.
13 So we have this information. If we want 14 to take the analysis further in the Reg Guide 4.26 15 parlance to go into step five, develop risk insights, 16 but we didn't do that. There was no need to for the 17 scope of this hazard analysis. We're doing the first 18 four steps. We have initial risk insights, our step 19 three, enough to determine that tephra could be a 20 potential hazard to the proposed facility, which 21 relies on air circulation for cooling. Well, tephra 22 could affect. I'm not saying adversely or negative, 23 cause failure, just it reasonably has a potential to 24 affect air circulation systems and air cooling 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 exchange. So there's our risk insight: tephra is 1
potentially significant.
2 So we're not taking the engineering option 3
in 4.26 to use SSC screening. We went to the next 4
step, step four, to evaluate the eruption potential 5
and hazard potential, which is what the outcome is.
6 We have our exceedance curves, and then we have this 7
additional information that can be used, if needed, to 8
gain those risk insights if that level of effort is 9
warranted.
10 MEMBER DIMITRIJEVIC: Well, thank you. I 11 mean, you know, I was just curious because you 12 presented some results with even some probability so, 13 you know, accumulation of the, you know, 100, you 14 know, whatever, 13 centimeters, but, you know, no 15 discussion about at what speed is that, you know, 16 occurring and what the possibilities of -- that's why 17 I was sort of curious how much we know when estimating 18 of the mitigation effect in this. Okay. Thanks.
19 MR. HILL: We have not observed a super 20 volcano eruption. We have very little understanding 21 from the interpretation of past --
22 MEMBER DIMITRIJEVIC: Absolutely, yes.
23 MR. HILL: -- what is the duration, the 24 dynamics. Do they open up in a single vent, multiple 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 vents, is it episode, what's the true mass flow rate.
1 There's huge unknowns in doing this for a super 2
volcano eruption, but, fundamentally, you're still 3
dealing with a tephra plume that has limits on its 4
density. There's only so much tephra that can be 5
buoyant in the air given this thermal input. There's 6
only so fast that that tephra plume in the super 7
volcano eruptions will diffuse through the atmosphere 8
because it's not blown by wind, it forms its own kind 9
of lateral flow, and that might be 300 kilometers an 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> based on modern analogy with smaller volcanoes.
11 So the rate of accumulation, who the heck knows? It's 12 probably pretty high.
13 MEMBER DIMITRIJEVIC: I know. I know. I 14 know. Believe me, I understand what type of 15 uncertainties you're dealing with, and super volcano 16 eruptions could be something which, you know, changing 17 the planet climate. But I was just, you know, curious 18 about this data, so thanks.
19 MR. HILL: You're welcome.
20 MEMBER MARTIN: So as one of those non-21 geologists and not yet a student of the reg guide, you 22 focused on existing volcanic fields, but, obviously, 23 their positioned sort of around the site at some 24 distance. Are you able to just discount 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
31 possibility of a new eruption in the middle of that?
1 MR. HILL: Absolutely. That detailed 2
discussion that was part of the tectonomagmatic model 3
is what it was called in the report, but it's looking 4
at what's the characteristics of the deep earth 5
beneath the proposed site compared to the 6
characteristics deep beneath existing volcanic fields.
7 And we know a lot from geophysical investigations and 8
also the chemistry and character of those old volcanic 9
fields. What sort of deep earth conditions formed 10 that volcanic system, and the bottom line is those 11 kind of conditions that form molten rock deep in the 12 earth, they don't exist beneath the proposed site.
13 And for the last 325 million years, there's no 14 evidence that any volcanic eruption has occurred 15 within 40 kilometers of the proposed site. So we have 16 reasonable confidence that a new volcano, if it 17 formed, would form within one of the existing volcanic 18 clusters and that, if a new random volcano formed 19 somewhere, it wouldn't be within 40 kilometers of the 20 proposed site.
21 CHAIR ROBERTS: So recapping what I think 22 Nick said, so there's a seven-step process. You 23 basically stopped at step four with the remaining 24 three stops you have to be resolved with the external 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
32 hazards PRA and whatever work comes out of the PLL 1
preparation; is that fair?
2 MR. HILL: I think that's very fair. It 3
is. They haven't developed the risk insights that 4
would be step five and determined whether any SSC 5
evaluations would be needed or mitigating actions 6
would be needed, given this level of external hazard.
7 CHAIR ROBERTS: Okay. Thanks. So one of 8
the things in the reg guide is it recommends use of 9
the Senior Seismic Hazards Assessment Committee, 10 SSHAC. I noticed in your report you said you didn't 11 do that. Can you give a little perspective on why 12 not?
13 MR. HILL: Sure. You know, the SSHAC 14 process is excellent for looking at systems that have 15 large amounts of uncertainty in them with 16 uncertainties that are very difficult to quantify or 17 very intractable given the state of the current 18 literature. When we first scoped this project, we 19 determined that the volcanic centers are well known, 20 that buried volcanoes are not an issue, and that the 21 characteristics of those volcanoes with the exception 22 of Yellowstone were pretty straightforward to estimate 23 based on what's available in the current literature.
24 So the initial thought was we don't need 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 to do a SSHAC process if the uncertainties are 1
manageable and the literature is sufficient to 2
quantify those uncertainties in a very reasonable, 3
transparent, traceable way. But we reserved the 4
option, if at any stage in the analysis we came to 5
something that was, wow, this is a real huge epistemic 6
uncertainty that is going to need a lot more 7
attention, then we could go and fall back into a SSHAC 8
process. Even a subset of that could be done at a 9
SSHAC, say level two, without having to invoke a fully 10 SSHAC-level multiyear-long process to answer this very 11 basic question.
12 The other aspect of that is that we took 13 a conservative approach in analyzing the potential for 14 a Yellowstone super volcano eruption. There's a lot 15 of debate in literature about whether Yellowstone is 16 capable of such a huge eruption or not. Rather than 17 falling down that rabbit hole of geologic interest and 18 forming a SSHAC to answer definitively, we took a 19 bounding approach based on conservative analyses by 20 the U.S. Geological Survey that gave us the 113 21 centimeters at the 95th percentile.
22 So I'm not arguing that we can screen it 23 from any consideration. It's just probably less than 24 a beyond design basis event, but it's so thick 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
34 really would want to have some documentary record of 1
we thought about it and here's why we're not going to 2
have to worry about it based on the current design of 3
risk insights.
4 CHAIR ROBERTS: Steve Schultz had his hand 5
up. Steve.
6 DR. SCHULTZ: Yes. Thank you. In 7
evaluating the tephra fallout, you used the ash plume 8
code in order to move forward and perform quite a few 9
analyses and evaluations associated with that. You 10 note in the report that you began with the rev 1 to 11 ash plume, and then you modified the code to develop 12 a revision 2 to the computer code; is that correct?
13 MR. HILL: That's correct.
14 DR. SCHULTZ: And you note that, for rev 15 1, the NRC applied all their QA requirements and some 16 confirmatory testing associated with it. With regard 17 to your modifications, did you perform that under a 18 TerraPower quality assurance program --
19 MR. HILL: Yes, I did.
20 DR. SCHULTZ: -- as you went through that?
21 So that was done.
22 MR. HILL: That's correct.
23 DR. SCHULTZ: Good. And then also the NRC 24 noted, I wanted to just prepare them for it or 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
35 can address it, but they indicated that they also did 1
some confirmatory calculations. I presume you 2
provided them with the computer code and input so that 3
they could do that evaluation?
4 MR. HILL: Yes, we did.
5 DR. SCHULTZ: Good. Well, thank you. I 6
just wanted to -- there's a lot of information that 7
was developed throughout the report by using that 8
methodology. It probably could provide more detailed 9
evaluations if the site was closer to the volcanic 10 hazard, but appreciate the work that was done there.
11 I like that it was done under a QA program.
12 MR. HILL: I'd like to, just to make sure 13 that everybody is aware, the modifications we're 14 talking about are very straightforward. In the 15 original ash plume code, the wind speed and wind 16 direction are hard wired in the code as subroutines 17 because the code was developed for use at Yucca 18 Mountain and only Yucca Mountain. The modifications 19 that I did was locked out those subroutines and put in 20 a stratified wind field, which is basically saying for 21 these 5 kilometers above-ground increments, what is 22 the average and standard deviation wind speed based on 23 NOAA re-analysis data. We then stochastically sampled 24 those wind speeds from the appropriate distributions 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 but always kept the plume directed at the proposed 1
site. So the only modification is, rather than a less 2
than 5-kilometer high wind, I'm using up to 25-3 kilometer high winds in 5-kilometer increments to just 4
sample based on the top of the plume. And post-5 processing is accounting for what is the likelihood 6
that the wind will be flowing in that sector directed 7
towards the proposed site from the volcanic source.
8 But it's a conservative assumption because, in this 9
simulation, every analysis center line, the highest 10 concentration of tephra, is always directed at the 11 proposed site. You don't get near hits and near 12 misses in there to dilute your runs.
13 DR. SCHULTZ: I thought that was quite 14 appropriate for this evaluation. I appreciate that 15 very much. Thank you.
16 CHAIR ROBERTS: Okay. Any other questions 17 from members or consultants?
18 MEMBER KIRCHNER: I have one. This is 19 Walt Kirchner. Thank you for your presentation. Just 20 taking it one step further, since we have an expert in 21 volcanism here, have you been looking at effects of 22 the tephra fallout on equipment in places like Iceland 23 where they had recent volcanic eruptions? Obviously, 24 they have to deal with it. Have you been getting any 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
37 information on component performance under those 1
conditions?
2 MR. HILL: Yes. For the past several 3
years, I've been part of a working group at the 4
International Atomic Energy Agency that's been 5
assembling information and international experience on 6
just that, what are known or observed effects on 7
different kinds of engineered systems both at nuclear 8
and non-nuclear facilities in respect to tephra 9
fallout hazards.
10 A consideration in Iceland is it usually 11 has a very high amount of adhered ions on the tephra, 12 so leaching of acidic fluids or acid is a longer-term 13 problem from Icelandic tephra that has come from time 14 to time up in the literature but not quite on nuclear 15 systems.
16 So there is some experience 17 internationally. It has not been assembled into a 18 unified or even curated collection of documents. We 19 can answer some very fundamental questions, like how 20 little matters, what's the minimum thickness to where 21 you say, oh, this is a nuisance level.
22 If you're talking about earthquakes, we 23 all have a minimum design standard that we're very 24 comfortable with and say, oh, below this, we don't 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
38 really care. We don't have anything like that. We're 1
just sort of starting out on tephra. Engineers for 2
earthquakes, they've got 40 - 50 years of experience, 3
so it's not fair.
4 MEMBER KIRCHNER: Thank you.
5 MEMBER MARTIN: Bob Martin here. When I 6
think of the most likely hazard, it would relate to 7
its impact less on equipment but on maybe the most 8
important piece of equipment and that is the people.
9 You know, of course, you highlight the need for 10 respirators, goggles, and such, you know. At the 11 least, those are inconveniences, but, at the most, it 12 really creates, you know, contribute to just the chaos 13 because, of course, this would be a situation that 14 we're definitely unfamiliar with. I would expect that 15 the likelihood of other hazards related to the 16 operator would be heightened. Is there a connection 17 from a document like this to feed into a PRA, you 18 know, type model, which would ultimately elevate the 19 likelihood of these kind of human errors associated 20 with that? I mean, it comes down to data, but I 21 think, you know, we all were alive during Mount St.
22 Helens and remember pictures of other places, and, you 23 know, it was worse than a fog, right. You really 24 couldn't see. Large lights couldn't really help, 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
39 know, help the people get through traffic and things 1
like that, and it was a mess, to say the least. But 2
I want to see how you go from a document like this 3
into state the analysis. That would be the most 4
likely thing I would focus on the most.
5 MR. HILL: There isn't a direct link in 6
the literature on human factors in the way that we 7
mean that in nuclear facilities and volcanic 8
eruptions. We do now have some very good experience 9
with what happened at Hanford during the Mount St.
10 Helens eruption because there were a number of nuclear 11 facilities that were operating. Even though Hanford 12 only received less than a centimeter of tephra, it was 13 south of the main plume from St. Helens, there were 14 impacts from all of that, especially in vehicle 15 operations. That's why part of that is discussed.
16 And remembering with a grain of salt, you 17 remember cars in 1980 versus cars today. How do the 18 electronics do? They may be better, they may be more 19 susceptible to ash ingress; I don't know. Nobody has 20 looked at it since really Mount St. Helens.
21 Getting people through the site, people 22 adapted very quickly both for the transportation 23 network, the busses. They started putting on external 24 air filters and increased the oil change. Washington 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 state did the same thing. They just really amped up 1
their maintenance cycle without any formal guidance.
2 It was just, well, we've got to clean out the air 3
filter and put a primary filter on top of that in 4
order to keep the cop cars running.
5 But I think from what I know from St.
6 Helens, it wasn't really chaotic. It was difficult 7
for about eight hours when the peak air fall fell 8
beneath the plume itself, but you weren't getting 9
blackout conditions at the Hanford facility. You got 10 a really smudgy day with the tephra falling out and a 11 lot of dust kicked up on the road.
12 So it's an inert particulate. It's a 13 nuisance particulate, and I have been in a number of 14 countries where people just put the umbrella up and 15 walk through the tephra falling out tens of kilometers 16 away. They're very non-plussed by it all.
17 So it's not a very thick fallout, except 18 during the peak. If you put your umbrella up, you'll 19 probably be okay from all of that. There are 20 considerations, of course. I'm not trying to pooh-21 pooh the idea.
22 MEMBER MARTIN: Right.
23 MR. HILL: It's just it is not an 24 immediate threat to human health and safety. It needs 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
41 to be managed, and that was part of the whole point of 1
the operational considerations is this is manageable.
2 It's not a huge flood coming out of nowhere. It's 3
relatively easy and straightforward to manage this.
4 MEMBER MARTIN:
But does it set 5
requirements for having, you know, respirators and 6
goggles on-site for the staff? And where is the 7
traceability of the requirement?
8 MR. HILL: That would depend on the 9
operational significance of this external event and 10 probability level. All I can say is it appears 11 practicable. If it's warranted, that's a risk 12 insight.
13 DR. BLEY: This is Dennis Bley again.
14 Maybe to be a little argumentative, that plume lofted 15 over Hanford. But if you talk to people on the 16 eastern side of Washington near the border, they got 17 a couple of feet of ash on their roofs. It really 18 came down hard over there, so it depends on where you 19 are.
20 MR. HILL: Oh, yes. If you were in 21 Yakima, that's really different, though, a different 22 experience than if you were down at the Hanford 23 reservation. I think Hanford is, like, 50 to 60 24 kilometers south of 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
42 DR. BLEY: Yes.
1 MR. HILL: -- so it wasn't like -- St.
2 Helens was a relatively small eruption in the scale of 3
volcanoes, but it still was a fairly narrow wind-4 driven plume and, if you were unlucky enough to be 5
right in the center line of the plume like Yakima, 6
yes, you were having tens of centimeters of tephra 7
falling out, and that was the day turned into night 8
and you couldn't even see the streetlights and you had 9
to hunker down for about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. And afterwards, 10 the tephra removal, the ash removal, was a lot worse 11 than snow because, if you get ash wet, it weighs about 12 a ton per cubic yard. That's heavy stuff.
13 DR. BLEY: I've heard it can almost turn 14 into concrete, too, after --
15 MR. HILL: Well, if you really get it wet, 16 it does indurate pretty successfully, yes.
17 CHAIR ROBERTS: Okay. If there's no more 18 questions -- looking around I don't see any hands up, 19 so, TerraPower, thank you very much for your 20 presentation. We'll now switch to the NRC staff.
21 All right. Stephanie, when you're ready.
22 MS. DEVLIN-GILL: Okay. Ready. Hello, 23 everyone. My name is Stephanie Devlin-Gill. I am a 24 senior licensing project manager at the NRC assigned 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 to the TerraPower Natrium project. I'm the lead 1
project manager on this topical report. Sitting next 2
to me today is the lead technical reviewer, Jenise 3
Thompson. She's an experienced NRC geologist and the 4
lead technical reviewer on this topical report.
5 This slide describes the agenda of the 6
NRC's presentation today. We will be reviewing the 7
chronology of the review, the purpose of the staff's 8
review, and the staff's review strategy of the topical 9
report, and then provide an overview of the contents 10 of the staff's safety evaluation report, and then, 11 finally, summarize the staff's conclusions regarding 12 TerraPower's topical report.
13 Regarding the time line, we started off 14 with a pre-application public meeting in July 2022.
15 TerraPower submitted the topical report in April 2023.
16 In June 2023, the NRC accepted the topical report for 17 review, and then in September and October the NRC 18 conducted an audit. In February 2024, the draft 19 safety evaluation was issued.
20 This slide shows the NRC staff and their 21 review team. The TerraPower project management team 22 has a few names on it: Mallecia Sutton, the lead, 23 TerraPower project manager, she started off this 24 review; Role Brusselmans led the audit; and I'm 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
44 to finalize the review.
1 And now I will turn over the presentation 2
to Jenise Thompson, and she'll start off by describing 3
the technical staff participation in this review.
4 MS. THOMPSON: Thanks, Stephanie. So in 5
addition to myself as the geologist and lead reviewer, 6
we brought in some additional support staff on the 7
hazards site. Jason White, a meteorologist. As you 8
heard, there was some meteorological data that was 9
important to the modeling, so we brought in one of our 10 experienced meteorologists to support that review. We 11 also had Scott
- Stovall, a
seismologist and 12 geophysicist. Typically, he's in the Office of 13 Research. He was on detail to NRR, which was great 14 for us because he was able to perform the independent 15 confirmatory calculations of the model that was used.
16 And then we also had Hanh Phan, who is a senior 17 reliability and risk analyst, and he's here today, as 18 well, because we did recognize that the hazard 19 component was the end of this topical report and there 20 is still an important interface between the hazard 21 that was determined in the topical report and what 22 comes next if there's a subsequent engineering 23 analysis, so we wanted to make sure that we were 24 already having discussions with the team that was 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
45 going to take over looking at the impact on the 1
overall facility risk from that particular hazard. So 2
that was our review team.
3 We'll go to the next slide, please. As 4
Stephanie said, we received the topical report, 5
conducted an audit, issued our audit summary. I'm not 6
going to spend a lot of time on this because I think 7
she covered it here.
8 Something I do want to emphasize is that, 9
because they kind of bifurcated the process in Reg 10 Guide 4.26, the scope of the topical report is 11 primarily focused on the hazard determination and we 12 didn't go into the effects on overall plant risk, any 13 necessary mitigating actions or enhancements to any of 14 their SSCs that may be impacted by these volcanic 15 hazards because that information was not provided 16 within the scope of the topical report. So we weren't 17 provided with the overall plant PRA, we weren't 18 provided with overall detailed design information of 19 potentially affected SSCs, so we focused our review on 20 the hazard determination only.
21 Moving on to the next slide, we're on 22 slide six, the regulatory requirements. For those 23 members who were part of the reg guide briefings that 24 we've given over the years, you're probably familiar 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 with the regulatory requirements entitled 10 GDC 2 and 1
then you may recall 100.23 is the specific regulation 2
that calls out volcanic activity as something that 3
needs to be considered in the context of licensing a 4
reactor.
5 Go to the next slide, please. The 6
applicable guidance here is Reg Guide 4.26. I know 7
there's been some discussion on the content of that 8
already. We were here in ACRS in February of 2020 and 9
then April of 2021. We issued rev 0, and then just 10 last summer we processed an administrative change. I 11 think you all were aware of that. And then last 12 September I came and presented an overview of how the 13 staff was planning to approach the review of any 14 topical report or application that was using Reg Guide 15 4.26 to perform their volcanic hazards assessment.
16 We've already talked a little bit about 17 the incorporation or endorsement of the SSHAC process 18 within Reg Guide 4.26. I want to emphasize that it's 19 not a requirement in 4.26. It's just a suggestion.
20 If you think it may be necessary for your particular 21 site and the hazards, particularly volcanic hazards, 22 that may need to be considered, and so this is 23 something that we are tracking as a potential 24 clarification in a future revision to 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
47 that SSHAC is one method that can be used for expert 1
elicitation but is not necessarily a please do this 2
for your volcanic hazards assessment to be considered 3
acceptable. So we are tracking that with the reg 4
guide project manager who was responsible for Reg 5
Guide 4.26.
6 And within 4.26, we have identified that 7
flow chart -- we'll go to the flow chart in the next 8
slide here, but there is an option to pursue what's 9
called an engineering analysis where you perform a 10 basic hazard assessment and then start to look at what 11 the impact would be on the SSCs in your particular 12 reactor design and what the impact would be of those 13 hazards on those SSCs. And that engineering analysis 14 would move forward considering a maximum magnitude 15 volcanic hazards. So what is that? Screened-in 16 volcanic hazards, remembering there are many 17 different types of volcanic hazards that may impact a 18 facility and then determining what would be that 19 magnitude to consider in any subsequent engineering or 20 risk analysis for that site.
21 Next slide, please. Most people are 22 familiar with this flow chart outlining the 23 methodology in Reg Guide 4.26. Again, we're looking 24 here for a maximum magnitude hazard for those 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 screened-in volcanic phenomena, recognizing that not 1
all phenomena are going to impact a particular site.
2 And just as a brief overview, we start with available 3
information, so we start with the geologic 4
information, geologic
- history, and site 5
characterization information looking particularly at 6
are there quaternary volcanoes in the site region, 7
which is a 200-mile or 320-kilometer radius around the 8
site, and are there quaternary volcanic deposits in 9
the site vicinity, so within a 25-mile or 40 kilometer 10 radius of the site, and the quaternary being the last 11 2.6 million years of geologic time.
12 And from that, an applicant would move 13 into step two to screen volcanic hazards and then 14 develop the initial risk insight. What we note in the 15 topical report here submitted by TerraPower is that 16 the subsequent evaluations of SSC performance or the 17 impact on a probabilistic risk assessment for the 18 facility is going to be deferred to the construction 19 permit review stage because we weren't provided that 20 information within the context of the topical report.
21 So these bottom steps five, six, and seven, those are 22 going to be deferred to later.
23 And I recognize, going back into Reg Guide 24 4.26, we did not state that that would be an 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 acceptable approach to essentially bifurcate the 1
hazard steps from the engineering analysis steps, and 2
so that's another area where we have already started 3
talking with our regulatory guide PM. His name is Ed 4
O'Donnell, and he's amazing. So we've already had 5
conversations with Ed about what does this look like 6
going forward for a potential revision to this guide 7
now that we have some experience with an applicant 8
using it because it's difficult, I would say 9
challenging, to know where you need to provide 10 additional clarification until you've gone through the 11 process of using the methodology, and then you have a 12 much greater ability to identify areas to focus on for 13 clarification in the future. So that is something 14 that we are looking at in the future for --
15 DR. BLEY: Dennis Bley. You really intend 16 that they complete the evaluation of SSC performance, 17 especially under tephra, for the CP? I would expect 18 they'll be able to put it off until the operating 19 license if they want to.
20 MS. THOMPSON: Yes. That's another 21 option. Either would work, the CP or the OL. It's 22 also possible that, once they have the detailed design 23 information, that they will be able to end the 24 assessment and document the results for why they don't 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 need to perform an additional evaluation of SSC 1
performance or implement mitigating actions. So 2
within the flow chart here, the methodology in 4.26, 3
any of those would be acceptable in the future. We 4
just don't have that information yet. An early end of 5
the assessment is, you know, well within the 6
methodology we outlined in 4.26.
7 DR. BLEY: And that would be great.
8 CHAIR ROBERTS: You used the term 9
screened-in volcanic hazards. The applicant just made 10 a distinction between screened-in but beyond design 11 and screened-in within design basis. Did I understand 12 that right? Are there two ways that you could be 13 still screened in but lead to a different level of 14 assessment of the risk?
15 MS. THOMPSON: Yes. There's a wide range 16 of volcanic phenomena that may pose a hazard to a 17 site. And in TerraPower's presentation, they talked 18 about flow hazards versus the suspended hazards. Not 19 every volcanic phenomena is going to pose a potential 20 risk to the facility. They talked about topography 21 and distance, and that's something that in this 22 initial screening here you would be able to say we're 23 over 100 miles over several mountain ranges from the 24 volcanic source to the proposed site; therefore, we 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 don't need to consider lava flow phenomena as a 1
potential hazard at the site. And that's what this 2
initial screening volcanic hazards stuff would 3
include.
4 The decision or the determination of 5
what's a design basis hazard versus a beyond design 6
basis hazard would be subsequent to that initial 7
screening of which phenomena need to be considered for 8
a particular site.
9 CHAIR ROBERTS: Okay. Thanks. So when 10 and how much you do in steps five through seven may be 11 informed by, it's screened in but beyond design basis 12 versus design basis?
13 MS. THOMPSON: Exactly.
14 CHAIR ROBERTS: Okay. Thanks.
15 MS. THOMPSON: Okay. So we can go to our 16 next slide, slide 9. The review approach, this is the 17 approach that we took as a staff is exactly what we 18 briefed to the committee back in September of 2023.
19 The goal of the reg guide is to start with the 20 available geologic information, so the geologic 21
- history, site characterization information.
22 TerraPower touched briefly on the tectonomagmatic 23 model. That's a very important consideration for us 24 in determining what volcanic sources could have 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
52 potential to induce a volcanic hazard that would need 1
to be considered for that site and whether there's the 2
potential for a new vent to open in a place where 3
there isn't currently a volcanic source.
4 We also recognized that Reg Guide 4.26 and 5
the applicants are using numerical modeling to 6
consider their screened-in volcanic phenomena, and so 7
we'll talk about that a little bit later in this 8
presentation. And then, again, emphasizing that, 9
here, we're looking at what is the magnitude of the 10 volcanic hazards that would or could be used if an 11 evaluation of SSC performance or mitigating actions 12 needs to be made at the CP or OL stage.
13 DR. BLEY: Can I ask you how -- have you 14 run into any difficulties reviewing the tectonomagma 15
-- I can't say it.
16 MS. THOMPSON: Tectonomagmatic model?
17 DR. BLEY: Thank you.
18 MS. THOMPSON: It's a bit of a tongue 19 twister. It is.
20 DR. BLEY: That's a fairly complicated 21 model. How do you review that?
22 MS.
THOMPSON:
So we're looking 23 specifically at the drivers of the volcanic system.
24 I wouldn't say that it's complicated if you're a 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 geologist. That's how I'd preface it. But you're 1
looking at the geophysical drivers of the current 2
state of the volcanic systems. Volcanic systems are 3
highly dynamic, so what conditions existed in the past 4
that resulted in an eruption may not exist presently 5
or have the potential to exist in the future.
6 A great example, think about a hotspot 7
track. So if you are, I don't know if you're familiar 8
with Hawaii, the big island there, that is where the 9
current hotspot is. That is where the volcanic events 10 are occurring. You want to go on vacation and not 11 worry about a volcano, go to Kauai at the far other 12 end of the archipelago where there have not been 13 eruptions there. So in looking at the tectonomagmatic 14 model for Kauai, it would be very difficult than the 15 island of Hawaii because of the change in the hotspot 16 tracking. We wouldn't expect that Hawaiian hotspot 17 would reverse and go back to one of the older islands 18 in that volcanic chain. Does that kind of address 19 your question?
20 DR. BLEY: Kind of.
21 MS. THOMPSON: Okay. All right. We'll go 22 to our next slide. We're on slide 10. We start with 23 the site geology and regional geologic history, and 24 this is where the basis of developing 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
54 tectonomagmatic model comes into play because we do 1
want to have a clear understanding of what are the 2
geologic processes that have driven things, like 3
volcanism, seismicity, just general rock-forming or 4
mountain-forming events, and how did the rocks that 5
are there now get to be there. So that overall 6
geologic history becomes an important component to 7
understanding the tectonomagmatic model.
8 So for this particular site, we looked at 9
all the information that was provided. The site under 10 consideration in this topical report is in the middle 11 Rocky Mountain physiographic province. It's that 12 green dot in the very center of this figure. The site 13 vicinity is the green line around it, and then the red 14 line, and I apologize to anyone who has trouble seeing 15 colors, but the far red line is the site region. So 16 we're looking at volcanic deposits within the site 17 vicinity or volcanic sources within the site region.
18 As you can see, there are several volcanic sources 19 here, and we'll get to the figure that was shared by 20 TerraPower, which is a little bit easier to see where 21 the volcanic sources are.
22 But in the site vicinity and particularly 23 underlying the Kemmerer site is a series of Paleozoic 24 and Mesozoic sedimentary rock, so we're not sitting on 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 any type of igneous rock, we're not sitting on 1
volcanic rock or volcanic deposits. Also, Paleozoic 2
and Mesozoic are very old geologically, so we're not 3
looking at young rocks by any stretch. And within 4
that, we also see that these sedimentary rocks have 5
been folded and deformed as part of a mountain-6 building event, which was the last 50 to 150 million 7
years. So we're sitting on old rocks that were 8
deformed and faulted a relatively long time ago 9
geologically. We don't see young volcanic within the 10 site vicinity. We don't see any of the, in any of the 11 features that we would expect for a potential volcanic 12 event within that site vicinity, and we don't have any 13 evidence geologically of volcanic eruptions in the 14 site vicinity for at least the last 150 million years.
15 So we have geologically from a regional geologic 16 history perspective a long history of no volcanism at 17 this particular site.
18 Next slide, please.
19 MEMBER HARRINGTON: Just one quick 20 question.
This is Craig Harrington.
The 21 tectonomagmatic model, is that more of a qualitative 22 model or a quantitative mathematical?
23 MS. THOMPSON: I would say that it's more 24 qualitative. It pulls together the information 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
56 available for the geologic history on that particular 1
site, so it's looking at the available geologic 2
information for the history of the region. So we're 3
not pulling out a numerical model that's telling us 4
something about it. We're looking at all of the 5
available data and information that we have for that 6
region to determine what could realistically occur, 7
given the current state of that volcanic system. And 8
I actually have a slide coming up, I think it's slide 9
12, where I talk about their tectonomagmatic model.
10 So I'll go into in a little bit more detail.
11 All right. So we can go to slide 11.
12 There we go. We also looked at site characterization 13 information. The topical report focused primarily on 14 all of the volcanic information, so we weren't looking 15 across the board at the entire geologic history but 16 focused on the volcanic sources in the site. And 17 there were seven regional volcanic sources within the 18 320-kilometer or 200-mile radius. Those are all 19 listed here. As you can see, most of them are towards 20 the periphery of the site region. They're not just 21 outside the site vicinity. Most are sitting greater 22 than 100 or more kilometers from the site. The 23 closest volcanic source to the site is the Leucite 24 Hills volcanic field, which is almost directly to 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
57 east of the site, and then you can see the other 1
volcanic sources within the site region here.
2 At the far southwestern edge of the site 3
region is the North Black Rock Desert Volcanic Field, 4
and that was something that the applicant determined 5
would screen out based on distance and other 6
considerations. It's past the Wasatch Range, which, 7
if you've been to Salt Lake City, there's a large 8
mountain range there, and it's easy to imagine that it 9
would take a lot for a lava flow to summit that 10 mountain and come back the other side into Wyoming.
11 So getting to Member Harrington's question 12 on the next slide, 12, we will discuss the 13 tectonomagmatic model that was presented by the 14 applicant. There are two main drivers of volcanism in 15 the site region, and those are volcanic sources that 16 are associated with the Yellowstone hotspot track, and 17 those sources are the Eastern Snake River Plain, which 18 is that sequence of black and blues in the 19 northwestern part of the site region; the Yellowstone 20 volcanic source, which is the red dots almost directly 21 to the north of the site; and then, finally, the Upper 22 Wind River Basin, which is just to the southeast of 23 the Yellowstone field. And all of those sources are 24 associated with the Yellowstone hotspot track, and, as 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 you can see from the map, the site is not located near 1
the track of that hotspot. So from a tectonomagmatic 2
model, we know that the Yellowstone hotspot is driving 3
volcanism in those particular sources within the site 4
region, but the site itself is not within the track of 5
that hotspot, so we wouldn't expect the site to be 6
subject to volcanic events originating from that 7
hotspot activity.
8 We also recognize that there are volcanic 9
sources in the basin range physiographic province, and 10 those are all caused by extensions, so the pulling 11 apart, the thinning of the earth's crust. And those 12 sources are the Black Foot Reservoir, the Leucite 13 Hills, Curlew Valley, and the North Black Rock Desert.
14 But if you go back to the first slide on geologic 15 history, this site is not located in the basin range 16 physiographic province. It's located in the middle 17 Rocky Mountains, so it's characterized by different 18 drivers of geology, different geomorphology, different 19 structural components that make it part of that Rocky 20 Mountain physiographic province, not the basin range 21 physiographic province. And so because it's located 22 within the Sevier overthrust within that middle Rocky 23 Mountains physiographic province, we would not expect 24 this site to be subject to volcanism from basin range 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 extension because we have the extension in the basin 1
range and we have compression at the site within their 2
physiographic province.
3 So from a
tectonomagmatic model 4
perspective, we looked at the information provided in 5
the available literature and were able to reach that 6
conclusion that neither the Yellowstone hotspot track 7
or basin range extension would result in volcanism at 8
the site.
9 Were there any questions on the 10 tectonomagmatic model? Okay.
11 So with all of that background 12 information, we then move into -- we're on slide 13, 13 thank you -- that screening question. So step two, 14 what hazards or volcanic phenomena could screen out 15 from further consideration, and the applicant 16 determined that three volcanic phenomena, those being 17 proximal hazards, lava flows, and pyroclastic density 18 flows, could be screened out based on the distance 19 from the volcanic source to the proposed site and the 20 topography in between. So we're in a mountainous 21 area. It's unrealistic to imagine that a lava flow is 22 going to summit mountains and come back to this 23 particular site.
24 So, in this case, topography and 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
60 distance is an important driver of whether a hazard 1
needs to be considered for the site or can be screened 2
out. In this case, these hazards can realistically be 3
screened out.
4 We also looked at whether there was a need 5
to consider sources of tephra beyond the site region, 6
and the cutoff point for that is are there quaternary 7
volcanic deposits within the site vicinity. And if 8
there are, then you may need to consider tephra 9
sources beyond the site region. In this case, there 10 are no tephra deposits within the site vicinity, so 11 there's no need to consider tephra from sources 12 outside of the site region, so that could also be 13 reasonably screened out based on the geology at the 14 site.
15 We'll go on to slide 14. The applicant 16 did consider the potential for a new vent opening at 17 the nearest volcanic field as part of their screening, 18 and that, again, is the Leucite Hills Volcanic Field 19 almost directly to the east of the site. It's still 20 greater than 100 kilometers from the site. I think 21 the closest point is about 117 kilometers from the 22 site. They used a code that was developed for the 23 Yucca Mountain project that went through an NRC QA 24 program, and that was PVHA_YM, and, essentially, 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 transposed the geographic co-ordinates from Yucca 1
Mountain to the Leucite Hills Field and determined 2
that there wasn't going to be potential for a new vent 3
opening in Leucite Hills that would impact the 4
facility. So you could screen out lava flow or new 5
vent opening from that Leucite Hills source based on 6
that modeling.
7 DR. BLEY: Jenise, Dennis Bley again. On 8
your previous slide, is there any guidance or 9
requirements on how deep and how near or far away from 10 the site one has to be to say that there have been no 11 tephra deposits there?
12 MS. THOMPSON: We don't have any specific 13 requirements for depth or distance -- or for depth.
14 We don't have specific requirements for depth at the 15 site. But I think it's safe to say that if you're 16 sitting on -- the youngest rocks are Mesozoic, and 17 what we're seeing within the stratigraphy that's 18 visible as you cross this section across the surface 19 of the site, that those rocks continue to get older 20 and we're not seeing tephra there, that it's 21 reasonable to assume that there isn't going to be 22 tephra in the subsurface or, if there is, it's going 23 to be older than what's exposed at the surface.
24 Now, if this were a different location 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 with younger rocks at the surface, then that would be 1
a different question to consider. And, in that case, 2
maybe it would be more appropriate to consider is 3
there tephra in the subsurface that's younger than 2.6 4
million years. But for this site, we're sitting on 5
very old rocks, and we wouldn't expect to see tephra, 6
we wouldn't expect to see younger tephra under older 7
rocks. Geologically, that's not something that we 8
would see. That would be somewhat alarming.
9 Okay. So the applicant performed a 10 screening and screened out lava flow and potential new 11 vent opening from further analysis.
12 So with that, I'll go to slide 15, and 13 there are hazards that screened in. So we've already 14 heard from the applicant that tephra was a source of 15 volcanic hazard within the site region. The applicant 16 moved forward with an analysis of both the silicic and 17 mafic sources, and the applicant, as you heard, also 18 considered debris flow from remobilized tephra on the 19 north fork of Little Muddy Creek and ultimately 20 determined that was not going to result in a hazard to 21 the site. So tephra from the regional sources was the 22 primary hazard considered here for additional 23 analysis.
24 We're now on slide 16. I'm going to go 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 back to this figure so that everyone can have a good 1
picture of what was considered in the tephra analysis.
2 So as we talked about, the applicant considered both 3
silicic sources and mafic sources, and the different 4
volcanic systems here are producing silicic or mafic 5
and, in some cases, both.
6 So the silicic sources that were 7
considered were the Black Foot Reservoir Volcanic 8
Field, the Eastern Snake River Plain, Curlew Valley, 9
and the Yellowstone Volcanic Field; and mafic sources 10 were the Upper Wind River Basin, Leucite Hills, Black 11 Foot Reservoir, and the Eastern Snake River Plain.
12 We'll go to the next slide. We're on 13 slide 17. The applicant used the Ash Plume 2 model as 14 part of their, for their numerical modeling of tephra 15 hazards, and they used this to analyze both the 16 silicic and mafic tephra hazards for all but the 17 Yellowstone super volcano eruption, and you'll see 18 that in a subsequent slide. As they used Ash Plume 2, 19 they used run intervals that were designed to maximize 20 the number of realizations in order to adequately 21 capture a range of uncertainty. And as I mentioned 22 before, we were greatly appreciative of Scott Stovall 23 who performed the confirmatory calculations using the 24 input files provided by the applicant, and we 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 confirmed the applicant's results in using the Ash 1
Plume 2 model.
2 So we're on slide 18 now. This is 3
essentially a summary of the hazards for potential use 4
in future analysis. You can see it's a combined mafic 5
and silicic sources here, and, as was touched on by 6
the applicant, all but the very last line here of the 7
Yellowstone volcanic field, VEI8 silicic eruption were 8
performed using the Ash Plume 2 code and confirmed by 9
the NRC staff. The Yellowstone volcanic field VEI8 10 was from a USGS code, Ash3d. We did not perform 11 confirmatory calculations for Ash3d, but we believed 12 that the incorporation of the USGS code is acceptable 13 and that's something that is considered kind of the 14 seminal approach for the Yellowstone volcanic field, 15 and we considered it acceptable for use here.
16 With that, we'll go to the limitations and 17 conditions. We've touched on this a couple of times 18 in the presentation. The conclusions here do not 19 adjust the content provided in Section 10, so an 20 applicant or licensee in the future referencing this 21 topical report will need to evaluate the specific 22 design mitigation or monitoring actions that may be 23 required to mitigate the effects of volcanic hazards 24 if necessary. It is also possible, as we saw in 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
65 flow chart for Reg Guide 4.26 that, as you apply the 1
additional risk insights, that it may not be necessary 2
to perform an additional evaluation of SSC performance 3
or implement mitigating actions, but we didn't have 4
that detailed design information or risk information 5
provided with the topical report, so that is not part 6
of our conclusions here.
7 And the limitations and conditions are 8
something where we worked very closely with the risk 9
analyst folks to ensure that we were not seeing 10 anything in our topical report conclusions that was 11 going to hinder their future review if it's necessary 12 based on the impact of these volcanic hazards on the 13 engineered systems for the proposed facility.
14 And then, finally, we weren't provided 15 with the overall plant risk, so the conclusions in 16 this SE do not address the impacts of those calculated 17 probabilities on the accumulative plant risk. That's 18 something that will be deferred to such time as the 19 overall plant risk is provided for the NRC staff 20 review.
21 And with that, I believe we're at the end.
22 Our conclusions are that the characteristics of the 23 volcanic hazards to the tephra hazard that was 24 determined for the Kemmerer site are appropriate 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
66 use as inputs to the evaluation of SSCs or the 1
efficacy of mitigating actions, if necessary. And 2
with that, I will take any questions that you may 3
have.
4 MEMBER KIRCHNER: Jenise, I have a 5
question. If necessary. The if necessary is going to 6
depend on some assessment of that bottom line, 5 times 7
10 to the minus 7th cutoff. Just could you lead us to 8
the next step forward? Even if you had a complete 9
risk profile for the planned plant, where would you 10 stop your analysis? You've got an input to consider, 11 but when do you actually consider it?
12 MS. THOMPSON: So, Stephanie, if we could 13 go back to slide 8.
14 MEMBER KIRCHNER: This is the problem of 15 cliff-edge effects. We've been dealing with other 16 applications that were seismic related, so I just want 17 to try to understand what the logic is to take it the 18 next step and then say, no, you don't have to consider 19 this for the plant in Kemmerer or you do. How do you 20 come to that decision?
21 MS. THOMPSON: So I'm going to refer back 22 to the flow chart here. So we've essentially stopped 23 the analysis at step four with the characterization of 24 the hazard information. We don't have the additional 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 risk insights that we would see in step five, and 1
that's something that we would expect the applicant to 2
provide either in a CP or OL referencing this topical 3
report. And they would be able to make the case for 4
why or why not this level of tephra hazard is or is 5
not consequential to their site. So it maybe, and I'm 6
just going to speak in hypotheticals, not about the CP 7
or any potential OL, but there's the potential if you 8
have, let's say, a closed system where you don't have 9
any air intake that tephra would come into and 10 potentially damage or hinder the performance of that 11 SSC. At this stage in step five, you would be able to 12 say we don't have any systems that tephra could get 13 into and potentially impact their ability to perform 14 their safety function. And that risk insight could be 15 used to document the results and end the assessment at 16 that point.
17 If you did have a system or determined at 18 stage five or step five in the methodology here that 19 there is a concern that the hazard might impact a 20 certain system or need to consider a mitigating action 21 to ensure continued performance of that SSC, then they 22 would come down to step six or seven and provide that 23 justification, which we would review at that time.
24 This isn't a staff decision of you need 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
68 move forward or you need to not. The goal of Reg 1
Guide 4.26 is that the applicant can make the safety 2
case for why it does or does not matter, and we will 3
review that for its adequacy. So I would expect that, 4
as this move forwards, we will see consideration of 5
these tephra hazards in the plant risk and in the 6
performance of SSCs that may be potentially be 7
impacted and we'll review that when that information 8
is provided to the staff. Does that kind of address 9
the question?
10 MEMBER KIRCHNER: Yes. Thank you.
11 MS. THOMPSON: Thank you.
12 CHAIR ROBERTS: If I were to summarize 13 that is the developed risk insights needs to include 14 more than numbers, and the key here is if you've got 15 numbers you think are favorable but the consequence is 16 really bad and the numbers don't mean as much in terms 17 of screening out, hopefully that's what you then can 18 do. Risk insights don't mean calculate a number and 19 stop. But, anyway, I just wanted to throw that out 20 there.
21 Any other questions from --
22 MEMBER MARTIN: Sure. I know you weren't 23 thinking along the lines of, you know, this is the 24 first advocation of the reg guide, and I'm wondering, 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 you know, in using this and maybe other -- there's not 1
necessarily enough hazard analysis guidelines out 2
there, as far as I'm concerned, but now that there's 3
one and, of course, the temptation would obviously be 4
to use this in a risk evaluation, I'm wondering about 5
collateral hazard. In the case of the volcanic 6
hazard, obviously, the direct hazards are what's been 7
discussed today. But like wildfire, I would think 8
wildfire would be highly probable collateral hazard 9
created by a volcano.
10 Who would be responsible for capturing 11 that hazard and propagating it into a natural 12 phenomena hazards analysis? You know, should the 13 folks working on this particular volcanic hazard be 14 evaluating and recognizing it? Is it someone that is 15 focused on the wildfire? Where do these two worlds 16 meet, and how do we know for sure it's going to be 17 addressed?
18 MS. THOMPSON: So I want to ask a 19 clarification question. Are you talking about a 20 wildfire resulting from a volcanic event --
21 MEMBER MARTIN: Sure, sure.
22 MS. THOMPSON: -- or just a wildfire that 23 occurs naturally?
24 MEMBER MARTIN: No. 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
70 case, it is a particular, it's occurred coincident 1
with this, so we're dealing with hot stuff. You know, 2
you look at -- of course I'm googling a little bit --
3 600 square kilometers were affected from Mount St.
4 Helen. That's a lot of area and a lot of it was 5
burnt.
6 MS. THOMPSON: So in the context of --
7 MEMBER MARTIN: That might be a bigger 8
issue than some of the other things we consider. But, 9
again, it's not the direct hazard that's under 10 consideration with this reg guide, but it may be an 11 important hazard to capture. So who's responsible for 12 at least identifying the hazard and considering its 13 risk in natural phenomena hazard?
14 MS. THOMPSON: So we have an entire branch 15 here in NRR, which is the External Hazards Branch. We 16 have a
team of geologists, seismologists, 17 meteorologists, and hydrologists who all cover the 18 external hazards that fall into our varying aspects.
19 We also have staff in the Division of Engineering and 20 Eternal Hazards that perform the human-induced 21 external events hazard analysis. They also look at 22 hazards from nearby facilities, and we also have our 23 geotechnical engineers who consider the geotechnical 24 engineering considerations.
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 I don't know exactly off the top of my 1
head who would consider wildfires, but I can take that 2
back and get you an answer --
3 MEMBER MARTIN: No, I'm not just asking 4
about wildfires. I'm asking about wildfire --
5 MEMBER HALNON: Bob, GDC 2 requires 6
appropriate combinations of effects. The licensee has 7
to do that as part of their effect. Now, you can 8
question it and they can say there's a fence that goes 9
around it and there's no a way a fire can come from 10 the outside in, which is typically, but the power 11 lines are an issue. That's been looked at --
12 MEMBER MARTIN: So the gap I'm trying to 13 point out is should there be some discussion in a TR 14 related to collateral hazards? And then, of course, 15 when you integrate it into a broader hazard discussion 16 and consideration in a natural phenomena --
17 MEMBER KIRCHNER: Debris flow is what 18 would fall into your collateral hazard example. The 19 debris -- so what was discussed was you get the tephra 20 fall, and then you get a flood or you get water. So 21 they did examine collateral damage --
22 MEMBER MARTIN: Well, the combination --
23 MEMBER KIRCHNER: -- to demonstrate that 24 the channels would divert any of that from the site.
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
72 (Simultaneous speaking.)
1 MEMBER KIRCHNER: A flooding event 2
carrying ash into -- that would fall in Chapter 2 type 3
analyses.
4 MS. THOMPSON: And I'll just add that, if 5
we're talking in the context of a volcano erupting at 6
one of the sources in the site region resulting in a 7
wildfire at that source, we are talking about 8
significant distances from the volcanic sources to 9
these site. So even if there is, let's say, an 10 eruption at Leucite Hills Volcanic Field that produces 11 a wildfire, there's over 117 kilometers of distance 12 between the site to that potential wildfire source, 13 and then we would also need to look at what are the 14 atmospheric wind conditions, are conditions right for 15 things to blow towards the site. And I also see that 16 Hanh has his hand up.
17 MEMBER MARTIN: Our assumptions are 18 different on that one because I'm thinking that ash 19 could still be hot and travel 50 - 60 miles and 20 contribute to, you know, be a source of ignition.
21 MS.
THOMPSON:
We wouldn't expect 22 transported ash to have a significant temperature to 23 it that would result in a fire. If it was in the 24 immediate vicinity, much like your campfire, an ember 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
73 just flies out and hits your toe, that's probably 1
going to burn you. If a little piece of ash floats 2
away a few miles down and lands on somebody's car, it 3
just looks like a burnt leaf.
4 MEMBER MARTIN: It's pretty dry out west.
5 You know, having lived out in Hanford and Idaho, fires 6
can get out of control pretty fast and be a mess.
7 MR. PHAN: Good afternoon, everyone. My 8
name is Hanh Phan, the senior PRA analyst in NRR, 9
Division of Advanced Reactors. So I have more than 37 10 years in reliability and PRA, 18 of those, almost 18 11 of those with the NRC. So according to records, 12 1.253, applicants who implement LMP, they don't have 13 to address a volcano PRA, not until the OL stage. The 14 staff expect that in the future at the OL stage. The 15 PRA will address everything, including volcanic 16 hazard-induced fire, induced vibration or movements, 17 or any impact by volcano later at the OL stage, and 18 the PRA should address those. And if not, the 19 applicants should explain or revise the basis why 20 those not impact the plant. But at this stage, not 21 available yet based on the staff guidance. So those 22 will be addressed later.
23 MEMBER MARTIN: Okay. So it's just not 24 really something that you would expect here. I'm just 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 thinking, from a completeness standpoint, you would 1
expect to have some at least acknowledgment in a 2
document like this, but I can certainly understand 3
where you're coming from.
4 MR. PHAN: Yes.
5 CHAIR ROBERTS: So I guess what you're 6
saying is the Regulatory Guide 1.253 acknowledges 7
there's a risk that the volcanic hazard might end up 8
being significant at the site and the construction 9
permit would then still be granted, and they could be 10 building the site and then not get it licensed; is 11 that right? It seems there's a judgment being made, 12 and maybe it as made just generically, that you can 13 always find a way to mitigate the volcanic risk or 14 hazard. Otherwise, you'd think you'd want to have a 15 little bit more at the CP stage to at least mitigate 16 that risk that the site might be found unacceptable.
17 MR. PHAN: Appendix A of Reg Guide 1.253.
18 In there, we endorse and encourage the PRA standard, 19 the advanced PRA standard. There are 1,233 supporting 20 requirements associated with the PRA in that standard, 21 many of those related to the external hazard, 22 including volcano. So in there, you will find that, 23 you know, not how to address volcano but what to 24 address, including the impact from the volcano. 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
75 that we expect applicant to follow up, you know, 1
conform to that standard and address all the hazard 2
impact from the volcano.
3 CHAIR ROBERTS: Okay. Thank you. Any 4
other questions here on the floor from members or 5
consultants online?
6 DR. BLEY: Yes. Dennis Bley. I've been 7
thinking about Bob's statement, and this has been a 8
problem over the years, you know, who's responsible.
9 First, the applicant is. Second, reviewers are. But 10 the standard Hanh is referring not now requires them 11 to essentially, in the language of the committee, 12 start with a blank sheet of paper to think of all the 13 things.
14 When they look at the hazards, they need 15 to identify knock-off hazards or whatever you want to 16 call them, like you were talking about, and it would 17 seem appropriate to me that, in a document like this 18 topical, the idea that the seismic, I'm sorry, the 19 volcanic event could lead to a fire. You know, 20 seismic events can also lead to fires. Those hazards 21 should be enumerated and then examined more thoroughly 22 later on. But if it's not here, in the end, the 23 committee has a backup to say nobody looked at this.
24 But we know, because you're using that standard, 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
76 by the time we get an OL coming in here, that issue 1
will be spelled out. So that's great.
2 MEMBER HALNON: Part of the problem is 3
there will be a fire if there's lava flow. The 4
distance and everything else you have to consider.
5 But you don't really know what it is until you get the 6
design of the plant to a point where you know if 7
you're, you know, where the meteorological portions of 8
the plant have to be figured out. So it's all in this 9
Chapter 2 evaluation and assessment in order to comply 10 with GDC 2.
11 So it's a little bit of cart before the 12 horse to say and you have to go look at fire. Well, 13 maybe there's other things you need to look at for 14 sure. So you don't want to pre-condition somebody to 15 not look at something. You're not really starting 16 with a blank of sheet of paper if this early in the 17 process you say here's some problems. I mean, there 18 will be a fire. It's just a matter of -- and there 19 will probably be some other consequences. The 20 consequential failure could dam failures. You'd have 21 to look at flooding, you have to look at other things 22 that are consequential to this.
23 So I don't want to pre-condition all that 24 LMP stuff in the license event blank sheet of paper 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 saying that this has to be totally all-inclusive 1
because then you'll pre-condition that thinking, in my 2
mind. That's the way I'm --
3 DR. BLEY: Yes. I kind of think 4
differently. I understand that point. I think all of 5
this you can accumulate that people have built up.
6 When you do your own look from a blank sheet of paper, 7
you ought to then play it against everything else that 8
was there. You shouldn't start with a list that says 9
fire coming from volcanic. You ought to start by 10 looking at the source and working out from there.
11 Then when you're done, you ought to go 12 back and check all the other lists. And it's true 13 that if you bias it ahead of time, somebody might not.
14 In light water reactor PRAs, people think they've 15 identified everything, so they don't look anymore than 16 they need to.
17 CHAIR ROBERTS: Okay. I think we're out 18 of questions. So just before I thank everybody, I'll 19 go out for public comments, this is an opportunity for 20 anything who has been listening here in the room or 21 out on Teams or the phone line, any member of the 22 public has a comment they'd like to make? Go ahead 23 and unmute yourself, state your name and affiliation 24 if appropriate, and your comment.
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 Okay. Hearing none, I'll speak for 1
myself. I thought these presentations were excellent 2
both from the applicant and from the staff, in terms 3
of informing things. And this next step is to have a 4
committee discussion. I wanted to observe the one 5
thing that diehard is that there is definitely work 6
underway to look at the Reg Guide 4.26 to factor in 7
the experience from the TerraPower work and to reflect 8
what seems to be a preferred approach, maybe not in 9
all cases but a preferred approach to define a hazard 10 first and then, at some point after that, other than 11 maybe a little bit of qualitative work just to try to 12 bound the problem, so to speak, at the beginning, then 13 sometime, maybe years later, do the actual risk 14 assessment and mitigations. And so that's something 15 I know you're looking at in the reg guide, and maybe 16 that's something that would be split out. And I'm 17 sure we'll have that discussion in the next couple of 18 years with the finalization of the Natrium CP just to 19 see how it is you've dealt with the topical report, is 20 it incorporated by reference, but you thought that was 21 sufficient. And I'm sure we'll talk again as we get 22 a little further along the Natrium process.
23 And so with that, my view is that there's 24 really no reason for us to write an ACRS letter on 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
79 this subject. I think a summary report would be just 1
fine, a paragraph in the meeting minutes. I think 2
what we heard is that the reg guide essentially works 3
in a bifurcated way. There was no real technical 4
issue with the hazard elicitation part of the reg 5
guide and that a respite is still yet to be exercised.
6 I kind of came in with that view, and I heard nothing 7
that would change that view. I don't think there's 8
any divergence on that view between us and the staff, 9
and so I don't think a letter would do a whole lot of 10 use, but I'm considering other comments.
11 Okay. Hearing none, it sounds like that's 12 the path we'll take on this one.
13 MS. DEVLIN-GILL: This is Stephanie 14 Devlin-Gill. Can I ask a clarifying question? Does 15 that have implications on a
full committee 16 presentation or not?
17 CHAIR ROBERTS: Yes. The intent is I'll 18 try to write something up tonight, and we can review 19 it on Thursday.
20 MEMBER HALNON: There won't be a full 21 committee presentation on it.
22 MS. DEVLIN-GILL: That's what I was 23 asking. Thank you very much.
24 CHAIR ROBERTS: So, actually, a lot of 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
80 committee is here right now, but this subcommittee 1
can't make that decision. We'll make a recommendation 2
to the full committee that we not write a letter, that 3
we put out a summary report and we put that in part of 4
the monthly meeting. So we'll see how that goes with 5
the full committee, but most of the full committee is 6
here; it's probably a pretty good bet.
7 Any other comments, discussion? Very 8
good. Once again, I want to thank the folks from 9
TerraPower who traveled here. Someone made a comment 10 this morning at least this discussion worked much 11 better in person. We got to hear from experts.
12 I wanted to just acknowledge for the 13 record, we ought to note that I didn't announce that 14 Dennis Bley was here at the outset of the meeting, so 15 I'll just get that on the record that Dennis has been 16 here. And with that, we are adjourned.
17 (Whereupon, the above-entitled matter went 18 off the record at 2:45 p.m.)
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 Staff Review of the Topical Report An Analysis of Potential Volcanic Hazards at the Proposed Natrium Site near Kemmerer, Wyoming, Revision 0A July 9, 2024 Presentation to the ACRS Subcommittee Jenise Thompson, Geologist Stephanie Devlin-Gill, Senior Project Manager Office of Nuclear Reactor Regulation
Agenda
- Review Chronology
- Topical Report (TR) Overview
- TR Review Strategy
- Safety Evaluation (SE) Overview
- Conclusions 2
Review Chronology
- July 12, 2022: Pre-Application Public Meeting (ML23030B893)
- April 25, 2023: Submittal of the TR An Analysis of Potential Volcanic Hazards at the Proposed Natrium Site near Kemmerer, Wyoming (ML23115A387)
- June 28, 2023: TR accepted for review by the NRC staff (ML23167B211)
- September - October 2023: Audit conducted (ML23338A047)
- February 28, 2024: Draft SE issued (ML24059A056) 3
NRC Staff Team
- Jenise Thompson, Geologist
- Jason White, Meteorologist
- Scott Stovall, Seismologist/Geophysicist
- Hanh Phan, Senior Reliability and Risk Analyst
- TerraPower Project Management Team
- Roel Brusselmans, Project Manager
- Stephanie Devlin-Gill, Senior Project Manager
- Mallecia Sutton, Senior Project Manager 4
TR Overview
- An Analysis of Potential Volcanic Hazards at the Proposed Natrium Site near Kemmerer, Wyoming submitted in April 2023 followed the guidance in Regulatory Guide (RG) 4.26 in performing the assessment of potential volcanic hazards at the proposed site.
- Audit conducted from September 11 to October 19, 2023
- Audit summary report issued on December 4, 2023.
5
Review Strategy - Regulatory Requirements
- Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criteria for Nuclear Power Plants, General Design Criterion (GDC) 2
- 10 CFR 100.23, Reactor Site Criteria 6
Review Strategy - Applicable NRC Guidance
- RG 4.26 Volcanic Hazards Assessment for New Nuclear Power Reactor Sites
- Briefed to ACRS February 2020 and April 2021
- Revision 0 issued June 2021 (ML20272A168)
- Revision 1 administrative change August 2023 (ML23167A078)
- Endorses Senior Seismic Hazard Analysis Committee (SSHAC) process for expert elicitation, when warranted.
- Options to assess volcanic hazard or pursue engineering analysis based on maximum screened-in hazard 7
RG 4.26 Methodology in Topical Report
- Determine maximum magnitude for screened in volcanic hazards
- To be completed as part of Construction Permit (CP) review
- Evaluate SSC performance and mitigating actions
- Evaluate impact on probabilistic risk assessment (PRA) 8 RG 4.26, Figure 3
Review Approach As described in September 2023 ACRS presentation
- Geologic History
- Site Characterization
- Tectonomagmatic model
- Numerical Modeling
- Outcome is acceptable maximum magnitude volcanic hazards for use in engineering analysis of SSC performance or mitigating actions review of the CP application.
9
Site Geology and Regional Geologic History
- Middle Rocky Mountain Physiographic Province
- Paleozoic and Mesozoic sedimentary rocks
- Faulted and deformed by compression during Sevier Orogeny (50-150 Ma)
- No evidence of volcanic eruptions in the site vicinity in the last 150 Ma 10 Topical Report Figure 14
Site Characterization -
Volcanic Sources
- Regional sources include:
- Yellowstone Volcanic Field (YVF)
- Upper Wind River Basin (UWRB) Volcanic Field
- Eastern Snake River Plain (ESRP) Volcanic Field
- Leucite Hills Volcanic Field (LHVF)
- Curlew Valley Volcanic Field (CVVF)
- Blackfoot Reservoir Volcanic Field (BRVF)
- Northern Black Rock Desert Volcanic Field (screened out based on distance from site) 11 Topical Report Figure 18
Tectonomagmatic Model
- Volcanic sources from Yellowstone Hotspot track - Eastern Snake River Plain, Yellowstone, Upper Wind River Basin
- Site is not located near the track of the hotspot
- Volcanic sources from Basin and Range Physiographic Province extension -
Blackfoot Reservoir, Leucite Hills, Curlew Valley and North Black Rock Desert
- Site is located within the Sevier Overthrust, characterized by compression, not extension.
12 Topical Report Figure 18
Hazards Screened Out
- Screened out based on distance to volcanic source and topography between the source and proposed site
- Proximal hazards
- Lava flows
- Pyroclastic Density Flows
- Screened out based on absence of tephra deposits in the site vicinity (25 mi/40 km radius)
- Tephra from sources outside the site region (200 mi/320 km radius) 13
Screening of Potential New Vent Opening
- New vent opening considered for the Leucite Hills Volcanic Field (greater than 100 km from site)
- The PVHA_YM code uses kernel density function to calculate vent density for points on a grid
- Developed for Yucca Mountain, geographic coordinates transposed for use at Leucite Hills
- Screened out lava flow from potential new vent opening from further analysis 14
Hazards Screened In
- Tephra from sources within the site region
- Analyzed both silicic and mafic sources separately
- Debris flow from remobilized tephra deposits on the North Fork of Little Muddy Creek.
15
Sources of Tephra
- Silicic
- Blackfoot Reservoir Volcanic Field, Eastern Snake River Plain, Curlew Valley Volcanic Field and the Yellowstone Volcanic Field
- Mafic
- Upper Wind River Basin, Leucite Hills Volcanic Field, Blackfoot Reservoir Volcanic Field, and the Eastern Snake River Plain 16 Topical Report Figure 18
Numerical Modeling of Tephra Hazards
- Applicant used the ASHPLUME2 code to analyze silicic and mafic tephra hazards
- Run intervals maximize realizations and adequately capture range of uncertainty
- Staff confirmed applicant results 17
Hazards for use in Engineering Analysis 18
Limitations and Conditions
- The conclusions reached in this SE do not address the content provided in Section 10 of the TR. Thus, any licensee or applicant referencing this TR must, evaluate specific design, mitigation or monitoring actions required to mitigate the effects of volcanic hazards at the site, including any monitoring requirements for notification of impending volcanic events.
- The conclusions reached in this SE do not address the impacts of the calculated probabilities of volcanic hazard events on the cumulative plant risk. Thus, any licensee or applicant referencing this TR should evaluate the effect of volcanic hazards on the overall plant risk.
19
Conclusion
- The characteristics of volcanic hazards as described in the TR are appropriate to use as inputs to further engineering analysis of the potentially affected SSCs in the Natrium reactor design and for consideration in assessing the potential need for mitigating actions in the event of an impending volcanic hazard arriving at the proposed site.
20
Abbreviations ACRS - Advisory Committee on Reactor Safeguards BRVF - Blackfoot Reservoir Volcanic Field CFR - Code of Federal Regulations CP - Construction Permit CVVF - Curlew Valley Volcanic Field ESRP - Eastern Snake River Plain GDC - General Design Criteria km - Kilometers LHVF - Leucite Hills Volcanic Field L&C - Limitation and Condition mi - Mile Ma - Millions of years old NRC - Nuclear Regulatory Commission PRA - Probabilistic Risk Assessment RG - Regulatory Guide SSC - Structure, System, or Component SE - Safety Evaluation TR - Topical Report UWRB - Upper Wind River Basin VEI - Volcanic Explosivity Index YVF - Yellowstone Volcanic Field 21
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- Topical Report titled, An Analysis of Potential Volcanic Hazards at the Proposed Natrium Site near Kemmerer, Wyoming (ML23115A387)
- Approximately 575 volcanoes less than 2.6 million years old are located 100320 km from the proposed Kemmerer Unit 1 site.
- A volcanic hazards assessment appears warranted for this proposed site using criteria in Regulatory Guide 4.26, Volcanic Hazards Assessment for Proposed Nuclear Power Reactor Sites.
- Goal is to quantify volcanic hazards probabilistically for potential use in subsequent analyses, as needed.
- Analyses follow guidance in RG 4.26.
Objective 2
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- Distance (greater than 100 km) and topography isolate the site from potential flows from seven different volcanic fields in the site region.
- Lava flows
- Pyroclastic density currents
- Debris flows
- Flow phenomena from greater than 100 km are screened from the volcanic hazards analysis.
VHA: Flow Hazards 3
ML23115A387, Fig. 18
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- Evaluation approach for all eruptions except the Yellowstone Supervolcano eruption (greater than 100 km3):
- Develop eruption volumes for past eruptions in the seven different volcanic fields.
- Evaluate recurrence rates of past eruptions for the seven volcanic fields.
- Analyze ranges of tephra thicknesses at proposed site using an accepted advection-diffusion-sedimentation model.
VHA: Tephra Fallout 1 4
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- Tephra fallout hazard curves at the proposed site from potential mafic (m) and silicic (s) eruptions.
- Tephra fallout is a less than 105/year event.
- Average thickness of approximately 0.1 cm with a 6106/year probability of exceedance.
- 95th percentile thickness of approximately 17 cm with a 5107/year probability of exceedance.
VHA: Tephra Fallout 1 5
ML23115A387, Fig. 45
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- USGS estimated a less than 10-6/year likelihood of a large volume (greater than 100 km3) eruption from the Yellowstone Supervolcano.
- USGS evaluated tephra fallout from Yellowstone Supervolcano eruptions using a complex tephra dispersal and sedimentation model.
- Multiple eruption scenarios analyzed.
- Estimated average deposit thickness of approximately 84 cm with a less than 5107/year probability of exceedance.
- 95th percentile thickness of approximately 113 cm at less than 7108/year probability of exceedance.
VHA: Tephra Fallout 2 6
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- Determine whether infrequent (0.5/year) floods could mobilize tephra and form debris flows that overtop channel banks in the North Fork of the Little Muddy Creek.
- Scour during peak discharge events can lead to small-volume debris flows.
- Existing channels can contain these potential debris flows.
- Debris-flow hazard screened out.
VHA: Debris Flows 7
ML23115A387, Fig. 44
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- The only potential volcanic hazard at the proposed site is the deposition of tephra fallout from volcanic eruptions 100320 km away.
- Tephra-fallout hazard from all volcanic sources has a 95th percentile thickness of 130 cm, which has a less than 5.7107/year probability of exceedance.
- Most (85%) of this hazard is from a potential Yellowstone Supervolcano eruption.
- Potential debris flows from remobilized tephra deposits would be contained within existing stream channels and would not affect the proposed site.
Conclusions 8
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SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved Meetings to Date Design Overview Presentation Regulatory Management of Natrium Nuclear Island and Energy Island Design Interfaces Topical Report Principal Design Criteria for the Natrium Advanced Reactor Topical Report TerraPowers Fuel and Control Assembly Qualification Topical Report Today - Volcanic Hazards Assessment Topical Report Topical Reports under NRC Review TerraPower Natrium Plume Exposure Pathway Emergency Planning Zone Sizing Methodology Topical Report Natrium HFE Program Plan and Methodologies Topical Report Radiological Source Term Methodology Topical Report DBA Methodology for In-Vessel Events without Radiological Release Topical Report Radiological Release Consequences Methodology Topical Report Natrium Stability Methodology Topical Report Reactor Seismic Isolation System Qualification Topical Report I&C Architecture and Design Basis Topical Report DBA Methodology for Events with Radiological Release Topical Report Partial Flow Blockage Methodology Topical Report Construction Permit Application submitted on March 28, 2024 and accepted May 21, 2024 ACRS interactions planned to begin November 2025 (ML24162A063)
ACRS Interactions 10
SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2024 TerraPower, LLC. All Rights Reserved ACRS - Advisory Committee on Reactor Safeguards BRVF - Blackfoot Reservoir Volcanic Field cm - centimeters CVVF - Curlew Valley Volcanic Field ESRP - Eastern Snake River Plain (volcanic field) km - kilometers LHVF - Leucite Hills Volcanic Field m - mafic RG - Regulatory Guide s - silicic UWRB - Upper Wind River Basin (volcanic field)
VHA - volcanic hazards analysis YS - Yellowstone (volcanic field)
Acronym List 11