ML24296A051
| ML24296A051 | |
| Person / Time | |
|---|---|
| Issue date: | 09/20/2024 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-0034 | |
| Download: ML24296A051 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Fuels, Materials, and Structures Subcommittee Docket Number:
(n/a)
Location:
teleconference Date:
Friday, September 20, 2024 Work Order No.:
NRC-0034 Pages 1-92 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
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1 2
3 DISCLAIMER 4
5 6
UNITED STATES NUCLEAR REGULATORY COMMISSIONS 7
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 8
9 10 The contents of this transcript of the 11 proceeding of the United States Nuclear Regulatory 12 Commission Advisory Committee on Reactor Safeguards, 13 as reported herein, is a record of the discussions 14 recorded at the meeting.
15 16 This transcript has not been reviewed, 17 corrected, and edited, and it may contain 18 inaccuracies.
19 20 21 22 23
1 UNITED STATES OF AMERICA 1
NUCLEAR REGULATORY COMMISSION 2
+ + + + +
3 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 4
(ACRS) 5
+ + + + +
6 FUELS, MATERIALS, AND STRUCTURES SUBCOMMITTEE 7
+ + + + +
8 FRIDAY 9
SEPTEMBER 20, 2024 10
+ + + + +
11 The Subcommittee met via 12 Video/Teleconference, at 9:30 a.m. EDT, Ronald G.
13 Ballinger, Chairman, presiding.
14 SUBCOMMITTEE MEMBERS:
15 RONALD G. BALLINGER, Chairman 16 WALTER L. KIRCHNER, Vice Chairman 17 DAVID A. PETTI, Member-at-Large 18 THOMAS ROBERTS, Member 19 BOB MARTIN, MEMBER 20 SCOTT PALMTAG, MEMBER 21 CRAIG HARRINGTON, Member 22 VICKI M. BIER, Member 23 VESNA B. DIMITRIJEVIC, Member 24 MATTHEW W. SUNSERI, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
2 ACRS CONSULTANT:
1 DENNIS BLEY, ACRS 2
4 DESIGNATED FEDERAL OFFICIAL:
5 CHRIS BROWN 6
7 ALSO PRESENT:
8 JOHN TSAO, NRC, Vessels and Internals Branch 9
DAVID DJAMCO, NRC, Vessels and Internals Branch 10 11 ANGIE BUFORD, NRC Branch Chief, Vessels and 12 Internals Branch 13 BRIAN HALL, Westinghouse Electric Company 14 DAVID RUDLAND, NRC, Vessels and Internals 15 Branch 16 COREY THOMAS, SNC 17 NATHAN CHAPMAN, GE Vernova 18 OSVALDO CRUZ SANCHEZ, Constellation Nuclear 19 SHANDETH WALTON 20 TAMMY SKOV 21 THOMAS DASHIELL 22 LESLIE FIELDS 23 LARRY BURKHART 24 ANEES UNDYAWAR 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 SANDRA WALKER 1
ROB KRSEK 3
PAUL GUILL 4
ROBERT MARTIN 9
JAMES MOLKENTHIN 10 WEIDONG WANG 11 ROBERT TREGONING 12 BRETT LYNCH 13 HOSSEIN NOURBAKHSH 14 JOHN LYONS 15 ELLIOT LONG 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 CONTENTS 1
PAGE 2
I. Opening Remarks 3
Ron Ballinger...............
5 4
II. Opening Remarks from NRC Staff 5
Angie Buford 9
6 III. Discussion of Topical Report PWROG-18068-NP, 7
Revision 1 8
Brian Hall
................ 11 9
IV Discussion of NRC Staff's Evaluation 10 of Topical Report PWROG-18068-NP, 11 Revision 1 12 David Dijamco............... 60 13 John Tsao................. 74 14 NRC, Vessels and Internals Branch 15 16 V
Opportunity for Public Comments...... 88 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
5 P-R-O-C-E-E-D-I-N-G-S 1
9:30 a.m.
2 MR. BALLINGER: Okay, it's 9:30, the 3
meeting will now come to order. This is a virtual 4
meeting of the Fuels, Materials, and Structures 5
Subcommittee of the Advisory Committee on Reactor 6
Safeguards. And I'm Ron Ballinger, Chair of today's 7
Subcommittee meeting.
8 ACRS Members in attendance, and I'm 9
probably going to mess this up --
10 (Off microphone comments.)
11 MR. BALLINGER: We're having some feedback 12 from somebody, can you mute your speaker or your mic?
13 Let's see. Members in attendance, and I'm 14 probably going to mess this up. Matt Sunseri. Tom 15 Roberts. Walt Kirchner, I think. Vesna Dimitrijevic.
16 Vicki Bier, I think. Dave Petti. Bob Martin. Scott 17 Palmtag. And Craig Harrington. ACRS consultants, 18 Dennis Bley and Steve Schultz are online. I don't 19 know whether Charlie Brown will be on, but maybe.
20 If I've missed anyone just please let me 21 know. Chris Brown with the ACRS Staff is the 22 designated federal officer for this meeting. No 23 member conflicts of interest were identified for 24 today's meeting. We have a quorum for today's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
6 meeting.
1 During today's meeting the Subcommittee 2
will receive a briefing on the pressurized water 3
reactor owner's group topical report, PWROG-18068-MP 4
Revision 1. Use of direct fracture toughness for 5
evaluation of reactor pressure vessel integrity. And 6
the draft safety evaluation for that document.
7 We last visited this topic in 2022.
8 Actually, probably a little bit earlier, as it related 9
to the embrittlement and surveillance requirements 10 rulemaking in, and in 2019, as it related to Reg Guide 11 1.99, radiation embrittlement of reactor vessel 12 materials. And we wrote letter reports on these 13 topics. I should also add that we also gave up at 14 least one presentation before the Commission.
15 This Topical Report proposes a methodology 16 that justifies the use of direct fracture toughness 17 data to evaluate reactor pressure vessel integrity as 18 an alternative to the requirements of PTS, pressurized 19 thermal shock rule, PTS 10 CFR 50.61, and the pressure 20 PT limit curves defined in 10 CFR 50 Appendix G.
21 The current approach uses empirical 22 embrittlement correlations based on Charpy data 23 correlated with material toughness. I might add, the 24 number of Charpy specimens I think was like about 180 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 or so when they first started this, now there is an 1
enormous amount of data.
2 The proposed approach in this revision 3
represents a departure, but with a significant 4
improvement in the estimation of the extent of 5
embrittlement since it makes use of actual toughness 6
data as opposed to empirical correlations. We are 7
reviewing this Topical Report because the reactor 8
pressure vessel is one of the most critical components 9
in the nuclear plant to ensure safety and reactor 10 pressure vessel integrity is a limiting factor in the 11 useful life of a nuclear plant.
12 The ACRS was established by statute and is 13 governed by the Federal Advisory Committee Act, or 14 FACA. The NRC implements FACA in accordance with its 15 regulations.
Per these regulations and the 16 Committee's bylaws, the ACRS speaks only through its 17 published letter reports.
18 All Member comments should be regarded as 19 only the individual opinion of that Member, not a 20 committee position. All relevant information related 21 to ACRS activities, such as letters, rules for meeting 22 participation and transcripts are located on the NRC 23 public website and can be easily found by typing 24 "About Us ACRS" in the search field on the NRC's home 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 page.
1 The ACRS, consistent with the Agency's 2
rules of public transparency in regulation of nuclear 3
facilities, provides opportunity for public input and 4
comment during our proceedings. We have received no 5
written statements or requests to make an oral 6
statement from the public. We have also set aside 7
time at the end of this meeting for public comments.
8 The Subcommittee will gather information, 9
analyze relevant issues and facts and formulate 10 proposed conclusions and recommendations, as 11 appropriate, for deliberation by the Full Committee.
12 A transcript of the meeting is being kept 13 and will be posted on our website. When addressing 14 the Subcommittee, the participants should first 15 identify themselves and speak with sufficient clarity 16 and volume so that they may be readily heard. I might 17 add that we have a new, or a different court reporter, 18 so we would ask that you be, adhere to this 19 admonition. If you are not speaking, please mute your 20 computer on Teams, or by pressing *6 if you're on your 21 phone.
22 Please do not use the Teams chat feature 23 to conduct sidebar discussions related to the 24 presentations, rather, limit use of the meeting chat 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 function to report IT problems. For everyone in the 1
room, well I don't know that there is anybody, please 2
put all your electronic devices in silent mode.
3 If you have any feedback for the ACRS 4
about todays meeting, we encourage you to fill out 5
the public meeting feedback form on the NRC website.
6 We will now proceed with the meeting. And 7
I now call on Ms. Angie Buford, NRC Branch Chief for 8
Vessels and Internals Branch for opening remarks.
9 Angie, I'm assuming you're there?
10 MS. BUFORD: I'm here. Yes. Hi, good 11 morning. Can you all hear me?
12 MR. BALLINGER: Yes, I think we can hear 13 you fine.
14 MS. BUFORD: Okay, great. Yes, good 15 morning. We are happy to be here this morning to 16 present to you our safety evaluation and information 17 regarding the PWROG-18068 Revision 1,
safety 18 evaluation on the use of direct fracture toughness or 19 evaluation of RPV integrity.
20 Introducing myself, I am the branch chief 21 for the technical review branch. And I am also joined 22 by Gerond George, who is the branch chief of the 23 topical reports branch in the division of operating 24 reactor licensing.
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 This topical report, as you'll hear, both 1
from the owner's group and from us, is that it 2
presents a methodology that uses direct fracture 3
toughness measurement approaches to evaluate the 4
structural integrity of the RPV.
5 It's an important time because the 6
domestic nuclear plants have requested to extend their 7
operating licenses to 80 years, and as such, fracture 8
toughness of the vessel shell material will be 9
affected by the neutron radiation and needs to be 10 monitored and evaluated. So this is timely that we 11 are getting this proposed methodology, which is 12 different from existing
- methods, being used 13 potentially to predict an assessed fracture toughness 14 of the vessel material and ensure structural integrity 15 of the vessel.
16 We understand, and per our review, that 17 the capital reporter in our assessment integrates 18 concepts of the master curve and embrittlement trend 19 curve into a useable and unified methodology to 20 evaluate reactor vessel integrity.
21 We would like to be open to answering any 22 questions from the ACRS. At this point we are not 23 requesting that a letter come from the ACRS at this 24 time, but we will be happy to answer any questions.
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 And so with that, Mr. Ballinger, I will 1
turn it back to you. Thank you.
2 MR. BALLINGER: Thank you. I would 3
comment that we are a bit on the irascible side and so 4
it's up to the sub, it's up to the Full Committee as 5
to whether we do a letter.
6 MS. BUFORD: Right. I'm aware.
7 MR. BALLINGER: So standby.
8 MS. BUFORD: Fair enough. Yes. And so, 9
at least for the purposes of this meeting.
10 MR. BALLINGER: Yes. Okay. So who is the 11 presenter for the owner's group?
12 MR. HALL: That's myself.
13 MR. BALLINGER: Oh. Oh yes.
14 MR. HALL: Brian Hall.
15 MR. BALLINGER: Okay, Brian Hall. Okay.
16 So, the floor is yours.
17 MR. HALL: Okay. I'm Brian Hall with 18 Westinghouse Electric Company. And this topical 19 report methodology was prepared on behalf, or for the 20 PWR Owner's Group.
21 Significant effort over the years. The 22 purposes of it is to justify the use of direct 23 fracture toughness to evaluate RPV integrity as an 24 alternative to the regulation in the pressurized shock 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 Rule 10 CFR 50.61, and the pressure temperature limit 1
curve development, 10 CFR 50 Appendix H.
2 The methodology justifies on how to 3
develop the T0 reference temperature according to the 4
standard ASTM E1921. Either in the irradiated or 5
unirradiated condition. How to take that data then 6
and adjust it to the RPV condition of interest. And 7
the ASTM E900 guide for predicating is embrittlement 8
is used.
9 And then it accounts for test result 10 uncertainties and material variabilities in the margin 11 term. And then applies that data using NRC endorsed 12 or codified methods cited in ASME Section 11.
13 So that's the high-level purpose. A 14 little bit of background on fracture toughness and the 15 traditional approach.
16 So the current approach in the regulation, 17 as well as for developing PT curves, is to calculated 18 a measured, generally RT-NDT. Which is done in the 19 unirradiated condition. Shift that for embrittlement 20 and then add a margin.
21 So RT-NDT was first established around 22 1972. It's a, composed of two measurements. One 23 we'll call a drop weight test, and the other is a 24 Charpy impact test.
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 Now the drop weight test is a measure of 1
transition temperature at crack arrest. So when a 2
crack, a propagating crack in the material, arrest or 3
stops. And initially PT curves were set using the K-4 1R curve, the crack arrest, however, with improved 5
methods over time now crack initiating curve is used.
6 And there is not a good correlation between the crack 7
arrest reference temperature and the crack initiation.
8 And so, that's an older methodology.
9 And then the secondary part that goes into 10 RT-NDT is the Charpy impact test. And as shown in the 11 specimen at the bottom is a impact test conducted on 12 a blunt-notch specimen. And fracture toughness 13 measurement is a more accurate and more limiting 14 condition than the blunt-notch test. And that's the 15 newer advancement in technology.
16 So with RT-NDT, as the top right figure 17 shows, for a given heat of material there is margin to 18 the, what was developed as the K-1C curve, which was 19 a lower bound curve developed to a specific data set.
20 And for a given material there is a unknown amount of 21 margin, or difference between the measured data and 22 that curve. And some materials may be close to the 23 curve but many materials are not.
24 And as shown in the bottom figure, RT-NDT 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 relative to T0, which I'm going to talk about in a 1
minute, T0 is a metric from fracture toughness based 2
measurement of reference temperature, there is not a 3
good correlation, okay?
4 And then the other point is shifting from 5
unrated condition to a high fluence prediction of 6
embrittlement can have uncertainties and a substantial 7
margin term is required. So there is an advantage to 8
being able to measure a new rated condition. So 9
that's a little bit of background on current methods.
10 So the top right figure is a large set of 11 fracture toughness data relative to the RT-NDT metric 12 for setting the temperature access. As you can see, 13 there is a substantial scatter in the data.
14 The bottom figure takes the same data, 15 applies, it calculates the T0 metric, which is per 16 ASTM E1921. And as you can see, the data is collapsed 17 into a smaller scatter ban. And there is a 18 statistical understanding or distribution in that 19 scatter ban. So we can draw confidence bounds of the 20 data of 95 percent bounding or 99 percent or what have 21 you.
22 So for homogeneous materials it's 23 statistically represented and understood. So it is an 24 improvement in the technology developed over the last 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 few decades and a better understanding of fracture 1
toughness.
2 So moving our assessment to RPV in that 3
direction reduces uncertainty. Reduces inconsistency 4
of the RT-NDT metric in the margin.
It's 5
statistically described well. And is an actual 6
fracture toughness measurement.
7 And the figure is the historic figure of 8
some testing done at Westinghouse from very large 9
specimens. So 12T means that specimen is 12 inches 10 thick. And that called a compact tension, CT, 11 specimen geometry. And a small specimen is shown as 12 a one inch thick specimen there. And we've been able 13 to even use smaller specimens, which I'm going to talk 14 about.
15 But why do we want to do this? So if you 16 look at the bottom middle figure here, the difference 17 between RT-NDT and T0 for a given heat of material, in 18 some cases there is no difference, or can even be a 19 negative difference, but for the majority of materials 20 there is a very large difference. 100F or even more.
21 And so that's where, for a lot of materials we can 22 claim credit for the inherent margin that exists now.
23 All right, I'll keep moving.
24 MR. BALLINGER: You were going to say, 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 this is Ron Ballinger. You were going to say a little 1
bit more about T0.
2 MR. HALL: Yes. And I probably should 3
have had another slide in here. So T0 is a, so 4
ferritic steels have what's called a transition 5
region. And it follows this shape of this curve here.
6 So at cold temperatures they fail in a brittle manner 7
with little absorbed energy. At warmer temperatures 8
it follows this with an increased amount of energy 9
required, or energy, or load required to initiate a 10 brittle fracture.
11 And for the measurement of T0, i.e. the 12 position of where this curve is for a given material 13 on the temperature access, it requires the testing of 14 a set of specimens, a set of fracture toughness 15 specimens like shown here, of at least six, but 16 typically more eight or 16 specimens. Is sufficient 17 to give a statistical understanding of where that, 18 what this T0 value is and where this temperature 19 relationship is for a given material in a given 20 condition. I.e., if it's irradiated or not irradiated 21 or what have you.
22 So that's --
23 MR. BALLINGER: So --
24 (Simultaneously Speaking.)
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17 MR. BALLINGER: And well also, where did 1
the 100 KSI revision definition come from?
2 MR. HALL: Yes, so that's a good point.
3 So T0 is defined as where this curve intersects at 100 4
megapascal root meter, which this is KSI root inch, 5
but they're different by nine percent. Where that 6
curve intersects 100 is 0, i.e. the definition of T0.
7 Since this curve shape is fixed, that's 8
just an arbitrary number, the 100. It could be any 9
number to define the reference temperature. But 100 10 is a reasonable round number to use and so that's the 11 definition of T0.
12 MR. BALLINGER: But it's generally above 13 the lower shell and below the lower shell, right?
14 MR. HALL: Right. Above the lower shell, 15 and below the upper shell, that's correct. It's right 16 in the region of the transition between the two.
17 MR. BALLINGER: To provide a little comic 18 relief, the picture on the left-hand side, at one 19 point Westinghouse would come to meetings and have a 20 full fracture toughness specimen of the size necessary 21 for the pressure vessel itself, which was a lot bigger 22 than 12T I think. And they would bring it to 23 meetings. I don't know how they got it there, it had 24 to weigh a ton.
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 MR. HALL: Yes.
1 (Laughter.)
2 MR. BALLINGER: But if you recall it was, 3
anyway, thanks.
4 MR. HALL: I don't recall that, it's a 5
little before my time.
6 MR. BALLINGER: I could say more about 7
that, but now, in today's culture that specimen and 8
its accompaniment would not work.
9 (Laughter.)
10 MR. HALL: I do have some pictures with 11 some people sitting onto of that specimen.
12 MR. BALLINGER: Right.
13 MR. HALL: So some of this data in this 14 figure is that data developed from large specimens 15 like that. It's from a variety of different size 16 specimens but yes.
17 With the beginning of the fractured 18 toughness technology in the '70s, we were testing very 19 large specimens. And for the warmer temperatures 20 required large specimens. So they were obviously very 21 expensive to test as very large specimens.
22 However, we understood as part of the 23 E1921 process, and it's also called master curve, 24 because this curve is applicable to all ferritic 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 steels, they crack front length. When you start to 1
load the specimen there, to initiate a brittle failure 2
there is an initiation site, or sites, along the 3
cracked front.
4 And it's a statistical distribution. And 5
it's called the weakest link theory. So the longer, 6
it's a function of how long your crack front is 7
because the longer it is the more likely you're to 8
have an initiator from your steel.
9 So there is a size adjustment based on the 10 thickness of the specimen. So that's why in the 11 master curve there is a 1T equivalent size described 12 here. So we can now know that, that statistical size 13 adjustment parameter has been proven over the decades 14 to well describe the data. And so now we can use 15 small specimens to make that adjustment. And it works 16 very well.
17 And this is an early data set shown here.
18 There's been much, much more data collected in 19 intervening years since this WRC bulletin was 20 published. And it still shows the same behavior and 21 the data well described.
22 So we have tens of thousands of points I 23 would say showing that this methodology is accurate 24 and robust. Any further questions before I go 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
20 No.
1 All right. So I also direct fracture 2
toughness. So testing an irradiated material has 3
advantages because you now know longer need to predict 4
embrittlement. As we move to higher fluences with 5
longer operating times our current predictions, as 6
shown here with Reg Guide 199, can deviate from 7
measured behavior from the prediction equation.
8 And as was mentioned earlier, that reg 9
guide was based on roughly 177 measurements. We now 10 have much more data. Roughly ten times that. And can 11 see that deviation is occurring.
12 However, if you measure fracture toughness 13 in the irradiated condition, the RPV condition of 14 interest, now you don't have any prediction error or 15 bias. You'll still have some uncertainty, which needs 16 to be accounted for. But there is great advantage in 17 measuring that irradiated condition.
18 MR. BALLINGER: This is Ron Ballinger 19 again. I might add that the E900 correlation takes a 20 lot of that away.
21 But at one point the staff in one of our 22 discussions developed a chart of which plants would 23 typically run into difficulty with the correlation at 24 subsequent license renewal. And there were quite 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
21 few plants that would, but many of them were going to 1
be shut down.
2 And now things are being reversed it 3
seems. And some of these plants are thinking, or 4
they're thinking about restarting some of these 5
plants. So this curve is very relevant.
6 MR. HALL: Yes. Yes. Especially as we, 7
subsequently since renewal for 80 years and consider 8
going beyond.
9 MR. PETTI: So this is Dave Petti. I had 10 a question on the radiation. Maybe you'll address it 11 later.
12 I was reading some of the other background 13 documents that were provided to us. And this concern 14 about data from a T0 reactor versus samples in actual 15 reactors and nuances and biases that potentially that 16 are in the accelerated irradiations and the MTRs. And 17 this concern about an acceleration of the 18 embrittlement.
19 And at least the paper that I read is very 20 foggy as to whether or not, they basically said you 21 just can't tell if it's scatter or if there is some 22 acceleration as one gets to higher fluence. What's --
23 MR. HALL: Yes, I agree. The experts, 24 when we get together and discuss MTR radiation, 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
22 flux, I call it a flux effect or fluence rate effect, 1
whether that, and the data varies so it's not clear, 2
I agree.
3 And I'll talk a little bit later because 4
there is a way to apply that data through this 5
methodology, however it's validated through a set of 6
PWR irradiated data so let me address that part of it 7
later if I may.
8 MR. PETTI: Sure, that's fine.
9 MR. HALL: Yes, okay. Okay, so a little 10 bit more on background and precedent of using the 11 master curve technology.
12 An early version was used for the Zion 13 reactor back in 1994. That plant has since closed.
14 And then there was a different approach used on 15 Kewaunee in 2001.
16 And then a initial unirradiated reference 17 temperature T0 was used for the high copper Linde 80 18 welds, which was used in the plants listed there, B&W 19 fabricated plants, which were both B&W design and 20 Westinghouse designs. That was used and approved by 21 the NRC and reset the initial value substituting RT-22 T0, I'll tell you what that is in a minute, but it's 23 a T0 plus a bias, in the unirradiated condition for 24 the Linde 80 welds. And that was used by all 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
23 plants listed.
1 And then it's also been adopted into the 2
ASME code in both Sections 3 and 11. But here we're 3
talking Section 11 specifically.
4 So RT-T0 has an alternative to RT-NDT that 5
was incorporated code case 629, that's been roughly 20 6
years ago for that. And then more recently into, 7
directly into Section 11 Appendix G.
8 And then code case, so those are an 9
adjustment to the K-1C curve. Where code case N-830 10 is actually using the master curve shape, which is a 11 little bit different than the K-1C curve but similar.
12 And all of those have been codified through 50..55a.
13 So we're --
14 MR. PETTI: This is Dave again.
15 MR. HALL: Yes.
16 MR. PETTI: Dave again. Just a question.
17 So are these older ones that are no applicable or can 18 somebody still use one of these code cases? You know, 19 are they still valid or do you, you know, the new ones 20 replace the old ones?
21 MR. HALL: Oh no, they're still, they're 22 still cited in the code 50.55a and still can be used.
23 MR. PETTI: Okay.
24 MR. BALLINGER: Yes, I might, this is Ron 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 again. I might add that if you're looking for the 1
more modern or the latest on N-830 there is an EPRI 2
document that's on the SharePoint site, MRP-418.
3 Which is the latest and greatest technical basis for 4
N-830.
5 MR. HALL: Correct. And that would show, 6
similarly to what I showed here, but with more data.
7 More, a lot more data. That's correct. So the 8
methodology points to precedent, and that's already 9
been approved and accepted and developed over, for 10 decades.
11 All right, we'll move on. So the actual 12 application of the methodology. So for the PTS rule.
13 So RT-PTS is calculated as TR-T0 plus adjustment and 14 margin. And RT-T0 is defined in a ASME code as T0 15 plus 35.
16 And what that 35 degrees does is shift the 17 master curve, 95 percent lower bound master curve to 18 approximate where the K-1C curve lies. So this was 19 kind of an intermediate step in the process of 20 adopting master curve in the code. And since the PTS 21 rule was based on that, that method is used here.
22 And then for applying PT
- curves, 23 developing PT curves, this is the K-1C curve, again, 24 using RT-T0. Or the master curve shape itself can be 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
25 used through code case N-380, which is simply T0 plus 1
adjustment plus margin. And this is the 95 percent 2
lower bound on, of fracture toughness.
3 Now the methodology. So this is all here 4
in code. ASME code. The methodology here defines on 5
how adjustments works and the margin term. As well as 6
the definition of how you produce it, the T0.
7 MR. BALLINGER: This is Ron again. I just 8
noticed N-830-0, we're on N-830-1, right?
9 MR. HALL: That's correct. So what N-831-10 1 added to the code case was a definition of the upper 11 shell fracture toughness.
12 MR. BALLINGER: Ah, okay.
13 MR. HALL: Okay? So this, the PTS rule 14 and Appendix G PT curves, are designed to prevent 15 brittle fracture. So this topical report only 16 addresses assessment of prevention of brittle 17 fracture. The upper shell fracture toughness is 18 different and assessed in a different manner outside 19 of the scope of this topical report. But good 20 observation.
21 All right. So I'm going to talk about 22 each of these terms. The adjustment term, the margin 23 term and how that all works. Okay, if I can get it to 24 advance. Here we 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
26 Before that, so the first part of it is, 1
how do you generate T0, okay. Obviously it has to be 2
done per the standard ASTM E1921, the 2020 version.
3 So in some cases we already have done 4
testing. The industry has done testing on a number of 5
materials. So that data could be applied. If it was 6
tested to an earlier version of the standard it would 7
have to be reassessed for compliance with the 2020 8
year version.
9 We could test fracture toughness specimens 10 machined from unirradiated archived material. So we 11 have archived material for most of the beltline 12 materials for the operating RPVs in the U.S. in 13 storage.
14 We also have an extensive archive of 15 irradiated material where specimens were irradiated in 16 standard PWR surveillance capsules. We have a very 17 large archive of broken Charpy specimens, and I can 18 show you how those can be used.
19 And then fourthly, if neither of those 20 options are available, specimens could be irradiated 21 in a material test reactor at a high flux. And, well, 22 the advantage of high flux is time.
23 So to get to an 80 fluence in a PWR 24 standard, PWR surveillance capsule location it will 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 take decades to do that. However, in an MTR you can 1
do that in months or less than a year. But there is 2
always the question is, well, what was the effect of 3
that high fluxes. And so it was brought up earlier.
4 So in order to use that, an MTR irradiated 5
material in through this topical report, you have to 6
validate that particular MTR irradiation produces data 7
that's representative of a PWR. Okay? Radiation.
8 So what that means is, so we broke 9
material into three groups according to copper, 10 because the data has shown that depending on the 11 copper level you can get different effects due to the 12 flux. Okay?
13 And so for an MTR radiation campaign, say 14 you have several materials in there that you want to 15 irradiate that are the same heat as what's in the RPV 16 of condition. The RPV of interest that you're 17 testing, you have to have a validation material for 18 each copper gripping.
19 And that validation material must also 20 have irradiated data available from a PWR irradiation.
21 And that material has to be in the MTR radiation 22 campaign such that when you test that, you compare it 23 to the PWR irradiation. And if, to demonstrate that 24 that MTR radiation is representative, okay?
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 And so what that, you could also have 1
other difference. You have the flux effect but you 2
could have, there could be a difference in spectrum.
3 Energy spectrum of the neutrons or temperature 4
uncertainties or other things that maybe we don't 5
completely know about. But this validates that that's 6
representative.
7 And if it doesn't produce conservative 8
results there is a method for adjusting the data to 9
make it conservative. Does that answer the question 10 on the potential flux effect?
11 MR. BALLINGER: Yes. I think we have, 12 Craig Harrington's got his hand raised and I probably 13 didn't notice it, but now I have. So, Craig, do you 14 have a question?
15 MR. HARRINGTON: No, I just raised it, 16 Ron, so not an issue. This is Craig Harrington. Just 17 a quick question, Brian.
18 In the technical report the terminology 19 there is slightly different, I think, of material in 20 each copper group. The slide suggests that you would 21 have samples from all three copper groups, and the TR 22 seems to say it's only the one that corresponds to the 23 material of interest. Can you clarify that?
24 MR. HALL: Certainly. So if you, in your 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 MTR irradiation campaign you have two material 1
groupings that you're irradiating, let's say low and 2
medium copper groupings, you need to have validation 3
specimens in each of those. If you don't have high 4
copper material in your radiation campaign you don't 5
need to validate that material grouping.
6 MR. HARRINGTON: Okay. All right, just 7
wanted to clarify. Thanks.
8 MR. HALL: Yes. All right, I will move 9
on. Okay, so the testing requirements to produce a 10 T0, as I have mentioned, is per ASTM E1921. So 11 generally the same heat of material is required to be 12 tested for T0 that you're assessing in the RPV of 13 interest.
14 There is, an exception is you can generate 15 generic unirradiated T0 values for a class or grouping 16 of material. And that requires at least four valid 17 T0s on four different heats of material for a weld 18 type, material class, such as 508 Class 2. You could 19 break that potentially into common manufacturers, if 20 that makes sense.
21 And then a statistical factor is applied, 22 which comes from standard statistics and is described 23 in NUREG-1475, the K-1 factor. So the fewer number 24 you have the larger your K-1 value is. So it's 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
30 advantageous to have a larger population than four.
1 And typically we use two to represent 95 2
percent confidence. But that's predicated that you 3
have a large population.
4 So the K-1 value, with a large population 5
of 20 or 30, it reduces to two, but this allows for 6
smaller data sets to come up with a generic value.
7 However, your K becomes significantly larger and it's 8
penalizing. So it's a conservative approach but it is 9
a way to generate some generic values for classes of 10 material that you may have, not have the direct 11 measurements for.
12 Secondly there is, obviously if you have 13 unirradiated data you then use your full embrittlement 14 prediction. And then you also have uncertainties 15 related to RPV radiation temperature, and then the 16 fluence calculations.
17 And then ASTM E1921 has a process for 18 screening a material data set in determining T0, 19 whether it's homogenous or inhomogeneous. Because the 20 statistical description for homogenous material is 21 what I showed you previously.
22 But there are some materials that have 23 some variability in them and do not behave in a 24 typical homogeneous manner and fracture toughness 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
31 therefore there is this inhomogeneity screening and it 1
provides a bias in a conservative manner to account 2
for that. If that shows up in your data set.
3 All right. And any geometry allowed by 4
the test standard can be used, including a Charpy size 5
specimen. Although there is a 10C bias added for that 6
because the data has shown that there is a bias with 7
that data. And then a miniature compact tension 8
fracture specimen, which I'm going to talk about in a 9
moment.
10 All right. So, the, what we call the 11 manager compact tension fracture specimen is compliant 12 with ASTM E1921. It's a roughly 4 millimeter thick 13 specimen. It's designed specifically to be removed 14 from Charpy size specimens. A Charpy size specimen is 15 10 by 10 millimeter by roughly 55 millimeters long.
16 You can remove four of these miniature 17 specimens from a broken Charpy specimen. So that's 18 highly advantageous when you have a very large archive 19 of irradiated Charpy specimens from PWR surveillance 20 programs. Then we can take broken specimens, and we 21 have in many cases, taken broken specimens, machined 22 miniature fracture specimens and tested them according 23 to ASTM E1921 and produced a T0.
24 The question has been raised, you know, 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 that small specimen, is it really representative of 1
larger specimens. And so in the appendix of the 2
topical report the is a significant data set where 3
given heats of material have been tested for T0 with 4
larger specimens and the small mini CTs. Both 5
irradiated and unirradiated in various steels, welds 6
and based metals.
7 And there is no statistical difference on 8
average. And the standard deviation between them is 9
what you would expect just from measurement 10 uncertainty. So all we can see that small specimens 11 do produce reliable results.
12 All right. Incidentally, if somebody does 13 raise their hand in Teams I can't see that, so if 14 somebody could speak up, appreciate it.
15 Okay. So once T0 is measured the 16 condition of measurement of your specimens is almost 17 never exactly representative of the RPV material 18 condition of interest, okay? Your fluence is always 19 going to be somewhat different. And the best estimate 20 chemistry for your source material might be different 21 as well.
22 So the ASTM E900 prediction methodology is 23 used to make that adjustment. It's currently the most 24 robust international consensus predication model 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 available. It's based on Charpy, 30 foot pound 1
transition temperature shift measurements comprised of 2
over 1,800 power reactor surveillance program 3
measurements. So significantly more modern and robust 4
than Reg Guide 199.
5 And it doesn't, these very small figures 6
on the right shows it doesn't have the same deviation 7
at high fluences that the reg guide has. So it does 8
better. The NRC has reviewed this and agreed.
9 Although not endorse the standard but they're 10 comfortable with it.
11 Okay. So the way the adjustment works if 12 we calculate the prediction for the RPV condition and 13 compare that to the measured specimens where T0 is 14 measured on those specimens. The difference between 15 those predictions is the adjustment. It's fairly 16 simple. And all the inputs to the embrittlement trend 17 curve, the chemistry, the radiation temperature and 18 the fluence feed into those predictions.
19 MR. BALLINGER: This is Ron, Ron Ballinger 20 again. I might add that the NRC, the Staff, has, to 21 their credit, been heavily involved on these 22 committees. And in fact, the committee that produced 23 E900 I think was chaired by an NRC employee. An NRC 24 Staff Member who has since retired from the Agency.
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 Am I getting that correct?
1 MR. HALL: Almost.
2 MR. BALLINGER: Almost, okay.
3 (Laughter.)
4 MR. BALLINGER: Okay. Okay.
5 MR. HALL: I'm actually the chair of ASTM 6
E, that's responsible.
7 MR. BALLINGER: Okay. But Mark Kirk was 8
involved in some way, right?
9 MR. HALL: He did lead, yes --
10 MR. BALLINGER: Okay.
11 MR. HALL: -- the development of E900.
12 MR. BALLINGER: So, I mean, the NRC is 13 very much, has been very much involved.
14 MR. HALL: That's correct. All right, I 15 will continue. So E900 is based on, as I mentioned, 16 Charpy 30 foot pound transition temperature shift 17 measurements.
18 However, in applying direct fracture 19 toughness we're measuring T0, which is a fracture 20 toughness based metric. So it's not quite a one-to-21 one correlation here, so we looked at, or the industry 22 has looked at, well what's the difference in T0 shift 23 relative to the Charpy-based T30 shift, okay?
24 And so you can see for welds this is 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
35 data, and for base metal it's the data here. For 1
welds its, the slope is.99 so we use a one conversion 2
factor. And then for base metals there is an average 3
difference. Here it shows 1.08. We use a 1.1.
4 Now there is a fair amount of scatter in 5
this data. However, because there is substantial 6
amount of data the error, the standard error on the 7
slope itself, which is the little dotted lines here, 8
is fairly tight. Fairly, has a good statistical small 9
standard error.
10 The scatter in the data is largely due to 11 measurement uncertainty. So for each delta T30 12 measurement you have two uncertainties. You have the 13 initial Charpy T30 measurement and you have irradiated 14 uncertainty. And then likewise for T0 you have the 15 initial unirradiated and the irradiated uncertainties.
16 And those add up. And I have error bars showing, on 17 average, the errors bars for those two measurements.
18 These error bars describe most of the 19 scatter, but there it's also some material of 20 availability involved because each measurement is from 21 a different piece of the material. So there is, 22 you're going to have some material availability. And 23 I have a little bit of an assessment on those 24 variabilities going forward in the subsequent slide.
25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
36 And so as I
mentioned, there is 1
measurement of T0, there is the adjustment. Now we're 2
going to talk about the margin. The uncertainties.
3 So there is a lot of uncertainties 4
captured in the margin term here. The first one is 5
the actual measurement uncertainty of T0 that's 6
defined in ASTM E121. So the more specimens you test 7
the smaller your uncertainty. The smaller that term 8
is.
9 Then you have your adjustment. So if you 10 have a small adjustment you should have a small 11 uncertainty on that adjustment. If you have a very 12 large adjustment, if you're adjusting from 13 unirradiated condition to a very high fluence, this is 14 likely going to, this is therefore large.
15 And then, so these are some of the inputs 16 into the ASTM E900 prediction model. So you have 17 temperature uncertainty for the specimens that were 18 irradiated. And then the specimens, or the 19 temperature, average radiation temperature of the RPV.
20 Which is a diacom of the collate temperature in the 21 plant.
22 If your specimens were irradiated in the 23 same PWR that's being assessed, then one of these is, 24 the test specimen is set to zero because they would, 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 temperature wise, be representative of the irradiation 1
temperature condition.
2 And then fluence uncertainty. So we 3
calculate the fluence of both the specimens, as well 4
as the RPV. And there is an uncertainty in that 5
fluence calculation, so that uncertainty feeds into 6
the margin term. And if you have, if your specimen is 7
in the unirradiated condition, obviously there is no 8
uncertainty with that so that's set to zero for that 9
particular case.
10 All right, I'm going to talk a little bit 11 more about each of these, some of these uncertainty 12 terms here. So the measurement uncertainty, as I 13 mentioned, is defined in E1921.
14 And also mention that there is a 15 homogeneous screening criteria that depending on the 16 data set size is designed to catch data sets that are 17 not behaving in the normal homogenous manner. So if 18 that's represented in your data set then there is a 19 bias added.
20 And I published a paper here looking at 21 several very large data sets, ten very large data 22 sets, of RPV steel, some irradiated and some not. And 23 typically when you're applying this you have a smaller 24 data set, you don't have hundreds of tests you have 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
38 dozen tests let's say.
1 So we looked at subsets from these larger 2
data sets and showed that might be representative in 3
actual conditions, test conditions. We choose the 4
least conservative data set and added the 5
uncertainties to it.
6 And did the homogenous screening criteria 7
and showed that we bound 95 percent of the data, even 8
choosing the least conservative data subsets and the 9
large data sets. So that was showing the robustness 10 of the methodology.
11 And this is just one example here. You 12 get some, quite a bit of scatter in this data set. By 13 using the least conservative subset you're still 14 bounding the data which is the red curve here.
15 All right, I will continue. The 16 uncertainty on the adjustment. So the consists, so 17 the adjustment consists of, the term here is the 18 uncertainty term for the ASTM E900 uncertainty on the 19 prediction. This term is a proportional term. So 20 it's proportional to the amount of adjustment relative 21 to the RPV prediction. Embrittlement prediction.
22 So few adjustment is, let's say you've 23 tested samples that are very close to your RPV 24 condition of interest, this would go close to zero, 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 and then this 9 Celsius term would be your minimal 1
value that could occur. So that would be set by 9C.
2 But if you're adjusting, for
- example, from 3
unirradiated condition this term becomes one. And so 4
now you have your full ASTM E900 uncertainty on your 5
prediction. So that's how the uncertainty adjustment 6
works.
7 So looking at, again, back at the 8
scattered data on these plots. So the typical T0 9
measurement uncertainty, 6 to 8 Celsius, typical 10 Charpy uncertainty of the T30 metric from a Charpy 11 curve can range from 4 to 10C, depending on which 12 paper you read.
13 So if I combine those, those are all 14 independent. So if I combine those using a square 15 root sum of squares I get a 14 Celsius uncertainty.
16 And so the residues on these fits is 17 Celsius 17 standard deviation. So the difference between those 18 two is 9C.
19 So that's where the, attributed to 20 material variability. It could be a little bit of 21 other things in there, but I think it's largely 22 covered by material of variability. So that's why 23 this 9 Celsius minimum is applied here because you're 24 always testing samples that are not from your RPV 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 that's in service.
1 All right. Hearing no comments I will 2
continue on.
3 All right. So at one point through the 4
REI process the Staff challenged me and said, prove 5
that your methodology works. And so the way that was 6
done is, and this is a published paper to this past 7
summer's ASME PVP conference.
8 We applied the methodology for data sets 9
for which there were more than one measurement of T0 10 for a given heat of steel. Okay? So first we're 11 looking at T0 measurements in the unirradiated T0.
12 And we also had a measurement of T0 for the same heat 13 of steel in the irradiated condition.
14 So we adjusted the unirradiated T0 to the 15 irradiated condition of interest using the adjustment 16 procedure ASTM E900 prediction. And then added the 17 more appropriate margin from the methodology and 18 compared, so this is, on this bottom access is 19 unirradiated T0 plus the adjustment, plus the margin 20 term, compared that to the measurement and the 21 irradiated condition. Measured T0.
22 So this is the, as if this was measured 23 from an actual RPV. And so any, this is the one-to-24 one line, any data below that is conservative. Data 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 falling above that, non-conservative. So as you can 1
see, all the data is bounded in this case for welds.
2 For base metals there is a point or two that are 3
slightly above the curve. But 98 percent of the data 4
is bounded.
5 And then, so each of these points in the 6
right two figures represents a measurement of T0. And 7
each T0 measurement is based on many fracture, 8
individual fracture toughness test. A minimum of six, 9
usually several more.
10 So here's an example of one of these that 11 are indicated in the top figure. The lower bound 12 curve shown here. And all these four data sets, these 13 are the purple ones here, are the individual fracture 14 toughness measurements that are all bounded. As you 15 would expect because these are all below the red line.
16 Then used the same process for irradiated.
17 So some of these data sets had T0 measured in two 18 different irradiated conditions for the same heat of 19 steel. And so the one, the lower fluent, irradiated 20 T0 was adjusted to the condition of the other 21 measurement at a other fluence, the higher fluence 22 condition using, again, E900 prediction. Difference 23 between the two. The margin was added.
24 In this case since adjustments aren't, are 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 smaller, the 9 Celsius minimal value is the governing 1
input to the margin equation. That part of the margin 2
equation.
3 And as you can see, 97 percent of the data 4
sets are bounded in both base metal and weld. And if 5
we pick the purple ones here and look at the 6
individual fracture toughness measurements on this 7
figure here, you can see almost every data point is 8
bounded. There is one red one here that lies below 9
the curve.
10 So even in the case where this point here 11 is, shows non-conservative on a T0, if you look at the 12 individual fracture toughness measurements behind that 13 T0 measurement, they're all bounded by the curve 14 expect one in this particular case. So again, a very 15 robust demonstration with lots of data showing that 16 the methodology is conservative at the expect level.
17 So to summarize, then I'll go through an 18 example. So basically the methodology provides a way 19 to use direct fracture toughness as an alternative to 20 the PTS role and developing PT limit curves. It's 21 based on the statistical understanding of fracture 22 toughness. It's an improvement in technologies.
23 Measurement of T0 adjustment from your 24 measurement condition to the RPV condition of interest 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 accounts for uncertainties. Uses codified methods in 1
ASME. And then, as I said, it's an alternative that 2
can be used for the PTS rule as well.
3 So now I'm going to go through an example 4
of how it works. So this was done for the Crystal 5
River Nuclear, which is now closed. So no risk in 6
applying it to a vessel as an example.
7 So the upper shell to lower shell 8
circumferential weld is, it's a Linde 80 weld which 9
has higher copper, so it does have pretty fairly high 10 embrittlement shift. It's a well designated WF-70, 11 Heat 72105. It is PTS limiting for that vessel.
12 So there is a, there is T0 data available 13 from, well there is material available from different 14 sources. So that same weld wire heat was used to 15 construct the Midland 1 reactor pressure vessel. That 16 plant never operated, and Oak Ridge took, and took 17 some pieces from that vessel, cut them up and did a 18 lot of fracture toughness testing on the weld that was 19 from both the beltline as well as higher elevation in 20 the RPV up at the nozzle region.
21 And then also this same heated material 22 was used in the Zion 1 vessel, and was contained in 23 the surveillance program for that vessel. So there 24 was specimens, materials available from that source of 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 material. So the surveillance weld for Zion.
1 And then this heat of steel, heat of weld, 2
was used in, irradiated in the Ford material test 3
reactor. This has been decades ago. Also irradiated 4
in Crystal River surveillance capsule, as well as the 5
Zion 1 surveillance capsule. So a variety of material 6
sources for that heat, as well as the radiation 7
locations conditions. So as I mentioned, those 8
irradiated in both Zion and Ford Reactor.
9 So in this particular case, so here I give 10 two examples of calculation of T0 for irradiated. So 11 Oak Ridge irradiated. The Midland source material in 12 the Zion, in the Ford Reactor, and tested for T0 in 13 that irradiated condition. Felt this T0 was also 14 irradiated for, in the Zion 1 surveillance program.
15 This T0.
16 There is a
screening process for 17 homogeneity. In this one case the screen does 18 homogenous, the other case it did not. So the one 19 that's screened in homogenous got a bias added to it, 20 which actually is very similar to the other data set.
21 So then if you were to assess whether the 22 Ford Reactor irradiation is representative of a PWR 23 irradiation, you can compare that to the Zion 1 24 irradiated material. Since that, those materials were 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 from different sources, the best estimate chemistry 1
for those sources is a little bit different.
2 And these are all the inputs to the E900 3
prediction. And then of course the fluence for the 4
two different irradiations is different. And the 5
radiation temperature.
6 So you calculate the predicted shift for 7
E900 for both conditions. And they're different by 10 8
Fahrenheit. You adjust for that difference. So you 9
can make an apples-to-apples comparison.
10 And then you adjust the T0 from up here by 11 this 10 Fahrenheit, so you add 103 plus 10, you get 12 113. And when you compare that to the Zion irradiated 13 condition it's higher, meaning it's more conservative.
14 So that, in this particular case, for this material, 15 this is a high copper grouping.
16 You would then say, well, other materials 17 in that same radiation campaign would be 18 representative and could be used for an PWR RPV 19 assessment. This is just an example on how that 20 works.
21 Continue with this example. So as I 22 mentioned, so there were different, four different 23 irradiations with different sources of material. And 24 this is the condition of interest. This is the 60 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 year fluence and best estimate chemistry for the weld.
1 The upper shell to lower shell circumferential weld in 2
the Crystal River RPV.
3 So if you, this is the predicted 4
embrittlement. If you compare that to the predictions 5
for the, these are the conditions at which the samples 6
for which T0 was tested for these other irradiations.
7 And these are the predictions. There all fairly 8
close. Not a large difference between them.
9 So you take those differences, this would 10 be your adjustment. You can go either way, up or 11 down. You then adjust, I'll show you in the next, the 12 next slide. Well, the following slide shows how it 13 all comes together, but here is the margin term.
14 So the first of each of these T0 15 measurements we have the uncertainty of the 16 measurement itself. That's a function of how many 17 specimens were tested. The adjustment uncertainty, 18 since these adjustments were all relatively small.
19 This is the minimum value of that 9 Celsius and 20 Fahrenheit.
21 And then you have the uncertainties of the 22 temperature of your radiation and your fluence 23 calculations. Both your specimens and your RPV.
24 You'll notice one of these is zero because 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
47 particular case, this is on the temperature of the 1
specimens, they were irradiated in Crystal River. So 2
there would be no added, since that is representative 3
of the RPV there would be no added uncertainty for 4
that particular part of it.
5 But when you add all these uncertainties 6
together and multiple by two you get roughly 40 7
degrees Fahrenheit as your uncertainty. So then here 8
is that margin.
9 So you take your T0 measurement, you 10 adjust it to your Crystal River condition of interest.
11 In this case PTS, so that's the inside surface. You 12 add your margin. And then, so this is your produced 13 value of, in this case you could use T0, or for PTS 14 you would use RT-T0.
15 If you have PWR, the methodology states 16 that if you have PWR irradiated data and you have MTR 17 data, the PWR data takes precedent and you would 18 actually zero out, you don't use the MTR irradiated 19 data.
20 And there's also a waiting procedure, 21 which I have not described. But the data that's 22 closer to the condition of interest gets a higher 23 weighting than data that's further away.
24 So this particular one is closer 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
48 condition of interest of Crystal River 3 at 60 years.
1 Then this one looks like it's a little higher 2
weighting. But combining these two weightings you get 3
a RT-T0 bounding value for Crystal River of 176 using 4
this methodology.
5 The traditional methodology in the 5061 6
would produce a PTS value of roughly 287. When this 7
was included in the license renewal application 8
resetting the initial value using T0. Using the 9
approved BAW-2308 methodology you get 254, which is an 10 improvement.
11 But this measuring data in the irradiated 12 condition gives you even a better improvement because 13 you don't have the uncertainty and potential bias with 14 a prediction. So that's how this example works. This 15 is in the appendix to the methodology. And there's 16 another example in there as well, which I'm not going 17 to describe for the Kewaunee Reactor vessel.
18 So, this is my last slide. So tested T0 19 data where the adjustment margin can be used for 20 evaluate RPVs. Pressurized thermal shock, which has 21 to be performed for any license renewal term.
22 And then any changes in operation due to 23 power uprates or operational changes can change that 24 value, so this could be used for the, those as well.
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49 And has, yes. And then you can also use it for heat 1
up and cool down curves that extend applicability to 2
existing curves if justified. Or improve the 3
operating margins giving the operators more room to 4
maneuver the plant during heat ups and cool downs of 5
the plant.
6 But I'll also point out that when 7
measuring and applying this there is no guarantee that 8
it would produce a better, a better result. Every 9
heat of material is different, and the conservatism to 10 the current approach is different for each heated 11 material.
12 Thank you. So that is the end of my 13 presentation. Any final questions?
14 MR. BALLINGER: Thanks. Thank you very 15 much. Members and Consultants, questions please.
16 MS. BIER: Yes. This is Vicky Bier.
17 Going back to a much earlier part of the presentation 18 you mentioned that in some cases there could be 19 extrapolation
- from, if I
remember correctly, 20 (technical difficulties) sometimes that might be all 21 you have and you try and do the best you can.
22 But you made the statement that the 23 extrapolation for that case was conservative. And 24 it's hard for me to interpret such a small number of 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 samples as being conservative, even if the adjustment 1
is trying to be conservative. So anyway, I just 2
wanted your comment on that part.
3 MR. HALL: So, I think you cut out for 4
part of your comment and I'm not sure exactly what, 5
can you point to a specific slide?
6 MS. BIER: Why don't you take some other 7
questions first, and I'll see if I can find the slide 8
that bothered me?
9 MR. HALL: Okay.
10 MR. BALLINGER: Other questions?
11 (No audible response.)
12 MR. BALLINGER: Well now, Vicki, you're on 13 the spot.
14 MS. BIER: I'll come back to this later in 15 the day maybe, if possible.
16 MR. HALL: All right, I'm trying to 17 refresh my memory as to where, where --
18 MR. BALLINGER: Yes, I think I remember 19 now, too. It was where the conversation about four 20 specimens.
21 MS. BIER: Exactly, and I can't remember 22 whether the four showed up on the slide. I was 23 listening and not watching, so.
24 MR. HALL: Do you mean the generic unrated 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 T0, which requires at least --
1 (Simultaneous speaking.)
2 MS. BIER: Yes.
3 MR. HALL: -- four measurements?
4 MS. BIER: Probably. That looks like 5
where it would come from.
6 And you know, the discussion was that yes, 7
very often there would be a lot more than four, but it 8
could be done with as little as four and the 9
correction would hopefully be conservative.
10 MR. HALL: So, this K value, if you look 11 at the tables.
12 MS. BIER: Yes.
13 MR. HALL: In NUREG-1475. For small 14 numbers such as four, this K value is very large.
15 MS. BIER: Okay.
16 MR. HALL: So, you're taking the asset 17 standard deviation, and you're multiplying it by, and 18 forgive me, I don't remember what --
19 (Simultaneous speaking.)
20 MS. BIER: Yes, that's okay.
21 MR. HALL: -- the K value is for the 22 number four. It might be 15, or something, I don't 23 remember.
24 But when you get up to 30, it goes down 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
52 roughly two --
1 MS. BIER: Got it.
2 MR. HALL: -- which is typically what we 3
use for a large population. But it's the 95, it's 95-4 95 confidence level for the given number of 5
measurements.
6 So --
7 MS. BIER: Okay.
8 MR. HALL: -- it's very penalizing to 9
have a small population.
10 MS. BIER: Got it.
11 MR. HALL: And so, it's a strong 12 statistical principles.
13 MS. BIER: Yes.
14 MR. HALL: It's not nothing extrapolated 15 or anything new.
16 MS. BIER: I, yes, okay.
17 I understand the logic behind that and 18 apologies for my bad internet today, but I think there 19 are a lot of statistical methods that say like, don't 20 even try this with fewer than five samples.
21 So, just kind of a word of caution on 22 that, but I don't have a specific basis to object or 23 anything.
24 MR. HALL: Okay.
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53 MR. SCHULTZ: Brian, this is Steve 1
Schultz.
2 Just a question in terms of application 3
here. Ron had talked, and you have discussed how much 4
information is now available that's allowed this 5
overall process to be developed, and used.
6 But if a utility is going to apply this, 7
what's the general situation within the industry?
8 Does everybody need to do this testing individually, 9
to move forward with its application?
10 Or is there a lot of work that has been 11 done that can be gathered together and applied?
12 Utility to utility, or where do things stand to move 13 forward with application?
14 MR. HALL: Okay, so there has been some 15 data produced both through industry programs, we've 16 done some testing for EPRI for example.
17 For irradiated T0 development, and there's 18 also been plant specific work. Some utilities for 19 supporting SLR have done some testing.
20 So, there is some data that could be used 21 now, but there would be still for more wider use, more 22 testing would need to be done.
23 And not all utilities, not all plants need 24 to use this. Many, once we discovered that copper 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
54 something you didn't want to have in your RPV beltline 1
materials, and that was removed in the let's say mid-2 70s, plants, vessel materials with lower copper don't 3
have a lot of embrittlement.
4 They have some obviously, but so some 5
plants could use this not for needing to do re-6 licensing, but for just improvement of as I mentioned, 7
PT curves, to reclaim some of that margin that exists, 8
currently exists.
9 Or just to, through the license renewal 10 extension, extend existing PT curves. That's easier 11 for them to do because then they don't have to change 12 their operating parameters, and retrain operators and 13 such.
14 So, yes, so going forward, not every 15 plant's going to use it but some will, and it's 16 definitely an option.
17 MR. SCHULTZ: All right, and I thank you.
18 Thank you. Go ahead, Ron.
19 MR. BALLINGER: Yes, I would say that I 20 think that most of the vessels that are now in license 21 extensions, were all fabricated probably before 1975 22 or thereabout in that same area.
23 Whereas, Vogel, forget it. Vogel is one 24 of the, is a modern vessel. And so, it does not 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 suffer, would not suffer from this at all.
1 Am I right?
2 MR. HALL: Yes, it would have minimal 3
embrittlement. But quite a few of the vessels that 4
are currently operating from the, I call it the 5
vintage fleet.
6 So, anything fabricated before the let's 7
say 90s. Maybe half of them have low copper.
8 MR. BALLINGER: Ah, okay.
9 MR. HALL: So it's not a major issue. So, 10 yes, they may not be as low as modern vessels, but 11 still decent condition.
12 MR. BALLINGER: And certainly any SMRs 13 that are being considered today that have pressure 14 vessels?
15 MR. HALL: Yes.
16 MR. BALLINGER: Yes.
17 MR. HALL: Anything fabricated this 18 century would have low copper specified.
19 PARTICIPANT: Yes, I was thinking of those 20 older vessels where the applicants for an 80-year 21 lifetime have indicated that there would, there would 22 be new methodologies and approaches they may have 23 referenced this work.
24 And, moving forward with 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
56 analysis that needed to be done to support the 80-year 1
life.
2 MR. BALLINGER: Yes, I'll have to track 3
down that chart that it's a few years ago. The chart 4
that one of the staff members, probably Mark Kirch put 5
together, which identified plant-by-plant, which ones 6
are likely to need additional analysis for 60 and 80 7
years.
8 MR. SCHULTZ: I do remember the 80-year 9
discussions, that's for sure, yes.
10 MR. HALL: Yes, nearly all the plants have 11 60-year licenses, so.
12 MR. BALLINGER: Yes, yes.
13 MR. HALL: They're good for that, but.
14 MR. BALLINGER: Well, thank you, Brian, 15 that helps a lot. Appreciate it.
16 MR. HALL: Okay.
17 MR. KIRCHNER: Brian, this is Walt 18 Kirchner.
19 How much of a impact does this have on the 20 PT curves? Does it give, there are a lot of factors 21 that go into something as, like load following.
22 But does that have a significant impact on 23 the, on that PT envelope that we typically see for 24 PWR?
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57 MR. HALL: It can. I'm trying to think of 1
a relevant figure here. So, I'll go back to this 2
figure, the difference between RT-NDT and T0.
3 So, if you have material where your 4
difference is this large, it could have a significant 5
impact on improving your PT curve.
6 So, this, the T0 or RT-NDT translates with 7
adjustment. Currently, it's called the ART, or 8
Adjusted Reference Temperature.
9 That then feeds in, we use this fracture 10 toughness curve to calculate pressure in, pressure 11 versus temperature, which governs the plants heat up 12 and cool down curves, which I don't have a figure 13 showing that.
14 But to prevent a plant from heating up 15 when the vessel's in a brittle state, okay, that's 16 what the curves are designed to do.
17 So, they have, I'm sorry, prevent a plant 18 from pressurizing at too cold of a temperature. So, 19 they have to heat up before they pressurize so you're 20 not stressing the vessel when it could be in a brittle 21 state.
22 So, but those PT curves with embrittlement 23 shift to the right and there are, you can't go too far 24 because now you can, you could cavitate the pumps 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 because you don't have enough pressure at a given 1
temperature.
2 MR. KIRCHNER: Right.
3 MR. HALL: So, with high embrittlement, 4
that can squeeze your operation and make your window 5
for heat up and cool down, very narrow.
6 And so, this can open that up and 7
alleviate that.
8 MR. KIRCHNER: Okay, thank you.
9 So, it's mainly in the heat up/cool down, 10 not in the normal operating range that this would have 11 the most impact on tech specs?
12 MR. HALL: Yes, when you're at normal 13 operating temperature, you're on the upper shelf, 14 you're in the ducted region, so.
15 MR. KIRCHNER: Yes.
16 MR. HALL: Yes.
17 MR. KIRCHNER: Right, right. Okay, thank 18 you.
19 MR. HALL: Uh huh.
20 MR. BALLINGER: Okay, other questions?
21 Walt has managed to get us precisely on schedule.
22 (Laughter.)
23 MR. BALLINGER: Without pejorative --
24 (Simultaneous speaking.)
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59 MR. MARTIN: Hey, Ron?
1 MR. BALLINGER: Yes?
2 MR. MARTIN: This is Bob Martin.
3 I just have kind of a, well a non-4 technical question and this is really not my technical 5
area.
6 But I wanted to ask you Brian, you 7
mentioned reg guide 199, and I know there's another 8
one out there, 154 that you didn't mention.
9 These were both written in the 80s. Kind 10 of in doing your work, do you think these need to be 11 revisited in any way, or do you think they serve, 12 continue to serve the purpose of industry?
13 MR. HALL: So, as the NRC has pointed out, 14 this is for base metals. At high fluence, the reg 15 guide does tend to go non-conservative.
16 Now, this is a very high fluence. Some 17 plants will see that high fluence at 80 years, many 18 will not. Many will never reach this high fluence.
19 So, in those particular cases, it should 20 be, you should look at another embrittlement 21 prediction, or use a different methodology such as 22 this one.
23 But I would also point out that the 24 current methodologies are very conservative. And even 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
60 if you did deviate somewhat from this, it's not a 1
safety issue it's just that I'd say the reg guide 2
prediction isn't really accurately predicting what's 3
going on.
4 MR. MARTIN: All right, I think that's a 5
good conclusion, thank you.
6 MR. HALL: Okay.
7 MR. BALLINGER: Okay, other questions, 8
please?
9 (No audible response.)
10 MR. BALLINGER: Okay, we're at a point 11 now where we're scheduled to take a break until 11:15.
12 So, we'll pardon for my cat, we'll recess the meeting 13 until 11:15.
14 MR. HALL: All right, thank you for your 15 questions.
16 MR. BALLINGER: And, thank you for the 17 presentation.
18 (Whereupon, the above-entitled matter went 19 off the record at 10:58 a.m. and resumed at 11:15 20 a.m.)
21 MR. BALLINGER: Okay, it is 11:15 and the 22 staff slides are up. So, David and John, you're on.
23 MR. DIJAMCO: Okay, thank you.
24 Good morning, ACRS members. My name is 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 David Dijamco, I'm one of the primary reviewers for 1
the subject topic of report.
2 The other reviewer is John Tsao, and we're 3
both in Angie Buford's branch of Vessels and Internals 4
Branch.
5 We also wanted to acknowledge Robert 6
Tagane, David Rudland, and Dan Vitervitz, for their 7
contributions to the report. And, I do apologize that 8
their names did not make it on this slide.
9 But I'm going to go ahead and proceed with 10 our presentation of our evaluation of the report.
11 So our presentation, it has four parts to 12 it. I'll talk about the five key aspects that we look 13 for.
14 We look for to make sure that the T0 15 testing is performed in accordance with an acceptance, 16 accepted standard.
17 That uncertainties in T0 are adequately 18 addressed.
19 The adequacy, we look to make sure that 20 the adequacy of the proposed method for embrittlement 21 protection. In this case, we heard a lot about E900 22 in Brian's talk.
23 When data from MTRs are used, we made sure 24 that the flux effect is adequately addressed.
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62
- And, we made sure that regulatory 1
exemptions for using the methodology are clear.
2 And then, John will talk about some of the 3
key REIs that we asked, and these have to do with the 4
delta T-30 to delta T0 correlation, and material 5
variability.
6 Then John will also talk about additional 7
observations during our review, and state our 8
conclusion.
9 So, this slide's just a reminder I think 10 Brian talked a little bit about this also. It's just 11 a reminder that coming into the review, we already 12 know that T0 is acceptable for use.
13 It's already in the ASN code, both 14 sections 11 and 3. There are ASME code cases out 15 there, and also as Brian also mentioned during his 16 presentation, specific applications.
17 One is circ weld, circ RPV weld approved 18 topical reports. BAW 2308, revisions 1 and 2 for 19 Linde 80 welds.
20
- And, these are publicly available 21 documents. And, this is not an exhaustive list.
22 There are others out there.
23 So, let's go ahead with the first topic of 24 our evaluation, which is about T0 testing. So again, 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 I think Brian covered a lot of this already.
1 But T0 must be determined in accordance 2
with ASTM E1921. The latest version of this standard 3
that's incorporated by reference in the regulations, 4
is the 2017 version.
5 And, that's incorporated by reference into 6
the ASME code, section 11.
7 So, as Brian discussed, the 2020 version 8
of this standard is used in the methodology, because 9
it has this procedure for screening and evaluating 10 inhomogenous datasets.
11 And, this adds a little conservatism into 12 T0 if the dataset is inhomogenous.
13 So, we really, what we look for in the 14 standard are really just two key aspects. First is 15 test specimen configuration.
16 So, the standard specifies the use of 17 standard or disc shape CTs, or your single-edge bar, 18 SE(B) specimens.
19 And, if you're using the SE(B) specimens, 20 you have to add 18 degrees Fahrenheit bias to the 21 data.
22 So another key aspect is that again, I 23 kind of mentioned this already. It has provisions for 24 inhomogeneous screening, and procedures 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
64 determining additional value to T0 to address 1
inhomogeneous datasets.
2 So, even though in 1921 doesn't specify 3
the size of CT specimens, this TR methodology does 4
provide a basis for using the mini-C(T)s.
5 And really the key point here is that 6
although E1921 has constraint adjustments for 7
different sizes of your CTs.
8 The question is, is that enough for the 9
mini-C(T)s because as you go smaller and smaller in 10 size, there's a potential loss of constraint. And, 11 that could lead to a non-conservative T0 value.
12 So, the key points here on this slide is 13 that the last two sub-bullets there, the constraint 14 condition difference between the mini-C(T)s and the 15 larger CTs were shown to be negligibly small.
16 And, the results of this round robin 17 testing showed that there was no significant 18 difference between the T0 values that was determined 19 by the different labs.
20 And the results also show that there was 21 no, the difference between the T0 values, between the 22 mini-C(T)s and the larger CTs on the average, was 23 small.
24 And from that table that Brian presented 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 in his slide, the average difference was just a little 1
under 1 degree Celsius, with a standard deviation of 2
7 degrees Celsius.
3 And, as I pointed out earlier, if you're 4
using your SE(B) specimens, another word for that is 5
your 3. Charpy bend, you have to add a bias of 18 6
degrees to the test value.
7 So, the second key aspect that we look for 8
in the standard is about material inhomogeneity. So 9
that this TR does follow the inhomogeneous screening 10 procedure, and the standard.
11 So, datasets are screened in for 12 inhomogeneity. If that fails, the dataset is 13 potentially inhomogeneous and will be evaluated 14 according to appendix X5 of the standard.
15 If that dataset is determined to be 16 inhomogeneous and this is kind of the key part here, 17 is that the T0 value is increased to a larger value 18 because that dataset was deemed inhomogeneous.
19 So, based on our evaluation of these two 20 key aspects of the standard, the staff finds that the 21 T0 testing used in the methodology to be acceptable.
22 So the next topic in our evaluation is 23 uncertainties in T0. So, these are the uncertainties, 24 these are the sources of uncertainty in using 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
66 methodology.
1 There's T0 uncertainty, there's adjustment 2
uncertainty, and I'll discuss that in the next set of 3
slides on E900.
4 There's uncertainty due to your radiation 5
exposure parameters in particular, fluence and 6
temperature.
7 And, there are also uncertainties due to 8
material variability and the delta T0/delta T30 9
correlation that John will talk about.
10 So as Brian showed in his presentation, 11 there are two equations for the margin term. A top 12 equation is when irradiated data is used; that bottom 13 equation is when unirradiated data is used.
14 So, in this slide, I sort of broke down 15 each of the sigma terms and put them side-by-side so 16 that it's really to highlight the difference between 17 the two equations.
18 So, for T0 specimen testing uncertainty 19 that's addressed by the standard. It has your sigma 20 E1921 and again, that's as defined in the standard.
21 If you're using unirradiated, existing 22 unirradiated T0 data, that's addressed through 23 statistics, and Brian talked a little bit about this, 24 this 95-95 statistical bound parameters from NUREG-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 1475.
1 And as Brian mentioned during his 2
presentation, if you multiply this k-1-S, that would 3
give you a 95 percent confidence level that the 4
resulting T0 bounds the 95th percentile or greater of 5
the data.
6 I'm sorry, I thought I was done but okay, 7
so the adjustment term uncertainty is addressed by 8
sigma adjustment, and that's equation 12 of the 9
report.
10 And then, now you have the uncertainties 11 from your temperature and fluence for the radiated 12 case.
13 There are two sources for that, both the 14 specimens, you're testing specimens, and your RPV of 15 interest.
16 For the unirradiated case, of course 17 because if we're not getting our T0 data from test 18 specimens, the only source for that would be your RPV 19 of interest.
20 So, this slide focuses on equation 12 of 21 the report. And again, this is the equation in sigma 22 adjustment that Brian presented. I'm not really going 23 to go through again what the individual components 24 are.
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68 But the key point here is that this sigma 1
adjustment term imposes a minimum of 9 degrees 2
Celsius, and this is based on statistics of the 3
minimum shift data, welds, and base metals.
4 And, this term also double counts the 5
fluence and temperature uncertainties. As you've seen 6
in the, on those two margin equations, they're already 7
separate fluence and temperature in the margin terms.
8 But since equation 12 is based on E900, 9
which is a function of fluence and temperature, some 10 of that fluence and temperature uncertainties are 11 already captured in the sigma adjustment term.
12 So, that's based on the above slides on 13 uncertainties. The staff finds that the sources of 14 uncertainties in T0 have been adequately addressed by 15 the methodology.
16 So adequacy of the ASTM E900 embrittlement 17 trend curve. So, E900 is used in the adjustment term 18 and again, coming into this review, we already know 19 that E900 has a lot of merit and potential as compared 20 to the reg guide.
21 Brian covered this earlier. It has an 22 improved accuracy as compared to the reg guide, 23 especially at high fluence. It is based on many more 24 delta RT-NDT data compared to only 177 from the reg 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 guide.
1 The exposure parameters are fluence and 2
temperature, compared to only fluence in the reg 3
guide.
4 And, this temperature parameter adds 5
robustness to the trend curve.
6 Also, there's similar scatter in predicted 7
delta RT-NDT, relative to measured delta RT-NDT, but 8
more are falling within the plus or minus 2 sigma 9
band, and I'll show that in the next two slides.
10 And all this is documented in the work by 11 staff, and that's referenced in the proposed 12 embrittlement rulemaking SECI paper. And both are 13 public documents.
14 So just a little background. So, we're 15 still waiting on Commission votes on this paper, but 16 in this potential rulemaking, E900 is a promising 17 candidate to be considered to be incorporated into the 18 reg guide.
19 So, I think a lot of you folks already 20 have seen this plot. So this is just comparing E900 21 to the reg guide, and this is predicted delta RT-NDT 22 relative to measured delta RT-NDT.
23 So, in both of these plots, it's really 24 predicted shift minus measured shift. So, if you're 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 above zero, you're over, your trend curve is over 1
predicting.
2 If you're below zero, your trend curve is 3
under predicting.
4 And you can see that for E900, a lot of 5
the, there's a lot of scatter kind of similar scatter 6
as in the reg guide, but more are falling within the 7
plus or minus two sigma bound, band.
8 And also note, as Brian already pointed at 9
high fluence for the reg guide, it severely under 10 predicts. This is for base metals.
11 This next slide is for weld metals. Just 12 thing to note here, there's not as many data for weld 13 metals and you don't really see that.
14 And because of the lack of data, you don't 15 really see that under prediction as much as in the 16 four base metals.
17 So, having gone over these comparisons 18 between E900 and the reg guide 199 trend curve, in our 19 evaluation we've really focused on how margin in the 20 use of E900, in the use of E900 is addressed.
21 And, this kind of goes back to the 22 discussion of sigma adjustment in slide 10.
23 So, as previously discussed, sigma 24 adjustment imposes a minimum of 9 degrees Celsius, 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
71 double counts the fluence and temperature 1
uncertainties.
2 Therefore, based on the above slides on 3
E900, the staff finds the use of ASTM E900 trend curve 4
acceptable for the methodology.
5 Okay, so the next topic of the staff's 6
evaluation is the flux effect from MTRs.
7 So, kind of Brian kind of covered a little 8
bit of this is we know that the flux effect is a very 9
complex phenomenon.
10 And, we know that MTR flux is higher than 11 PWR flux, but the advantage of MTRs of course, is that 12 you can get irradiated data much faster than you can 13 from PWRs. And thus, the option in this methodology.
14 So, when MTR irradiations are used such as 15 in an MTR campaign, the MTR irradiated data must be 16 validated against the PWR irradiation data.
17 And, that's the key point that we really 18 look for. Despite the complexities of flux, we have 19 these validation.
20 This validation really has two pieces to 21 it. The MTR irradiated data must be from the same 22 copper grouping as the PWR validation material, since 23 flux effect on embrittlement is dependent, is highly 24 dependent on a copper level.
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72 It has to be from the same heat as the PWR 1
validation material. It has to be within plus or 2
minus 50 percent of the PWR fluence.
3 And the second piece of this validation is 4
if needed, you increase the MTR irradiated data to the 5
radiation level of the RPV material of interest.
6 And how you do that, is that you compare 7
the adjusted MTR irradiation T0 with the PWR 8
validation material T0. And that's given by equation, 9
that's an inequality actually, not an equation. But 10 it's equation 9 of the report.
11 And if the former is a larger value, then 12 no increase is needed. But if it's smaller, then you 13 increase the MTR irradiation for equation 10 of the 14 report.
15 And the staff finds that this above 16 approach reasonable for handling the potential flux 17 effect from MTR irradiations.
18 Okay, regulatory exemptions. Basically, 19 there are three. 10 CFR 50.61, an exemption is needed 20 because the definition of RT-PTS in the methodology, 21 is different than the definition in 10 CFR 50.61.
22 Appendix G to 10 CFR 50, an exemption is 23 needed because of the specific section in the 24 regulations that is cited here, which specifically 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 states RT-NDT.
1 Appendix H to 10 CFR 50, an exemption is 2
needed when the Charpy specimens in a surveillance 3
program are modified and tested for T0.
4 However --
5 (Simultaneous speaking.)
6 MR. BALLINGER: So, this is Ron Ballinger.
7 MR. DIJAMCO: Oh, yes.
8 MR. BALLINGER: Now, once this is 9
- approved, then these exemptions are basically 10 administrative, correct?
11 MR. DIJAMCO: That's correct. But they 12 would still have to, it's still in application, but 13 yes, correct.
14 MR. BALLINGER: Yes.
15 MR. DIJAMCO: Correct, that would just be 16 I guess an administrative burden. Yes.
17 MR. BALLINGER: Thank you.
18 MR. DIJAMCO: And just that last point 19 there. No exemption is needed when small fracture 20 toughness specimens are from broken Charpy specimens.
21 Or untested heat affected zone specimens 22 are used for T0 testing.
23 Okay, I think this is starting John's 24 portion. John, are you on?
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74 MR. TSAO: Yes, yes, I am on.
1 MR. BALLINGER: Okay.
2 MR. TSAO: This is John Tsao, from the 3
Vessels and Internals Branch. Brian and Dave have 4
done the heavy lifting here, so my slides are relating 5
to high-level summary of the staff reviews.
6 So, I'm going to talk about the data 7
management, and then I'm going to focus on two, two 8
issues. One relating to adjustment uncertainties, and 9
another one is related to the margin terms.
10 And then, I'm going to talk about 11 regulatory implications, and then staff observations.
12 And finally, conclusion.
13 Okay, for the data management as you have 14 heard, there are a whole bunch of data that relate to 15 this method, proposed methodology.
16 You have unirradiated and irradiated data, 17 and from this data, there are uncertainties. So, the 18 staff is trying to make sure there are appropriate 19 guardrail to make sure the datas are analyzed 20 properly.
21 By the way, I will go through the slides 22 pretty quickly because most of the information has 23 already been discussed.
24 Okay, next slide, slide 18.
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75 And, this is a reiteration of E900 and 1
E1921. The good thing about this proposed methodology 2
is that it is established with the E900 and E1921, so 3
in other words, the proposed methodology is not 4
something that comes from nowhere.
5 It does have the foundation of the 6
previous studies in the E900 and E1921. And, the 7
major point of this slide is that we have not approved 8
the E900 and E1921.
9 So, this, our approval of this proposed 10 methodology does not imply or infer generic approval 11 of the standards.
12 Slide 19.
13 Okay, I'm going to go into adjustment 14 terms.
15 MR. BALLINGER: This is Ron Ballinger 16 again. Back up one slide?
17 MR. TSAO: Okay.
18 MR. BALLINGER: Is there any process by 19 what E900 and E1921 will be approved?
20 MR. TSAO: Oh, yes.
21 Dave had a slide that says we are, the 22 staff has a rulemaking in place to maybe approve E900.
23 MR. BALLINGER: Yes, I think I remember 24 that's part of one of the discussions we've had 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
76 past.
1 Okay, thank you.
2 MR. TSAO: Right, yes.
3 And then, the status of that rulemaking 4
package is that we are waiting for commissioner 5
approval right now.
6 It has been up there for many years for 7
some reason.
8 MR. BALLINGER: Yes, that's true.
9 MR. TSAO: Yes.
10 MR. BALLINGER: Thank you.
11 MR. DIJAMCO: Probably like 3 years now, 12 I think, so just wanted to add that.
13 MR. HALL: This is Brian Hall. I'd point 14 out that E1921, the 2017 version is approved through 15 the ASME code.
16 MR. BALLINGER: Ah, okay.
17 MR. TSAO: Okay, slide 19.
18 This so this is a, the parameter in the 19 adjustment terms I'm just going to talk about the 20 correlation between delta T30 and delta T9.
21 Next slide, slide 20.
22 Okay, some background. Brian and Dave 23 already talked about the background but I just want to 24 focus on this.
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77 The staff when we reviewed this topical 1
report, we found that an adjustment for model 2
uncertainties, uncertainties between the delta T30 and 3
delta T0, was not included in the methodology.
4 This is when we were reviewing it. Of 5
course, later on the proposed methodology revise it 6
and include that.
7 Anyway, so the methodology does have the, 8
demonstrate or show there is a measurement difference 9
between embrittlement shift in delta T30 and delta T0.
10 And, then they should be correlated and 11 adjusted.
12 Slide 21.
13 And then, so like Brian said, the proposed 14 methodology they did perform statistical analysis to 15 show the difference between delta T30 and delta T9.
16 And
- then, the proposed methodology 17 includes a 9 degrees Celsius as part of adjustment 18 uncertainty.
19 So, the staff found this acceptable 20 because the proposed methodology does include a 21 correlation of a slope of 1.1 for base metal, and 1.0 22 for welds.
23 And, it does include, the proposed 24 methodology does include 9 degree Celsius as part of 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 adjustment certainty in margin term.
1 Even though I am talking about adjustment 2
terms, but the adjustment is embedded in the margin 3
terms, which I will talk about later.
4 Okay, slide 22.
5 Okay, I'm going to talk about the margin.
6 This slide shows that I want to compare the margin in 7
the existing methodology, which is in the regulatory 8
guide 1.99 Rev 2, and 10 CFR 50.61.
9 As you can see, it met the margin in the 10 existing methodology consider the margin, consider the 11 uncertainty in the initial RT-NDT, and in the delta 12 RT-NDT.
13 As a comparison, the proposed method for 14 RT-PTN, RT-PT equation include, include an adjustment 15 term and a margin term.
16 Slide 23.
17 Okay, for the margin terms in the proposed 18 methodology. As the Dave and Brian talked about 19 before we have tests uncertainty, adjustment 20 uncertainties. But I'm going to focus on this 21 material variability.
22 Slide 24.
23 Okay, material variability. The RPB 24 material embrittlement relies on prediction model, 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 which is based on shift, and shift measurement.
1 And
- then, the issue is
- the, if 2
embrittlement trend curve in E900 reflects 3
uncertainties of material variability and chemistry 4
variability, and then in the ASTM E1921 also 5
discusses, describes homogeneity and inhomogeneities.
6 And, it has specific analysis to deal with 7
the homogeneity and inhomogeneities.
8 So, the measurement of T0 based on 9
fracture toughness, reduces uncertainties associated 10 with RT-NDT, correlated fracture toughness.
11 Slide 25.
12 So, because in our request for additional 13 information on this issue of material variability, the 14 proposed methodology, they did consider that 15 measurement of direct pressure toughness reduces 16 uncertainties associated with correlation of RT-NDT 17 to fracture toughness.
18 And the measurement of irradiated fracture 19 toughness reduces uncertainty associated with 20 embrittlement prediction.
21 So, in the staff evaluation, we initially 22 we have a concern whether the material variability 23 uncertainty is, was not considered in the margin 24 terms.
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80 And then, so the PWOG, they respond to our 1
REI and then the staff find that the TR methodology 2
does include 9 degrees Celsius as part of the 3
adjustment certainty.
4 And then, that the margins uncertainty 5
request by ASME code, there's a typo there, ASME code, 6
section 11, are sufficient to account for material 7
variability uncertainties.
8 Also, the evaluation of embrittlement and 9
the quality location of RPD show that provides some 10 structure margin as compared to RPV shell service, 11 that the driving force at a corner T location is 12 higher than at the surface.
13 And then, the proposed methodology does 14 use a large amount of T0 data, which reduces 15 uncertainty as compared to a small dataset.
16 So, based on these adjustment certainty 17 and other associated margins, the staff found that the 18 proposed method addresses material variability 19 uncertainty satisfactorily.
20 Slide number 26.
21 Okay, the regulatory implication. By the 22 way, this proposed methodology is not a regulatory 23 requirement. It's an option.
24 A licensee could use this methodology 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
81 address the RPV as a rule. In the 10 CFR 50.61, the 1
licensee could also use this methodology to develop 2
potential limit curve so that it could operate the 3
reactor efficiently.
4 The proposed methodology specify that 5
licensee who plans to use the proposed methodology 6
needs to submit exemptions from the appropriate 7
regulations.
8 And, we want to also include that a 9
licensee not only need to submit exemption, but also 10 a license amendment request if they want to use this 11 methodology. Because that's two different submittal.
12 And during our review, there was a 13 question about rulemaking, include this methodology in 14 the rule.
15 The staff felt that we need to review a 16 actual licensee submittal using this methodology, to 17 determine if visibility of the methodology so that we 18 can achieve some regulatory stability, prior to 19 exercise rulemaking.
20 Okay, next slide.
21 MR. BALLINGER: This is Ron Ballinger 22 again.
23 Could these examples which are provided go 24 a long ways in that area?
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82 MR. TSAO: Yes, also a licensee, a 1
specific plant, they have to come up with their T0 2
data and then they, of course, they can use the 3
example in the methodology in this report.
4 For example, Brian show how the Crystal 5
River and how the Kewanee data was used. So, the 6
licensee can do that.
7 MR. BALLINGER: Thank you.
8 MR. TSAO: The thing is, this methodology, 9
this is just a methodology. This is not a plant-10 specific submittal.
11 So, we just know the methodology. We 12 don't know what the licensee would do using their 13 plant-specific data.
14 And so, that's one where we need at least 15 review some plant-specific report to see how good this 16 methodology is, or how viable.
17 Okay, next slide.
18 MR. BALLINGER: So, the -- this is another 19 question.
20 MR. TSAO: Sure.
21 MR. BALLINGER: I guess it's for the 22 Westinghouse folks.
23 Is there a licensee that's prepared to do 24 this?
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83 PARTICIPANT: Jim Molkenthin, are you 1
aware?
2 MR. MOLKENTHIN: I would have to defer to 3
Brian Hall with that question. I'm not aware of, 4
we've, I'll defer to Brian.
5 MR. HALL: We have some interest. I'm not 6
going to make a commitment for any of the licensees, 7
but we do have some owners group support to help the 8
first few through the process.
9 MR. BALLINGER: Thank you.
10 MR. TSAO: Next slide, please.
11 Okay, the observations. This is kind of 12 a high-level of staff observations during our review.
13 First of all, the proposed methodology is consistent 14 with NRC approved precedent.
15 And then, we think the proposed method is 16 adequate to ensure integrity of the RPV material, 17 which is the fundamental of our concern is how good 18 this methodology is.
19 And, whether it will make sure the RPV 20 material will be protected 80 years. And then, this 21 methodology uses in-depth extenders.
22 Okay, slide 28.
23 And, we think the proposed methodology 24 provides fracture toughness that is closer to actual 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
84 transition temperature, fracture toughness of reactor 1
vessel, shell material than the fracture toughness 2
determined by the existing method.
3 I see a hand raised?
4 MR. BLEY: Yes, this is Dennis Bley. Just 5
the last little discussion about who might step up to 6
try this out.
7 How many vessels are out there for which 8
this would even be a useful process? I don't think 9
there are very many, right?
10 MR. BALLINGER: I'm trying to remember 11 that. No, I've been searching through that table and 12 I haven't found it.
13 I've been trying to remember how many SLRs 14 vessels would need this, and I'm guessing from now 15 from just memory that there are probably four or five.
16 MR. BLEY: That's kind of what my memory 17 was saying, too. I mean, we're doing a lot of work 18 for not many of these plants.
19 But okay, I just wondered how extensive 20 this might be. Thanks.
21 MR. TSAO: But even if there are not too 22 many licensees using this methodology, I think this 23 methodology provide some engineering and analytical 24 work.
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85 We can at least see the difference between 1
two prediction methods, so maybe it will be useful 2
when the plant get into, when they are 70 years old, 3
or when they reach the 80 timeframe.
4 I think it will still provide good 5
database.
6 MR. BLEY: Yes, I agree. Thanks.
7 MR. HALL: This is Brian. I would chime 8
in say you're probably right for PTS. It might exceed 9
PTS screening criteria at 80 years on the order of a 10 handful.
11 But it can also be used for improvement of 12 PT curves, and that would be applicable to many more 13 plants.
14 MR. TSAO: I'm thinking about for PT 15 limits, what you would do, what this proposed 16 methodology would help is to allow a plant to heat up 17 their vessel faster than now, so that the plant can 18 start making money right away. Faster than yes, and 19 be online.
20 MR. BLEY: I guess this null thing, that 21 makes sense. Okay, thanks.
22 MR. TSAO: Yes.
23 Okay, and so the rest of the bullets show 24 that they can, licensee can use this for RT-PTS, 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
86 they can use for PT limits.
1 Okay, next slide?
2 Okay, also with this method, we can, the 3
margin can be gained back from this methodology. And 4
then, okay, oh, yes.
5 As Brian showed that using the Crystal 6
River example, there is a, about 78 degree margin 7
gain.
8 By the way, this is only example. Plant-9 specific data may result in different margin gain.
10 But still, even if there is a 10 degree gain is still 11 is better than not.
12 Also, if the RT-PTS has a 78 degree gain, 13 then the PT limits could also have, be gain some 14 margin, too.
15 Okay, next slide, 30. Slide 30.
16 Okay, the conclusion is that the proposed 17 TR method using the irradiated or unirradiated T0 data 18 in lieu of a current approach, is acceptable because 19 the staff finds that TR method has provisions for 20 determining adjustments and margins applied to T0 21 data, that is sure the final T0 is adequate in 22 maintaining RPV integrity.
23 This ends my presentation. Just want to 24 say that this has been a arduous and rigorous review 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
87 because we wanted to make sure the prediction method 1
in this PR is adequate. And provide reasonable 2
assurance.
3 Any questions?
4 MR. PETTI: Yes, this is Dave again.
5 Just at a high level, I understand that 6
there's margin that's out, but in terms of the major 7
sources of uncertainty across the actual database.
8 Is it largely chemistry MTR versus PT, PWR 9
radiation fluence effects, and material variability, 10 are those the top three uncertainties that dominate in 11 the methodology when you go through all the 12 calculations?
13 MR. TSAO: Yes, yes. For example, copper 14 chemistry.
15 MR. PETTI: Right.
16 MR. TSAO: That chemistry variability is, 17 produces uncertainty, that's right.
18 MR. PETTI: Right.
19 MR. TSAO: And --
20 MR. PETTI: Copper is sort of called out 21 special relative to that broader material homogeneity 22 issue that you mentioned earlier.
23 MR. TSAO: Right.
24 MR. PETTI: Right.
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88 MR. TSAO: Also, there is a environment, 1
the environment meaning nuclear fluence for the plant 2
versus the specific specimen versus through the 3
fluence in the test specimen.
4 MR. PETTI: Right.
5 MR. TSAO: The test reactor.
6 MR. PETTI: Right.
7 MR. TSAO: And that also we have another, 8
we have uncertainty associate with using a different 9
heat material in a test specimen versus different 10 heating material in the reactor vessel itself.
11 So, and then we have uncertainty relating 12 to E900 train curve applies to the RPV material in the 13 field.
14 MR. PETTI: Okay, thank you.
15 MR. BALLINGER: Questions from members 16 before we go out for public comment?
17 (No audible response.)
18 MR. BALLINGER: I don't hear one but 19 there's a flag raised somewhere. Oh, Steve Schultz.
20 MR. SCHULTZ: That's me, Ron, thank you.
21 Just a comment on number of plants that 22 might apply this in the future. Thinking about those 23 plants, PWRs that have already or will be applying for 24 the extension from 60 to 80 years.
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89 I just see the real benefit having 1
personal experience with the Yankee Rowe vessel back 2
in the early 90s and PT vessel rupture issues, of 3
having something like this which allows margin to be 4
demonstrated with not only the technical area 5
evaluations, but the testing opportunities that could 6
be used in the event that margin is questioned.
7 Demonstrating additional margin would only 8
be a benefit in those, in some circumstances where it 9
might be needed.
10 MR. TSAO: Yes, yes.
11 MR. SCHULTZ: I appreciate both the work 12 that the owners group has done, and the industry has 13 done in this area over the last several decades.
14 And, it's really coming to fruition here 15 and the NRC review is, John has indicated is very 16 detailed and very extensive in the work that has been 17 put in here is well appreciated.
18 I now it's appreciated by industry.
19 MR. TSAO: Yes, agree with you about the 20 margins and like someone said that regulatory guide 21 1.99 was prepared back in 1980, and that's 40 some 22 years ago.
23 And then, they are during this 40 years we 24 have more data coming out so why not take advantage of 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
90 the more data, and then try to improve the pressure 1
vessel operation, and try to ensure the pressure 2
vessel shell material fracture confidence integrity.
3 MR. SCHULTZ: I couldn't agree with you 4
more, John, thank you.
5 MR. TSAO: I guess back then, back 40 6
years ago, 50 years ago, the engineers and scientists 7
was not sure what's going to be in future so in their 8
prediction method, it's lot more conservative than 9
now.
10 We can tweak our, tweak our prediction 11 method to be more accurate, I suppose. But still, 12 time to tell.
13 MR. BALLINGER: Okay, without hearing any 14 other questions from the members and consultants, I 15 think I've already forgotten whether we've asked if 16 there were public comments.
17 I think we have and I don't think there 18 have been any. So if that's the case --
19 MR. MOLKENTHIN: Member Ballinger, do you 20 want to wait just wait a few minutes just to make sure 21 there's no public comments?
22 MR. BALLINGER: Yes, I'm looking for hands 23 up and stuff like that but don't see anything. I 24 don't know what the phone numbers are.
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91 (Pause.)
1 MR. MOLKENTHIN: Okay, you can proceed.
2 MR. BALLINGER: Okay, I think we're 3
probably, we don't really find any members of the 4
public that would like to make a comment.
5 So, thank you again for your presentation.
6 Both of them were very informative. Now, we need to 7
have a discussion amongst the members and consultants 8
related to what the path forward, what we think the 9
path forward should be.
10 I think the reason that the subcommittee 11 wanted this kind of meeting is because, and people 12 kind of alluded to it in one form of discussion or 13 another.
14 But a lot of this information has been 15 around for a long, long time. And, 1.99 is old but 16 it's actually worked.
17 And so, with subsequent license renewal 18 being a fact, the fact that we now can use actual data 19 to deal with pressure vessel embrittlement is a very 20 positive, positive thing.
21 And so, that's the reason why we were 22 interested in hearing from the staff about this.
23 Although the staff has actually explicitly not 24 requested a letter, that's up to us to make 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
92 recommendation to the full committee.
1 So, I'm anxious to hear people's comments 2
about what we, what you think we should do.
3 MR. MORE: Chair Ballinger, this is Scott 4
More, the Executive Director. Do you want the court 5
reporter on for this discussion?
6 MR. BALLINGER: I don't think, I don't 7
know what our, I forgot what our rules are. Walt, 8
what do you think?
9 MR. MORE: Yesterday we did not.
10 (Simultaneous speaking.)
11 MR. KIRCHNER: At this point, I don't 12 think we need the court reporter.
13 MR. BALLINGER: Okay, good enough, thank 14 you.
15 So, thank you again for the -- thank you 16 for the court reporter, and I think you're off the 17 hook.
18 (Whereupon, the above-entitled matter went 19 off the record at 12:06 p.m.)
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- One Voice PWROG-18068, Rev. 1, "Use of Direct Fracture Toughness for Evaluation of RPV Integrity" J. Brian Hall - Westinghouse ACRS Meeting of the Fuels, Materials, & Structures Subcommittee-September 20, 2024
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PWROG-18068-NP, Rev. 1, Use of Direct Fracture Toughness for Evaluation of RPV Integrity o The methodology justifies the use of direct fracture toughness data to evaluate RPV integrity as an alternative to the requirements/methods of pressurized thermal shock (PTS) (10 CFR 50.61) and pressure-temperature (P-T) limit curves (10 CFR 50, Appendix G). The topical report discusses a methodology to:
Generate irradiated or unirradiated ductile-brittle transition reference temperature (T0) in accordance with the ASTM E1921-20 Standard Test Method Adjust the data for differences between the tested and RPV material of interest in accordance with the ASTM E900-15 Standard Guide for predicting embrittlement Account for the resultant test uncertainty and material variability of the Reactor Pressure Vessel Apply the data using NRC-endorsed methods in ASME Section XI Direct Fracture Toughness for Evaluation of RPV Integrity
=
Background===
- Current Approach: RTNDT + embrittlement shift prediction + margin
- RTNDT is not a good transition temperature fracture metric:
- The margin for any given material is unknown and inconsistent
- The embrittlement shift has substantial margin () and prediction uncertainty
- The baseline RV material transition temperature (RTNDT) is based on a very conservative method from 1972
- RTNDT is composed of the drop-weight nil-ductility transition temperature (TNDT) and Charpy blunt-notch impact tests
- TNDT is a measure of the crack arrest transition temperature
- The KIR (crack arrest) curve for P-T curves is no longer used
- The KIC (crack initiation) curve is used
- The initiation fracture toughness transition temperature (T0) and RTNDT are not correlated ASME PVP201428540, 2014 Direct Fracture Toughness for Evaluation of RPV Integrity
- ASTM E1921 Transition Temperature Fracture Toughness (Master Curve)
- Reduced uncertainty
- Reduced inconsistency
- Characterizes margin statistically
- Based on actual fracture toughness measurement WRC Bulletin 457 Why Direct Fracture Toughness Direct Fracture Toughness for Evaluation of RPV Integrity NUREG-1807 WRC Bulletin 457 WRC Bulletin 457 1TC(T)
- Testing Irradiated Material
- Reduced embrittlement prediction uncertainty
- Reduced embrittlement prediction error (bias)
- e.g., Reg Guide 1.99, Rev. 2 high fluence non-conservatism
- Uncertainties are accounted for explicitly Why Direct Fracture Toughness Direct Fracture Toughness for Evaluation of RPV Integrity ML21270A002 NRC presentation, Oct. 2021
NRC Approval and Precedent of Master Curve Technology
- Successfully used for the following RPVs
- Zion - 1994
- Kewaunee - 2001
- Used for CR 3, TMI 1, ANO 1, Oconee 1, 2 & 3, Davis-Besse, Point Beach 1&2, Turkey Point 3&4 and Surry 1&2
- ASME Boiler and Pressure Vessel (B&PV)Section XI Code, (Reg Guide 1.147, incorporated in 10 CFR 50.55a)
- RTT0 as an alternative to RTNDT was incorporated into
- Code Case N-629, 2003 (replaced by N-851)
- ASME Section XI, Appendix G, Subarticle G-2110, 2013
- Code Case N-830, 2020 (T0 with master curve toughness-temperature curve at the 5% lower bound)
Direct Fracture Toughness for Evaluation of RPV Integrity
- For PTS evaluations, the following is used:
RTPTS = RTT0 + adjustment + margin where:
- Using ASME Section XI, Appendix G, 2013
- KIc = 33.2 + 20.734 exp[0.02 (T - {RT0 + adjustment + margin})] (KIc curve with RTT0)
- OR
- Using Code Case N-830-0 as modified by the NRC condition
- KJc-lower95% = 22.9 + 33.3 exp[0.0106 (T - {T0 + adjustment + margin})]
- This topical report contains a methodology to determine the adjustment (from the specimen test condition to the RPV condition) and margin terms Methodology for Application of Master Curve Test Data Direct Fracture Toughness for Evaluation of RPV Integrity RT0 = T0 + 35F
- Irradiated T0 can be obtained by
- Using existing fracture toughness data, or
- Testing fracture toughness specimens machined from unirradiated archived material, or
- Testing specimens machined from material irradiated in a PWR surveillance capsule, or
- Irradiating specimens in a high flux test reactor & testing; e.g. a material test reactor (MTR)
- MTR irradiation must include a validation material in each Cu group Low Cu: Cu weight percent (wt. %) 0.053 Medium Cu: Cu wt. % between 0.053 and 0.28 High Cu: Cu wt. % > 0.28
- Ensures that MTR irradiated specimens are representative of PWR irradiated specimens Potential neutron flux effect Other differences: spectrum, temperature, unknown Ensures a well-designed MTR irradiation of specimens Generation and Validation of T0 Data Direct Fracture Toughness for Evaluation of RPV Integrity
- Irradiation of the same heat of material is required to evaluate the RPV material of interest, except
- A generic unirradiated T0 method is also discussed A minimum of 4 valid T0 from a common manufacturer, material class, or flux types (i.e., the material purchase or welding fabrication specification and heat treatment must be consistent with the RPV material of interest)
A 95/95 one-sided tolerance limit factor (k1) is used rather than 2, which is typically used for large populations (NUREG-1475, Revision 1)
- Testing in accordance with ASTM E1921-20
- Data sets are screened for inhomogeneity in accordance with Paragraph 10.6 of ASTM E1921-20
- Data sets that fail the screening criterion are evaluated in accordance with Appendix X5 Treatment of Potentially Inhomogeneous Data Sets, of ASTM E1921-20 with T0IN (as calculated in Appendix X5) substituted for T0
- Any geometry that meets ASTM E1921-20 which includes A 10°C bias is added for the Charpy size (10mm x10mm) bend specimen (ASTM E1921)
Miniature C(T) specimen Direct Fracture Toughness for Evaluation of RPV Integrity Specimen Testing
Mini-C(T)
(TR Appendix A)
- ASTM E1921 compliant Compact Tension Fracture Toughness specimen
- Thickness: ~0.16 inches (4 mm)
- 4 mini-C(T) specimens can be machined from a broken irradiated Charpy specimen
- Extensive testing has been conducted by numerous labs with various unirradiated and irradiated RPV steels using the mini-C(T) specimen geometry with results that are statistically indistinguishable from larger specimens Material (as Described in Reference)
Mini-C(T)
T0 (°C)
Larger Size T0
(°C)
Larger Size Specimen Geometry T0 Difference
(°C)
Reference Midland Linde 80 Weld irradiated 1e19 n/cm2 17 27 1/2TC(T) and 1TC(T) 10 58, 68 Midland Linde 80 Weld irradiated 1e19 n/cm2 32 27 1/2TC(T) and 1TC(T)
-5 70, 68 A533B1 steel B irradiated to 1.1e20 n/cm2
-11
-24 Charpy-size 3PB
-13 65 A533B1 steel B
-90
-94 Charpy-size 3PB
-4 65 A533B1 steel B
-90
-97 1TC(T)
-7 65 Midland Linde 80 Weld
-53
-54 1/2TC(T) to 2TC(T)
-1 66, 68 A533B1 JRQ
-68
-67 Charpy-size 3PB 1
68 A533B1 JRQ irradiated to 1.85e19 n/cm2 lab A 32 44 Charpy-size 3PB 12 68 A533B1 JRQ irradiated to 1.85e19 n/cm2 lab B 40 44 Charpy-size 3PB 4
68 SFVQ1A steel (A508 Cl3 forging) irradiated to 7.2e19 n/cm2
-1 13 1/2TC(T) 14 47 SFVQ1A steel (A508 Cl3)
-104
-96 1TC(T) 8 54 22NiMoCr37
-107
-95 1/2TC(T) to 4TC(T) 12 57 22NiMoCr37
-107
-102 Charpy-size 3PB 5
57 Low Sulphur Base Metal
-122
-126 1/2TC(T)
-4 62 Weld Metal
-76
-77 1/2TC(T)
-1 62 Mid Sulphur Base Metal
-116
-123 1/2TC(T)
-7 62 SFVQ1A (A508 Cl3)
-101
-102 0.4TC(T) to 4TC(T)
-1 53 SQV2A Heat 1 (A533B1)
-84
-90 0.4TC(T) to 4TC(T)
-6 53 SQV2A Heat 2 (A533B1)
-114
-120 0.4TC(T) to 4TC(T)
-6 53 JRH
-106
-106 0.4TC(T) & 1TC(T) 0 69 JRM
-95
-88 0.4TC(T) & 1TC(T) 7 69 Steel A
-67
-66 1TC(T) 1 69 Steel B
-91
-97 1TC(T)
-6 69 JRL
-112
-108 0.4TC(T) & 1TC(T) 4 69 Standard Deviation 7.2°C Average 0.7°C Direct Fracture Toughness for Evaluation of RPV Integrity
- Tested specimens will rarely reflect the exact same irradiation conditions and chemistry as the represented RPV material
- Adjustments are made using the embrittlement trend curve (ETC) in ASTM E900-15
- The latest and most robust international consensus embrittlement shift prediction model available
- Based on a Charpy 30 ft-lb transition temperature shift (T30) database comprised of 1,878 power reactor surveillance program shift measurements Best-estimate E900 inputs are used for the irradiated data adjustments Inputs: Cu, Ni, Mn, P, Temp., Fluence ETC shift prediction of RPV - ETC shift prediction of specimens Direct Fracture Toughness for Evaluation of RPV Integrity Data Adjustment ML21270A002 NRC presentation, Oct. 2021
- The adjustment uses the T30 Charpy shift
- Correlation to T0
- Weld = 1.0 and Base metal = 1.1
- The slope standard error is small
- Most of the scatter is a result of the measurement uncertainty
- Most of the remaining scatter is material variability Direct Fracture Toughness for Evaluation of RPV Integrity Data Adjustment Consistent with draft ASME Code Case N-914 & cites EPRI MRP-462
- Accounts for uncertainties
- T0 measurement
- Adjustment using a proportion of E900 with a minimum value
- Irradiation temperature (the effect of the uncertainty on embrittlement using the ETC)
- Test specimens; 0 if the test specimens were irradiated in the assessed RPV
- RPV; (2°F can conservatively be used)
- Fluence (the effect of the uncertainty on embrittlement using the ETC)
- Test specimens (0 if unirradiated)
= 2
2
+
2
+
2
+
2
+
2
+
2
- E1921 is calculated in accordance with Paragraph 10.9 of ASTM E1921
- The uncertainty is due to material variability
- In 2019, a homogeneity screening procedure was added to ASTM E1921, Appendix X5
- Identifies datasets which do not follow the expected normal material Weibull distribution where the 95%
lower bound curve would not bound 95% of the data
- Inhomogeneity can result from the variation in initial toughness (i.e.,
segregation) or uneven embrittlement due to variation in the chemical composition
- The cited paper showed that for large fracture toughness datasets, even using the least conservative T0 from a subset of the data, with margin, the result is still conservative Direct Fracture Toughness for Evaluation of RPV Integrity Determination of E1921 Basis: J. B. Hall, E. Lucon, and W. Server, Practical Application of the New Homogeneity Screening Procedure Added to ASTM E1921-20 and Appendix X5 Inhomogeneous Data Treatment, Journal of Testing and Evaluation 50, no. 4 (July/August 2022): 2190-2208.
https://doi.org/10.1520/JTE20210716
- adjustment is proportional to the ASTM E900-15 with a minimum value of 9°C
- Adjustment from unirradiated results in use of the entire E900
- With small adjustments, 9°C is the value used
- 9°C uncertainty due to material variability
- Typical E1921 ranges from 6°C to 8°C
- Typical T30 ranges from 4°C to 10°C 0
2
+ 0 2
+ 30 2
+ 30 2
= 2 + 2 + 2 + 2 = 14.4°C
- The standard deviation on fit residuals = 17°C for base metal and welds 2. 2 = 9°C (material variability)
Determination of adjustment Data is mostly from NUREG/CR-6609 Direct Fracture Toughness for Evaluation of RPV Integrity
- The method was used with measured fracture toughness data to evaluate if sufficient margin exists
- The TR method was used with measured fracture toughness data to evaluate if margin is sufficient using multiple T0 measurements from the same steel heat
- Unirradiated T0 was adjusted to the irradiated T0 condition (i.e., the 2nd specimen condition) using the E900 prediction, with margin added and compared to the measured irradiated T0 (irradiated T0 as if from an assessed RPV)
- Adjustment from unirradiated results in use of full E900
- 100% of the data is bounded for welds
- 98% of the data is bounded for base metals
- The majority of the data is from NUREG/CR-6609 Margin Evaluation Basis: J. B. Hall, B. Golchert, and D. Simpson, An Examination of Margins Needed to Ensure Conservative Application of T0 to RPV Fracture Toughness, ASME PVP2024-125225 Welds Base Metals Direct Fracture Toughness for Evaluation of RPV Integrity
Margin Evaluation Basis: J. B. Hall, B. Golchert, and D.
Simpson, An Examination of Margins Needed to Ensure Conservative Application of T0 to RPV Fracture Toughness, ASME PVP2024-125225
- The method was used with measured fracture toughness data to evaluate if sufficient margin exists
- Irradiated T0 was adjusted to 2nd irradiated T0 condition using E900 prediction, margin added and compared to the measured 2nd irradiated T0 (2nd irradiated T0 as if it was from an RPV)
- With small adjustments, 9°C is the value used
- 97% of the data is bounded for welds and base metals
- The margin is sufficient using actual T0 data under various conditions Welds Base Metals Direct Fracture Toughness for Evaluation of RPV Integrity
Summary of PWROG-18068, Rev. 1 The benefits of an irradiated direct fracture toughness data evaluation methodology are:
- It establishes a robust fracture toughness basis to protect the health and safety of the public by reducing the toughness uncertainties from use of RTNDT and utilizing a statistical understanding of the actual irradiated fracture toughness
- Specifically, this topical report discusses a methodology to:
- Determine the ductile-brittle transition reference temperature (T0)
- Adjust the T0 data for differences between the tested material and the RPV component of interest via an adjustment term
- Account for the test result, adjustment, input uncertainties and material variability in the respective RPV component via a margin term
- Apply the T0 data using the NRC endorsed ASME Section XI Code which is codified in 10 CFR 50.55a for PT limits
- Apply the T0 data for RTPTS of limiting/near limiting material as an alternative to 10 CFR 50.61 Direct Fracture Toughness for Evaluation of RPV Integrity
PWROG-18068 Crystal River 3 Example CR 3 Upper-Shell to Lower-Shell Circumferential Weld
- Heat 72105 was available from
- The Midland 1 RPV beltline,
- The Midland 1 RPV nozzle elevation, and
- The Zion 1 RVSP weld
- This heat was irradiated in
- The Ford MTR and CR 3 and Zion 1 surveillance capsules Direct Fracture Toughness for Evaluation of RPV Integrity
- Heat 72105 was irradiated in
- The Ford MTR and Zion 1 surveillance capsules
- The capsules contained different material sources: the Midland 1 RPV beltline and the Zion 1 RVSP weld
- They fall into the high Cu group, so a comparison can be used to validate the Ford MTR irradiation
- After adjusting for differences in the material source chemistry and irradiation conditions
- The beltline weld Ford MTR irradiation result provides a higher T0 relative to the irradiation in a PWR
- If the MTR mesurement was non-conservative, it would be adjusted to be conservative Example Linde 80 Weld Heat 72105 (Appendix C.2)
Direct Fracture Toughness for Evaluation of RPV Integrity
- Adjust for all differences to the RPV location of interest using ASTM E900 Heat 72105 Adjust to the CR-3 RPV Weld Direct Fracture Toughness for Evaluation of RPV Integrity
- Include uncertainties for
- T0 determination
- ETC [adjustments are small, therefore 9°C (16.2°F) is used]
- Irradiation temperature
- Specimens
- Fluence
- Specimens
= 2
2
+
2
+
2
+
2
+
2
+
2
Linde 80 Heat 72105 Applied to CR-3 US-LS Circumferential Weld
- Weighting factor When PWR irradiated data is available, MTR data is not used Wi is the summed function of the difference of each E900 input from the RPV condition
- Adjusted to the 60-year PTS with fluence = 1.56E19 n/cm2 Current 10 CFR 50.61 RTPTS 287°F IRTT0 from BAW-2308A RTPTS = 254°F (LRA)
PWROG-18068 RTT0 (RTPTS) = 176°F Direct Fracture Toughness for Evaluation of RPV Integrity
Implementation Direct Fracture Toughness for Evaluation of RPV Integrity
- Tested T0 data with adjustment and margin can be used to:
- Evaluate the RPV for PTS (10 CFR 50.61) for license renewal, for power uprates or other operational changes
- Heat-up/Cool-down (P-T) limit curves (10 CFR 50, Appendix G)
- Extending the applicability of the P-T curves or
- Improve operating margin
Questions?
Direct Fracture Toughness for Evaluation of RPV Integrity
David Dijamco John Tsao Office of Nuclear Reactor Regulation Division of New and Renewed Licenses Vessels and Internals Branch
NRC Staff Evaluation
of PWROG-18068-NP, Revision 1 Use of Direct Fracture Toughness for Evaluation of RPV Integrity Presentation to the ACRS Fuels, Materials, & Structures Subcommittee September 20, 2024
2 Staff Evaluation - key aspects we were looking for T0 testing is performed in accordance with an accepted standard Uncertainties in T0 are adequately addressed Adequacy of the proposed method for embrittlement prediction (i.e., use of ASTM E900)
When data from material test reactors are used, flux effect is adequately addressed Regulatory exemptions for using methodology are clear Data Adjustments and Uncertainties - key requests for additional information (RAIs)
T30-T0 correlation Material variability Observations How much margin/relaxation in RPV integrity is gained?
How does TR methodology fit in the broader sense with respect to use of T0?
Regulatory implications Conclusion Why we find the methodology acceptable Content
Approved Use of T0 is Not New
- ASME Code,Section XI, G-2110
- ASME Code,Section III, NB-2331 Materials for Vessels
- ASME Code Cases N-830, N-629
- Kewaunee circumferential RPV weld (ML011210180)
- Approved topical reports BAW-2308, Revisions 1 and 2, for Linde 80 welds (ML052070408 and ML080770349) 3
Staff Evaluation T0 must be determined in accordance with ASTM E1921 Latest version incorporated by reference in the regulations is 2017 (via IBR of ASME Code,Section XI) 2020 version is used in the methodology because it has procedures for screening and evaluating inhomogeneous datasets (adds conservatism in the T0 if dataset is inhomogeneous) 2 key aspects
- 1) Test specimen configuration Specifies use of standard-shaped or disk-shaped compact tension, C(T) or DC(T), and single-edge notch bars, SE(B), specimens.
Specifies additional 18°F if SE(B) specimens are used
- 2) Has provisions for inhomogeneous screening and procedures for determining additional value to T0 to address inhomogeneous datasets.
4 T0 Testing
Staff Evaluation The TR methodology provides basis for use of mini-C(T) specimens.
The mini-C(T) geometry is C(T) fracture specimen geometry scaled to a smaller size such that specimens can be machined from a broken Charpy half and is designed to be compliant with ASTM E1921.
Up to four of these mini-C(T) specimens (per half Charpy specimen) can be machined from a broken Charpy specimen.
Japanese lab sponsored an international round robin with seven test labs participating to compare T0 values using mini-C(T) and larger C(T) specimens.
Dataset comprised of RPV base metals and welds.
Constraint condition difference between mini-C(T) and larger C(T ) was shown to be negligibly small.
The results show no significant difference between the T0 values determined by the different labs, nor is there a significant difference regarding T0 values between the mini-C(T) and the larger-size C(T) specimens (avg. difference = 0.7°C, standard dev. of difference = 7.2°C)
If SE(B), i.e., 3-point Charpy bend, specimens are used, adding a bias of 18°F to the T0 test value is required.
5 T0 Testing (continued)
Staff Evaluation The TR methodology follows inhomogeneous screening procedure in ASTM E1921 Datasets are screened for inhomogeneity.
If screening fails, i.e., the dataset is potentially inhomogeneous and will be evaluated in accordance with Appendix X5 of ASTM E1921.
If dataset determined to be inhomogeneous, T0 value is increased to a larger value, T0IN, because the dataset is inhomogeneous.
Thus, staff finds T0 testing used in the methodology acceptable.
6 T0 Testing (continued)
Staff Evaluation Sources of uncertainty in using the methodology T0 uncertainty Adjustment uncertainty (next set of slides on ASTM E900)
Uncertainty due to radiation exposure parameters, fluence and temperature Uncertainties due to material variability and T0-T30 correlation (John) 7 Uncertainties in T0
Staff Evaluation 8
Uncertainties in T0 (continued)
Margin term for irradiated data Margin = 2(E1921 2 + adjustment 2 + tempspecimen 2 +
fluencespecimen 2 + tempRPV 2 + fluenceRPV
- 2)
Margin term for unirradiated data Margin = [(k1S)2 + (2adjustment)2 + (2tempRPV)2 +
(2fluenceRPV)2]
Staff Evaluation 9
Uncertainties in T0 (continued)
Uncertainty Source Margin term Irradiated Margin term Unirradiated Explanation T0 specimen testing E1921 n/a As defined in ASTM E1921 Unirradiated T0 data n/a k1S NUREG-1475 95/95 statistical bound parameters Adjustment term adjustment adjustment Equation 12 of TR Specimen temperature tempspecimen n/a Specimen fluence fluencespecimen n/a RPV temperature tempRPV tempRPV RPV fluence fluenceRPV fluenceRPV
Staff Evaluation Equation 12 of TR adjustment is the standard deviation of T30 (i.e., RTNDT) of RPV as defined in ASTM E900 scaled to the ratio of the adjustment term to RPV T30.
Multiplier of 1.1 for base metal Minimum 9°C (based on statistics of embrittlement shift data of welds and base metals)
Double-counts fluence and temperature uncertainties; there are already separate fluence and temperature margin terms, but since Equation 12 is based on E900, which is a function of fluence and temperature (among four other parameters), some fluence and temperature uncertainties are included in adjustment.
Thus, staff finds that sources of uncertainties in T0 adequately addressed.
10 Uncertainties in T0 (continued)
Staff Evaluation Improved accuracy of E900 compared to RG 1.99 Rev. 2, especially at high fluence Based on 1878 RTNDT data (compared to 177 for RG 1.99 Rev. 2)
Exposure parameters are fluence and temperature (compared to only fluence RG 1.99 Rev. 2); temperature parameter adds robustness Similar scatter in predicted RTNDT relative to measured RTNDT but more falling within +/-2 (next two slides)
Documented in work by staff (ML21314A228) referenced in proposed embrittlement rulemaking SECY (ML21314A215) 11 Adequacy of ASTM E900 Embrittlement Trend Curve
Staff Evaluation E900 compared to RG 1.99 Rev. 2, predicted RTNDT relative to measured RTNDT BASE METALS E900 RG 1.99 Rev. 2 12 Adequacy of ASTM E900 Embrittlement Trend Curve (continued)
Staff Evaluation E900 compared to RG 1.99 Rev. 2, predicted RTNDT relative to measured RTNDT WELD METALS E900 RG 1.99 Rev. 2 13 Adequacy of ASTM E900 Embrittlement Trend Curve (continued)
Staff Evaluation In our evaluation, we focused how margin (in the use of E900) is addressed (slide 10)
As previously discussed, minimum of 9°C and double-counting of uncertainties by the adjustment term and separate terms for fluence and temperature uncertainties for both the test specimens and RPV of interest.
Thus, the staff finds the use of ASTM E900 trend curve acceptable for the methodology.
14 Adequacy of ASTM E900 Embrittlement Trend Curve (continued)
Staff Evaluation When material test reactor (MTR) irradiations are used, such as in an MTR campaign, the MTR irradiated data must be validated against PWR irradiation data.
The MTR irradiated data must be:
from same Cu grouping as the PWR validation material (since flux effect on embrittlement is dependent on Cu level) from same heat as the PWR validation material within +/-50% of PWR fluence If needed, increase MTR irradiated data to irradiation level of RPV material of interest Compare the adjusted MTR irradiation T0 with the PWR validation material T0 (Equation 9), and if former is a larger value, no increase is necessary.
If former is a smaller value, increase MTR irradiation T0 per Equation 10.
The staff finds the above a reasonable approach for handling the potential flux effect from MTR irradiations.
15 Flux Effect from Material Test Reactors
Staff Evaluation 10 CFR 50.61 As stated in draft SE, exemption is needed because the definition of RTPTS in methodology is different than the definition in 10 CFR 50.61.
Appendix G to 10 CFR 50 As stated in draft SE, exemption is needed because Section IV. Fracture Toughness Requirements of this regulation states:
For the reactor vessel beltline materials, including welds, plates and forgings, the values of RTNDT and Charpy upper-shelf energy must account for the effects of neutron radiation, including the results of the surveillance program of Appendix H of this part.
Appendix H to 10 CFR 50 As stated in draft SE, exemption is needed when Charpy specimens in a surveillance program are modified and tested for T0 in a three-point bending configuration (or another configuration).
As stated in draft SE, no exemption is needed when small fracture toughness specimens from broken Charpy specimens or untested heat-affected zone specimens are used for T0 testing.
16 Regulatory Exemptions
Data Management How to manage data to ensure data integrity in prediction Prediction of RPV Embrittlement involves various parameters Unirradiated and irradiated T0 T30 data vs. T0 data Data from Test specimens vs. RPV materials (same heat vs different heat)
Fluence and flux in pressurized water reactor vs material test reactor Uncertainties in measurements Uncertainty in prediction method 17
ASTM Standards As part of data management, TR uses ASTM E900-15 and E1921-20 E900-15 provides guidance on predicting transition temperature shift (i.e., embrittlement) of RPV material based on surveillance data.
Contains statistical methods to evaluate uncertainty in shift prediction.
E1921-20 provide guidance on the test method using compact or bend bar specimens to determine T0 in the transition range.
contains master curve.
Provides statistical analysis of test data,
- consideration of margin adjustments, material inhomogeneity vs.
homogeneity, evaluation of uncertainty.
Staff has not approved E900-15 and E1921-20. Approving the TR does not imply or infer generic approval of these standards.
18
Adjustment Term in TR Methodology TR equations # 1, 2, and 3 include an adjustment term to adjust test specimen data to irradiation level of RPV material of interest; this adjustment term depends on :
Chemistry Temperature Fluence Correlation between T30 and T0 ; Will focus on T30 and T0 correlation 19
Adjustment Term - Correlation between T30 and T0
Background
Correlation is needed to address the difference between T30 and T0.
No industry accepted embrittlement trend curve model is based on T0 TR uses T30 for embrittlement shift because ASTM E900-15 data are based on T30 data.
Use correlation between T30 and T0 to justify the use of T30 data in the adjustment term.
Staff found that an adjustment for model uncertainty (uncertainty in correlation between T30 and T0) was not included in the methodology TR Methodology Measured difference exists between the embrittlement shift T30 and T0 Difference in embrittlement shift T30 and T0 data are correlated and adjusted.
20
Adjustments -Correlation between T30 and T0
- TR performed statistical analysis of embrittlement shift between T30 and T0 data for base metal and welds.
- TR method bounds greater than 95% of the measured T0 values and fracture toughness values.
- TR derives a linear correlation slope of 1.1 for base metal and 1.0 for welds T30 and T0 data which is applied in the margin term.
- TR methodology includes 9°C (16°F) as part of adjustment uncertainty (adjustment) in the margin term.
Staff Evaluation
- Staff finds acceptable that no model uncertainty associated with correlation of T30 and T0 data needs to be included because statistical analysis of correlation of T30 and T0 data demonstrates linear correlation with a slope of 1.1 for base metal and 1.0 for welds.
TR includes 9°C (16°F) as part of adjustment uncertainty (adjustment) in the margin term.
21
Margin in Existing Regulation A margin term is used to ensure that the evaluation is conservative.
The margin term in 10 CFR 50.61 and Reg Guide 1.99 Rev 2 RTPTS = RTNDT(U) + RTNDT + Margin; U =unirradiated Adjusted Reference Temperature (ART) = Initial RTNDT + RTNDT + Margin Margin = 2 I 2 +
2 where I is the standard deviation of the initial (or unirradiated) RT NDT and is the standard deviation of shift RTNDT If a measured data for initial RTNDT is used, use the precision of the test method. If a generic mean value is used, I is the standard deviation from the set of data used to obtain the mean.
The value of to be used is 28 0F for welds and 17 0F for based metal. The value of need not exceed the on-half of RTNDT If surveillance data are used, may be reduced by half.
As a comparison, TR methodology for RTPTS equation includes an adjustment term and a margin term 22
Margin Term in TR Methodology
- TR equations # 1, 2, and 3 include a margin term to account for uncertainty which includes (as previously discussed):
- Testing Uncertainty, E1921
- Adjustment Uncertainty, adjustment
- Temperature Uncertainty, tempspecimen or tempRPV
- Neutron Fluence Uncertainty, fluencespecimen or fluenceRPV
- Material Variability Uncertainty not explicitly included in margin term; Will focus on material variability 23
Material Variability Background -
RPV material embrittlement relies on prediction model which is based on shift (embrittlement) measurement of materials Empirical Embrittlement Trend Curve in ASTM E900-15 reflects uncertainties of material variation and chemistry uncertainties in the prediction.
Chemistry variation and initial fracture toughness variation need to be considered Material variability is addressed in ASTM E1921-20 which describes homogeneity screening procedures to detect if dataset can be representative of macroscopically inhomogeneous material.
ASTM E1921-20 prescribes evaluation guidance for datasets that failed homogeneity screening criterion.
Inhomogeneity in fracture toughness could be caused by the initial material properties and embrittlement effects.
Measurement of T0 based fracture toughness reduces uncertainties associated with RTNDT correlated/based fracture toughness.
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Material Variability TR Methodology TR does not change safety factors in 10 CFR 50, Appendix G nor 10 CFR 50.61 TR does not explicitly include material variability uncertainty as part of the margin term aside from homogeneity screening in E1921-20.
TR considers that (a) measurement of direct fracture toughness reduces uncertainty associated with the correlation of RTNDT to fracture toughness, and (b) measurement of irradiated fracture toughness reduces uncertainty associated with embrittlement prediction.
Staff Evaluation Initially, staff had concerns that material variability uncertainty was not considered in the margin term. Staff requested for additional information.
Based on the PWROGs response, staff finds that (a) the TR methodology includes 9 °C (16
°F) as part of adjustment uncertainty ( adjustment) in the margin term, (b) the margins currently required by the SAME Code,Section III are sufficient to account for material variability uncertainty, (c) evaluating embrittlement at the 1/4T location of the RPV shell provides structural margin as compared to the RPV shell surface because driving force at the 1/4 T location is higher than at the surface, and (d) the TR methodology uses large amount of T0 data which reduces uncertainty as compared to small datasets.
Based on the adjustment uncertainty and other associated margins, the staff finds that the TR methodology addresses material variability uncertainty satisfactorily.
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Regulatory Implication The proposed TR methodology is not a new regulatory requirement; it is an option that licensee could use.
Licensee could use the TR methodology if its PTS value will exceed the screening criteria of 270 °F for axial welds, and forgings and 300 °F for circumferential welds at the end of license.
Licensee could use the TR methodology to develop its Pressure Temperature limit curves so that it could operate its reactor efficiently.
The TR specifies that licensees who plan to use the proposed methodology needs to submit exemptions from the appropriate regulations.
Rulemaking Rulemaking would eliminate the need for exemptions.
Staff did not consider rulemaking during its review.
Staff would like to review an actual licensee submittal to determine the feasibility of the methodology; achieve regulatory stability prior to exercise rulemaking.
Staff would not rule out rulemaking in the near future.
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Observations
- Additional staff considerations on the proposed methodology
- The proposed methodology is consistent with NRC approved precedent.
- The proposed method is adequate and ensures the integrity of the RPV material.
- The TR uses industry standards ASTM E1921-20 and E900-15 consistently although staff has not officially (i.e., not generically) approved these two standards.
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Observations - continued
- The proposed methodology provides fracture toughness that is closer to actual transition temperature fracture toughness of reactor vessel shell materials than fracture toughness determined by the existing method.
- The TR methodology can be used by plants whose RTPTS values are approaching the PTS screening criterion.
- The proposed methodology may assist PWRs to generate P-T limit curves that are not as restrictive as P-T limit curves using the method in the current regulations.
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Observations - continued Margins may be gained back from the use of the TR methodology.
As a comparison, TR presents RTPTS results based on the existing method and TR methodology Based on the existing method, TR obtained a RTPTS of 253.8 °F, taken from Crystal River 60-year license renewal application.
Based on the TR methodology, TR calculated a RTPTS of 176.2 °F This is a 77.6 °F margin gain. This is only an example; plant-specific data may result in different margin gain.
This specific result shows that the RPV embrittlement does not appear to be as severe as it is predicted using the existing method.
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Conclusion
- The proposed TR methodology using irradiated or unirradiated T0 data in lieu of current approach of using RTNDT for evaluating RPV structural integrity is acceptable because the TR method has provisions for determining adjustments and margins applied to T0 data that ensure the final T0 is adequate in maintaining RPV integrity.
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31 BACKUP SLIDES ONLY
3 scenarios that calls for use of methodology 32
- You want to determine an irradiated T0 for use in PTS and PT limits for an RPV material of interest (MOI).
Typically, there is no irradiated T0 data for the RPV MOI, but there is irradiated T0 data elsewhere. What to do?
Three scenarios:
- Scenario 1: Have irradiated T0 data from specimens that are same heat as RPV MOI from other PWRs or;
- Scenario 2: Have irradiated T0 data from specimens that are same heat and same Cu grouping as RPV MOI from MTRs or;
- Scenario 3: Have unirradiated T0 data from material similar to RPV MOI (doesnt have to be same heat)
BACKUP Scenario 1:
Irradiated PWR Data 33 To determine T0 for RPV MOI if you have irradiated T0 data from specimens that are same heat as RPV MOI from other PWRs:
For each specimen, Calculate Adjustment Term (Equation 6)
Calculate Margin Term for irradiated data (Equation 11)
Add both to T0 of each specimen dataset Compute weighted average to determine final T0 for RPV MOI (more weight given to specimen closest to condition of RPV MOI)
BACKUP Scenario 2 Irradiated MTR Data 34 To determine T0 for RPV MOI if you have irradiated T0 data from specimens that are same heat as RPV MOI from MTRs:
Must first validate MTR data; for each MTR specimen, Must be in the same Cu grouping Fluence must be +/- 50% of PWR validation fluence Calculate Adjustment Term (Equation 6)
Add to T0 of each MTR specimen validation dataset Compute weighted average to determine adjusted T0 for the MTR specimens (more weight given to MTR specimen closest to condition of PWR validation material)
- If above weighted average adjusted MTR T0 is greater than PWR validation T0, MTR T0 is considered representative of or conservative relative to the RPV MOI.
- If not, increase MTR T0 such that MTR T0 used is representative of or conservative relative to the RPV MOI.
BACKUP Scenario 2 (continued)
Irradiated MTR Data 35 After validation, for each MTR specimen, If needed, add increase to T0 of each MTR specimen (from validation against PWR irradiation)
Calculate Adjustment Term (Equation 6)
Calculate Margin Term for irradiated data (Equation 11)
Add both to T0 of each MTR specimen Compute weighted average to determine final T0 for RPV MOI (more weight given to MTR specimen closest to condition of RPV MOI)
BACKUP Scenario 3 Unirradiated Data 36 To determine T0 for RPV MOI if you have unirradiated T0 data from specimens that are similar and that is similar to the RPV MOI:
Must have at least 4 heats (doesnt have to be the same heat as RPV MOI)
Calculate standard deviation (S) and one-sided 95% tolerance factor (k1) from NUREG-1475 Is there irradiated T0 data from a heat in the generic grouping?
If no, calculate average T0 value of the unirradiated data If yes, adjust generic unirradiated T0 value by adjustment term (Equ. 6) and unirradiated margin term (Equ. 5) the resulting adjusted generic value must bound 95% of the irradiated KJc1T data (if not bounded, cannot use unirradiated data)
Calculate Adjustment Term (Equation 6)
Calculate Margin Term for unirradiated data (Equation 5)
Add both to generic unirradiated T0 to determine the final irradiated T0