ML20209D107
| ML20209D107 | |
| Person / Time | |
|---|---|
| Issue date: | 06/29/1999 |
| From: | NRC ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW) |
| To: | |
| References | |
| NACNUCLE-T-0131, NACNUCLE-T-131, NUDOCS 9907130040 | |
| Download: ML20209D107 (173) | |
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1 O RI G h A ._ ACN/d7;&3/ i OFFICIAL TRANSCRIPT OF PROCEEDINGS i V NUCLEAR REGULATORY COMMISSION ADVISORY COhlh11TTEE ON NUCLEAR WASTE 1 l I
Title:
51EETING: 110TII ADVISORY l I COhlh11TTEE ON NUCLEAR { WASTE (ACNW) TROS ; Ac,g REmn ag33 Nn y ,i L -WITE B
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Docket No.: Work Order No.: ASB-300-838 9907130040 PDR 990629 D~ ! 1 T-0131ADVCM NACNUCLEPDR I l 1 LOCATION: San Antonio,TX j DATE: Tuesday, June 29,1999 PAGES: 262 - 434 ANN RILEY & ASSOCIATES, LTD. 1025 Connecticut Ase.,NW, Suite 1014 q Washington, D.C. 20036
. (202) 842-0034 A0f4WOFFICL'Com RETAINFOR
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-UNITED' STATES NUCLEAR REGULATORY. COMMISSION'S ADVISORY COMMITTEE ON NUCLEAR WASTE JUNE 29,.1999
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1 The contents of this transcript of the proceeding of-the United. States Nuclear Regulatory. Commission Advisory () Committee on Nuclear' Waste, taken on June 29, 1999, as reported.herein, is a record of the discussions recorded at the meeting held on the above date. This transcript had not been reviewed, corrected and edited and it'may contain inaccuracies. i l l l r: : l t !
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- f 262 l 1 UNITED STATES OF AMERICA l
[ } 2 NUCLEAR REGULATORY COMMISSION l
%J 3 ADVISORY COMMITTEE ON NUCLEAR WASTE 4 ***
5 MEETING: 110TH ADVISORY COMMITTEE ON 6 NUCLEAR WASTE (ACNW) l 7 *** 8 1 9 Southwest Research Center 10 Building 189 11 6220 Culebra Road 12 San Antonio, Texas 13 1 14 Tuesday, June 29, 1999 l t'% k ,) m 15 16 The Committee met, pursuant to notice, at 8:30 17 a,m, I 18 l 19 MEMBERS PRESENT: 20 B. JOHN GARRICK, ACNW Chairman 21 GEORGE HORNBERGER, ACNW Vice Chairman 22 RAYMOND WYMER, ACNW Member l 23 CHARLES FAIRHURST, ACNW Member 24 25 iO ANN RILEY & ASSOCIATES, LTD. (l Court Reporters 1025 Connecticut Avenue, NW , Suite 1014 Washington, D.C. 20036
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I 263 1 PROCEEDINGS ( 2' [8:30 a.m.] 3 MR. GARRICK: Good morning. The meeting will now 4 come to order. This is the second day of the 110th meeting 5 of the Advisory Committee on Nuclear Waste. l 6 My name is John Garrick, Chairman of the ACNW. 7 Other members of the committee include George Hornberger, i 8 Ray Wymer, and Charles Fairhurst. l 9 This meeting will be open to the public. 1 l 10 Today the committee will continue its review of 11 center activities and also later on today we're going to be 12 touring several of the laboratories of the institute. 13 Howard Larson is the Designated Federal Official j 14 for the initial portion of today's meeting. f ( 15 This meeting is being conducted in accordance with 16 the provisions of the Federal Advisory Committee Act. I j 17 don't think we've received any written statements or ! 18 requerts to make oral statements from members of the public 19 regarding today's session. However, should anyone wish to 20 address the committee, please make your wishes known to one 21 of the committee's staff. I 22 As usually, it is requested that each speaker use i l 23 a microphone, introduce themselves, and speak with 24 sufficient clarity and volume so that they can be readily 25 heard. 1 C)
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1 264 l 1 Today we're going to talk about design issues, for i 2 the most part, and the committee member that's going to -- l 3 the committee members that will be leading these l 4 discussions, for the most part, will be Charles Fairhurst 5 for the first presentation and George Hornberger for the 6 second presentation. 7 So with that, I guess our first speaker is Raj and 8 our second one will be Simon Hsiung. So with that, we will 9 proceed. Raj, you're on. 10 MR. NATARAJA: Good morning. The presentation 11 this morning will consist of three parts; a short 12 introductory part that I will be doing, and a more detailed 13 presentation by Dr. Hsiung, Simon Hsiung, from the center, 14 at your end, and we'll try and finish this presentation in () 15 16 about half the time that is allotted ~o us, so that there will be enough time for discussion at the end. 17 My name is Simon Nataraja I am a Senior 18 Engineer, working in the engineering section, and I am also 19 the group manager for this particular KTI, repository design 20 and thermal-mechanical effects. And Dr. Hasad Choli is my 21 counterpart at the center. He is the group manager for this 22 KTI. And Simon is the main presenter. However, he is being 23 supported by several others; Ray Chen, Mr. Ghosh, you 24 probably have seen him and probably have talked to him 25 before. They are all rock mechanics experts, experienced in l N ANN RILEY & ASSOCIATES, LTD. Court Reporters ! 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
F , l? !- I L 265 1: design and~modeling. ( 2' And a new addition to this group is Doug Gute, who l (
- 3 is a mechanical engineer, and we are.looking forward to his 4 ' participation in the pre-closure aspects of this particular
[ 5 KTI, which have been under development for a while now. 6 In~ fact, I used to be a single man team and thanks 7 to the new organization, our budget was doubled. And 8 another person working on this end is Bernard, and since we 9, have two people now, he is able to attend the NWPR review 10 and, at the same time, attend this meeting here. 11 .The outline of this morning's presentation l 12 includes a statement of the issue, and we will-also go into
- 13 statements of sub-issues within this main issue, and we will 14~ talk about pre-closure design aspects of the repository.
() 15 Then we will talk about our understanding of -- our limited 16 understanding of integrated safety analysis, As you know, 17 'Part'63 requires that DOE perform an ISA to demonstrate that 18 the pre-closure performance objectives have been met.
- 19. We are going to start on a fast-track to learn, 20 this group at least, because there is no experience applying 21 .ISA to repository design,.either at the center or on the 22 staff here; I l
23 Then we will touch on some of the post-closure 24 aspects of thermal-mechanical. effects on the repository 25 performance,'and we.will list a few insights that we have
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p 1 l 266 1 developed by our exercises of providing input to the system l jf'} l %' 2 performance assessment. 3 .And we will discuss how we are reviewing the 4 fast-changing repository designs, the various options being 5 considered by the Department of Energy, and we're looking at 6 the analysis using engineering models, how we are developing 7 capabilities to be able to review their designs, and we will-8 summarize the progress that we have made in Rev. O and Rev. 9 1, which you probably have there, and we'll discuss the path 10 forward for resolving the many issues before license 11 application. 12 You have all received this, I believe, in Budhi's 13 presentation yesterday. Our particular KTI, the main 14 contribution comes in the box under the engineered barriers, p)' s 15 specifically EBS-2, which is the mechanical disruption of 16 waste packages. 17 We have done some preliminary work using the rock fall model 18 and the effect of rock fall in repository performance, and 19 we also are continuing to review those models. 20 We also have some contribution to the other boxes, 21 EBS-1, perhaps even four, but mostly in a secondary fashion, 22 not in a primary fashion, and we have some contributions to 23 make under GS-1, which is the spatial and temporal 24 distribution of flow. 25 During Simon's presentation, you will hear some J i l 1
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F 267 i l' details about the changes of geometry due to excavation, and 2 the effects on flow and so forth. O(/ 1 3 This particular KTI, the main issue statement is 4 the adequacy of design, construction and operation of the { 5 geologic repository operations area, GROA for short, to meet I 6 both pre-closure and post-closure performance objectives, 7 taking into account long-term thermal-mechanical processes. l 8 We had another portion which we dropped because of the Part 9 63 changes. We will go through some of those discussions 10 later. 11 The sub-issues that I have listed here, you may 12 not find all of these in the current versions IRSR, the zero 13 and one, because the definition of KTI was focusing mostly
-14 on the post-closure and because of the descriptions, we had O
Q 15 no application to work on the pre-closure aspects. 16 The next revision, we hope to revise it and 17 include some of the sub-issues with pre-closure. 18 The first three items that I have listed there I 19 under pre-closure sub-issues, mainly effectiveness of design ! 20 control process, design of seismic events, direct fault 21 disruption, and thermal-mechanical effects, all those three 22 items affect both pre and post-closure attributes of the ! 23 repository design. 24 The last item there, the item dealing with the 25 pre-closure performance objectives, those are next under the O ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 t- i
l 268 4 1 two design basis events. And the design meeting the options ! 2 (-s'l s_/
-- the ability to retrieve and the ability of the design to l 1
3 accommodate the performance confirmation program, all those 4 three aspects are pre-closure issues, as far as design is 5 concerned, and also the implications for post-closure 6 performance confirmation program. 7 And as far as the post-closure issues are 8 concerned, it is the effects of thermal-mechanical events, 9 including seismic, on post-closure performance. And as I 10 mentioned, we dropped the issue'that used to be part of the 11 post-closure sub-issues. i 12 With this brief introduction, I will get into some 13 details and I'd request Simon to pick up from here. 14 MR. HSIUNG: Raj, you can take it off now. Good l
you're going'to -- I'think that increase the 25_ permeability for the horizontal' joints, so the water will ANN RILEY & ASSOCIATES, LTD.
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309
- j. 1 come into that. I think the. percentage-wise, it's about 30 2 percent, also, in terms of differences.
3 MR. GREEN: I think it's good to keep in mind that 4 the repository is not going to be uniformly heated. The 5 line load is going-to help smooth out within the drifts, but 6 there's still going to be' hotter and colder areas, and those 7 hotter areas are going to incur different stresses than the 8 cooler. areas and you can have some redirected shedding. 9 I think that's something that we're trying to look
.10 at. -
I 11 MR. FAIRHURST: I think this goes to your point of 12 what you were'saying you will see overlap between the 13 various KTIs and areas. 14 MR. GREEN: Yes. 15 MR. FAIRHURST: Because it's very definitely 16 that's what is happening. 17 MR. GREEN: Okay. I'm going to just comment on -- l 18 briefly.' introduce some lab studies we've done, without going
;19 into any detail at this point. I would just note that we 20' have a-test assembly. You will see the framework of this in 21 the lab this afternoon.
22 But we infiltrate water up here, we have a heater 23' down-here. We've conducted two tests, we're setting up a 24 ' third. In the first two, we had concrete blocks and the 25 idea was to infiltrate water and then monitor it, as best ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025. Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
7 310 1 possible, and see the nature of flow along the fractures
/7 2 back to the heater.
U 3 MR. GARRICK: Can you make that heterogeneous? 4 MR. GREEN: Well, by nature, it is heterogeneous. 5 Even though the blocks were uniformly shaped, we did have 6 some heterogeneities. Our third experiment is going to be 7 with crushed tuft, and that will be more heterogeneous. We j 8 have different objectives for that. 9 I will discuss those in the lab when we're there. 10 It will be a little easier.
~ _
31 ~~
--But-just to note, briefly, that the -- we 12 monitored the movement of moisture. The best way we could 13 do it was through thermocouples based throughout the test 14 assembly and looking at along the fracture immediately r"N
() 15 co-planar with the heat source, we find that the boiling 16 isotherm, we had no indication that the boiling isotherm 17 penetrated the drift during the experiment. 18 This is important because DOE is using 19 thermocouples in their drift scale tests to give them an 20 indication whether they have reflux into the drift. 21 However, in the drift, we placed these drip 22 sensors and both test one and test two and in both cases we 23 had dripping into the drift. In test one, we were able to 24 look through the Plexiglas side, so we know that the 25 dripping occurred throughout the experiment when the boiling i ("N ANN RILEY & ASSOCIiTES, LTD (_) Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 1
311 i l 1 isotherm was at some distance. 2 I'm not going to try to say that we can scale ( 3 these up. However, you can use some empirical analyses, 4 like Philips that we use, in order to get an idea of that. 5 But what we found here is that there was dripping throughout 6 about 75 percent of the drift in the first experiment. This 7 damage down here was caused by the heater. 8 The heater was at about 500 degrees C, but it was 9 only one inch in diameter, and that pushed the boiling 10 isotherm about ten etntimeters into the rock. 11 But what we found was that we had these drips of 12 this real nasty mud-like material and there has always been
' ~~~
'13' discussion about what kind of water will drip back into the 14 canister and there has been some feeling that it will be a
() 15 condensate, so it will be relatively pure, it will come 16 down, it's not going to have much impact on the canister's 17 performance, because water, in itself, isn't going to 18 degrade the canister. It's going to be the solutes in the 19 water. 20 What we found here was this stuff was oozy mud and 21 that's what we found here. And in test two, we found the 22 same thing. In the first one, I don't want to get into the 23 details now, because that's a discussion itself, but in the 24 first one, the drift air temperature was less than 100. But 25 in the second one, it was 200 degrees C and that was -- () (_,/ ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
l 312 l 1 there are some reason for that, and we can_get into it 2 later. v 3 But the performance of dripping into the drift was 4 the same over -- it was a little harder to tell what 5 percentage dripped in the second one, but it was for the i 6 most part of the drift anyway, and you can see how this ' 7 material completely degraded the drift sensor in parts of 3 8 both one and two. 9 MR. FAIRHURST: Are you saying this is some sort 10 of counter-current flow that is going up? l 11' MR. GREEN: Yes. 12 MR. FAIRHURST: And water is coming down. 13 MR. GREEN: Yes, exactly. 14 MR. CAMPBELL: Ron, it would be very interesting O) (, 15 if you could actually collect drips and do an analysis of 16 the water chemistry, design an experiment to do just that. 17 MR. GREEN: Well, we actually put ports on the 18 side of the first one to collect it, but that water 19 evaporates almost immediately. But we did do XRD analysis 20 of the precipitate that formed on the fracture and on the 21 drip sensors, We did a chemical analysis of the water we 22 infiltrated, and in the second experiment, we did have some 23 drainage through the bottom of the cell and we did a 24 chemical analysis of that, and we have all that information. 25 Now, just briefly, I think this next slide is l l i I '\ ANN RILEY & ASSOCIATES, LTD. k- Court Reporters l 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 t
313 1 really interesting, because this is water quality analysis () 2 3 of water that was collected from the drift at the DOE drift scale test. We only have one analysis at this time, so we 4 have a? working hypothesis, and we'll have to revisit this 5 when we get more results. 6 But you have two samples that were taken below the 7- drift. .These are from the hydrology holes that are directly 8 below the drift, and you have one sample collected from 9 above. This'one happens to be right above this one. 10 And if you notice, the concentration of the ions 11 in these two are considerably lower than what you find above 12 the drift. In particular, look at the sultates and the 13 chloride. This is 600 times above compared to below. 14 Now, I had this hypothesis and one of the first () 15 places I went with it was Bill Murphy, because he shoots 16 down every chemical concept that I have, and he didn't 17 disappoint me on this one. What he said was that we can't 18 go much further than a hypothesis at this time because we 19 don't know where we are in the gradient, the thermal 20 gradient and the potential gradients. We just might be 21 taking that sample at a different place in the gradient than 22 from above from below. 23 And I have posted in the lab some chemical 24 analyses from DOE and we'll see that they're symmetric, that 25 they show that the chemistry is the same above as below. So N ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
314 1 we're' going to watch very closely what they're doing and [\
.C) 2' what they're collecting at the drift scale test, and it has i 3 profound effect upon our conceptual model of the refluxing.
4 MR. GARRICK: So what is your hypothesis? 5 MR. GREEN: The hypothesis is that the water 6 below, as it moves down, keeps getting more condensate, 7 which has no solutes in it, but above, the closer you get to 8 the drift, you're nearing the end of the evaporation 9 . pathway. So.when that first water gets to the drift, it 10 just has a little bit of moisture in it and it's almost all 11 solute, and that's what goes into the drift. ' 12 So it's a highly mineralized water that goes into 13 the drift, and this is consistent with it. That's a 14 hynothesis, but until we get a little more data, we won't () 15 know for certain. 16 MR. WYMER: And yor would expect that to change 17 with time, then. 18 MR. GREEN: Yes, you will. But through the 19 thermal period, I think it will stay this way. However, 20- there is another discussion I had with Bill, he feels that 21 later on, after the thermal pulse has cleared the drift, 22 that you're going to have the clean water come through and 23 flush things out. 24 MR. WYMER: That was my point. 25 MR. GREEN: Yes. And that's something we'll have O, ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, u.C. 20036 (202) 842-0034
315 1 to see, And we can use some of these tests to support or /'~'T 2 strike down our understanding. \.j 3 MR. CAMPBELL: Can I ask? To what extent, Bill, 4 do you think this is due simply to evaporation or also to ! 5 water / rock interaction? That could make a big difference 6 over the long term. 7 MR. MURPHY: This is Bill Murphy. I was glad to 8 see chemistry brought up. I can only speculate at this ! 9 point about the significance of these particular chemical ! i 10 analyses. The high concentration waters that Ron showed l l 11 from above the drift are calcium chloride waters. Their 12 origin is something of a mystery to me. I wonder about the 13 potential influence of draught. I 14 The notion that very concentrated waters may form o) (s_/ 15 during a refluxing epic in the history of the repository is j 16 a very reasonable hypothesis. But in the absence of that 17 refluxing, one might expect a return gradually to ambient l 18 water chemistry. There certainly will be water / rock l 19 reactions and in my talk, which is next in this series, I 20 will be talking about some of our water / rock interaction 21 calculations to illustrate what we think or where we stand 22 on that subject. 23 MR. GREEN: Just to reiterate two points. One is 24 reflux is not detected with the thermocouples, and that's 25 due to the spatial and the temporal collection of data.
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316 1 You have to have'that thermocouple right up at the (' \J
) 2 right point, taking the reading at the right time in order 3 to detect it.
4 They did detect that at the large block test. So 5 that's sort of a fortuitous thing if you do detect it and I 6 don't think you can state that you're not going to see it if 7 you don't get that information. 8 DOE doesn't have any other confirmatory way of 9 letting them know whether they have dripping into the drift 10 scale test, other than a camera, which they have not been 11 using. 12 Then the last point is issue we just discussed 13 about the concentration of water above the drift relative to 14 below. () 15- Moving ahead to the DOE design, I will not spend a 16 lot of time on this. Simon went over the high points of 17 this. Other than to mention that ventilation will have a 1 18 profound effect on the thermal or the hydrologic conditions 19 in the drift. 20 That raises a point that we've identified with the 21 drift scale test. The way they're conducting the drift 22 scale test is they have a leaky bulkhead, they're not 23 monitoring the moisture or the heat loss through that 24 bulkhead, and it's hard for us to model it. It's hard for 25 us to understand everything going on in the absence of that ANN RILEY & ASSOCIATES, LTD. ((~) _/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
317 1 lack of measurement. l \ 1 [~'Y 2 Ideally, they would have conducted the test by 3 putting a very large bulkhead in there in order to allow the l 4 drift to come up to perhaps some moderate pressures. 5 However, it may be just beneficial to them or fortunate on 6 their-regard because now they're going to consider 7 ventilation. But they're not monitoring it and that was a 8 point that we brought up at an Appendix 7 meeting a couple 9 months ago that Dr. Fairhurst participated in. 10 MR. GARRICK: Ron, can you give us a hint of your 11 opinion of the profoundness of the effect? 12 MR. GREEN: They -- yes. In the DOE preliminary 13 calculations, this was mentioned by Simon, is that they're 14 assuming 50 percent heat loss during ventilation. They're f~s i 15 not putting ventilation in their calculation. They're 16 putting the assumption of heat loss. So the mechanical 17 effect of ventilation isn't in there. 18 We conducted a laboratory scale ventilation test 19 about a year ago and we only had about 20 percent heat loss 20 through ventilation and we're still looking at our results. 21 We're a little -- we're not completely through that, but we 22 don't buy off on their 50 percent at this point. So it's 23 somewhere in that range. 24 If you put in a 50 percent heat loss in your heat 25 load, you're going to -- you're not going to experience the 1 1 h ANN RILEY & ASSOCIATES, LTD. l
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318 1 coalescence of the boiling isotherm between the drifts. [) V 2 That's one of the reasons they opted to go with this design. 3 But it's all predicated on that one assumption. 4 So-that is a profound effect. Plus, it removes 5 moisture and that's another reason I don't think they will 6 see dripping in the drift scale test. They have the 7 ventilation going out, and so they're not going to see 8 -dripping. 9 We've told them that we don't -- we're 10 uncomfortable with them saying they're not going to 11 experience dripping in emplacement drift based upon the 12 results of this drift scale test, in the absence of 13 ventilation. If they add ventilation, I don't think they'll 14 see the dripping during the ventilation period. O) y 15 The progress to date. I mentioned that we've 16 conducted two laboratory tests and we've learned an awful 17 lot from these. We have a third one in preparation. That 18 will be -- that's jointly conducted lab tests with the CLST 19l group and the primary objectives are actually geared towards 20 them. We're going to use crushed tuft and we're going to 21 infiltrate water again. 22- We're only going to get the temperature up into 23 the 80 to 100 degree range, because that's where corrosion 24 is of interest. And we're going to monitor it as best as 25 possible to understand the corrosion environment. i /\ ANN RILEY & ASSOCIATES, LTD. l (_s/ Court Reporters ! 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202)~842-0034
319 1 And one of the criticisms that our group has had () 2 3 of the drift scale test is that they're putting coupons in their drift scale test and they're going to take these out 4 at the end of the eight-year test and they're going to say, 5 well, we'va experienced this much corrosion or we haven't, 6 but they- tven't been monitoring the corrosion environment. 7 So Sridhar's group is actively trying to identify 8 the sensors that they want to put into this drift and we can 9 talk about that a little bit this afternoon. 10 The results from our lab scale tests are 11 consistent with the drift scale test. However, they both 12 illustrate different aspects. We observe penetration of the 13 boiling isotherm in the lab test. I don't know if they will 14 see that in the drift scale test. I would be surprised if (Oj 15 they do see a drip into the drift itself. 16 And as I've mentioned, I think it's very important 17 that we both observed these elevated solute concentrations 18 above the drift. 19 One critical point is once again, the penetration 20 of the boiling isotherm by flow down a fracture. DOE has ! 21 not included that and at this point does not intend to 22 include it in their performance assessment. I think that's 23 a concern. 24 These last three items, as I alluded to earlier, 25 address, somewhat on a mechanistic level, analysis of fi
\_s/
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320 1 seepage, dripping into a cavity, flow back to a heat source.
'T
[d 2 3 This past December, we had an internal workshop, we had about 15 people participate, NRC, center staff and some 4- consultants, because we feel this issue is very important. 5 We have identified some tasks out of that and 6 we're working actively on those. 7 So the path forward, we're going to assess the new 8 repository design. As I mentioned, the time and the flux of 9 water arrival at the waste package is of critical concern 10 and we're doing an awful lot of work in that area. 11 We're going to continue to scrutinize the 12 fundamental assumptions taken by DOE in their performance 13 assessments, continue our sensitivity analyses, using the 14 process level models and TPA to continue to explore what's D) g v 15 important to TEF, and then finally, we've most recent -- 16 just recently completed our recent revision to the IRSR and 17 we'll continue working on that. 18 That concludes my presentation. 29 MR. HORNBERGER: I'll start. I just have a couple 20 questions. Why do you decide to use crushed tuft rather 21 than try to simulate'more a fracture matrix thing, like you 22 did with your concrete blocks? 23 MR. GRhPN: The main reason is it would be very 24 difficult to have -- we have 520 concrete blocks in the 25 earlier one. It cost 100,000 -- $200,000 to prepare a tuft JJRJ RILEY & ASSOCIATES, LTD. s_ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 ; (202) 842-0034 l
321-1- like that and we learn an awful lot about fracture matrix 2 flow. We're.not going to try to replicate that in this 3 experiment. 4 .I think what you're' going to learn, the best 5- . things you can lear.n about fracture flow is in the' field in 6- the drift ~ scale test. It's very hard to capture matrix 7 fractures on a rea.3onable representative elemental volume in 8 the lab, and'it's mostly because of that. 9 We're going to use crushed tuft, from gravel size 11 0 to powder, and the reason we're using the entire fraction of 11 the crushed rock is so that we have a very high surface area 12 for the chemical interaction of the infiltrating water, so 13 to create the environment as close to what'they might expect 14 in the emplacement drifts, j ) 15 MR. HORNBERGER: Because of the backfill? 16 MR. GREEN: No. Just so that the water coming 17 into-it will be close to water that's dripping through tuft. 18 MR. HORNBERGER: Of course, by crushing tuft,
'19 you're creating lots and lots of fresh surfaces. So you'd
.20 ^probably get an argument on that.
21' 'MR GREEN: Yes. We got it from Bill. We already 22 'got that argument from Bill. That's correct. And anytime 23 .you do a' laboratory experiment, you have to make compromises 24 'and that's one I thought we would make, 25 This afternoon -- we're still in the preparation [\
's-).
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322 1- of this and this afternoon, I would really like to hear your [d'l 2 assessment of a different way of doing this. We may go 3 forward with this experiment, but if you have some ideas on 4 an alternative approach, I'd be glad to hear that. l 5 MR. HORNBERGER: It strikes me as quite 6 interesting, but it also seems to me that it will be I 7 critical that you do get the involvement of the geochemists, ' 8 because a lot of the important data you're going to get will 9 depend upon making those measurements as well as the i 10 physical measurements. 11 MR. GREEN: Yes. They are involved and we've met 12 with them. Our most recent discussions are on what 13 chemistry should the water be that we infiltrate. 14 MR. HORNBERGER: That you infiltrate, right. (~~ i 15 MR. GREEN: Yes. s And we're doing some just low 16 scoping experiments, where we're putting different waters in i 17 a bucket with the crushed tuft and allowing that to ' 18 equilibrate for a couple weeks and look at it. i 19 So the question is still open as to the chemistry 20 of the infiltration water, yes. Plus, we're going to look 21 at this experiment and try to use our models to replicate 22 the reaction path. We've looked at some -- we had it as a j 23 higher priority to look at the past experiments, but that 24 was a concrete environment. And it had some relevance with 25 the former design, where they had concrete ground support, hV ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
f l-323 1 but it has very little relevance now, other than giving a 2 nice example against which to test your code. l 1 3 So we've dropped out -- we've dropped the priority 4 on that analysis, but at this point, we're going to go 5 forward with the chemical analysis of the tuft, the reaction 6 path. 7 MR. HORNBERGER: That's good. The other query 8 that I have has to do with your modeling, your MULTIFLO 9 modeling. You said you're doing 3-D modeling and you're 10 particularly interested in this reflux problem. 11 It. strikes me that that reflux problem must be an 12 instability problem; that is, you're talking about flow 13 fingering. How do you model this in a continuum sense? 14 MR. GREEN: Well, we're not. Some of those () 15 analyses are mechanistic. They're looking at single i 16 fractures. ! 17 MR. HORNBERGER: This is the.Philips solution.
)
18 MR. GREEN: That's one of them, yes. We're l 19 looking at others. We're coming at it from about three ! 20 different directions to look at it. We're looking at 21 continuum, but we're also looking at these mechanistic that 22 don't look at it as a continuum. It's a single fracture. 23 MR. HORNBERGER: But that single fracture, that's 24 a one-dimensional analysis, again, isn't it? So how do you 25 determine the frequency of the fingering?
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l 324 1 MR. GREEN: No, it's a two-dimensional, actually. O 2 MR. HORNBERGER: Oh, it is? 3 MR. GREEN: There's different approaches. I 4 didn't have an opportunity to go into detail. We're looking 5 at groove, . groove flow. 6 MR. HORNBERGER: Okay. Yes. 7 MR. GREEN: That's one approach, along with 8 fracture flow, and at different potentials, matrix l 9 potentials, you're going to have different contributions. 10 And your biggest contributions are from the grooves and 11 that's -- you know, my feeling of flow down a fracture in 12 this environment, the best image I can get is water flowing 13 down a windshield or a window during rain. 14 And what you see is that water will be held up D Q 15 until it reaches a threshold potential and release and go 16 very rapidly over a short distance. I think that's how the 17 fractures operate. And a groove fill flow is one of the -- 18 it's about one of the better ways that we've come up with 19 for looking at that mechanism, along with the fill-ups, and 20 we have a couple other approaches that aren't as -- 21 MR. HORNBERGER: And I gather you're doing 22 percolation thresholds from one of your slides, right? So 23 you're looking at percolation models, as well. j 24 MR. GREEN: Yes. Yes. And I think Debra is back, 25 she's looking at some other -- the effects of capillary I O V ANN RILEY & ASSOCIATES, LTD. Court Reporters l 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 e
1 325
-1 diversion and the geometry of the drift.
cy 2 If you look;at the.VA,.everything has a nice D
- 3. . uniform geometry,'with a continuum, and if you put water 4 fdown there, it's going to go around every. time. Well, that's not how -- if you notice, the DOE folks, the people
~
5 6 doing the process level are essentially all physicists and 7 the people doing all their performance assessment are all
- 8. mechanical engineers.
9 If you're an earth scientist, you look at things 10 ' differently. You know,. rocks are very heterogeneous. I mean, even as uniform as we_try to make them in the lab,
~
11 12 they're' heterogeneous. 13 The fractures are very heterogeneous. The fluxes 14 are heterogeneous. The medium is going to act very () .15 ; differently than these nice continuum. If you have any 16- protrudence off the top of a drift wall, that's where 17 . dripping is going to go. You can see that anywhere. You
.18 -can go in a mine and if there is a rock there and dripping 19 is coming off that, or just any jagged edge, and that's not 20 captured in their models and they have very high -- in their 21 -base cases, they have very high diversions, and I'm not 22 comfortable with that at all.
23 MR, HORNBERGER: But one last question. 24 MR. GREEN: Yes. 25 MR. HORNBERGER:- With a C-22 outer shell on the j O ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 l l I Washington, D.C. 20036 l (202) 842-0034
[ p 326 1 canister, does dripping matter? What do-your corrosion l 2 people tell you, does it matter? 3 MR. GREEN: I think the vulnerability -- I had it , j 4 on a slide, I didn't mention it, but the vulnerability will 5 be in the closure seams -- the closure welcis. So I know 6 I've talked to Darrell Dunn and his -- and their group and 7 that's an area that they're now focusing a lot of their 8 efforts-. 9 MR. HORNBERGER: Charles, do you have anything? 10 MR. FAIRHURST: I notice you're talking about
)
11 putting the steel ground support in. 12 MR. GREEN: Yes. 13 MR. FAIRHURST: You know, the recent drift 14 stability panel advised against that and I suspect that is 15 going out. But what is the significance of that, as far as i 16 you're concerned? 17 MR. GREEN: Well, two things. One, with the type 18 of medium we have, with this next test, that's crushed, 19 we're going to have to have something to keep it open. 20 And because of the EBA-2 recommended steel ground 21 support, we're going to use steel similar to that to 22 replicate the environment. 23 MR. FAIRHURST: So it has significance from the 24 chemical point of view. 25 MR. GREEN: Yes. I mean, to some degree, yes. It
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327 1 1 would be better to use than a ceramic -- we used ceramics to { 2 hold'upcour instrumentation in the second test, for q
-3 instance.
4' MR. FAIRHURST: The idea is to use lock bolts and ! 5, reinforcement, because steel sets. It may look like a nice 6- -- butzit.doesn't-work that way in practice. It's not easy 7' to put those in. 8 MR. GREEN: I'd like to discuss this a little more 9 when we go to the lab and you can give us some ideas. 10 ~ MR. FAIRHURST: Fine. Okay. . 11 -MR. GREEN: That measure closer to what they're 12 going to go for. 13 MR. FAIRHURST: I'm not sure they know what 14 they're. going to go for. At-least the last train around,
~
15 that got low marks. 16 MR. GREEN: I went to the thermal abstraction 17- _ meeting, which was on a Tuesday, people prepared their 18 slides on Friday, and they were out of date because they 19 made: changes on Monday, and we have to appreciate it. 20- So in our acceptance criteria, we had this 21 discussion last week, they're changing things, and so the 22: discussion was should we remove these acceptance criteria. 23 :The feeling was no, we'll leave the acceptance criteria in, 24 we'll'close them till some point where they may bring these
'25 concretes back in, and then it will be reopened.
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328 l. 1 So there is a moving target out there and that's a [) 2 challenge to keep the crosshairs on the correct rabbit V 3 .that's running around. 4 MR. WYMER: I just have one comment. I thought 5 that the viewgraph you showed where the water composition 6 changed so dramatically above and below the drifts was 7 interesting. 8 But I wonder if that is really very important as 9 far as corrosion is concerned, because the period during l 10 which you get that concentration is when it's hot and that's 11 not going to last very long. Then you get the more dilute 12 water-coming down and you'll flush the system, and does it 13 matter? 14 MR. GREEN: That's very possible and our challenge 15 is to find.out -- to determine how much water, when it gets 16 there, and how long it comes in before it's diluted, and 17 whether the canisters will be vulnerable to that exposure, 18 and, if they aren't, our problem is half done, we can go on 19 half days, sleep until noon, and come in and then just worry 20 about source term in the afternoon. But that's exactly ] 21 correct. I 22 MR. FAIRHURST: Ron, even with the backfill l l 23 scenario, the idea, I think, is not to actually fill right 24 up to the roof. 25 MR. GREEN: Right. l [D
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329
.1 ;MR. FAIRHURST: .And to maintain even with natural 2l ventilation.--
3- MR. GREEN: A gap. 4 RMR . FAIRHURST: -- a gap with air. 5 MR. GREEN: Yes. 6 .MR. FAIRHURST: Presumably; at least if the 7 ' climate doesn't change that much over the next 10,000 years, 8 is generally low humidity. So how much will the fact of 9 having a constant ventilation eliminate or reduce the
- 10 dripping?
11 MR. GREEN: One of the - there are a lot of 12- analyses'we'd like to do and we've put on our to-do list and 13 we've never'gotten around to them. One is them is natural 1-4 convection that.would form, even in the case where the () 15 ' emplacement drifts are closed'off.and you can get natural 16- ventilation, along the' lines of Ed Weeks' work, that you can
- 17. -get something formed.
18; Especially if you have a variable heat load and l 19 4 you have heterogeneities in the medium, if you have an area 20 of lower permeability and-higher permeability, variable heat 21 load, you can get natural ventilation. If it's closed off, l ~22 ,the humidity is. going to be essentially 100 percent. 23 If: you have a source of air from the outside, it's 24 going to be low enough that you're going to remove all the 25' moisture.
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r. L 330 1 MR. FAIRr.1TRST : That's the key issue. If you have ! - [~) 2 a source of air from the outside, it's going to eventually QJ 3 remove all the moisture. Okay. 4 MR. GREEN: Right. So it's not been tempered by 5 the moisture. The mountain is very moist. The matrix
- 6. saturation is over 90. They've changed it a little bit in 7 light of recent measurements.
8 MR. GARRICK: I have no questions. Staff? Andy? 9 All right. Thank you very much. That was very interesting.. 10 Okay. I think we'll take our break, a 15-minute break. 11 I That will allow us to get a five-minute jump on the restart. 4 12 So by that clock, we want everybody in here by 20 minutes 13 to. 14 [ Recess.] f (j 15 MR. GARRICK: We're now going to get to the 16 chemical side of things, among other things, evolution of 17 the near field environment and committee member Ray Wymer 18 will lead us in this discussion, and Bill Murphy will be our 19 presenter. 20 MR. MURPHY: Thank you very much. I would first 21 like to acknowledge, in my first slide, there are quite a 22 lot of people involved in this project. It's very 23 multi-disciplinary field. 24 I would like in particular to acknowledge English l l
- 25. Pearcy, my manager, and Brett Lesley, NRC, the program 1 l
i (~T ANN RILEY & ASSOCIATES, LTD. (_s) Court Reporters 1025 Connecticut A"enue, NW, Suite 1014 i Washington, D.C. 20036 ! (202) 842-0034
331 ; 1 manager, have both contributed a lot, and a large number of i 2 people on both the NRC and CNWRA staff, and I will note some 3 of them as I go along. They have all contributed to this. I 4 In my next slide -- my next slide is the l 5 presentation outline, which is not the slide I'm looking at. 6 But.the presentation outline is essentially the same as in 7 the agenda. It's essentially the information that's in your ,
)
8 handouts and in the presentation outline, you will see it in 9 your agenda. 10 I will talk first about our view of 11 thermo-hydro-chemical effects on performance and that's a 12 major theme of the near field key technical issue; some of 13 the technical bases; some risk insights from performance 14 assessments; some of my personal views on design changes 15 significance, this is all relatively new; some of our
.16 progress, and some ideas for the future.
17 This diagram illustrates one set of systems for 18 organizing the various aspects of performance for the waste 19 repository, the proposed waste repository. The near field 20 key technical issue has direct connections with, I think, 21 seven of these 14 key integrated sub-issues. I won't go 22 through them in detail. But once again, I will emphasize 23 the fact that this is a very multi-disciplinary and 24 integrated study. 25 We've alluded to that already this morning, as O V ANN RILEY & ASSOCIATES, LTD. Court Reporters l 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
332 1 you've heard in the talks on the thermo-hydrology work and fs 2 the RETME work and also we're very close integrated with the (V) 3 container life and source term work, and also with 4 performance assessment people and so forth. 5 So Wes mentioned yesterday the advantages of the 6 kind of integration that can occur in a place like the 7 center and I appreciate that myself, as well, that there are 8- interactions among -- close interactions among many of us 9 and many of us are sufficiently good friends that we can 10 make off-the-cuff remarks about one another up here. 11 MR. GARRICK: You've been the victim of a few of 12 those already. 13- MR. MURPHY: The thermo-hydro-chemical effects on 14 performance are organized here in regard to the five key -- () 15 of the five sub-issues of this key technical issue, being 16' all focused on thermo-hydro-chemical effects or processes; 17 first, on seepage and flow of ground water; on the waste 18 package chemical environment; on the chemical environment of 19 the waste forms; on the chemical environment affecting 20 radionuclide transport in the near field; and, on 21 criticality in the near field, 22 There are potential THC processes on all of these 23 areas of the physical evolution of the near field 24 environment and they all have potentic.1 effects on 25 performance. Once again, I'll note integration with many I" ANN RILEY & ASSOCIATES, LTD. (_)/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
333 1 other key technical issues and a lot of that integration 2 occurs through the integrated sub-issues structure that's 3 been developed. 4 The summary of our current technical basis is a 5 rather generic survey of the kinds of information that we 6 make use of; site characterization data, lab data, et 7 cetera. You can read through this list. Performance 8 assessment in general and sensitivity studies and 9 abstractions for performance assessment in general. I refer 10 not only to the center's work, but to the DOE's work and 11 work outside of the NRC and the DOE, where we make an effort 12 to have a broad view of sources of our technical basis for 13 the conclusions and analyses we're doing. 14 In the next couple of slides, I'm going to show 15 rather in some detail, as much detail as we need, some 16 examples of results of the technical work that we've done , 17- that i .ustrate a variety of uses of these bases. I 18 In the next slide, this slide is -- I'll give you 19 the jargon first. It's a MULTIFLO calculation of one ! 20 component, dual continuum, two-phase fluid flow, about nine 21 kinetically reacting minerals, about 20 aqueous and gas 22 species, 60 metric tons of uranium per acre of thermal l 23 loading, which is the new DOE design. These are results of 24 the MULTIFLO calculations to separate -- somehow I went 25 forward. Can I go back a slide, please? ANN RILEY & ASSOCIATES, LTD. s Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
334 1 To put this in more general terms, this is a plot 2 of one particular chemical characteristic, the pH of the 3 aqueous solution as a function of depth in the repository, 4 calculated for both the ambient geochemical conditions, on 5 which there is quite a bit of uncertainty at present still, 6 and for thermally perturbed environment. 7 One sees that depending on how one interprets 8 measurements of the ambient chemistry in the near field i 9 environment or in the natural system, one can have various 10 boundary conditions for this kind of coupled reactive 11 transport modeling. One sees that the thermally perturbed I 12 case illustrated here is for a time of 50 years, which is 13 approximately the maximum temperature given by their dotted 14 curve, reaching near the boiling point of water. One sees 15 an excursion, a significant excursion in the pH. 16 That's not the only variation that occurs due to 17 coupled thermo-hydro-chemical effects. There are changes in , 1 18 chloride, there are changes in oxygen, there is mineral l i 19 dissolution and precipitation. 20 Our development and utilization of the MULTIFLO ' 21 code to model these processes is represented in this figure. 22 This, I must attribute much of the work here to Loren 23 Browning and Debra Hughson, who presented this graph in part 24 of an AGU presentation last fall. 1 25 I can go into -- or they could go into a great f ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
335 1 deal more detail, if you're interested. But one of the 2 points that I care to make is that we are making an effort (V~'i 3 to integrate aspects of our characterization of the site, 4 our knowledge of the site design, our knowledge of the 5 properties of the materials and the environment, are 6 modeling capabilities that were developed to couple 7 thermo-hydro-chemical effects to generate models relevant 8 for the repository. 9 MR. WYMER: What did the temperature go to there? 10 MR. MURPHY: Well, the temperatures on the upper 11 scale, the maximum temperature is about 100 degrees C. 12 MR. WYMER: I'm sorry, I see it. I didn't see it. 13 MR. FAIRHURST: What is the black bar? 14 MR. MURPHY: The black bar represents roughly the () 15 variation in pH due to -- during the thermally perturbed l 16 condition due to differing assumptions about the initial 17 conditions of the infiltrating solution, depending upon 18 differing interpretations of the analytical data for the 19 unsaturated zone ground water chemistry. 20 MR. FAIRHURST: Is it just essentially covering 21 the three analyses? 22 MR. MURPHY: Yes. 23 MR. FAIRHURST: It's just the span. 24 MR. MURPHY: Yes. The span of the three different 25 models illustrated in this graph for the thermally perturbed (
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336 1 system.and for the -- and the various -- this is something 2L that needs to.be clarified. 3 There are different models here. APPS is a 4- reinterpretation of the ambient ground water chemistry. 5 Yang's data are-the literal analytical values for the ground 6 Ewater chemistry.which can be demonstrated to be wrong, and 7 this is not a criticism of those data, they're very -- it's 8 a very hard thing to know, very hard to sample, but it -- I 9 .think it requires a reinterpretation in order to get more 10 realistic view of what the ground water chemistry is. 11 APPS has done that, we've done that. These 12 'various. approaches have been used for the modeling only to 13 set the initial conditions at the top of the model. 14 Everything below that depends on those initial conditions () 15 ,and then the subsequent reactive transport calculation of 16 gas and water. flow and mineral, gas, water, rock 17 interactions. 18 So there is one complicated slide that illustrates 19 many different aspects of our studies. The next slide, 20 which I can't get to either, it's that one, the next slide 21 shows another example of some of our relatively recent work 22 supported by the evolution of the near field environment 23 KTI, and once again, the jargon, this is a CCDF for 24 potential Yucca Mountain repository modeling the probability 25 of exceedence of peak annual doses, given on the horizontal ANN RILEY & ASSOCIATES, LTD. ss) Court Reporters j 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 , (202) 842-0034
337 1 axis, for a critical group located 20 kilometers from the ( ; 2 emplacement area, for time periods of 10,000 and 50,000 L ,/ 3 years. 4 And we have three different curves shown in this 5 diagram. The curves labeled by the lower cased symbols, 6 which are a little difficult to see, but they're the three 7 on the left, are for a 10,000-year period of performance in 8 which corrosion doesn't influence performance at 20 9 kilometers. The three curves on the right, indicated by the 10 upper case symbols, are three alternate models for this 11 CCDF, for a 50,000 year performance period. 12 And the three models are the results of complete 13 performance assessments, sampling, all the variables 14 generally in the way the 3.2 TPA code samples variables and () 15 calculates performance, varying only the source term for the 16 various comparisons. 17 The curves labeled B are the base case NRC source I 18 term model, which perhaps you'll hear about or have heard l i 19 about. I won't go into that in detail. The curves labeled j 20 N are based on an interpretation of the maximum average rate 21 of oxidation of urananite at the Pena Blanca natural analog l 22 site, which has been interpreted based on our field data and 1 i 23 radiometric dating of the site, and scaled to the Yucca l 24 Mountain system and applied to this performance assessment 25 calculation.
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338 1 And the curves labeled S are based on our
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{} 2 secondary schoepite, secondary uranium mineral, solubility 3 model. Dick Codell spoke yesterday about these alternate 4 source term models and this is an example of the work that 5 Dick and I have worked on together, along with others. 6 One sees that both the natural analog and 7 schoepite alternate source term models give substantially 8 lower doses than the NRC base case model. I'd prefer not to e-9 make the case that either of these is a conservative model 10 in every respect, in many regards, particularly the 11 schoepite model can be criticized for being non-conservative 12 in many regards, 13 But I think there are very large uncertainties in 14 the NRC base case model and in the natural analog and () 15 schoepite solubility models and that an appropriate approach 16 to dealing with this uncertainty through sensitivity 17 analyses, such as these, in which we consider the system 18 from various points of view and take alternate conceptual 19 and numerical models to evaluating the significance of the i 20 source term. 21 Now, this is work sponsored by the near field 22 environment key technical issue, because, to a large extent, 23 the evolution of the waste forme depends on the chemistry of 24 the near field environment, the oxidation of the waste forms 25 in particular, and the potential incorporation of secondary ANN RILEY & ASSOCIATES, LTD. C-)' Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 I
339 1 -- of radionuclides in secondary phases. ( } 2 I can talk about this in a great bit more detail, 3 if you'd care, but once again, my main point is to 4 illustrate that v e are coupling our work with performance 5 assessme'nt. We're drawing from our natural analog studies, 6 from our understanding of the Yucca Mountain system, and we 7 have a fairly integrated approach here. 8 The next slide illustrates my view of some risk 9 insights from performance assessment and for those of you i 10 who saw Dick Codell's talk yesterday, you will recognize 11 that it's not necessarily an easy thing to do to e 1blish a 12 unique way to identify where the potential risk is and where 13 it's not. 14 He showed a variety of ways of testing () 15 sensitivities to the model. In one of the sets of slides he 16 showed, he illustrated the quantity and chemistry of water 17 contacting the waste package has a major ef fect on predicted 18 performance. 19 Among the integrated sub-issues, this one 20 repeatedly comes out as being a dominant issue. It's 21 strongly affected by the evolution of the near field 22 environment to the extent that the evolution of the near 23 field u;aironment af fects permeability and porosity of the 24 surrcunding rocks and it affects flow, it affects the 25 chemistry of the water that may interact with the waste O ANN RILEY & ASSOCIATES, LTD. k s/ m Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842 0034
340 1 package and the waste form. /T 2 I showed in the previous slide how alternate b 3 source term models can have a large effect on predicted 4 performance, and so one of the risk insights I drew is that 5 alternate source term release rates can have a major effect 6 on predicted performance assessments, even though that 7 wasn't illustrated by the particular judgment of relative 8 significance of key technical or integrated sub-issues in 9 Dick's talk. j 10 That showed up very clearly in his ranking of 11 alternate models and the sensitivity studies, in which he 12 showed that these particular natural analog and secondary 13 phase-based source term models showed the very lowest 14 releases in all of the alternate models he tested. 13 Q 15 In contrast, there are a number of risk 16 uncertainties that still exist in performance assessments as 17 they have been performed, and in my view, part of the reason 18 for this is the exceptional complications associated with 19 coupled thermo-hydro-chemical and mechanical effects, and I 20 know this is an issue that the ACNW is aware of and has made 21 a point to pay attention to the development of the way and 22 the manner in which we address these coupled processes. 23 Some things are simply not in NRC's performance 24 assessments at present. Near field criticality is not 25 considered at all. I think that's a very reasonable thing. ANN RILEY & ASSOCIATES, LTD. A Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
341 l l 1 It's one of the sub-issues in the near field key technical l /~N 2 issue that I believe will be resolved or closed eminently. b 3 I think that's a reasonable thing not to include in our I 4 performance assessments, based on auxiliary analyses. 5 Our near field chemical effects on the flow regime j 6 are not presently included in NRC's performance assessment. 7 Now, there as some discussion in the previous talks about 8 the potential effects of thermal-mechanical effects on the 9 flow regime. The potential effects of chemistry on the flow 10 regime in the near field are really very enormous and there 1 11 are a lot of field data, there are a lot of lab data, and 12 there are emerging modeling data to sustain this idea from 13 our work, as well as in work supporting the DOE TSPA. 14 In the near field altered zone models report, () 15 there is a sensitivity study presented in which there is a 16 one chemical component reactive transport model presented, i 17 and this is the most sophisticated model I've seen applied 18 in performance assessment at that level, and they showed 19 enormous variations in permeability and porosity due to l I l 20 formation of a silica cap above the emplacement horizon. l l
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21 None of this is taken into account in anyone's , l 22 performance assessments strictly at present, and this is a l 23 big uncertainty, I think, that still needs to be addressed 24 and it's one that we're working toward and the DOE is I l 25 working toward. This is not intended to be a criticism of (g ANN RILEY & ASSOCIATES, LTD. (m,/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 l (202) 842-0034 I
342 1 anyone's work. It's just a statement of where we stand at 'A 2 present. 3 Temporal changes in near field chemistry are 4 potentially included in our TPA code. It's designed to be 5 flexible to adapt to various conditions, but presently, 6 chemical environments for each realization in the NRC TPA 7 code are constant, regardless of the thermal regime. 8 Infiltration changes, temperature changes, 9 chemistry is constant for every realization. This is not 10 very realistic at all. I think that DOE recognizes this, as 11 well. In TSPA/VA, they've taken a step, what I think is an 12 important step forward in recognizing the temporal variation 13 in chemistry during the thermal period and in their TSPA/VA, , 14 they have, I think, five periods of different chemical () 15 environments that may interact with the waste package and 16 the waste form, and I think this first attempt in TSPA/VA is 17 a laudable or important advance and I think we need to be 18 moving in the same direction in our own performance 19 assessments. 20 MR. FAIRHURST: Is there any general statement you ; i 21 can make about the effect of chemistry, such as it will it l 22 increase the permeability and then decrease it further out? 23 MR. MURPHY: I think that the general statement 24 that can be said is that, yes, it will increase the i' 25 permeability in porosity in some places and decrease the I~' ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenae, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
343 1- permeability in porosity in other places. rs ( 2 MR. FAIRHURST: In some places and other places -- (_ 3 I asked more specifically, is it going to be in the 4 immediate vicinity of the excavation, it's likely to be 5 dissolution, and, therefore, probably precipitation further 6 out. { { 7 MR. MURPHY: In general, precipitation will occur 8 in areas of evaporation, where water is evaporating or water 9 is becoming more concentrated, minerals will be precipitate, 10 precipitation will occur where water .xists, that's 11 predominantly in the matrix. The fractures will be 12 predominantly gas fill. Dissolution will occur where water 13 condenses, because the water vapor is essentially distilled I 14 water. It may have elevated CO2 pressures, it may be () 15 slightly acidic. Dissolution will occur predominantly where j 16 water condenses. This may be on fracture linings, where 17 there may be particularly susceptible minerals to 18 dissolution, such as calcite. 19 So that's a general answer to your question. 20 'Maybe I can be more specific. 21 MR. FAIRHURST: We'll talk about it later, Bill. 22 MR. MURPHY: I'd be happy to. 23 MR. FAIRHURST: Yes, I'd like to. 24 MR. MURPHY: I think that with regard to the 25 extent of these changes, it will -- it depends on time and i ANN RILEY & ASSOCIATES, LTD.
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i 1 1 i 344 I 1 it will depend on the thermal loading very much. I l [~'\
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2 So in my following slide, that's one of the points ) 3 that I address explicitly right up front. { I think that i 4 there are potentially a lot of responses of the evolution of 5 the near field environment to the proposed DOE design 6 changes, the abr.ence of concrete liners affects near field 7 . chemistry, *he iltroduction of backfill affects the near 8 field chemistry, addition of titanium drip shields, I don't 9 think anyone has looked very carefully about the extent to 10 which this might affect near field chemistry. 11 People have considered it in regard to flow, maybe 12 it's inert, maybe it's not, I'm not sure. The lower thermal 13 loading will affect the chemical regime in the near field 14 environment. The line loading, as well, could affect the l () 15- distribution of flow and the distribution of chemical 16 ' effects due to a couple of thermo-hydro-chemical effects in 17 the near field. I 18 So I think that there are potentially important 19 consequences of the DOE design changes to the evolution of 20 the near field environment and I thi.1k that for the most 21 part, these changes make the problem somewhat easier, make 22 the technical aspects of the problem somewhat easier. 23 The non-coalescing boiling isotherms between the 24 drifts allows the system to remain relatively more like the 25 ambient system in the pillars. That's much easier to model
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345 1 than more or less continuous silica cap that might cover ["') x_- 2 square kilometers. 3 The-absence of concrete greatly simplifies the 4 chemistry in the near field. The lower temperatures greatly 5 simplify the calculations of the evolution of the water 6 chemistry and the mineral chemistry. So for the most part, 7 I think the DOE design changes make the technical aspects of 8 the_ evolution of the near field environment and particularly 9 the chemical environment somewhat easier to address. 10 On the other hand, there are some new issues 11 introduced in the design changes, the effect of titanium I 12 touched on, the effect of backfill on seepage is an issue 13 that hasn't been very well studied, to my knowledge. I've 14 heard people speculate about certainly asparities in the f e 15 drift walls, but how about the flow field of the backfill N. I 16 material and its evolution with time due to l I 17 thermo-hydro-chemical effects. 18 The steep thermal gradients, steeper thermal 19 gradients as a consequence of backfill may have some impact 20 that I don't think has been studied very seriously at 21 present, and there may be interactions newly introduced 22 materials that haven't been thoroughly considered. 23 So I think we need to respond to DOE design 24 changes, we need to be aware of it, and we need to be 25 flexible in adapting to their design changes. /~ ANN RILEY & ASSOCIATES, LTD. ( ,N/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
346 l' In the next slide, I'd like to report en some 2 recent progress and accomplishments. ( ) We've revised the 3 evolution of the near field environment IRSR with 4 applications of the acceptance criteria developed in 5 previous revisions of the IRSR, specifically to a review of 6 DOE's TSPA/VA with some very specific comments about whether 7 or not we believe that their VA performance assessment meets 8 the acceptance criteria, as we have posed them. 9 We have done a number of sensitivity studies of 10 alternate source term models based on natural analog data 11 and secondary mineral solubility. Some of those results I 12 showed you previously. We're planning for laboratory and I 13 theoretical studies on cementitious materials and for the i 14 role of secondary uranium minerals in the evolution of the l m ( \ ) 15 near field environment and on performance. 16 We're developing, we're continuing to develop our 17 coupled reactive transport model, MULTIFLO. We've done some 18 serious benchmarking exercises with other well established 19 codes and analytical solutions recently, and we're making 20 applications, as I showed in a previous slide, to the new 21 design, thermal design for the Yucca Mountain, proposed 22 Yucca Mountain repository. l 23- Also, we are trying to maintain close interactions 1 24 with the DOE. We've attended the DOE workshops on how they { l 25 plan to deal with near field and waste form issues. l l /~^ ANN RILEY & ASSOCIATES, LTD. l k_ Court Reporters ! 1025 Connecticut Avenue, NW, Suite 1014 i Washington, D.C. 20036 ' (202) 842-0034 l
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347 1 Particularly, Brett Lesley is a regular participant in the (yj r 2 thermal testing workshops. We participate in the natural 3 analog working group, which is an international organization 4 .that deals largely with -- not largely, but among other 5 things, with evolution of waste forms in a repository 6 environment. 7 I'll mention incidentally that our natural analog 8 work, which is supported by the near field environment 9 project, has progressed quite far and this week, the 10 Department of Energy is making their first research trip to 1 11 Pena Blanca. !
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12 We also attend other public meetings and make ! 13 publications and presentations and so forth. So we're quite 14 active in trying to keep up with the moving target and with (Or,j 15 developments in our own abilities and data. 16 Then the path forward, we're interested in closing 17 KTI sub-issues. I think near field criticality is one 18 likely to be closed in the near future. We're looking 19 forward to a revision of the near field IRSR with the 20 movement of acceptance criteria into the license application 21 review plan, to which we're contributing. l 1 22 We're not closing interactions. We have close 23 interactions with other KTIs to address integrated 24 sub-issues. We're continuing to do and contemplate i 25 sensitivity studies regarding design changes and our own O
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348 11 enhanced modeling capabilities, and enhanced and enlarged database coming from the thermal testing regime in L 2 3 particular. 4 We have laboratory and theoretical studies of
'5 cementitious~ materials.and secondary minerals in the 6_ planning and underway. We. plan to continue making use of 7' our natural. analog studies at Pena Blanca to address issues 8 of. alteration rates,-as an alternate source term 9 consideration.
I 10 We're reviewing DOE FEP, feature-event-process 11 data list for coupled thermo, hydro, chemical and mechanical 12 -issues specific to Yucca Mountain. It's not clear that l 13 their feature, event and process list is necessarily 14 comprehensive with regard to the things that we think need () 15 to be considered. 16 And furthermore, and finally, we're planning for 17 performange confirmation period, partly because this is a 18 difficult' issue. Not every question is going to be answered l 19 to-everyone's satisfaction. We anticipate that the DOE will 20- state that in their license application and will have a plan 21' for future studies and a plan for confirmation, and we need l l 22 to be aware in planning for that as well. 23 That finalizes my formal presentation and I'll
'24 entertain questions. Also, I'll be in the lab this I i
25 afternoon. ) ANN RILEY & ASSOCIATES, LTD. O- Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 i (202) 842-0034 i
l l 349 l l 1 MR. WYMER: I think you've done a very good job of I'^)
'uJ 2 pointing out the complexity of the chemical system and, in l
3 particular, the way it couples to all these other areas. 4 You said seven out of the 14, and maybe there's even more 5 than seven. 6 MR. MURPHY: It may be more, right. 7 MR. WYMER: So it's an extraordinarily complicated 8 system. I made a couple of notes as we went along. One is, 9 I'm always concerned about what abstraction of the model 1 j 10 does in the way of losing important things. This is, I l 11 think, particularly important in the case of coupled 12 chemical processes. 13 In general, when you talk about coupled processes, 14 in general, here at the center, you're talking about (r\ N. j 15 coupling among the various systems and subsystems that you 16 show on your flow-down chart, but there also is a l 17 refinement, as you know better than I do. The coupling of 18 the chemical processes themselves, which are so 19 inter-dependent one upon the other as things change, which 20 is a good deal mcre subtle than coupling these other 21 processes. l 22 MR. MURPHY: It appears you understand that very 23 well, too. 24 MR. WYMER: So you worry about the abstraction 25 sort of losing those sorts of things. How comfortable are
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350 1 you about that? 2 MR. MURPHY: [')) I will address that in the way I 3 perceive that you intend it. There are a lot of coupled 4 chemical interactions simply regarding the system as a 5 chemical system, and the first order way in which that is 6 addressed is to regard parts of the system to be at 7 equilibrium, to be representable by chemical equilibrium 8 relations in which we have mass action relations. They can 9 be solved sometimes analytically, in general, numerically, 10 and where we have data to support those equilibrium 11 relations, that's a very nice abstraction for a performance 12 assessment. 13 Now, in other cases, at the other extreme, there 14 are reactions that simply don't occur, even though there is ("% () 15 a chemical potential for those reactions to occur, they 16 don't occur over very long timeframes. 17 This goes not -- this ranges not only from the 18 natural system where there is metastable glass at Yucca 19 Mountain that's 12 million years old tc metals that are 20 predicted to persist for -- in an oxidizing environment at 21 Yucca Mountain for tens or hundreds of thousands of years. 22 There are some reactions that are so slow that chemical 23 equilibrium is an inappropriate approach and one needs to 24 address various aspects of the kinetics. 25 At one limit of that, one assumes that certain
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351 1 parts of the system are inert. In our ambient system [~^ 2 models, I think it's reasonable to consider that quartz is 3 inert in the ambient system. The reaction rates are -- it's 4 a dominant component of the natural system, but the reaction 5 rates are just too slow for it to be an important component 6 of the chemical evolution of the ambient system. 7 It's persisted there for 12 million years, but the 8 waters are ten times super-saturated with respect to quartz. 9 Other parts of the system do react kinetically. 1 10 The glass in the ambient system at Yucca Mountain has 11 altered substantially to a secondary suite of minerals, 12 zeolites and smectites. There is secondary calcite in the 13 system. 14 The introduction of a thermal field, the () v 15 introduction of coupled thermo-hydro-chemical processes in 16 the repository will induce these kinds of alterations to the 17 environment in which some kinetics will have to be regarded. 18 MR. WYMER: Can I -- 19 MR. FAIRHURST: Had enough? 20 MR. WYMER: Can I assume from that that you are -- 21 MR. HORNBERGER: You deserved it. 22 MR. WYMER: -- that you are comfortable -- my 23 question is, are you comfortable. 24 MR. MURPHY: Well, there are -- I'm comfortable 25 with some things and very uncomfortable with other things.
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1 l i 352 j 1 MR. WYMER: That's what I would have said from 2 what you just said, yes. (
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3 MR. MURPHY: And I will tell you that some of the l 4 things I'm very uncomfortable with are the properties of the ! l 5 secondary phases that ultimately will control much of the 6 source term at the repository. 7 MR. WYMER: I couldn't agree more. l { j 8 MR. MURPHY: I'm very uncomfortable with that at l 9 the present, and we have an experimental program that was 10 initiated under the NRC research program many years ago and i 11 terminated when research support for this program was { l 12 terminated. l l 13 It's now reinitiated, and so we're trying to make 14 progress there again. I'm uncomfortable with the virtual fI 15 complete neglect of the changes to the hydraulic system due 16 to chemical processes in the near field in performance 17 assessments, and that's an area in which we're making an 18 effort through our coupled thermo-hydro-chemical modeling to 19 address those things we're most uncomfortable with, l 20 MR. WYMEE Grnat. Okay, fine. That takes care l 21 of that. That's ri 's what I would expect as an 22 answer. 23 One of your viewgraphs says the near field 24 transport phenomena have small effects on performance. Of 25 course, that's in the context of the current design and l l I ANN RILEY & ASSOCIATES, LTD.
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i 353 1 everything else. I~ \ 2 MR. MURPHY: And in the context of the current () 3 performance assessments. 1 4 MR. WYMER: There are ways that things could be
-5 changed where that would not be true.
l 6 MR. MURPHY: That's true. In fact, DOE has done l 7 some sensitivity analyses in which they have increased the 1 8 porosity-of the invert materials to a substantial degree, l 9 such that the flow transit times coupled with the sorption 10 on the invert materials actually can lead to a significant 11 retardation in the near field. 12 One can imagine some cases where near field 13 chemical effects could effect transport potentially, but in 14 the present generation of performance assessments, m [dl 15 particularly in NRC's present generation of performance 16 assessment, near field transport issues are not. 17 MR. WYMER: Which is an artifact of their 18 particular -- 19 MR. MURPHY: Well, it's part of the process of 20 abstraction. l 21 MR. WYMER: Yes. Another viewgraph, you say some 22 near field, new near field coupled technical issues are 23 relatively unstudied, and you say the effects of backfill on 24 seepage. I just wondered why you didn't add chemistry. 25 MR. MURPHY: I think that that's a -- I should add i
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354
.1 it. I think that the effects of the backfill on the
(~'J 2 chemistry will be -- and I'm speaking very, very ws 3 spontaneously now. 4 MR. WYMER: Please do. 5 MR. MURPHY: I think that the chemical effects 6 will be similar or that we'll be able to handle them in a I 7 manner very similar to the way in which we are addressing i 8 the chemical effects in the ambient system, because the 9 backfill is envisaged to be crushed tuft or maybe silica 10 material, and I think that in general, the tools that we've i 11 developed over the years to characterize the natural rock 12 system will be very appropriate for addressing questions 13 about the chemistry of the backfill, unless someone comes up 14 with some exotic backfill, which I wouldn't advocate, i )j t' 1S MR. WYMER: And on the progress and 16 accomplishments viewgraph, you said planning for laboratory
-17 and theoretical studies of cementitious material for 18 secondary alteration phases.
19 That means the cementitious materials are the 20 kinds of things that would form due to the stuff that's 21 coming in and the things that dissolve and the reactions. 22 It's not cement contained in the drift. These are 23 cementitious materials. 24 MR. MURPHY: In fact, what I intended by that 25 slide was to address two related, but somewhat different - (~h ANN RILEY & ASSOCIATES, LTD. () Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
355 1 sets of studies, one in which we're looking at the stability 2 of uranium minerals, and one in which we're looking at the ()) 3 properties of the phases that make up what would potentially 4 be a concrete or cement, as a function of temperature. 5 MR. WYMER: That's a little bit broader than I 6 picked out of that, but that's fine. 7 MR. MURPHY: I put those both in the same line, ) 1 8 but there really are separate studies involved. I 9 MR. HORNBERGER: Is this because you anticipate 10 that the DOE design of a month may return to concrete liner ! 11 or is it because you already had the studies started and you 12 want to see it through? 13 MR. MURPHY: Both. We already had those studies 14 started. I think it's reasonable to see them through and b] 15 that I am not convinced that concrete won't come back. 16 MR. WYMER: That's all I had. 17 MR. LESLEY: This is Brett Lesley, from the NRC 18 sta,ti. The other aspect of it is if they're going to go for 19 a rock fall, as suggested, they would build a fully grouted 20 rock fall. So one of the actions I've taken is to make sure 21 that the center's work on the cementitious materials is 22 relevant both not just to the cement liner, but also to 23 grout material. 24 MR. WYMER: Yes. One of the questions that I had 25 was just how much cement is there in the drift in the new ANN RILEY & ASSOCIATES, LTD. O) (. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
356 1 design, but that's another issue. We won't talk about that
#'T 2 here.
3 MR. LESLEY: Actually, I would like to follow up 4 on that. In fact, what we have noticed, that in terms of i 5 alcove seven and also in the drift scale heater test, in 6 fact, Debra Hughson made this observation, is that the 7 dripping that occurred even under ventilation was only under 8 the rock fall. 9 So when she was wheeling along on the floor, she 10 noticed that there was concrete type of deposits -- 11 MR. WYMER: Stalagmites. 12 MR. LESLEY: -- on the floor and those were 13 associated with the dripping of a cementitiously grouted 14 rock fall. () 15 MR. WYMER: I see. Okay. 16 MR. MURPHY: This is Brett Lesley speaking, by the 17 way. Thanks, Brett. 18 MR. WYMER: Yes, thanks. 19 MR. GARRICK: Bill, this committee visited Europe 20 last week or last year and had discussions with the Germans 21 and the French and the Swiss and what have you, and they 22 made the frequent observation that the United States is 23 living up to its reputation of continuing its search for the l 24 most complicated possible design to dispose of high level l 25 waste. l (~}
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ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
357 1 Of course, we've always been preaching that one 2 way to decrease the uncertainty in the performance 3 assessment would be to move, wherever possible, in the 4 direction of simplicity. 5 One way to eliminate the uncertainty of a specific 6 phenomena or reaction is to eliminate it. 7 Are you convinced that the design changes that are 8 being proposed -- and you have delineated some advantages
'9 and disadvantages here. Are you convinced that these design 10 changes are indeed moving in the direction of simplicity as 11 far as the overall decign is concerned?
12 _- MR. MURPHY: I wouldn't say that I'm absolutely 13 convinced, but I'd say I'm persuaded in that direction. I 14 believe that the design changes have simplified things with () 15 regard to the thermal loading in particular. I'm not sure 16 that the backfill or the drip shield simplifies things in 17 that regard. 18 MR. GARRICK: Are you -- one of the members of 19 this committee, of course, is very high on changing the 20 natural setting in such a way, engineering the natural 21 setting in such a way that we get some real advantages from 22 it in terms of eliminating some of the uncertainties. 23 What is your perspective on that? 24 MR. MURPHY: I'll be frank. My perspective is 25 that Yucca Mountain is a mountain and it's hard to change a (~ ANN RILEY & ASSOCIATES, LTD.
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358 1 mountain. i j 2 MR. SAGAR: As simple as that. 3 MR. GARRICK: You can't make a mole hill out of a 4 mountain? 5 MR. SRIDHAR: Dr. Garrick, can I take a shot at l 6 your question regarding simplicity and complexity? 7 MR. GARRICK: 'Yes. 8 MR. SRIDHAR: Perhaps give a corrosion engineer's 9 perspective. Again, just for the record, Narasi Sridhar, 10 from the center. 11 I also have had discussions on various MRS 12 meetings with Europeans and Japanese regarding complexity of 13 design and simplicity of design, and most people, when they
-14 refer to simplicity of design in terms of waste package only O 15 and not addressing other issues in terms of repository,
( j 16 would say, well, copper and steel are very simple materials 17 and very_ simple designs, we know archeological artifacts of 18 steel-and copper have existed, so why can't we design. 19 And it is not, in my opinion, that simple. From a 20 corrosion and electro-chemical perspective, copper and 21 steel, especially in an oxidizing environment, like Yucca 22' Mountain, are the most complex materials to understand. 23 When we initially did have copper in the program, and when
'24 we started looking at it, we felt that as opposed to 25 nickel-based alloy, like C-22, the number of environmental O ANN RILEY & ASSOCIATES, LTD.
Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
359 . i 1 parameters, chemistry-wise, that we need to understand to (} 2 characterize the behavior of copper is much, much more 3 complex than that of something like alloy C-22. Because 4 copper, for-example, if you have five different species, 5 bicarbonate chloride, sulfate, they all have an interactive 6 effect. 7 So you have a five-term interaction to 8 characterize the-copper behavior, but as for an alloy like 9 C-22, the one thing you need to most necessarily understand 10 is chloride concentrations. 11 So it is actually more -- maybe metallurgically 12 more' complex than copper, but electro-chemically, it would 13 be actually a simpler material. 14 So what some may consider to be simple and complex D i) s 15 design perhaps from a geochemical perspective may not be the 16 same from some other perspective. That's all I want to say. l 17 MR. GARRICK: Stay here a minute. Do you think l 1 18 that there is opportunity for simplicity with respect to 19 something like, for example, welding? As one speaker of a 20 meeting several times ago indicated, there's 30,000 feet of 21 welds in this. 22' Based on what we heard earlier today, the welds could be one l 23 of the vulnerable points of the integrity of the containers. I l 24 MR. SRIDHAR: Yes. I think this is something, ! l 25 maybe I'm stealing Gustavo's thunder, but basically we are ANN RILEY & ASSOCIATES, LTD. k Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 l Washington, D.C. 20036 l (202) 842-0034 L
360 1 addressing that. The main concern is not with all the
} 2 30,000 meters or'whatever it is'of weldments, because most 3 of the weldments that are premanufactured will be annealed, 4: and Tna are not-concerned as much about those weldments.
5 What-we are concerned about.are the-closure welds, 1 l 6 which cannot be' annealed because of the temperature 7 limitations on'the cladding. 8 So those are the ones we are focusing on. Having 9 said th'at, what we are finding, and this is something we are 10 continuing our experimental work to confirm, that the weld i 11 corrosion resistance may be lower than that of the unwelded 12 material, but it may not be sufficiently low to have a big l .13 difference in the performance. That is something we need to 14 complete our determination. O) ( 15 So I think we are simplifying the problem a little 16 bit in terms of focusing on only the welds that are of 17 importance, and we feel that we have a way to handle the 18' -effect of weldment on performance. I think Gustavo will 19 talk about that this afternoon. ; 20 MR. GARRICK: Y e' s . ! l 21- MR..FAIRHURST: With regard to C-22, I think 22 'Shumaker has suggested that there is a temperature below i 23 which a' lot of these issues will go away, right? l 2:4 MR. SRIDHAR: Right. l
)
25 MR. FAIRHURST: And the same with humidity. Now, l i l O ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 l (202) 842-0034
361 1 as I understand, with C-22, humidity is not that serious a 2 problem. 3 MR. SRIDHAR: In the sense that in a -- 4 MR. FAIRHURST: The other design, with the carbon 5 steel on the outside. 6 MR. SRIDHAR: Well, the alternate wet and dry 7 environment is not as serious a problem with C-22 as with 8 carbon steel. You have a humid and then a dry environment. 9 MR. FAIRHURST: And as far as an engineering 10 designer, would you say that if we can keep the humidity 11 down below X percent and the temperature below X degrees, 12 that will simplify these problems? 13 MR. SRIDHAR: Right. 14 11R . FAIRHURST: What are those numbers for I () 15 carbon-22? 16 MR. SRIDHAR: Well, for the C-22, the current 17 assumption that DOE is making is 80 degrees Centigrade is 18 the limit. 19 We are examining the technical basis for it. So 20 far, our experimental work has shown that that is a 21 relatively conservative temperature limit, lower, for { l 22 localized corrosion. . 1 23 MR. FAIRHURST: They bring it down to 80. 24 MR. SRIDHAR: Yes. I think they have a range 25 between 80 and 100 that they sampled and our experimental i C') k_/ ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
362 1 work has indicated, again, I may be talking in advance on m I ) 2 what Gustavo is_ going to be saying, that that is a V 3 relatively conservative temperature as far as what we have 4 examined. 5 It's something that we would like to continue to 6 examine and welding the C-22 will tend to affect that 7 temperature, so that's something we are examining, too. 8 MR. FAIRHURST: And in the absence of water, you 9 greatly simplify the problem. These are specifics. Like I 10 want to come to Bill and say give me some specifics that you 11 say you can do that, and I don't have a problem with it. 12 That's, I think, what the intent of John Garrick's question, 13 to say what is the simplification. 14 MR. MURPHY: I think I would like to say that I () 15 answered the last question rather glibly about effects on 16 Yucca Mountain of engineered materials and design and 17 simplicity. I'm saying that the question was directed in 18 particular towards the oxidation state of the environment. 19 Clearly,.when you take a massive amount of highly 20 reducing materials, like spent nuclear fuel and the metals 21 of the containers and the steel sets and so forth, and you 22 put it in a thoroughly oxidizing mountain with a gas phase 23 that's air and no reducing capacity at all, it will generate 24 huge potential gradients that will, over a very long time, 25 have to reequilibrate and will reequilibrate. 1 1 ANN RILEY & ASSOCIATES, LTD. O' Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
363 1 And I think that where circulation will occur in
'N
[d 2 3 the system, there will be oxidants reintroduced through that system and that is where corrosion will occur and releases 4 will occur and transport will be a problem. 5 So it's hard to change a mountain, but 6 nevertheless, I think putting a repository in there will 7 lead to some big effects. 8 MR. HORNBERGER: Well, you just said that by 9 putting the stuff in, you're changing the mountain. You're 10 changing the equilibrium, right ? 11 MR. FAIRHURST: Bill, in an earlier part, one of 12 the rock mechanics concerns is the long-term degradation of 13 the joint strengths. Now, is it feasible, from what you're 14 saying, that you could actually have a long-term () ( 15 augmentation of joint strengths by precipitation along those 16 joints, so that degradation may not be as serious a problem? 17 MR. MURPHY: I think, absolutely, in parts of the 18 system,-there could be strengthening of rock joints. 19 MR. FAIRHURST: Th.it's what I would look for. I 20 know-that this is -- my comment about your paper was complex 21 as hell, because that's the message I got. You're te.'. ling 22 us what is the truth, of course, but I'm saying out of that 23 complexity, what can we find that's either something we've 24 got to design to avoid or something that we will be helpful. 25 There are some codes right now, mechanical, }
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1 l 364 l 1 thermal-mechanical codes which will allow you to consider i ['T O 2 the possibility of changing things like cohesion, joint 3 stiffness, et cetera, as a function of time, over extended l 4 periods of time. They're not in a very advanced state, but l 5 the idea is to include chemical and we need good chemists to ! 6 come and sit with us and say, well what weight of l 7 strengthening are we going to get or are we not going to ' 8 get. 9 And this has considerable implications for doing 10 it in a thermal environment, you're clamping the joints at 11 the same time, does the process accelerate or decelerate 12 under a -- it's like when you're welding, slam them together 13 and then weld them. 14 MR. MURPHY: Thank you for another complexity. I (S) 15 MR. FAIRHURST: It's a complexity which is either l l 16 beneficial or counter. So then you sit down and say, well, ; 1 17 you design to include it or you design to avoid it. I 18 MR. MURPHY: That's a complication and it's one 19 that I think could be very interesting to pursue at some 20 point. I have a counter question. I still have five 21 minutes for discussion, I think. I think that the most 22 vulnerable phase at Yucca Mountain to alteration is glass. 23 Much of the mountain is volcanic glass. 24 During its 12 million or 14 million year history, 25 that is the phase that has been altered. Much of it has ANN RILEY & ASSOCIATES, LTD. U(N Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
365 1 been changed from glass to zeolites. Is that going to have () V 2 an effect on the mechanical behavior of the system? 3 MR. FAIRHURST: How fast is it happening? 4 MR. MURPHY: That's a big -- in the natural 5 system, that's somewhat of an open question. There are 6 certain people who say that it happened very rapidly during 7 a relative -- on a geologic time scale -- shortly following 8 the eruption of the volcanic materials during a sort of 9 -thermal cooling event, which may, in some regards, be 10 comparable to the thermal conditioning due to the 11 repository. 12 MR. FAIRHURST: Well, I think it's a good thing to 13 explore. 14 MR. HORNBERGER: Bill, in terms of your lab and ('N! g 15 theoretical studies on secondary alteration phases, when x_/ 16 you're looking at these uraneal minerals, you're also 17 looking at the incorporation of important things like 18 neptunium. 19 MR. MURPHY: Yes, indeed, and that's a very hot 20 topic right now, because of particular speculations that 21 that may occur because laboratory data from Argonne have ' 22 showed that in vapor phase tests, there is neptunium 23 incorporated in secondary schoepite that may be ten times 24 its concentration in spent fuel relative to uranium. 25 There are crystallographic arguments that there's j l l l l ,C') ANN RILEY & ASSOCIATES, LTD. (,/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
366 1 space in these secondary uraneal phases for maybe a 2 relatively broad suite of the second -- of the minor ( 3 radionuclides.
.4 Our tests are designed ultimately to look at 5 issues of what we call co-precipitation. A dominant phase 6 will be precipitated. That will be a uraneal phase, it may 7 be schoepite, it may be uranifane. We're choosing to study 8 uranifane. It is the dominant secondary uraneal phase. The 9 dominant secondary phases at Yucca Mountain are calcium 10 phases.
11 I think that uranifane is a likely dominant 12 secondary phase in the long-term for Yucca Mountain. So 13 that's one of the reasons we have chosen to study it. 14 We're considering and designing experiments to (A) 15 look in particular at neptunium co-precipitation in 16 uranifane. 17 MR. HORNBERGER: So you're looking at the 18 'co-precipitation and then you're subsequently going to look 19 at remobilization, kinetic controls on dissolution? 20 MR. MURPHY: I'd love to, yes, and that sounds -- 21 and people -- that sounds like fun. People have talked 22 about that, in fact. That's discussed in the performance 23 assessments, that in particular, in regard to the Argonne 24 experiments, which are very long-term experiments, five and 25 ten and 15 year experiments, and very short experiments ANN RILEY & ASSOCIATES, LTD. Os Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
367 1 compared to the' evolution of the near field environment at
'2 Yucca Mountain. repository.
3 What.they see and what one can envisage is initial 4 precipitation of a relativelyf less stable phase, maybe 5 schoepite, which mayLbe-less crystalline, have'less 6 crystallinity, more capacity for co-precipitation, a
- 7. secondary species, a subsequent recrstyallization or f
8 ripening, crystallization of more stable phases which may.or 9 may not incorporate the secondary components as easily. 10 In some cases, there may be. crystalline sites in 11 the more stable crystalline phases that better accommodate 11 2 - the trace radionuclides. That's a problem that I don't 13 think that short-term. experiments or crystallographic i I 14 studies or natural analog studies alone can address, but I () 15 think it's a good one to be looked at. 16 MR. WYMER: Do you have the capability here at the 17 center to do experimental work of things like neptunium and 18 technetium? 19 MR. MURPHY: Yes. We have done and are doing 20- experiments with' neptunium and plutonium and technetium and 21- other things. 22, lMR . 'WYMER: Just at the tracer level. 23 MR. MURPHY: At tracer levels. The institute has 24 hot cell facilities that we at present have not used for -- I 25- in support of the Yucca Mountain work, to my knowledge. ANN RILEY & ASSOCIATES, LTD. 0s"- Court Reporters 1025 Connecticut' Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 n
368 1 MR. WYMER: I think we've wrung you out. () '2 MR. MURPHY: I'm willing to stay longer. 3 MR. GARRICK: I think we're in very good shape. I 4 want to thank all the presenters for following the rule of 5 allowing some-of the time for questions and discussion. It l 6 was an excellent job, both today and' yesterday. 7 All right. I guess now it's time for us to 8 adjourn for lunch and as I understand it, we're going to 9 have the tours of the labs following lunch. Where do we 10 rendezvous after lunch? l 11 MR. SAGAR: We would be with you at lunchtime and 12 would direct you_to the labs 13 MR. GARRICK: And we'll be back here at 3:15, 14 [Whereupon, at 11:45 a.m., the meeting was
) 15 recessed, to reconvene at 3:15 p.m., this same day.)
16 17 18 19 20 21 22
- 23 24 25 ANN RILEY & ASSOCIATES, LTD.
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l 369 1 AFTERNOON SESSION ( 2
) [3 :00 p.m.]
I 3 MR. GARRICK: The meeting will come to order. We 4 are now going to hear about container life and source term. 5 Please introduce yourself before that. 6 I should note that Ray Wymer will leave the 7 discussion on this topic. Proceed. 8 MR. CRAGNOLINO: Good afternoon. My name is 9 Gustavo Cragnolino. I am a member of the corrosion science 10 and process engineering element. I am going to talk 11 precisely about containment life and source term. 12 Here I have listed the technical contributors in 13 this part of the program. You met, down in the laboratory, 14 Mr. Brossia, Mr. Pan, Mr. Pensado, who currently is a member (~h () 15 of the PA group, as well as Mr. Mohanto, Narasi Sridhar is 16 the man &ger of our group, and this shows again integration 17 in our activities because Jay Weldy is a member of the PA 18 group, Dave Pickett is from the near field environment, and 19 -both Charlie Greene and T. Ahn are members of the NRC staff. 20 Charlie Greene was visiting with us in the 21 technical exchange, something that was mentioned by Wes 22 yesterday. 23 Now, the first slide is sr.mething that you have 24 seen already, and I refer to the flow-down diagram for the 25 total system performance assessment. I am going to (~' ANN RILEY & ASSOCIATES, LTD. (ms Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
l 370 1 concentrate on the issues related to the subsystem, the
/ ')
2 engineering barrier system. LJ 3 This is a description in terms of the analysis in 4 total system performance assessment, but the engineering 5 barrier system, from the physical point of view of the 6 component, consists of a waste package and other elements of 7 the engineering barrier, such as the options that DOE is 8 planning, drip shield, backfill. 9 Here you have the so-called four elements that 10 reflect the integration in between differing aspects of the l 11 key technical issues in the containment life and source l l 12 term, You can see these much more clearly in your handout. 13 I will show you in the next slide the correlation l 14 that exists in between these keys that I've used in terms of I (~N () 15 the total system performance assessment. One is related to 16 the waste package corrosion in terms of humidity, chemistry 17 and temperature, and as related to the KTI that deal with 18 effect of corrosion on container lifetime. 19 The mechanical disruption of the waste package is 20 related to the effect of materials stability and mechanical 21 failure on container lifetime. That reflects the 22 interaction with the near field chemistry, the quantity and 23 chemistry of water contacting the waste package and the 24 waste form is important in terms of the corrosion of the 25 container lifetime, but also in terms of the rate of [T ANN RILEY & ASSOCIATES, LTD. (_l Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
(. 371 t 'l- degradation of the spent fuel and the high level waste.
- 2. Last, the fourth of the key'ISI included here is J}
3 the radionuclideErelease rate and solubility limits and
- 4. these are~in some ways clearly related to two of the other 5 key technical issues, sub-issues that I mentioned before,
- 6. the rate of degradation on the spent fuel and radionuclide 7 release from the spent fuel, and the rate of degradation of 8 high level-waste glass and the release from the glass.
9 We'have two additional sub-issues that.are not 11 0 included or listed, and one refers to the criticality inside 11 'the waste' package and another one makes provisions for 1 12 . alternate material selection at the site for the engineering 13- barrier system, that in some way feeds within this-picture 14 of the other pieces. It's a currently integrated sub-issue () 15- because reflecting integration in between different KTIs. 16 From the point of view of performance assessment, j 17 we can come out to what we consider insight in potential
.18 risk'for the performance of the repository. I listed here
! 19 what we consider the most'important coming out from the 20 performance assessment. 21 .One is the importance of initial failures that has 22- become dominant as a consequence of the design change. The 23 performance of the container materials has been improved by 24 the choice of alloy C-22. Improved in this context means i 25 the're is a low -- that.it is less prone to localized' I O ANN RILEY & ASSOCIAT3S, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 l Washington, D.C. 20036 (202) 842-0034 ;
r , l 372 I 1 corrosion. Therefore, it's very important, the passive 2 ( ) . corrosion rate in the life of the container, but DOE will 3 still consider variations to the VA design. 4 C-22 was introduced for the VA design as a way to I 5 improve the performance, but they will consider an alternate 6' design and the first choice was to do the revirion of the VA 7 design, removing carbon steel as the outer barrier and 8 including, as an outer barrier, the alloy C-22. 9 But in order to provide. integrity, structural 10 integrity, the new design that is currently considered, as 11 you have probably seen in design number two, design 12 alternative number two, is the use of a stainlesc steel, in 13 order to provide the necessary mechanical restraints. 14 This design could be altered with additional n ( ,) 15 features that are part of the EBS, like the drip shield or 16 even the option of the backfill. 17 One of the important things in this type of 18 material is the effect of fabrication process, that now we 19 are starting to deal with, since it's much more clearly 20 defined that the DOE is considering it for the license 21 application. 22 In this context, the importance of the near field 23 chemistry becomes clearly up a range, and I think that near i 24 field chemistry is a real narrow term, because here we i 25 consider also part of the environment as the definition of ANN RILEY & ASSOCIATES, LTD.
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373 1 the temperature-that we are going to have in the container ( 2 itself.or other environmental factors, like the application
'3 of a stress or thermal loads.
4 It should go beyond purely the chemistry, even ! z- 5 though the chemistry is extremely important in terms of 6 corrosion process. 7
~
The importance of penetration rate is related to 8 release -and this ,:Us very much related with the way that (
.9 water comes into contact'with the waste package. And I have 10 included.in this list the aspect of cladding, because this 11 affects the performance in the analysis that has been done
-12 by the DOE, due to the relatively high rate of release that 13 they have from the spent fuel. '
14 The important thing, and I am going to mention I 15 this later on, is that we can deal with the corrosion 16 problem of flooding material with the same approach that we 17 use for container material. j 18 And, finally, the last point to stress is that 19 once.the waste package are penetrated'or breached, internal 20 environment is very important in terms of release. 21 These are important factors in terms of 22 performance assessment, and I want to emphasize. ! 23 In addition, you have to realize that this is 24 going to be affected by the relatively high variation field 25 'and, therefore, will change the composition of internal -- l ANN RILEY & ASSOCIATES, LTD. l
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E 374 1 it will happen.on release, as well as the high corrosion () 2 3
;being. emplaced:inside the waste package.
Let's go now to some of the points that I 4 c mentioned before and the specific aspect of initial 5 . failures. Initial failures, as was mentioned before very 6 bri'efly by Sridhar, is dealing a very different way in DOE 7 ~TSPA/VA and in'the TPA code, because in the case of the DOE ' 8 -- essentially, inLthe case of the DOE, faulting and seismic 9 effects are included, while the TPA has a separate 1 10 consideration of'the faulting and seismic effect on ' 11 performance of the waste package. 12- .There is'a clear difference in the probability of 13 ' failure. release effects, in which DOE is assuming one in ' 14 10,500 waste packages, the order of ten-to-the-minus-four, I) 15 and the initial failure time for this type of initial 16 failure of 1,000 years, while in the TPA code, the average
~
17 failure range from ten-to-the-minus-four to 18 ten-to-the-minus-two, and for subarea, and the assumed 19 failure is at time zero. 20 If you are interested, I can go into more detail 21' in the type of associated problem related to initial failure 22 -definition later-on. But I will proceed and show you a 23' compilation of performance calculations by using, in the TPA
- 24. 3,2' code. The initial DOE failure rates, i l
25 If-we'take the value of the TPA code, the NRC, ! l I O ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
375 1 where you have this type of distribution for the expected /~') 2 dose, by using the value assigned by the DOE, obviously the C/ 3 expected dose increase for almost an order of magnitude, 4 which essentially has been done here in order to refer to a 5 starting point, the initial failure at 0 EF for both cases. 6 This is an indication, even at 10,000 years, that 7 there is a significant impact related to the number of 8 initial failures. 9 The main contribution of these analysis that was 10 presented, the last thing that is changed that we have with 11 DOE in' performar: ne assessment, is that the initial failure 12 are essentially on spheres in a related system application. 13 'They are using many type of application, also fuel rod from 14 the nuclear industry, and there is a difficulty in defining () 15 the mechanism for initial failure, because they're all 16 lumped together. 17 A very important point is that there is no 18 relationship between the type of effects and what is the 19 process that could lead to failure starting from the 20 initiation effect. l 21 And the effect of experience on initial failure rate is not I 22 considered, and I think that's a very important point, the 23 experience in the construction of fuel for a nuclear power 24 plant, has demonstrated very clear that initially the rate 25 of failure was almost an order of magnitude larger than the ANN RILEY & ASSOCIATES, LTD. (} (_, Court Reporters 10?5 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 i
376 1 failure rate, and this reflect the experience that'was 2 acquired-in process application and improvement in the
.3. techniques.
l 4 The'following figure shows the~effect of the 5 ' container material on the system performance. These are
) :6- calculations conducted with the TPA code in a different 7 version. But there are two comments I want to say here.
8 One is that here we have the fraction of waste 1 91 package. failure as a function of time and it's very obvious 10 that the choice of alloy 22 produces significant increasing 11' failure at a given' time, especially for short times, because 12 the failure with alloy 22 in this case appears essentially 13 starting from about 10,000 years. 14' The difference in between A-825 and 625, not
. 15 significant; therefore, significant move forward from the 16 point of DOE who made a' choice of alloy 22. And I want to 17 make'a point here. We never believed that alloy 825 was a
-18 good choice of a container material. Therefore, when we
~ 19 study our activity, decide to look at some preliminary work 20 with alloy 22 that was at the time a reference material.
l 21 We have a good database, but very limited at that 22 time on this material, that we couldn't propose it because 23 it was'not within the scope cf our regulatory system to the ; 24 NRC. It was only a reference material for comparison. l 25' ' Alloy 625 came into the picture and finally alloy 3
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377 1 22. l
-() 2 Another point I want to make for here is that we 3 able by a simple change of input parameters in the code to l
4 deal with the choice of three different materials, because 5 all these materials belong to a class of material, the base 6 alloys. 7 Therefore, the corrosion failure mode were 8 essentially identical. We used the same approach. When we 9 got into the laboratory, they put parameter -- their basic 10 mechanistic bases were fair. 11 We did calculations for the waste package lifetime 12 using the TPA code and in the baseline case that was used 13 for the analysis of the TSPA/VA, we felt corrosion rate that 14 we use would essentially was derived from wrong data and bq ,/ 15 data from the literature for 825. We didn't have enough 16 data for C-22 at that time. 17 And we came out with a medium for that time of 18 70,000 years, assuming the base case, which we don't have, l 19 was in the material. It's base matter. Later on, we start 20 to come back experiment in the lab to measure more accurate 21 the passive density of alloy C-22, in which this new data, 22 we were able to demonstrate that the life could be extended, 23 as I show here in the solid plot, up to 60,000 years. 24 And it's interesting to illustrate the point that 25 the design the viability assessment, waste package in which ANN RILEY & ASSOCIATES, LTD. Oe s_- Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
r I h 1 378 1 you put the C-22 outside and the carbon steel, that was tne (~ ) 2 material inside, essentially exceed the same lifetime.
\- / '
3 These two curves that are here are obtained with the same l 4 essential passive carbon density. ' 5 But illustrate one important point, that really 6 what provides corrosion resistance in the waste package is 7 C-22. And this is why DOE made a choice of getting rid of 8 the carbon steel, that could lead to certain problems in 9 that sense that it would release corrosion product and it 10 will affect the behavior of the near field environment and 11 introduce a lot of uncertainty, and use C-22 as the alloy 12 that provides. 13 What is the main consideration has been the 14 lifetime of the container material, to decrease release l Ch s < 15 rates. x.d 16 In the following one, what I wanted to stress is 17 some of the limitation that we see in the approach of the 18 DOE fc? one side, and, on the other side, the lack of 19 sufficient data. This is the previous calculation that I I l 20 showed for the base case. 21 This is tha calculation which allow to modify 22 corrosion data, but by the way, this is data that was I i 23 obtained in the laboratory doing electro-chemical experiment ! I 24 that lasts for 24 to 48 hours. 25 . DOE has conducted tests for almost a year, in some l t [~'} ANN RILEY & ASSOCIATES, LTD. (_/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 i (202) 842-0034 I 1
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379 1 cnse, two years, to measure the corrosion rate of C-22 and [} 2 they come out with the same value. 3 The expected life in this case will be of the 4 order of 50,000 years. That is here. However, if they use 5 what.they have in the TSPA/VA as a rate of corrosion for l 6' C-22, raise it on expert elicitation, they are -- the l 1 7 failure on the container, and you can see that atter 100,000 l { i 8 years, only 20 percent of the waste packages failed. 9 Well, for us, this is completely unrealistic and la is a problem of the compounding of the opinion of many 11 experts, that the spread of range of corrosion rates over an 12 incredible large range of corrosion rateo. There is a 13 clearer way tc distribute the dose. 14 How is our approach' Our approach was, first of I (O) 15 all, consider failure modes, corrosion, stress corrosion 16 cracking, hydrogen embrittlement, mechanical failures, 17 according to the class of materials. We have carbon steels 18 on one side, nickel-based alloys, titanium alloys. 19 And on top of this, to evaluate a wide range of 20 environmental conditions, in terms of anion concentrations, 21 temperature, pH, redox potential, that are expected to 22 contact the waste package, the water in the waste package. 23 On the basis of these, to be able to develop 24 abstracted models for performance assessment that can be 25 supported by mechanistic models. And finally, to try to
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380 1 raise confidence on the performance assessment by t t 1 2 focused experimental measurements of important parameters. (% )) 3 What are the important factors that ai ect the l 4 performance of the so-called corrosion resistant materials? 5 For corrosion materiu'., because this material', what they 6 have is a surface fill and reaching, most of the cases of 7 alloys that we are considering, that provide resistance to 8 uniform corrosion, because corrosion rates can be extremely 9 slow. But over the life of these materials, this it the 10 order of -- therefore, this material could be extremely 11 prone to localized thermal corrosion, 12 It exists through a very delicate balance, at 13 equilibrium with the media. The chemistry, therefore, of 14 the water is especially important and chloride is the main () 15 element that is able to break down this passive thing and 16 . initiate localized corrosion. 17 And we come to this conclusion through 18 experimental work in which we demonstrate that of the 19 various species that you have in the ground water or in the 20 repository, the only one that you have to essentially 21 concern as aggressive is chloride. Chloride, nitrate, 22 sulfate, and also important in thermal effectiveness of the 23 system, 24 Another important factor is the redox condition in 25 terms of the corrosion potential, because it will be a () (/ ANN RILEY & ASSOCIATES, LTD, Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
l 381 L 1 design - .if particular, if you reduce the wall thickness, t-(
- 2. 'the shielding effect.that you have already in the original 3 VA design with the very thick carbon steel is significantly l 4 reduced, and, therefore, you have a condition on the waste 5 package.
6 A matter of concern I mentioned before is the 17 microstructure of the material in terms of the welding or ! I 8 eventually any heat treatment that could be wrongly done, 9 where.you have 10,000 containers to be in the heat 10 treatment, and this could lead to problem. Because 11 .everything lies on this, on the passive dissolution rate, 12 'and it's a very important parameter to measure. 13 In the case of. localized corrosion process, you 14' shave'to consider an active dissolution rate, this active 3 () 15 corrosion rate has an order of magnitude larger. And we 16 need to include pit growth rate, because of the geometry of 17 .the pit. 18 This is the methodology we applied. Some of this 19 ~ was already described in the laboratory. I'm going to go
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20 very fast. It's to measure corrosion potential, after ] 21 . calculation this from a basic electro-chemical kinetic law, ! 22 but doing experimental determination of the repassivat ion 23 potential as a bounding parameter for localized corrosion in i 24 e t.rms of temperature, pH and chloride concentration, and be 1 25 able to sustain this process of repassivation potential for , l ANN RILEY & ASSOCIATES, LTD. ! Court Reporters l 1025 Connecticut Avenue, NW, Suite 1014 Washington, D C. 20036 (202) 842-0034
382 1 localized corrosion, to analyze the electro-chemical / 2 conditions for the stress corrosion cracking. D) 3 There is an additional requirement in terms of
~
4 effects. Later on, we can go over a little the localized 5 corrosion rate, and we can do some evaluation, from the i 6 experimental point of view, of the effect of welding or 7 thermal treatment in some of these critical parameters, and I 8 combine all these approach in the use of parameters that can 9 be used in the TPA code, but size it to one point. 10 We are talking about, as was mentioned as a j 11 challenge here, the long-term behavior that we need to I 12 predict. We have to have some fundamental modeling of l l 13 passivity in the localized corrosion process to be able to, 1 14 on the basis of a model and a fundamental basis, essentially 73 i () 15 model existing -- we have to modify and adapt to get an 16 understanding and be able to consider factors that could 17 affect the passivity in the long-term. 18 This is another way to look to the importance of 19 repassivation potential and the concept that is embedded as 20 a criterion for localited corrosion using the TPA 3.2 code. l l 21 I put this plot as a representation of the l 22 repassivation potential as a function of the chloride 23 concentration, and we have only the lines describing the 24 behavior of 825, 625, in order to stress the improvement 25 that you have with alloy C-22. Only a very high chloride / ANN RILEY & ASSOCIATES, LTD. (_s\/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
383 1- concentration goes to the critical concentration l [~') 2 corresp'onding to this calculation of chloride. You have a
' (.)
3- sudden drop of the repassivation potential to low values
~
L 4 that are' typical of other alloys. 5 'However,-in all this regime, even at very high 6 potential,'you will have various corrosion, as indicated by 7 the open circles. We have very high potential there, but 8 youtdon't have localized corrosion. This potential is 9 really associated with the solution with alloy, but not to
'10- ' localized corrosion. While the point, the cross-point 11- reflects localized corrosion.
12; This means that at about 95 degrees C, the point 13 that is' mentioned here in this ledger, there is a window of 14 susceptibility for C-22. C-22 is not a immune to localized () 15 corrosion. But it's susceptible very close to the volume of 16' water, at a very high chloride percentage. 17 In order to understand better this type of process llB that takes place close to the boiling point, what we have
-19 done is this, to go beyond the boiling point, and we can see 20 very clear here that you have a sharp decrease in the 21 repassivation potential precisely about 95 degree, that this 22 is even the case for one more solution, and for .5 more 23 : solution, even though corrosion is not at the 95 degree in l
- 24 .5. l 25' But you reach one more solution in between 95 and
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384 1 120, but you can reach temperatures about boiling, you have (% 2 concentration of the chloride, you can have a sudden
%]
3 decrease in the.repassivation potential for alloy C-22 and 4 it's clearly a matter of concern. 5 But this is for the base metal. What happened 6 'with the welded material? The welded material showed a 7 significant drop with respect to the base makeup, as you can 8 see here. And the same can be demonstrated for a heated 9 material for 24 hours and even for 240 hours, the behavior 10 of this material cannot be considered as a highly resistant 11 alloy. It's an alloy that is similar to the-other alloy 12 that we considered before in the program, but we can't 13 consider this is a bounding value that we have here for the 14 purpose of making sure that there is a significant trend in t) l 15 terms of repassivation potential as a sensible parameter, 16 and we don't anticipate that this condition can be expected 17 in any container. 18 But the one here, obviously, are potentially 19 possible and you can see the potential values are relatively 20 low. 21 The next block shows the localized corrosion 22 propagation rate and unfortunately, from the point of view 23 of somebody that wants to do experiments in the laboratory, 24 C-22 is highly corrosion resistant. It's very difficult to 25 repeat it in a way that we can measure. What we have done [N (_) ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
385 1 is an experiment, as a model alloy, with 316L, in which we I~h 2 have two -- it is not plotted to demonstrate, but this L) 3 reflects ten-to-the-minus-one, the peak growth is controlled j 4 by diffusion, but what's interesting is the fact that we
.5 were able to collect field data obtained for alloy 625, the 6 second alloy chosen by the DOE, that shows the rate that we 7 are using for localized corrosion propagation in the TPA 8 code is in the right range of value.
I 9 It's interesting, however, to point out that in 10 the TSPA/VA code, the highest value of corrosion rate for j 11 localized corrosion is one order of magnitude lower than l 12 this. But the most important point is that the median rate 13 is several rders of magnitude lower. 14 . any circumstance, C-22 falls within this window 7m () 15 of stabilitf, the life of the container cannot be assessed 16 on the basis of this expert elicitation value. It has to be 17 assessed on the basis of hard data. 18 To close this relationship in between, laboratory 19 data and the parameters that are important in the TSPA code, 20 I want to bring your attention to this table. This table is 21 more clear in your handout. I 22 Since the corrosion rate of C-22 is extremely 23 important in determining life, you can see, and this is 24 something like -- it's some stretch of the imagination, but 25 this made the point, that there is relatively high potential ANN RILEY & ASSOCIATES, LTD. ()) %_ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
386 1 in the passive region with this chloride concentration, 2 there is 1,000 ppa in chloride, corrosion rate can be ( 3 calculated by using an electro-chemical approach through the 4 measurement of anodic current densities, and the lifo could 5 be of the order of one million. 6 However, if the temperature reduced, and this is 7 shown here, up to 95 degrees C, the current density 8 increases; therefore, the corrosion rate increases, and the 9 life comes to something that is perhaps more understandable, 10 in the order of 60,000 years. 11 As you go to bigger CDPH, and this is one of the 12 beauties of C-22, it's an alloy that is not affected in this 13 passive behavior by pH effects and essentially the rate is 14 the same. i ) 15 It's in this range, the life is reduced by 16 substantial amount of years, but you have to take this with 17 all the uncertainty that is related to this type of 18 measurement and we can't estimate uncertainty, too. 19 Another point I wanted to make here is if we go to 20 the same pH as before, but we go to a very concentrated 21 chloride solution, again, it's very sensitive to the 22 chloride concentration. It's more or less in the same 23 range. Finally, if we go to a higher potential, that can be 24 reached by the presence of a species, again, we have a rate 25 of the same order, I would say. But these rates are very ANN RILEY & ASSOCIATES, LTD. (~)N (, Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
387 1 comparable with the one that we use in the TSPA/VA code. () 2 3 This rate was used without experimental data, put in the code. Now, we are more confident to use rate in this 4 order, mean that the life of C-22 will be extended, if C-22 5 behaves as a passive matter. But if C-22 becomes 6 susceptible to localized corrosion, we cannot predict that 7 the life is this order. 8 And I want to point out that, as I mentioned 9 before, this is the order of rate that we measured in a 10 couple of ways in the laboratory and are very similar to the 11 rate that were measured by the Department of Energy in the 12 laboratory. Immersion tests, after one year, one year and a 13 half period, and this indicate how probable it would be that 14 electro-chemical, they need to measure very low corrosion () 15 rates. 16 At about 400, they're difficult to obtain; 17 however, these materials suffer passiv dissolution. 18 Nevertheless, we didn't observe that these condition of 19 dissolution or localized form of corrosion, but there is 1 20 another process that leads to the solution. 21 In summary, the approach used by the NRC and the 22 center is a flexible approach, because allow us to 23 accommodate DOE design changes in terms of material 24 selection. Has allowed us to use new data to update the 25 models, new data obtained in the laboratory, and even data ANN RILEY & ASSOCIATES, LTD. O-m Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
388 1 that is obtained in many different conditions, but we have a (
) 2 way to connect this because we can put everything in what we )
3 call a performance map. A performance map in terms of 4 electro-chemical parameters, like the corrosion potential or 5 electro-chemical potentials in general, and environmental 6 factors, like the chloride concentration, the temperature, 7 and eventually any other species. 8 On a positive note, I should mention that these 9 approaches are being seriously considered by the DOE. They 10 are not making material selection here. If we decide a 11 ' methodology appropriate for long-term prediction, 12 appropriate for long-term prediction, the sensitivity 13 analysis has helped us to focus this type of a study and we 14 believe that the assumptions in the modeling are not unduly O) ( 15 conservative. 16 What are the progress that we have in resolution 17 of all these issues that are so important in terms of the 18 license application? We have several components of 19 sub-issues that have been resolved or became moot with the 20 post VA design and materials changes. For instance, I want 21 to mention the dry air oxidation. At one point in time, we 22 had a conservative dry air oxidation, brought up by an NRC 23 staff member, and he had more reason to believe that this 24 could be a potential detrimental problem for the carbon 25 steel. (~D ANN RILEY & ASSOCIATES, LTD.
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389 1 What we did is we solicit the expert in the field. 2 Professor Bob Jott, member of the National Academy of l 3 Engineering, was willing to do an analysis of these problem. 4 We came to the conclusion that this was not an important 5 issue for the material of choice, and we resolved this with 6 the DOE. It was a design change and it was not necessary to I 7 pursue it anymore. 8 As well as the case of aqueous corrosion, wet or
]
l 9 dry cycles of carbon steel, because they're changing the 10 design made this issue moot. 11 We've resolved, coming to the same conclusion 12 regarding thermal embrittlement of carbon steel. It's 13 unfortunate that we have to put this effort at that time in 14 this issue, it became moot. But this is life. And we deal 15 with the issue of galvanic coupling effects and we resolved 16 this, and, again, ceramic coating has been a problem that { j 17 has been out of the picture due to the choice of the new
'18 design.
19 However, we cannot expect full resolution of all l 20 the issues until DOE makes a final selection of the design, 21 complete their laboratory tests, and, above all, make a 22 detailed plan for performance confirmation period. 23 Because here is one of the issues. We don't L 24 believe that the DOE will be in the condition at the time of 25 the license application to provide sufficient data. They l O [d ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 L
390 l Lwill provide minimal data, maybe'they provide necessary () '2 3-
' data,~ but we doubt that they will provide sufficient data.
Therefore, the issue of the performance 4 confirmation period is very' critical for the license 5 application process. Very critical. 6 We recognize that we-have to complete the study of 7 container fabrication effects. How I am doing on time? I 8 We recognize that we have to complete the study of 9 the container fabrication effects. During the last several 10 years, we were put in the situation that we have to defend 11 .not to do a status of welded material and we didn't try i 12 because there was not clear decision from the part of the 13 DOE in which direction to move. l 14 Now we know the material. We are following very \(K -15 closely what we are learning and we can cross this issue. !( ) 16 We have.to consider what is the most important aspect of the 17- . alternative design, the drip shield, we have a concern with : j-l 18 the drip' shield made of titanium-16, is apparently the alloy 19 of choice. We have started an experimental program in this 20~ direction. But, again, it's unfortunate. 21 The Department of Energy, the only alloy at the 22 present time is another type of titanium alloy, that is not 23 the material of choice. And this made very clear that they 24 will have to use data in the literature that is not so 25' abundant and rely a lot in the performance period. We need D A ,/ m ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
l 391 1 -- and this is a very critical issue -- better define the 2 near field environmental condition of the waste packages. ()) 3 This is an integrated activity. Ron Green described in some 4 detail what we are doing in thermal effects on flow in 5 relation with the near field, and I say that this will be 6 extremely important to define the conditions that may lead l 7 us not to look at less corrosion of alloy C-22. 8 If we can't come to a clear conclusion that 9 concentration plus the saturation of chloride in the 10 condition of the repository, C-22 is going to last much more 11 longer than if susceptible to localized corrosion. 12 And when I talk about C-22, I'm using a very broad 13 term, because what you're going to have in the repository is 14 a variability. There will be containers that perform (OJ 4 15 according to what is predicted in the labora, tory on the 16 basis of experiments, but will be in some places of 17 malfunction associated to wrong heat treatment that were not 18 detected and so on. l 19 An important issue to continue the discussion with 20 DOE in terms of methodology, because this is the part that 21 we are influence them. Not in selecting the material, but 22 in to try to use approach that could be defensible. It has 23 not to be our approach, but has to be defensible. And the 24 necessary data for assessing corrosion and mechanical 25 failure, as I mentioned, we have an Appendix 7 meeting next I l I () (_/ ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
392 1 week and future interaction, and this the point that I want [b
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2 to confess that it is.necessary to identify tools, 3 techniques and areas of performance confirmation testing, 4 because this is going to become an important issue to be 5 seen at the time of license application. 6 Currently, DOE claim that in the drift heater 7 test, they are doing measurement, but they are doing purely 8 and by the length and measure emplaced on top of the drift. 9 And what they have in term of corrosion is a group of 10 coupons exposed close to the waste package and their 11 conditions are not heat transfer conditions and without any 12 way to assess the behavior as a function of time. It's a 13 matter of picking them from time to time, if they are able 14 to go there, and examine, they cannot make any type of () 15 correlation that could be related very easy to what this ; 1 16 experimental work going on in the laboratory. ' 17 And these are a matter of concern and this is the 18 reason why we believe that it's extremely important to 19 continue these discussion with DOE in term of approach that 20 we are going to use for assessing corrosion and mechanical 21 failure and safety in terms of the performance confirmation j 22 testing. 23 This is -- if you look in the VA, the description 1 24 of the part, where it was supposed to be the license 25 application plan, it's extremely limited. Extremely ANN RILEY & ASSOCIATES, LTD. [~)h N Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. '0036 (202) 842-0034
393 1 limited. L () 2' 3 I think that we are in good condition to provide
. support to the license activities, the activities related to 4 license application. We are updating IRSR in terms of these 5 changes in design on1the basis of data that we are obtaining I 6 ~in our laboratory and trying to make very good use of what 7 .is available in the literature, because we believe that the 8 DOE is going to use a lot of data from the literature and we i 9 have.to evaluate these data. .
I 10 And even'though we all know, because we're 1 L 11L . publishing papers,.that their papers are peer-reviewed, they I 12! are peer review papers and there are peer review papers, j l' 13 MR. WYMER: Absolutely. 14 MR. CRAGNOLINO: We want to make sure that these l () 15- fit with this approach in terms of this performance model. 16 It's very appropriate to describe this domain of failure for 17 materials in terms of environmental and electro-chemical. 18 I'm open to any questions. I answer or I had the 19 ' idea in mind that I will tell you ask me question along the
'20 top, but I know I allow questions.
211 MR.-WYMER: I'll start off. I have a couple. I 22 assume that from the lack of mention of them, that you're 23 not putting a whole lot of emphasis on radiolytic effects on 1 1 1 24 corrosion or biological effects. 25 MR. CRAGNOLINO: Let me separate the two issues. 1 O ANN RILEY & ASSOCIATES, LTD. Court Reporters
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.1 WE didn't put -- at one time, we were giving thought to 2 this, when they originally decide with this thin wall
(
-3 container in a bore hole. By later on, when the design 4 evolved to a much more robust type of container, with thick 5 1 wall, we consider that the issue of radiolysis was not so )
6; important. Now it's coming into the picture again and we 7 are going to: pay attention to it. 8 Nevertheless, in the past, we have the literature 9 and we.came to the conclusion that a dominant species 10- produced'by gamma radiolysis was hydrogen peroxide. It's 11 the dominant species, that they form at a steady-state 12 concentration, because they aren't radical, but are not that 13 stable. Essentially, it's defined by the concentration of 14 hydrogen peroxide, and we did some experiment with hydrogen () 15 peroxide to measure the evolution potential and the 16 corrosion potential, and we came to a very interesting 17 conclusion that particularly important in the case of 18_ copper. 19 In the literature reported that this type of' alloy 20 are not very susceptible to the effect of metabolic product 21 produced by bacteria, and this is a point ' chat is important 4 22- to clarify. Many people talk about metallurgical effects, 23 thinking that the backfill matters. That is not true. 24' What happens is that the backfill uses r.etabolic 25- . products that change the local composition and in some case, I l O ANN RILEY & ASSOCIATES, LTD. Ceart-Reporters 1025 Connecticut' Avenue, NW,-Suite 1014 i Washington, D.C. 20036 l (202) 842-0034
l I j 395 ! I when you produce a film, the environment inside this could f~h 2 be significant, and this would be extremely detrimental. l 3 Nevertheless, look like this, high nickel, high 4 chromium alloys are extremely resistant to microbial 5 influence corrosion. It is an issue that we are in the l l 6 condition to look, but it's not in the priorities. It's in 7 the list below the line. 8 If we have an indication that this becomes l l' 9 important, I think that we are in the condition to address 10 this issue, at the level of having enough information to 11 evaluate what DOE iF doing, because Lawrence Livermore is 12 working very actively in this field. 13 MR. WYMER: Okay. Another tact now. You have one 14 viewgraph that caught my attention. Initial failures, TPA (D qj 15 versus TSPA/VA, and the second bullets on each of them were 16 the assumptions of the failure probabilities, and they're so 17 different between DOE and NRC. I wondered -- 18 MR. CRAGNOLINO: It's one order of magnitude. 19 MR. WYMER: I'm sorry? 20 MR. CRAGNOLINO: One order of magnitude different. 21 MR. WYMER: Right. 22 MR. CRAGNOLINO: As I mentioned before in this 23 presentation, that they did the technical exchange with the 24 DOE and I think this counts from the fact that although 25 implicit in the definition that we follow for the initial l
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396 1 failure are rather similar,.what they are doing is that they ) () 2
-3 compose the probability with the assumption that it's a l'
double-wall container. Take' data that exist for boilers and 4 multiply the probabilities and come out with this value. 5 This is the rationale behind it. 6 In our approach, we were completely different, was l 7- to dol-- at that time, we didn't know that the initial 8 failure would play'such an important role in the dose at 9 10,000 years,. for the reason, field engineering evaluation 10 that was done here in the center in '94 and it was - 11 . evaluated, but we also evaluate a steam generator tubes and 12 partially some boilers, and come out with :his number. That 13 was an upper bound. We'd rather be conse'rative in this 14 case and use an upper bound. () 15 This is something that we are going to -- it is 16 .not satisfactory for us because it has not been a basis.
- 17. . DOE knows that their approach has no technical basis either
.18' and they are'trying to look for an approach that is more 19 justifiable.
20 'And the approach-is something like consider that we have 21 some type of effects and how can we -- these type of effects 22 or initial flow has to be-evaluated also in terns of the 23- level of the -- from non-destructive examination techniques. 24 MR. GARRICK: Given the importance of initial 25 failures, is there something that could be done in the l I l l
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l l 397 {, 1 operational phase -- that'is, in the pre-closure phase -- l 2 th6t would bring the two -- give us greater confidence in 3 some assumed value for such failures? 4 MR. CRAGNOLINO: I think that an effort has to be 5 done earlier than that. I think that this is something that i 6 we have in our -- Sridhar can give more detail to you. I 7 assume this is something that we are planning to pay more 8 attention and I think that the DOE has to evaluate more, 9 Unfortunately, valuable data could come from the i 1 1
'10 manufacturer of these type of component, and they don't 11 provide this data. When we get data, for instance, behavior 12 of boiler material, it will be something more close, even 1
13 though the container is much more a passive system with { 14 respect to a boiler, and it is combined because of pure i I) 15 operational failure. It's not necessary what we try to 16 consider here in initial effects. We have to find a way to 17 discriminate with a more mechanistic basis. l 18 MR. GARRICK: What about something like an on-site 19 elaborate inspection process? 20 MR. CRAGNOLINO: Right. There is no doubt that 21 has to be in place. Yes. We start from the point of view 1 22 that there should be a very elaborate place of i 23 non-destructive examination prior to put any of these i 24 containers in the emplacement drift. l 25 MR. GARRICK: But you don't think the inspection [ ANN RILEY & ASSOCIATES, LTD.
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.1 process can be a basis for bringing some rationale to an =I~ \' 21 assumption of a failure rate. .G
, 3 MR. CRAGNOLINO: Well, I think that when the DOE J
- 4. are. going to do more and more --
5 MR'. McCARTIN: This is Las Vegas. Can you guys
'6 hear us?. Could you stand in front of the mic, Gustavo?
7 MR. CRAGNOLINO: Yes, I'm sorry. I tend to move 8 around. I'm sorry. I think that will improve that process, 9 but the -- you know, even in cases in which a 10 non-destructive examination-technique has to improve a lot, 13 like in the nuclear industry for a steam generator tubes,
.12 the fact that you have"still failures, and some of them are 13 real initial failures, manufacturer defects and so on, many 14 of the case that we have to anticipate we.can maybe bound 15 b'etter these with an improvement in non-destructive 16- examination technique.
17 But'on the other side, let me tell you, this is 18 not such an extremely complex technology nowadays. What
-19 'made it seem a little bit complicated in this particular
-20 case is that this corrosion resistant alloy in-the design 21- are brought to.the maximum currently used and I think 22 DarrelI can correct me if I'am wrong, but I think they are 23 very close to what the. manufacturer can produce.
.24 MR. DUNN: No, It's 20 millimeters a day for the I
L 25- maximum. The current design uses a 20 millimeter thick l i l 1 0 ' ANN RILEY & ASSOCIATES,-LTD. Court Reporters 1025= Connecticut Avenue, NW,. Suite 1014 Washington, D.C. 20036 (202) 842-0034
399 1 C-22, I think the maximum thickness is about 55 mitlimeters f') v 2 thick. 3 MR. CRAGNOLINO: For the 316L, that is going to be 4 55 centimeters, you are right. 5 MR. GARRICK: For the benefit of the court 6 reporter. 7 MR. DUNN: Darrell Dunn, from the Center for 8 Nuclear Waste Regulatory Analysis. 9 MR. WYMER: I had two more questions. One is sort 10 of trivial and the other has maybe a little more substance 11 to it. 12 ON your table, uniform corrosion rates of alloy 13 C-22 and values used in the TPA 3.2. 14 MR. CRAGNOLINO: Yes. r~ ( 15 MR WYMER: I believe it's page 18, I think. 16 MR. CRAGNOLINO: Let me project it. 17 MR. WYMER: I'm not sure that you need it to 18 answer my question. But it's page 18. It looks to me like 19 you have chosen your data here to make -- to enable you to 20 make a crude pass at deriving a rate equation and also get 21 an activation energy from it. 22 Have you done that? 23 MR. CRAGNOLINO: Not yet, but we are in the
- 24. process of doing this and really this is going to be input 25 in the modeling effort for a passive film. He's trying to
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400 l
'l look at the variation of what is called a point effect
(} -2 .model, have that type of model for passive film, and th-3 data,'the one that you have-in this table, is going to be 4 used for this' purpose to precisely analyze. The most important aspect that you see here in
~
5 6 this table is the activation related to the variation in 7 corrosion. We need intermediate data. Sure. We cannot 8 build this with -- 9 MR. WYMER: I was justJcurious how far you'd gone. j 10 Finally, the last question is on one of your final
-11 viewgraphs, issue resolution. I guess that's page 20. The 12 last bullet, importance of performance confirmation testing 13 enhanced by the anticipated lack of sufficient data at 14 . license application.
() 15 I don't quite see how you can get much out of l 16- pe:.formance confirmation during the pre-closure period, 17- Lbecause the conditions would be so different from the 18 closure period. I don't know how you -- really what value I 1 19 the. observations you make pre-closure will be to you. Can ! o 20 you comment'on that just a little? ! 21 MR. CRAGNOLINO: Yes. This is pretty much !
-22 dictated from our own approach. It's probably an 23 extrapolation, however. An extrapolation of our own 24 approach. 1 25 I think and we believe strongly that if you have a
( l N ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut. Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
401 1~
- solid model, mechanistic model, and you have data, you can I)~h 2 input your data in the model, you're in the condition of 3 doing a verification. And this is the approach you have 4 seen-in the laboratory. We have a model for localized 5 corrosion. We create a condition in'the experiment and we 6 are doing test in the laboratory now for almost 40 years.
7 We have to. remove the sample from the vessel every 30 days l 8- and we put this back and we establish the condition. 9 We have done this for 40 years, a very limited. 10 period'of time with respect to performance of the l' 11 repository.. But this gives a lot of confidence that our l approach in terms of model.and the previous data that we I l 12 13 obtain in short-term experiment is valid for this type of 14 short prediction. () 15 Now, if the DOE use the same approach or at least 16 another approach of this type, until the period in which 17 they start to put the things in the repository, we have 18' plenty of time to get good data from other things and so and 19 ,later on go to the performance under conditions that are 20 different, you <an predict later on, if your models are
'21 appropriate, you can predict other conditions.
22 You can use activation energy, as you mentioned 23' before. You can use parametric equation on the basis of a 24 model that could you lead you to understand variation on 25 environmental effect like chloride.
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402 1 MR. WYMER: So the value of your confirmatory ( .. (
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'2 testing is'directly related to the validity of your model.
3 So you really need to -- 4 MR. CRAGNOLINO: Yes. And I look at it from the 5- 'very. narrow point of view of container lifetime. I don't 6- want to go beyond the boundary of what I know as the 7' subject. 8~ In other areas, it would be other type of 9 complications. But also have an important effect if the 10 environmental condition are well monitored, too, because 11 this can compliment any assessment in term of corrosion.
- 12. But when I --
13 MR. McCARTIN: I'didn't mean'to cut you off. I 14 . thought you were at a stopping point. Part 63 does require () 15 the performance confirmation period all the way through to 16 ' closure and the waste package, as specifically mentioned in 17 the rule, has tolbe tested and they have to do it under 18 conditions that are representative of what's going to occur
!19 at the mountain. So that there should be a -- I mean, 20 that's starting at construction, all the way through the
- 21. waste -- to facility closure.
22 So you're looking at at least 50 to 100 years of 23~ performance confirmation. 24 'MR. WYMER: But it does seem, if that can't be
!25 .directly related to a model, you have a lot of confidence JuRJ RILEY & . ASSOCIATES, LTD.
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' 1( in, it doesn't really give you n.uch confidence in an
, '2 extrapolation of the future. .So the model is extremely 3 important, the mechanism is extremely important. f
- 4. MR. CRAGNOLINO: Yes.
5 MR. WYMER: That's all I have. l
'6 MR. CRAGNOLINO: We are doing -- it was mentioned i 7 by Bill ~in his presentation, that'these are serious
)
8 technological challenges. 9 RMR . WYMER: They are. 10 MR. CRAGNOLINO: And the spatial variation is not 11 so big, so important, I tend to believe, because in the last 12 ten, 15, 20. years,. big project has been built that has 13 something -- but the long extension -- you know, I.think 14 that the spatial. variability can be handled. The long-term () 15 provision, nature has an expected way to behave and who
'1'6 knows. But we can do the base.
17 MR. HORNBERGER: Just out of curiosity, your 18 opinion. If the repository were designed such that the l 19 temperature never went above, let's say, 80 degrees C, would
- 20. 'that enhance or detract from the container lifetime? 1 21 MR. CRAGNOLINO: I think that for this choice of 22 alloy, it increases. Sometimes, when you answer these type 23 of question, you don't consider other ranges. For these 24 ' type of value basically will be beneficial, it will be i
25 beneficial in term of life. ANN RILEY & ASSOCIATES, LTD.. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
404 1 MR. WYMER: Your voice is dropping a little too /~ \ 2 much. U 3 MR. CRAGNOLINO: Will be beneficial in term of 4 life. I take the point. Will be beneficial. 5 MR. HORNBERGER: Okay. 6 MR. CRAGNOLINO: And what you can -- you should l 7 consider, we didn't pay attention, because we concentrate 8 too much in this regime of more higher temperature close to ) 9 the volume, it is a corrosion mode that could become l 10 predominant in the other condition. 11 Bar-isally, we don't expect, but if you tell me about, for 12 instance, other material, carbon steel or low alloy or 13 stainless, would be much more prone to microbial corrosion 14 at an earlier time, and, therefore, will not be a solution. () 15 It will be more of ability of water under such condition and 16 will shorten the life. 17 But it's something that has to be thought. I l 18 believe personally, from what we were discussing, that go 19 down from 85 to 60 was a step in the right direction. l 20 MR. GARRICK: Charles, do yoa have any questions? 21 MR. FAIRHURST: No, none. Thanks. 22 MR. WYMER: Thank you very much. It was extremely 23 interesting, to me certainly. 24 MR. CRAGNOLINO: Thank you. 25 MR. AHN: Good afternoon. My name is Tae Ahn, of (~ ANN RILEY & ASSOCIATES, LTD. A-m Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
405 1 the Division of Waste Management, NMSS, of NRC headquarter. f} V 2 Gustavo introduced container life and source term 2 issues in general. Also, presented path forward actions in 4 ) general and focused on the container life. j i 5 In my presentation, as a continuation, I would ) 6 like to focus on waste form status. And many colleagues who 7 contributed to this talk, Richard Codell, John Contardi, 8 Charles Greene, V. Jain and Narasi Sridhar. Also, I would 9 like to acknowledge Paul Casado and Gee Cavaluno for their 10 later support. 11 As shown also in Gustavo's presentation, I would 12 like to highlight this flow diagram. We are in engineered 13 system and under engineered barrier, I will focus on the 14 last one, EBS-4, radionuclide release rates and the (f's) 15 solubility limit. Gustavo addressed EBS-1 and 2 for 16 cor*ainer life. ; 17 The next slide shows the outline of the 18 presentation. I would like to focus on three different 19 areas, spent nuclear fuel, cladding performan- and high 20 level. waste glass. 21 For each element, I would like to address risk 22 insights, technical basis, and the progress and the current 23 status, and the path forward, 24 The next slide shows the spent nuclear fuel at 25 degradation. The risk insights may be described as follows. (}
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406 1 The dose is sensitive to the types of spent fuel dissolution (m)
\_/
2 processes, and you see in these two figures on this page 3 three types of spent fuel dissolution models in very high 1 4 rank order when you plot peak mean dose versus for various 5 contributors. 6 This vertical element of various types of 7 contributors, such as no retardation of plutonium in hot 8 rock. The next three are dissolution models of spent fuel ) I 9 and you see those are contributors and contribute to dose. 10 That applies to mean peak dose for 50,000 yearc as well. 11 The NRC base model for spent nuclear fuel 12 dissolution is more realistic compared with the DOE model. 13 The dissolution rate from tests in J-13 well water is much 14 slower, as adopted by NRC. Therefore, in NRC TPA 3.2, no (f~')' 15 credit was given to cladding and more realistic juvenile 16 failure of a container was allowed. This means we did not 17 have to introduce additional uncertainties associated with 18 cladding credit, as well as very low juvenile failure rate 19 of a container by using the realistic dissolution rate of ! l 20 spent nuclear fuel. ) 21 Page four describes tue technical basis for spent 22 nuclear fuel. We considered all categories of spent nuclear 23 fuel, including commercial spent nuclear fuel, as well as 24 DOE-owned spent nuclear fuel. We identify all likely 25 processes for spent nuclear degradation, including matrix (~h ANN RILEY & ASSOCIATES, LTD.
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407 1 dissolution, colloid formation, prompt radionuclide release,
/ \
( ) 2 and dry oxidation.
%J Among these processes, we have agreement 3 with DOE'in many areas.
4 I would like to address later only areas where we
~
5
.still have not arrived at issue resolutions.
6 I would like to show the typical numbers of 7 dissolution model for spent nuclear fuel in this table. The 8 first one is the NRC base case dissolution rate in the range 9 of ten-to-the-minus-two scale per day. On the other hand, 10 DOE's conservative or accelerated test result shows about 11 two orders of magnitude higher than ours, and even higher
'12 under drip conditions.
13 The basic difference is we used the data from i 14 immersion tests in J-13 well water. b) y 15 Another topic to be considered as a basis is the 16 retardation of plutonium. This is one potential aspect of 17 colloidal contribution of plutonium. The left figure is the 18 TEDE for base case and the right figure ~shows no retardation 19 of plutonium on hot rock. 20 Within 10,000 years, because of the containment, 21 we don't see much increase of TEDE anyway. However, if you 22 exceeded 10,000 years and lose the integrity of a container, 23 there is a potential for significant contribution of 24 plutonium released to dose. We would like to investigate 25 this aspect to improve the colloidal contribution model more ANN RILEY & ASSOCIATES, LTD. [~/) N- Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 , (202) 842-0034 l L
408 l 1 realistically. ) ('N 2 On page six is the chemistry surrounding spent ' 3 nuclear fuel. In TSPA 3.2, we vary the chemistry of ground 4 water on a drip to scale. However, we have not conceded 5 that the chemistry inside waste packages. 6 These three are highlights of the current i 7 understanding of the chemistry inside a waste package. We 8 expect very high concentration of chloride and metal 9 chloride complexes inside a waste package. For instance, 10 sustaining localized corrosion requires presence of metal 11 chloride complexes at the concentration of about 15 percent 12 of-saturation. Hydrolysis of metal cations leads to 13 extremely acidic pH values. 14 Also, we expect the dilution of this solution, (m) 15 which may lead to cessation of pit growth. 16 Also, waste package internal environment is packed 17 and hence has many crevices where high concentration i 18- electrolytes will prevail. That's one aspect of chemistry. i 19 The other aspect is oxidizing conditions. We 20 expect oxidizing conditions near waste form for two reason, 21 one, alpha radiolysis will create highly oxidizing 22 conditions close to the surface of spent fuel; the second 23 is, the packed regions near the fuel may have other oxidized 24 species such as Iron-3+. 25 However, currently, there is insufficient [~) \_/ ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
409 1 understanding of the range of environments that may be l (A; 2 present inside the waste package. We have two comparative 3 phenomenon. One, localized concentration, the other one is l l 4 bulk dilution. 5 However, we have modeling and experimental tools 6 to investigate the extent of variation of this internal 7 environment, which may affect spent fuel dissolution rate in 1 8 a more conservative way. 9 On page seven is progress and current status, as I l 10 addressed before. Most of the processes of degradation 11 model was resolved between NRC and DOE. However, we still 12 need to resolve a few more based on TPA sensitivity analysis 13 which we conducted this year and last year. 14 We would like to evaluate further potential
..( p) 15 localized reducing environments such as with the effect of 16 iron and iron products.
17 The other one is to evaluate inter-laboratory 18 data, including our European data, on spent fuel dissolution 19 rate. 20 We would like to sample model parameters based on i 21 these further studies in future TPA 3.2 and we would like to 22 assess the chemistry inside the waste package further. l 23 Again, the path forward, in general, was presented 24 by Gustavo. We will have continuous interaction with DOE l 25 and so on, particularly to emphasize apply current models to { O ANN RILEY & ASSOCIATES, LTD. kms Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 l 2 84 b34 i \
410 f 1 new designs that may result in different temperature and ( 'Y 2 chemistry of ground water, and we will elaborate with new G' l 3 DOE data and modify the current assessment with the l 4 confirmatory testing program. 5 Page eight is on the cladding performance. Again, 6 the risk insight is the dose is sensitive to cladding 7 protections. If I go back to page three, the histogram of i 8 peak mean dose for 10,000 years and 50,000 years, you could l 9 compare the second, third and fourth spent fuel dissolution 1 10 model with a clad model, clad MI, you could see a very 11 sensitive protection of cladding in this plot of peak moat. 12 dose. l 13 However, we have many uncertainties associated 14 with the cladding performance. Those need to be () 15 investigated in the future. 16 As a technical basis, we identify likely processes 17 for cladding degradation, such as localized corrosion, 18 stress corrosion cracking, hydride embrittlement, creep, 19 mechanical failure, and initial damage and conditions. 20 I would like to particularly address the initial 21 damage and conditions, because DOE relies on the cladding 22 protection in their compliance assessment. 23 Restrictions on temperature applies only to retrievability 1 24 after storage. What this means is during the storage, the 25 environment could be pretty high, increasing the 1 (\ ANN RILEY & ASSOCIATES, LTD. (m / Cotrt Reporters 1025 Connecticut Avenue, NW, Suite 1014 i Washington, D.C. 20036 ! (202) 842-0034 i {
~
f' L 411
- 1. temperature, causing these failure processes.
(} 2 We agreed with DOE in-some of these aspects,.but 3 not all of them. To resolve unresolved sub-issues, we 4 conducted a TPA' sensitivity analysis and pursuing to (- 5' evaluate localized corrosion. 6 'As part of NRC rotational' assignment to the 7 center,- Charles Greene carae here to initiate the localized l l 8 corrosion cladding, as is shown in figure nine,:which shows ! l 9 .the tendency of the localized corrosion as a function of l l -10 ' chloride concentration. At the very high concentrated 11 environment, there is a tendency to initiate the pitting i 12 corrosion and cladding. 13 Currently, the center staff are continuing to 14 finish this subject. Also, Southwestern Research Institute
) 15 scientist Ki Chan is working with us to evaluate the
'16 mechanical failure of cladding.
l 17~ Future path forward is, again, things presented by V
~ 18- Gustavo and I would like to emphasize we will apply current i 19 'models to new designs that may result in different 20 temperature'and chemistry._of ground water, and we will 21- extend'to-evaluate other failure modes, like localized 22 . corrosion or mechanical failure.
23 The-last one.is high level waste glass
-24 degradation. Here, unlike the spent nuclear fuel and 25 . cladding performance, DOE, current DOE models do not result \ ANN RILEY.& ASSOCIATES, LTD.
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412 1 in dose contribution in the TPA 3.2 exercise. We took the rn (d' 2 DOE models and used in our TPA code and the contribution of 3 glass dissolution was negligible to ours. 4 The technical basis that we identified include 5 various degradation processes, such as stage three leaching 6 processes, colloid formation, hydride of glass surfaces 7 prior to wetting, iron container effect, and microbial 8 actions. 9 We agreed to most of the aspects with DOE. 10 However, we'd still like to include three aspects. One is 11 hydration. During the hot humid environment, the gla' can 12 be hydrated and become soluble when water came in. T~ e can 13 cause a very high dose later. We would like DOE to consider 14 that. And the colloidal from glass leaching,'especially f) t s y 15 plutonium release was 100 colloid, compared with plutonium j 16 l release from spent fuel. Therefore, we need to consider 17 colloidal aspect in glass leaching. ! l 18 In leaching of high level waste glass, there are 19 three stages. DOE considered only the first two stages. In 20 stage three, there is really accelerated leaching. We'd 21 like DOE to consider that, too. We will evaluate all these l 22 three aspects. j 23 Also, probe some important aspect, currently the 24 center initiated a scoping test of high level waste glass, 25 initiated by V. Jain here. He would study effect of [^\
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413 1 corrosion species in solution chemistry, representative 2 conditions near waste packages, and.long-term PCT and
- 3 pressurizedLunsaturated flow test.
4 Also, we_will continuously' evaluate the 5 uncertainties associated with various added degradation 6 modes. 7 The path forward is to apply current methods to ' 8 new designs. That.may result.in.different temperature and. 9 chemistry'of ground water. 10 _ In suntnary, using TPA ~ 3. 2, we conducted the system 11 level' performance of waste' form. In other words, we found
- 12. out waste form degradation models are very important in 13 determining dose.
14 Second one is the dose is sensitive to modes of
~15 spent nuclear fuel dissolution and cladding performance. A 16 more realistic model'for spent nuclear fuel dissolution was
- 17. used in.performancejassessment of NRC. Consequently, we did 18 .not need to introduce uncertainties associated.with cladding
-19 . protection or failure of container life.
20- The technical bases for waste form degradation are 21, established for licensing review of DOE application.
-22 Uncertainties associated with spent nuclear fuel, cladding 123- _ performance, and high level waste glass are further 24 investigated and modeling will continue.
25' Tests of simulated high level waste glass and O d ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025. Connecticut Avenue, NW, Suite 1014 Washington,_ D.C. 20036 (202) 842-0034
414 1 cladding have been initiated. [^ 'uJ
) 2 Thank you. Any questions? l 3 MR. WYMER: I just have a couple sort of minor 4 ones. On the high level waste glass degradation issue, you 5 had three items numbered here. One is risk insights, the 6 second one was technical basis, and then you had iron 7 effects. Can you say a bit more about what iron effects is?
8 MR. AHN: Yes. I believe I wrote that. Yes. 9 Page 10, technical basis, iron effect. Iron has very low 10 solubility. Therefore, it tends to form colloid. It could 11 be significant, yes. 12 MR. WYMER: Okay. All right. 13 MR. AHN: Yes. Yes. Yes. Yes. 14 MR. WYMER: Another-- it's not a question, it's a A 15 comment. i%) It seems to me you don't really need to worry too 16 much about plutonium in there, because there is not much 17 plutonium left in the high level waste glass, of course. 18 That was what they were af ter in the reprocessing, but it 19 produced a waste that made -- there is a whole lot less 20 plutonium than there is in the spent fuel. 21 MR. AHN: Yes, absolutely. The absolute amount of 22 release is less compared with that from spent nuclear fue] I l 23 MR. WYMER: By orders of magnitude. 24 MR. AHN: For instance, let's consider solubility 25 limits. Solubility, once you reach solubility limit with a l /~'N ANN RILEY & ASSOCIATES, LTD. k) Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 l Washington, D.C. 20036 (202) 842-0034
415 1 limited amount of water, it wouldn't matter how'much you f~ ) 2 have inventory, unless you deplete inventory. There is N-3 always a solubility limit. The value of the solubility 4 limits are the same for spent nuclear fuel and high level 5 waste glass. 6 Therefore, you would have a similar amount of l 7 concentration, as long as you do not deplete the inventory 8 of plutonium. 9 MR. WYMER: That's the point, of course. 10 MR. AHN: Yes. 11 MR. WYMER: You probably won't deplete the 12 inventory in spent fuel. You may well in glass. 13 MR. AHN: Yes. That takes quite a long time. I 14 don't think it would happen instantaneously. (O j 15 MR. WYMER: Yes. Okay. I don't have any other 16 questions right now. 17 MR. GARRICK: I just wanted to comment. You 18 indicated that you did a more realistic analysis of the 19 spent nuclear fuel dissolution. 20 MR. AHN: Yes. 21 MR. GARRICK: In the performance assessment. And 22 that was the reason you didn't take credit for cladding. l I 23 And then you commented that there is a lot of uncertainty 1 24 associated with the cladding analysis. l 25 MR. AHN: Yes. ) l / ANN RILEY & ASSOCIATES, LTD. I (s T) Court Reporters i 1035 Connecticut Avenue, NW, Suite 1014 I Washington, D.C. 20036 (202) 842-0034 l
416 1 MR. GARRICK: What if you did a realistic fuel fN _ 2 dissolution analysis in combination with a realistic 3 consideration of the effect of cladding? 4 MR. AHN: We did that, actually, in sensitivity 5 analysis.. You can barely see the dose in the histogram 6 there. 7 MR. GARRICK: So the difference is -- 8 MR. AHN: Right. We couldn't see the difference, 9 yes. 10 MR. GARRICK: But you also make the point that 11 they have to reduce the uncertainties associated with the 12 cladding analysis. 13 MR. AHN: Yes. Even without cladding protection, 14 our dose was very low. Therefore, we did not have to (m. n) I 15 introduce the uncertainties associated with the cladding 16 performance. This is the kind of a systems approach. 17 MR. GARRICK: Right. 18 MR. McCARTIN: Could I add one thing, Tae? When 19 you're saying you're adding in a realistic cladding model, I 20 think you want to be careful on that. I mean, that's using 21 DOE's model and it's not to say -- I don't think we know ; 22 what a realistic cladding model is for the behavior of 23 cladding over thousands of years. 24 MR. AHN: Yes, right. As I presented it in the 25 cladding section, the cladding itself has about seven, eight i ANN RILEY & ASSOCIATES, LTD.
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1 417 1 different degradation modes. I don't think we understand Ii 2 all of them at the present time. All we know is a range of
'd 3 failure in a given time, even though that is still ,
4 uncertain. 5 We took some of those failure rates in TPA 6 exercises and found out it is sensitive to dose. That's 7 what I meant. 8 MR. GARRICK: I'm still -- Tim maybe able to 9 straighten me out on this. I'm still trying to understand 10 the difference between understanding how to address cladding 11 dissolution, for example, and failure versus understanding 12 how to address the dissolution of the fuel. l 13 It seems to me, if you could do one, you ought to 14 be able to do the other. f ()) 15 MR. McCARTIN: I think Tae or Gustavo or some of ) 16 the materials people probably can answer that better. Some 17 of the problem with the cladding is you have unzipping and 18 other failure modes beyond dissolution and I guess what the 19 cladding -- how it behaves over thousands of years with 20 potential rock fall hitting it and causing mechanical 21 disruptions. 22 MR. GARRICK: I guess my point, though, Tim, is 23 you have the same problem with the fuel. You're talking 24 about -- 25 MR. AHN: Yes. [) ANN RILEY & ASSOCIATES, LTD.
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418 1- MR. GARRICK: -- it and how it behaves over f' (N x.s
) 2 thousands of years.
3 MR. AHN: DOE has studied fuel at a long period of 4 time and accumulated a database. On the other hand, 5 cladding credit has been given only on a few years ago. So 6- they have a limited database compared with the fuel itself. 7~ MR. GARRICK: Okay. We maybe we need to talk 8 about that some other time. 9 MR. WYMER: We have a little bit more time anyway. 10 I'd like to hear you say a few things more about the actual 11 degradation dissolution of the spent fuel material. l l 12 MR. AHN: Yes. 13 MR. WYMER: The oxidation and solubilization by 14 carbonate complexes and things like that. What more can you
/"
(N) 15 add in detailed chemical dist .asion? 16 MR. AHN: There are two types of release of 17 radionuclide. One is the release of very highly soluble 18 radionuclide, such as technetium, iodine. The other one is 19 a very low solubility radionuclide release, such as l 20 plutonium. Neptunium is in between. In the release of low 21 solubility radionuclides, always releases depend on either 22 solubility limits or colloid concentrations, times flow rate 23 is the release. 24 On the other hand, highly soluble radionuclides 25 will be released congruently with the matrix dissolution of I 'l ANN RILEY & ASSOCIATES, LTD. (_s/ Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
419 1 ' fuels. That's why it's so important to determine that the
] 2 solution of bare spent' nuclear fuel because technetium and l 3 iodine measures contribute to dose.
4 MR. WYMER: .I'm sure you know, because I've seen 5- some stuff that has been written about -- 6 MR. AHN: Yes.
-7 MR. WYMER: --
technetium. But you do know it, 8 but I'll say it for the benefit of everybody here, some
- 9. people may not know that in the spent fuel, approximately a 10 third.of the technetium is metallic particles. I know you 11 ,know that.
12 MR. ARN: Right, yes. 13 MR. WYMER: So there is -- and the rest of it is 14 probably dispersed maybe dioxide in the field.
/')
( 15 MR AHN: Yes. 16 MR. WYMER: And that has to be further oxidized I 17 and there'is a kinetic -- that's kinetically controlled and i 18 it's kind of refractory. It doesn't just leap up to the -- l 19 MR. AHN: Yes. 20 MR ' WYMER:
. So have you factored that into your --
21 'MR..AHN: Our approach is conservative. In other I 22 words, once' particles are released as a matrix, we assume
~23 all particles contribute to dose. They may not contribute 24 to=the dose.
25 MR. WYMER: So you're not taking any credit for
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420 1 about a one-third reduction in the dose, because -- (/y 2 MR. AHN: No. 3 MR. WYMER: -- it's not going to go anywhere. 4 MR. AHN: Right, right, right. 5 MR. WYMER: Okay. 6 MR. GARRICK: Any other -- Charles, do you have 7 any questions? 8 MR. FAIRHURST: No. 9 MR. GARRICK: George? 10 MR. HORNBERGER: No. 11 MR. GARRICK: Thank you. 12 MR. AHN: Thank you. ! l 13 MR. GARRICK: The program calls for this to be an i 14 open discussion. I guess one way to interpret that would be () 15 to ask the committee if -- on reflecting on the various 16 presentations that were made today, are there questions, 17 comments that you either forgot earlier and would like to 18 pick up on now or do you have some second thoughts about 19 some of the things that were said? Charles, do you have any 20 follow-up? 21 MR. FAIRHURST: In the talk by Dr. Cragnolino, I 22 know that you carried out the performance calculations up to 23 10,000 years. Did you carry them out any longer? 24 MR. CRAGNOLINO: Yes. We've done calculation for 25 longer time, but I don't see that we're exploring this
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421 1 particular issue at a longer time. l 2 MR. FAIRHURST: As far as maximum dose, how high 3 did it go? Of course, it varied for a lot of other factors. 4 MR. CRAGNOLINO: Yes. I can't recall. I have to 5 look in the notes. 6 MR. FAIRHURST: That's all right. Maybe we can l 7 just talk about it. 8 MR. WYMER: While we're waiting for him to come 9 back, I'll make a general observation. It disturbs me some 10 that the chemistry of these systems are so complex and the 11 databases, in many cases, are so inadequate at the moment, 12 what's in the literature is either not directly applicable 13 or it isn't in the literature, that you can't really take 14 advantage of a lot of the things that I think many of us I ( ) 15 feel are there that would allow you to get rid of some of 16 the conservatism that's in these estimates. 17 The doses are low anyway, so maybe the 18 conservatism isn't a problem, but if it turns out that it is l 19 a problem, it would be nice to be able to use some of these 20 chemical attributes of a system that tend to reduce the dose 21 as a backstop, as a backup for the possible contingency that 22 there is something unexpected comes up. 23 So just a general observation, I'm disturbed that R24 we don't -- we aren't further along with the chemistry. We 25 spent too much time on the geology. ('/ (_
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l 422 1 MR. GARRICK: That's true for a lot of things. (-s) 2 MR. AHN: Dr. Wymer, this is Tae Ahn. I presented 3 in page seven a current status the localized environment and
.4 the iron effects.
5 MR. WYMER: Yes. We need all of that we can get. 6 MR. AHN: As Dr. Wymer suggested, we are 7 evaluating potential reducing environment and iron effect 8 for spent fuel dissolution, as well as glass leaching. 9 MR. WYMER: I'm just concerned that the timeframe 13 is such that with the time you're having to evaluate this 11 license application, you atill will not have been able to 12 acquire all the information you need or by the time the 13 model changes again and there are other factors that are 14 important, there won't be time enough to patch up the holes () 15 wit'h data and that information. 16 MR. AHN: We have limited effort to conduct 17 experiment icself. However, we do analyze the performance 18 assessment based on literature data. 19 MR. WYMER: I certainly am supporting a much 20 increased effort. 21 MR. AHN: Thank you. 22 MR. CAMPBELL: Tae Ahn, before you get away from 23 th~e mic, let me turn that question around a little bit. 24 What would appear to be seen, and certainly in the tech 25 exchange back at the and ol May, are the microrem doses, [ ')
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v. 423 1- tens.of'microrems typically,.certainly in the 10,000 year l 2 period. Because of that, you are using and DOE is using 3 conservative ~ assumptions. 4 Would you feel that there are specific problem
- 5 areas that the NRC would have in terms of reason,ble 1
6 assurance thut would prevent licensing from going forward, 7 .even'if1you don't have all the data that you want at 8 . licensing? 9 MR. AHN: I have one concern. Suppose you uae any 10 conservative dissolution rate obtained in pure carbonate
~
11 solution, without cladding, the dose may go up to ten l 12 millirem. Then it's 25. If you consider uncertainties and 13 so on, then you might consider once more the cladding 14 protection and so on. p-15 MR. CAMPBELL: So the' issue is that you have -- 16 you believe that they have a very conservative dissolution 17 model. 18 MR. AHN: Right. 19 MR. CAMPBELL: And they make up for it with a more 20 optimistic, if you will,. approach to cladding. 1
, ;21 ' MR. AHN: Right. ,
i 22 MR. CAMPBELL: If that -- ) 23 MR. AHN: If that is the case -- l I 24 MR. CAMPBELL: In support of adversarial ; 25 discussion and it becomes not accepted, then you're stuck l i ANN RILEY &'ASf,0CIATES, LTD. i 4 Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington,'D.C. 20036 (202) 842-0034 1 l E .
<- i I; l L j 424 s 1: with it.
.2 MR. AHN: Right. That's what we are going to
-3 discuss next-week. -Yes.
.4 MR. WYMER: Also, if you don't have enough 5 information on secondary phase formation that sort of stands 6- in for the failure of cladding.
7 MR. AHN: Yes. 8' MR. WYMER: If you haven't got a convincing 9 ' database and models,;then you're also in trouble. l 10 MR. AHN: Right, yes. 11 MR. WYMER: So it seems to me that this is an 12 important area to pursue.
~13 MR. AHN: Yes.
14 MR. WYMER: Aggressively. 15 MR. AHN: Yes. l 16 MR. McCARTIN: Tim McCartin, NRC. Once again, 17- though, DOE is going to have to collect all that information 18 and support their models and we aren't trying to develop 19 these models for the. 20 MR. WYMER: No. But urless you can evaluate their 21' .models based on good'information that you believe, it may
~
22 not be good enough. 23 MR. McCARTIN: Well, their license application 24 will have to contain that information. There will have to 1 25 be support, with a recognition that there is a performance I ANN RILEY & ASSOCIATES, LTD. l O- Court Reporters 1025 Connecticut Avenue, Nh, Suite 1014 Washington, D.C. 20036 (202) 842-0034 l
425 1 ' confirmation period that lasts a very long time, which will 2 supplement the information.
- 3. MR. WYMER: .Okay.
4 MR..SRIDHAR: Can I add something to this? I hope 5' .I1can add something to it. But my -- I understood your 6' question'mainly' pertaining to spent fuel dissolution, not to 7- 'the waste' package. 8 MR. WYMER: That's right. That's what we were 9 talking about.here, yes.
- 10. MR. SRIDEAR: I think there are two questions that 11' we are trying to answer in relation to the cladding failure.
12 It's really how the holes in the container are going to be
'13 situated, because that seems to be a very critical 14 parameter, and we.have.this backed up model and we are doing
() 15. sensitivity analysis on the height of the hole and so on, 16: but that -fus something we need to know and that would 17 actually have more of an effect in eventual release.
- 18 We don't want to be prisoners of the chemistry 19 issue in some-way. I think in the container corrosion 20 issue, we have addressed.that by saying that based on our
.21- experience, on experimental data and so on, we limit the 12 2 number of species chat we need to understand. Otherwise, we 23- would be chasing all kinds of cats and dogs in the mountain, H2 4 . and we are raying in the container corrosion, we are mainly 25 interested in the chloride and the corrosion potential. ' : / ANN RILhl & ASSOCIATES, LTD
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426 1 I believe that in doing spent fuel dissolution l '2 type of modeling, we have been using mainly DOE data based V) 3 on the immersion corrosion tests, but we haven't really 4 taken a mechanistic approach to predicting spent fuel 5 dissolution rate. 6 One of the things the Canadians have done a lot 7 better job than we have is really approach it from a l 8 mechanistic point of view on why spent fuel corrodes the way 9 it does. They're using an electro-chemical approach, 10 because spent fuel does dissolve and is electro-chemically 11 active. I think that would provide us a mechanism, that's 12 my hope, to eliminate a lot of the unnecessary information 13 needs and help us focus on the few chemistry details that we 14 need to know. O) ( 15 For example, redox potential, we need to know that 16 and perhaps carbonate and sulfate and so on. But we may not 17 need to know everything about the environment. 18 MR. WYMER: That gets back to the earlier point, I 19 think, of the importance of understanding mechanisms r.c 20 opposed to just phenomenological experimentation. 21 Your confidence in extrapolations into the future 22 and your confidence in the information you gather in the 23 pre-closure period is pretty much based on your 24 understanding of the mechanisms that really are controlling 25 things rather than just taking data. j I I
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I 427 1 I know you're going after mechanisms and I think () 2 3 that's the right thing to do. MR. SRIDHAR: Right, and we need to do more of 4 that for spent fuel. 5 MR. WYMER: Yes. And it needs to be more broadly f l 6 applied, that concept. That's right. Thank you. 7 MR. GARRICK: George, anything? 8 { MR. HORNBERGER: No. i l 9 MR. GARRICK: We have a sidebar going on here. l 10 MR. CRAGNOLINO: We're getting a copy of that. ) 11 This clarifies only one question that I had before from Dr. 12 Fairhurst, and this referred to the multiple realization to 13 calculate radionuclide dose, and obviously it was not 14 presented in detail here, but for the technical excuar.ge () 15 with the DOE on May 27, we showed the calculation up to 16 100,000 years for the base case and the peak expected dose 17 was four millirem per year. Answering your question. 18 Let me make a point. I have a little disagreement i 19 with what Sridhar said before regarding the spent fuel. I 20 think that it is very important in this approach, the 21 electro-chemical approach to the dissolution rate of the 22 spent fuel. But one of the conclusions that they have is 23 that even though this approach gives you the maximum rate of 24 dissolution, and allows you to map out the behavior in terms 25 of the redox condition there was the issue of alteration ,C') ANN RILEY & ASSOCIATES, LTD. A/ m Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 m
428 1 products on the spent fuel surface that could come. s-s
) 2 The potential effect of the slowing down the process, but 3 also later on, by exfoliation, produce release, and I think 4 that this is an issue that has to be addressed mostly by the 5 DOE,'obviously, but we have to have a more solid type of 6 approach.
7 I don't think they have the standard that we have 8 here about this problem and I think that this is something 9 that has to be -- and it has to be done also in relation to 10 the models that we have for spent fuel. We need to keep 11 looking at these and trying to improve these and improve the 12 technical basis for these. 13 14 MR. FAIRHURST: Could you help clarify for me () 15 something? Because in the VA analysis, these doses were up i 16 to 25 millirem or more. ' 17 MR. HORNBERGER: That's DOE's anElysis. 18 MR. FAIRHURST: I know. But I'm L.fi ng to say 19 what is -- could you identify roughly what was different in
)
20 those realizations than these. I see you've got some 21 specific statements about
- ravel time in the unsaturated 22 zone and so on.
23 MR. WYMER: Time scale. 24 MR. CRAGNOLINO: I think that I -- this was my 25 intention to answer your question, because he is more in the i [ ANN RILEY & ASSOCIATES, LTD.
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429 1- condition of'this, but that Gordon might clarify this L2 particular issue. 3' .MR.'FAIRHURST: Okay. Good.' 4 MR.'WITTMEYER: Gordon Wittmeyer, from the center. 5- 'Sitiganta:has. graciously allowed me to answer instead.
'6 Really, it's very hard to compare the VA and TSPA/VA to the ,
1
-7. .TPA results here because there-are so many different 8 ' approaches, that they mask what the essential differences i 1
9 are. 10 One thing I could point to, and, Tim, please chime 11 ~ .in when you' feel it's appropriate. One thing is we have a
- 12 much'different approach to computing the concentration in 13 the. dose at the receptor location. That alone could account 14 for a difference that if we're following the numbers here,
() 15 the difference between four. millirem and, I believe, 25 16 millirem. .A factor of roughly six. 17 , .But there are so may things. It's very hard to 18 tell you what the differences are unless we go'through and 19 kind of do one-up analyses on each one of the models very 20 carefully. 21" So.that's a very good non-answer, I think. 22 MR. EAIRHURST: Let me come back to the second 23 ' question. If your-answer is.not quite an order of magnitude 24 .differents four to 25 is getting close,'first, that yours -- 25 .I'm saying if this is not the real license application, but I ANN RILEY & ASSOCIATES, LTD.
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0 430 ll yours is lower, but what -- you're Lne one'that has to , ('2h 2i- decide whether it's acceptable or not, right? So how are
%.)
3' you going to get at these hidden assumptions that are made 4 _ in the' differences? 5 MR. WITTMEYER: We get in there and we actually 6~ . probe 1very carefully each of'the model assumptions used in
- 7. the:TSPA/VA. We have done that. In some cases, we'll take l 8 our best understanding of their models, try and mimic them 19~ .with our models by changing parameters.
10 We always get -- we can't always do that in a 11 straightforward way, but we think -- 12 14R. FAIRHURST: I understand. 13 MR. WITTMEYER: But we think try to see what those 14 differences are. It's just hard, dirty work going through () 15 there one at a time. 16 MR. FAIRHURST: Thank you. 17 MR. GARRICK: Now, before we sign off, I want to 18' ask Washington and Las: Vegas if they have any comments that l 19 they would care to make. Let's start with Washington, since 20 it's later there. 21 MR. McCARTIN: I think we're all pretty happy l 22 here, I guess. Dick, did you have something that you wanted
'23 -to add?
24 MR. CODELL: This is Dick Codell from NRC. I 25 would be interested in getting.the committee's view on the O ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, 'IM, Suite 1014 Washington, D.C. 20036 (202) 842-0034
1 i 431 ) 1 importance of colloids, if they have anything to add to our
'N (d 2 3
performance assessments. I personally feel that it's blown ' out of proportion, but the little studies that we've done at 4 NRC are on very over-simplified modeling. 5 I don't think that they're realistic at all. 6 They're put out there really to generate some controversy so 7 we can get some discussion going. When you see concerns 8 about colloids, like tne recent discovery of plutonium 9 colloids at the Nevada test site from the Benham nuclear 10 test, that raises public's concern about it. That's why we 11 need to put it to rest, if we can. 12 So does the committee have any thoughts on this 13 issue? 14 MR. GARRICK: I don't know if we've advanced our () 15 C. linking on it to a point of -- but, Ray, I know you have 16 some thoughts about it. 17 MR. WYMER: These are just off the cuff, but 18 that's all you're going to expect to get. 19 I think that primary colloids, like americium and 20 plutonium, are not too likely to make any real contribution. 21 The importance of secondary colloids, like the solutions 1 22 material or clays or the iron hydroxide type colloids, I 23 think you've got to take a pretty good look at those because j 24 they do absorb things pretty strongly and you'll have 25 conditions where the colloids will form. But I don't think ) l i [9 ANN RILEY & ASSOCIATES, LTD. (_ / Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0014 1 l J
I I 432 l,
; 1 you can write it off without a little bit more attention.
t , ,~s ( ) 2 MR. GARRICK: Do you have any comments about
%./
-3 colloids?
4 MR. HORNBERGER: Well, there is no doubt that 5 certainly in the saturated zone, as you indicated, Dick, in i 6 the Benham test, there is a very clear indication that there 7 has been movement over a kilometer or so, several hundred
'8 meters anyway.
9 The real question really is whether or not any of l 10 the colloids will be mobile to any extent in the unsaturated 11 zone and there are -- I think there are serious doubts that 12 the colloids will ce an issue because of that. 13 Again, how do you lay it to' rest? I think that 14 there is some work going on, there is some work going on at !
/s
( ,) 15 Lawrence Berkeley and elsewhere, I guess at Sandia. DOE is l 16 certainly doing, I think, doing enough experimental work, l 17 that data should be available. 18 MR. GARRICK: Any other comments? 19 MR. McCARTIN: We have one more comment from 20 Washington and it's just somewhat of a supplement to what 21 Gordon said about comparing the DOE and the NRC results. 22 He's absolutely correct, there are many, many 23 different aspects to the two analyses that are different and 24 it's<hard to get a one-to-one correspondence. However, in 25 doing the -- when we do a license application, we are going (~)' s-ANN RILEY & ASSOCIATES, LTD. Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 i u-
433 1 to have to understand where the differences are and what it ( 2 means, whether we ask DOE to do some additional analyses 3 with slight changes in parameters, or we do them. 4 Obviously, we'll have to wait and see what the 5 analyses look like, but we will -- we certainly have a good j 6 idea of where our differences are and the fact that we have 7 four versus 25, we're certainly in the same ballpark. 8 But let me say that one thing.that really makes a 9 comparison difficult is the fact that there is a strict time j l 10 limit there. And you can change that dose by moving a j 11 little bit further or a shorter time period or a longer time ; 13 period and there are things that delay the dose. l 13 If we're going all to a peak no matter when it I 1 14 occurred, it might be that the comparison would be easier, l fg 1 ( ) 15 but I think some of that could be just due to where in time 16 we decide to cut off the dose. 17 MR. GARRICK: That's a good comment. Any other 18 comments with Washington? How about Las Vegas? Any 19 comments from Les Vegas? Did we drop them or lose them? 20 MR. 7 S: Not to my knowledge. 21 MR. GARRICK: Just no comment. At least there 22 ought to be 6 comment that there is no comment. I think 23 they've had enough. All right. Any other comments from the 24 room or from the staff? 25 I know that Andy has an announcement he wants to l O ANN RILEY & ASSOCIATES, LTD, l \s- Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034 l
434 1 make, do you not? Or Lynn. j r~s I i 2 MS. DEERING: I just wanted to announce
- hat there (G
3 is a one-on-one informal discussion planned with George 1 4 Hornberger tomorrow. It's going to take place at 7:30 a.m. 5 here and the subjects would include thermal effects, 6 saturated / unsaturated zone or igneous activity, those are 7 possible topics. We don't have anything particular planned. 8 But I think Dr. Fairhurst will also join us. J l 9 The plan was to get a room, and I don't have a 10 room yet here, but we were going to contact Robert Johnson 11 in the morning and let them know what the bridge number is, 12 if there is anybody in Washington who would like to join 13 that discussion. 14 Thanks. (),
/'
15 MR. CAMPBELL: And as far as the other individual 16 meetings, those will be at 1:00 tomorrow. i 17 MR. GARRICK: Central time. All right. Any 18 parting comments from anybody? I thought we had a very good 19 day., covered a lot of material, saw some very interesting 20 experiments, heard some especially insightful remarks, and I 21 with that, I think we will adjourn. j 22 [Whereupon, at 5:00 p.m., the meeting was 23 recessed, to reconvene at 8:30 a.m., Wednesday, June 30, 24 1999.] 25 l
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nr ; i REPORTER'S CERTIFICATE This is to certify that the attached proceedings j) 'before the United States Nuclear Regulatory Commission in the' matter of: NAME OF PROCEEDING: .110TH ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW) CASE NUMBER: PL7CE OF PROCEEDING: San Antonio, TX I were held as herein-appears, and that this is the original
-transcript.thereof for the file of the United States. Nuclear Regulatory Commission taken by me and'thereafter reduced to typewriting by me or under the direction of the court reporting company, and that'the transcript is a true and
. accurate record of the foregoing proceedings.
V 4.s n
, n.wn 3
Penny Bynum Official Reporter Ann Riley & Associated, Ltd. g sJ t I' .}}