ML12332A234
| ML12332A234 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/18/2012 |
| From: | NRC Region 4 |
| To: | |
| References | |
| NRC-1798 | |
| Download: ML12332A234 (46) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Augmented Inspection Team Exit Meeting with Southern California Edison Company DVD 1/4 Docket Number: (n/a)
Location: San Juan Capistrano, California Date: Monday, June 18, 2012 Work Order No.: NRC-1798 Pages 1-46 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005 (202) 234-4433
1 1 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +
4 AUGMENTED INSPECTION TEAM EXIT MEETING WITH SOUTHERN 5 CALIFORNIA EDISON COMPANY 6 + + + + +
7 MONDAY 8 JUNE 18, 2012 9 + + + + +
10 SAN JUAN CAPISTRANO, CALIFORNIA 11 DVD 1/4 12 + + + + +
13 The meeting convened in the Community Hall 14 at the San Juan Capistrano Community Center at 25925 15 Camino Del Avion, San Juan Capistrano, California, at 16 6:00 p.m., Richard Daniel, presiding.
17 NRC STAFF PRESENT:
18 RICHARD DANIEL, Facilitator 19 THOMAS BLOUNT 20 ELMO COLLINS 21 GEORGE CRAVER 22 EMMETT MURPHY 23 JOHN REYNOSO 24 JOEL RIVERA-ORTIZ 25 GREGORY WARNICK NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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2 1 PRESENT: (CONTINUED) 2 GREGORY WERNER 3
4 ALSO PRESENT:
5 PETER DIETRICH, Southern California Edison Co.
6 DOUGLAS BAUDER, Southern California Edison Co.
7 THOMAS PALMISANO, Southern California Edison Co.
8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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3 1 P-R-O-C-E-E-D-I-N-G-S 2 (10:10 a.m.)
3 FACILITATOR DANIEL: (Joins during 4 progress) with you tonight. First gentleman to the 5 right -- we'll start to the right -- is regional director 6 for Region IV, the NRC, Elmo Collins.
7 Immediately to his left is Tom Blount. He 8 is the acting director for division of reactor safety.
9 The gentleman in the red shirt is Greg 10 Werner. He is the branch chief in the AIP team lead.
11 And finally the guy with the good haircut 12 there is Greg Warnick, senior resident inspector.
13 Peter Dietrich, Southern California, soon 14 I'm going to allow you to introduce your own folks.
15 MR. DIETRICH: Yes. Thank you. Good 16 evening. Pete Dietrich, the senior vice president and 17 chief nuclear officer for Southern California Edison, 18 and we are pleased to be here tonight to be able to talk 19 about the status of our steam generator situations with 20 concerned members of the public and other stakeholders.
21 MR. BAUDER: Good evening, Doug Bauder, 22 state vice president, San Onofre.
23 MR. PALMISANO: Good evening. I'm Tom 24 Palmisano, vice president of engineering, projects and 25 site support.
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4 1 FACILITATOR DANIEL: Okay. So without 2 further ado, I'm going to turn this over to Mr. Elmo 3 Collins. Elmo?
4 MR. COLLINS: Thank you Rick. I hope the 5 microphone is working.
6 FACILITATOR DANIEL: Hang on a second.
7 MR. COLLINS: Does that sound better? I 8 want to make sure that everyone --
9 Is this better? I hope everyone can see 10 me. I might need a stool you know, maybe. Maybe a 11 pulpit, you know, like church, but not that, I'm not 12 going to do that tonight. Thank you Rick.
13 Southern California residents, Mr.
14 Dietrich and other Edison employees, members of the 15 media, NRC representatives, good evening. I think I 16 would also like to introduce to you tonight another NRC 17 representative who is here. This is Tom Hipschman.
18 He is a technical assistant for the NRC chairman -- Tom's 19 in the back there -- the NRC Chairman Dr. Gregory Jaczko.
20 So we are glad Tom could join us tonight for the meeting.
21 Thank you, Tom, for being here.
22 I want to thank everyone for taking the time 23 to come out tonight to hear the Nuclear Regulatory 24 Commission present results of our augmented team 25 inspection.
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5 1 I can see we have a large crowd. I trust 2 that represents the large amount of interest that you 3 have here in the results and what's going on at San 4 Onofre.
5 I expect that many of you had to travel to 6 get here and so I appreciate the time, the effort that 7 you made to come and listen to what you have to say to 8 you tonight.
9 We all know that both units at San Onofre 10 are shut down because of what has proved to be very 11 difficult technical issues which their steam generators.
12 And I'll just start tonight by saying, so 13 far these issues are not resolved to the NRC's 14 satisfaction. Understandably --
15 (Applause) 16 MR. COLLINS: Understandably, I think there 17 is a lot of concern on your part, and I think that concern 18 is warranted.
19 For tonight's meeting we are here to present 20 the team's preliminary results to Edison, licensee, and 21 to you tonight, and we are going to talk to you about 22 those results, and NRC is glad to be here to share with 23 you what we know so far at the end of this stage of our 24 review.
25 This is a different public meeting from what NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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6 1 we normally conduct. As Rick indicated, this is an NRC 2 inspection exit meeting. This marks the end of the 3 augmented team inspection which we started several 4 months ago and what you are going to hear tonight are 5 the preliminary inspection results.
6 There's no inspection report yet. That's 7 to come, we are guessing, in about 30 days. But tonight 8 you will hear what the inspection team found.
9 Additionally, the augmented inspection teams are 10 directed to focus on fact finding and information 11 gathering.
12 We have not yet made any decisions about 13 the resumption of power operations at San Onofre. Nor 14 have we made decisions about whether violations occurred 15 as a result of that inspection.
16 Those will be indicated to you, there is 17 requiring additional follow-up -- as follow-up items 18 when the team gives its findings. So I ask you tonight 19 to keep the issues that the team describes within that 20 context, remembering that the issues are not final agency 21 conclusions.
22 Rick talked about the comment and question 23 period we are going to have after we complete the business 24 part of the meeting. I think, at the risk of stating 25 the obvious, I know there are a lot of questions out NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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7 1 there, and so we are going to be here to answer those 2 questions.
3 We'll tell you what we know and we'll tell 4 you when we don't know, and we'll tell you when we think 5 more work is needed, and I think the questions are going 6 to fall into all three of those categories.
7 I'll also just indicate for you, tonight's 8 meeting is what NRC views as the first in a series of 9 public meetings that we are going to have to conduct 10 associated with the follow-up on these technical issues.
11 We are going to be conducting additional 12 inspection. We are going to be getting submittals from 13 Edison in writing that we'll be following up on, so as 14 they work through the issues and the NRC inspects them, 15 we will continue to conduct public meetings with you.
16 We do believe additional work by Edison is 17 needed and we do believe additional NRC inspection is 18 needed, and that will have to happen before NRC is in 19 a position to make a decision about the acceptability 20 of a resumption of power operations at San Onofre.
21 I want to thank you again for being here, 22 and we hope the meeting is informative for you, and with 23 that, I think Tom Blount will introduce the Augmented 24 Inspection Team, and we'll get into our presentation.
25 MR. BLOUNT: Thank you, Elmo. Is this all NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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8 1 right for everyone. I kind of thought we'd go through 2 that. Sorry. I would like to offer my thanks and 3 appreciation for everyone coming out this afternoon, 4 or this evening, as well.
5 Before we get into the inspection results 6 itself, I did want to take just a couple of minutes and 7 give you some appreciation or perspective regarding the 8 team and the team's background.
9 We recognize that this is an important and 10 pretty serious issue, and the agency as a whole engaged 11 in this inspection team and provided the resources 12 necessary to support that.
13 We had support from not only Region 4, but 14 from our four other offices as well, including Research 15 and our Nuclear Reactor Regulation. Region 2 also 16 supplies some support.
17 Some of the talent that we had on this team 18 included a steam generator tube integrity engineer, a 19 thermal hydraulics specialist, steam generator material 20 engineer, quality assurance and control engineer, design 21 and evaluation engineer, all led by a Branch Chief from 22 Region 4, Greg Werner, who is going to give you the AIT 23 results here momentarily.
24 This team had over 130 years of total 25 experience that they brought to the table on this issue, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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9 1 not only as the team was doing their work, but we also 2 had the rest of the agency engaged in supporting our 3 efforts.
4 So I just wanted you to be aware, we took 5 this very seriously and want to get the right resources 6 to apply to this issue and will continue to do so.
7 With that, then, I'd like to ask Greg 8 Warnick if he'd give us an overview of the event and 9 the steam generators themselves.
10 MR. WARNICK: Sure, thank you very much.
11 Good evening. I'd just like to give a high level 12 overview of the steam generator tube leak event, the 13 licensee's response to that event, and what I personally 14 observed on January 31st, 2012.
15 The San Onofre plant is designed to rapidly 16 detect small amounts of radioactivity, small amounts 17 of leakage from the reactor system to the steam system 18 using sensitive radiation monitors that continuously 19 monitor and sample for radioactivity, samples of steam 20 that makes it way from the steam generator to the turbine 21 generators.
22 Procedures are in place that should, on 23 indication of steam generator tube leaks, actions are 24 prescribed to put the plant into a safe condition to 25 protect public health and safety.
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10 1 Finally, operators are trained on these 2 types of events such that they can quickly diagnose 3 problems, implement procedures and make the necessary 4 decisions to minimize any radioactive release to the 5 environment.
6 On the afternoon of January 31st, I had just 7 returned to my office from performing a plant tour as 8 part of an inspection. At that time, I heard a PA 9 announcement about a secondary plant system radiation 10 alarm.
11 John and I, John is a Resident Inspector, 12 we were both in the office. We went directly to the 13 control room when we heard that PA announcement. Our 14 offices are less than 100 yards from the Control Room, 15 so we were there within moments.
16 Both John and I went there and observed 17 actions to ensure that -- to assess the conditions and 18 ensure that the appropriate actions were being taken.
19 Upon arrival, I determined that the plant had 20 appropriately responded to the tube leak by identifying 21 leakage from the Reactor Coolant System and alerting 22 the operators to the abnormal condition before any 23 licensed release limits had been exceeded.
24 The operators responded in accordance with 25 their procedures to accurately diagnose a steam NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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11 1 generator tube leak. They accurately assessed 2 conditions to determine that a rapid power reduction 3 and a plant shutdown was necessary.
4 After the plant was shut down, the operators 5 promptly isolated the affected steam generator to 6 terminate the radiation release and continued on to cool 7 down and depressurize the plant.
8 Because of the plant design, the 9 established procedures and the skill and training of 10 the operators, SONGS Unit 3 was placed into a safe 11 condition and the radioactive release that did occur 12 was minimized.
13 Our regional experts have independently 14 quantified the release and concluded that it was only 15 a very small percentage of the release limits allowed 16 by the plant license, such that the release associated 17 with this event did not represent a threat to workers 18 on site, to the public or to the environment. Next slide 19 (Question off-mic) 20 MR. WARNICK: Excuse me?
21 PARTICIPANT: What percentage?
22 (Question off-mic) 23 MR. WARNICK: It's a very small percentage 24 and that will be a -- go ahead and bring that up during 25 the question and answer period and I'll be happy to answer NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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12 1 that.
2 MEMBER OF AUDIENCE: And what was it that 3 was released, what kind of radioactivity?
4 (Question off-mic) 5 FACILITATOR DANIEL: Folks, hang on a 6 second. We're going to have a question and answer period 7 of time, comments and everything. Let the gentleman 8 finish his presentation and we will take your questions 9 at the appropriate time, okay? Thank you.
10 MR. WARNICK: Okay, again to reiterate, I 11 work at the plant every day, went to the Control Room 12 and assessed conditions. I'd like to now just talk 13 briefly about the steam generator function and some of 14 the structural components so that you will understand 15 some of the terms as we go through the balance of this 16 presentation.
17 The function of -- or the purpose of a steam 18 generator is essentially to make steam out of water.
19 It does this by acting as a large heat exchanger that 20 transfers heat from the primary radioactive system to 21 the clean steam system where it boils water into steam.
22 Hot radioactive water enters into the 23 bottom of the tube area and travels up through the inside 24 of the tubes, around the U-bend, back down to the cold 25 side of the bowl area and returns to the reactor to be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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13 1 reheated.
2 The clean secondary water enters into the 3 steam generator, it flows down around the outside of 4 the tube bundle, it is then directed up around the outside 5 of the tubes of the tube bundle region, where it is heated 6 up, it boils into steam and that steam acts as the top 7 of the steam generator to go to the turbine to make the 8 electricity.
9 Now I'll point out a few other structural 10 components, just, again, to aid in understanding of terms 11 we'll be using throughout the balance of this meeting.
12 A divider plate separates the hot and cold 13 bowl areas. That divider plate also helps to direct 14 flow of the primary water up through the U-tubes. It 15 also acts as a support for the divider plate and the 16 steam generator internals.
17 It is hard to see in this picture, but the 18 vertical section of the tube bundle is supported by tube 19 support plates. Those tube support plates provide 20 structural support to that vertical section.
21 In this picture, again, it's hard to see 22 but there are small holes throughout the tube support 23 plates. There are several of them that go up through 24 that vertical section. There are also flow channels 25 throughout the middle of the tube bundle region.
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14 1 The upper U-bend section of the tube bundle 2 is supported by a system of anti-vibration bars and 3 retainer bars. The steam generators are 65 feet tall, 4 they are 14 feet in diameter and they have a little less 5 than 10,000 tubes throughout them to perform that 6 function of transferring heat to the water.
7 It was one of these tubes in one of these 8 steam generators, one of these 10,000 tubes that 9 developed a leak, and resulted in the event that I just 10 briefly highlighted, that happened on January 31st.
11 ***time test 103406 12 FACILITATOR DANIEL: Folks, we are going 13 to take a short break here. Basically we have too many 14 people in the room, over capacity and we are going to 15 take a short break and move some folks out in the 16 courtyard on the side -- over on this side of the 17 building.
18 So, there are speakers out there and I 19 promise you I will come out and take your questions.
20 So if you could slide out the door. So you folks along 21 the back wall, if you move outside.
22 (Pause for organization of audience) 23 MR. COLLINS: I appreciate everyone's 24 cooperation. I apologize that we have to take this pause 25 and it's a disruption to our meeting, but this is, we NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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15 1 have been informed, important for safety, and important 2 for adherence to the fire code. So thank you so very 3 much for giving us this consideration.
4 (Pause while audience organized) 5 FACILITATOR DANIEL: Gil Leone (phonetic),
6 could you come back so I can speak with you please?
7 Gil?
8 (Off mic discussion about facility director 9 and fire code) 10 FACILITATOR DANIEL: For those folks that 11 are still standing there, okay, all right. We are going 12 to continue. Sign down, please. If you want to hold 13 up your sign, you can go outside and hold it up, but 14 not while you are seated.
15 (Off-mic remarks) 16 FACILITATOR DANIEL: I understand, but I 17 asked at the beginning, I asked at the beginning, that 18 signs be held in the back, because we are afraid somebody 19 might get hit in the head. We had that happen in another 20 meeting.
21 Okay, so -- ready? All right. We are going 22 to hear from Mr. Greg Werner here.
23 MR. WERNER: Good evening. I am Greg 24 Werner, the Augmented Inspection Team leader. I am 25 going to go ahead and briefly discuss the decision to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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16 1 conduct the augmented inspection.
2 During the pressure testing of the 129 tubes 3 on the Unit 3 steam generator, eight of the tubes failed 4 to meet the strength requirements necessary for tube 5 integrity.
6 Because the teams failed, this resulted in 7 conducting augmented inspection. Even before we made 8 a decision to perform the augmented inspection, two 9 Region 4 inspectors were already on site, accomplishing 10 the Unit 2, in-service inspection of the steam 11 generators.
12 This was part of the normal NRC inspection 13 program. We always complete an in-service inspection 14 that looks at 100 percent of the tubes after the first 15 outage for a replacement steam generator.
16 After the tube leak on Unit 3, we also 17 brought in Emmett Murphy from headquarters to assist.
18 Emmett has over 30 years of steam generator experience.
19 SONGS inspected 100 percent of all the steam 20 generator tubes on Unit 2 and 3, almost 40,000 tubes.
21 The NRC independently reviewed and analyzed the results 22 of the tube inspections and based upon our review of 23 the type of flaws on the Unit 3 tubes and the large number 24 of tubes with deep wear and over a long length of the 25 tube, the NRC had very good reasons to believe there NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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17 1 had been multiple failures of tubes on Unit 3.
2 So even before the first tube failed, Region 3 4 was working to put together an inspection team and 4 inspection charter. Because of this, we had inspectors 5 on site during the pressure testing.
6 The Augmented Inspection Team was initially 7 on site for two weeks. However, the team has continued 8 to review large quantities of documents, including the 9 cause evaluations, the 50.59 evaluations, draft 10 operational assessments, thermal hydraulic and 11 vibration computer simulation models, as well as 12 numerous other documents.
13 In addition, various team members, 14 including myself, have traveled back to SONGS to observe 15 expert panels on the cause evaluation, computer 16 simulation operational assessment.
17 To date, the Augmented Inspection Team has 18 expanded well over 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> associated with this issue.
19 Next slide, slide 11.
20 As Tom Blount mentioned earlier, 21 individuals with specialized expertise were brought in 22 from Region 4, Region 2, Office of New Reactors, the 23 offices of nuclear reactor regulation research at 24 headquarters in Rockville, Maryland.
25 I'm going to discuss the key items or NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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18 1 objectives that the augmented team was tasked to look 2 at. We developed an event time line to look at the 3 design, construction, shipping, installation and 4 operation of both unit steam generators, reviewed 5 information to determine the causes. We looked at the 6 operational activities on the units to see if there was 7 impacts associated with those. We compared the 8 differences in the design manufacturing between the two 9 units, reviewed quality assurance and quality control 10 associated with the design and manufacturing of both 11 units' steam generators. We also reviewed 12 implementation of the generic communications and 13 industry lessons learned, to see if they incorporated 14 lessons learned that we gathered over the last 30 or 15 so years of steam generator use, reviewed the steam 16 generator simulation models. We also collected 17 information for the NRC risk assessment. We also looked 18 at other areas such as radiological controls that Greg 19 discussed.
20 One of the key areas that we wanted to 21 understand was the differences between Units 2 and 3.
22 Why was there more wear on Unit 3 than Unit 2, because 23 essentially the designs were identical?
24 It's important to note that for a number 25 of items we not only looked at what SONGS did, but we NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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19 1 also gathered information from Mitsubishi. We looked 2 at what the residents collected during the rapid shutdown 3 of Unit 3. We wanted to make sure that the operators 4 of the plant responded appropriately to the event.
5 The team looked at hundred and hundreds of 6 documents, including design, manufacturing and 7 operational information. We did our own independent 8 comparison of the information between the units. We 9 compared manufacturing information with design 10 information to check to see if the steam generators are 11 built in accordance with the design.
12 Where there were differences, we reviewed 13 the justification or the associated change 14 authorizations. Slide 12, please.
15 Now I plan to discuss what the Augmented 16 Inspection Team found. Throughout the US nuclear 17 industry, this is the first time that more than one steam 18 generator tube failed pressure testing.
19 As I discussed earlier, because of the 20 failure of the Unit 3 tube leak, 100 percent of the tubes 21 were inspected with subsequent pressure testing of 129 22 of those tubes on Unit 3.
23 During this pressure testing on Unit 3, 24 eight tubes failed. The pressure testing identified 25 the strength of the eight tubes was not adequate, and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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20 1 structural integrity might not be maintained during an 2 accident.
3 It is important that both SONGS and the NRC 4 understand what occurred and why. This is a serious 5 safety issue that must be resolved to prevent further 6 failures from occurring again. This information will 7 be shared throughout the nuclear industry.
8 SONGS did use multiple independent 9 consultants and steam generator manufacturers.
10 Personally I have never seen such a vast collection of 11 experts working together. They had academia, 12 independent consultants, industry experts from 13 different utilities as well as the industry itself, and 14 they also had four different steam generator designer 15 and manufacturers looking at the issues.
16 Next slide. These next two items that I'll 17 be discussing are really the most important items that 18 the NRC identified during inspection activities. These 19 are the ones that everybody, including us, were 20 interested in.
21 Actions will have to be taken to address 22 these to prevent the vibration that leads to the 23 tube-to-tube wear from occurring again.
24 The team identified the primary cause of 25 the unexpected tube wear was higher than expected flow NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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21 1 velocities in the steam generators.
2 Early in our inspections, we independently 3 developed a simplified mathematical thermohydraulic 4 computer simulation model of the steam generators in 5 Units 2 and 3.
6 Using this, we determined that the computer 7 simulation used by Mitsubishi during the design of the 8 steam generators had underpredicted velocities of steam 9 and of water inside the steam generators by factors of 10 three to four times.
11 San Onofre also had three other steam 12 generator vendors conduct computer simulation. The 13 results of their computer simulation also showed 14 significantly higher steam velocities and confirmed our 15 results.
16 Now the next item that I am going to discuss 17 deals with the differences between Unit 2 and 3. We 18 looked at a number of different items. However we only 19 identified one item that we could essentially determine 20 as the cause.
21 The cause of the difference in the tube wear 22 between the Units 2 and 3 is associated with the 23 manufacturing differences of the tubes and 24 anti-vibration bars.
25 For Unit 3, the anti-vibration bars do not NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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22 1 come in contact with the tubes as tightly as they do 2 on Unit 2, along with the higher steam and water flows 3 created to the conditions necessary for the high 4 vibration.
5 So essentially the tubes are not held in 6 place securely enough so it allows them to slide or 7 vibrate. SONGS has continued to analyze and develop 8 additional actions to fix and prevent this from happening 9 again. Next slide.
10 Now what I'd like to talk about is the item 11 or the items that the team identified that require 12 additional follow up. However on this 10, we only --
13 we believe that only two are related to the tube-to-tube 14 wear. I am just going to very briefly discuss these 15 items.
16 There's a post trip and transient 17 procedure. SONGS did not conduct a formal review of 18 the reactor trip because they considered a plant trip 19 when they shut down the unit. So we are going to look 20 at the procedure as well as the operator actions to assess 21 if it was appropriate.
22 We are going to evaluate and disposition, 23 look at the numerous Unit 3 loose part monitor alarms.
24 The NRC needs to review how these alarms were evaluated.
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23 1 what we call nuisance alarms, versus being evaluated 2 in accordance with procedures.
3 The retainer bar design was not evaluated 4 for vibration impacts. Although this sounds familiar, 5 this wear is not related to the tube-to-tube wear. We 6 are reviewing the design basis of the retainer bars.
7 We are also going to look at the evaluation 8 of and control of the Unit 3 divider plate repair. This 9 by far was the most significant difference between the 10 two units and it has been discounted as a potential cause 11 for the tube-to-tube wear.
12 The bowl of the steam generator that directs 13 the reactor fluid into the tubes as well as the plate 14 that separates the hot and cold reactor coolant had to 15 be cut out, repaired, re-welded and re-tested. Again, 16 we did not identify an issue related to the tube-to-tube 17 wear for this repair.
18 Unit 3 steam generator shipping 19 requirements were changed form what was required as 20 compared to Unit 2. There's nitrogen pressure, dew 21 point, and oxygen contents were not controlled or 22 monitored. These items are supposed to be controlled 23 to minimize corrosion of the internals of the steam 24 generators.
25 Item number 6. Lack of tube bundle support NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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24 1 for the steam generators during shipment. The shipping 2 specification did not initially have a requirement for 3 a tube bundle support, or it have a requirement for tube 4 bundle support, but it was not used during shipment.
5 So again, we are going back to look at that to see how 6 that was dispositioned.
7 We are going to look at the shipping 8 accelerometer data for Unit 3. Steam generator 88, 9 which was one of the generators for Unit 3, had all 10 accelerometers register an excessive force, which could 11 indicate mishandling during the transportation of steam 12 generators. The NRC was not able to determine if this 13 was properly reviewed.
14 We are looking at the 50.59 adequacy. The 15 NRC is continuing to review the adequacy to SONGS 50.59.
16 We did identify a concern with the potential for using 17 a different methodology than what was described in the 18 updated final safety analysis report.
19 SONGS changed their structural analysis 20 method as well as a tube-stress calculation, and we need 21 to do some additional reviews on that to determine if 22 they should have asked for an amendment.
23 The next two follow-up items, number 9 and 24 10, are the ones that the NRC believes are related to 25 the unexpected tube wear. As I discussed previously, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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25 1 the manufacturing differences, Mitsubishi improved the 2 manufacturing process, which sounds like it should be 3 good.
4 However, they didn't go back and look and 5 see what that would do to the original design dimensions.
6 They didn't go back and compare, should they have 7 reviewed, revised, shrunk the design dimensions. So 8 this resulted in a less rigid tube bundle, which 9 contributed to the vibration issue.
10 And as I discussed before, item number 10, 11 the computer simulation model. Again, the Mitsubishi 12 model underpredicted the behavior of the steam and water 13 in the steam generators.
14 Again, as described earlier, the 15 combination of those two, the higher than predicted steam 16 water flow and the less rigid tube bundle for Unit 3, 17 they vibrated and caused the tube-to-tube wear.
18 The NRC will be conducting additional 19 inspections to review each of these issues. We have 20 been and will be requesting additional information from 21 SONGS as part of our follow-up inspection activities.
22 This completes my discussion of the 23 augmented inspections activities. I'm going to let Tom 24 Blount, turn it back to him. He's going to summarize 25 the key points associated with this inspection. Thank NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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26 1 you.
2 MR. BLOUNT: Thank you, Greg. So what we'd 3 like you to walk away from this inspection understanding, 4 is the NRC does understand what the mechanistic causes 5 of the tube degradation are. The thermal hydraulic 6 conditions were not accurately predicted during the 7 design phase.
8 However, additional actions, as Greg has 9 pointed out, additional actions are being evaluated and 10 developed by the licensee, and these additional actions 11 will need to be inspected by us to ensure that this 12 condition will not exist in the future.
13 The NRC is not done. We have not reached 14 any conclusion. We have got more inspection to do.
15 We recognize that and we want you to understand that 16 we recognize that. We'll take as much time as necessary 17 to ensure safety, the safety of these facilities, and 18 no decision to this point has been made. Okay?
19 With that, I'd like to ask Pete Dietrich 20 if he'd like to provide his response.
21 MR. DIETRICH: Thank you, Mr. Blount. I'm 22 Pete Dietrich, the Senior Vice President and Chief 23 Nuclear Officer for Southern California Edison.
24 In our comments tonight, we'd like to update 25 you on the actions Southern California Edison has taken NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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27 1 and will take as we work to completely understand the 2 conditions of our steam generators and the effect on 3 San Onofre.
4 I'll make some opening remarks and then Doug 5 Bauder, our site vice president, will provide some 6 comments about the current conditions of the units, the 7 planned response to the tube leak and our learnings, 8 because we are a learning organization. We learn from 9 all things that occur in our facility. But Doug will 10 discuss our learnings in the area of our response.
11 Then Tom Palmisano, the vice president of 12 engineering, will summarize our technical evaluation 13 and the conclusions that we have reached to date. Much 14 work has been done, yet we still have much work to do 15 to fully understand and address what we have learned.
16 And then I will provide some closing remarks.
17 Just to start with, Southern California 18 Edison's overriding interest is the health and safety 19 of the public and our employees. Consequently, both 20 San Onofre units are shut down and will remain shut down 21 until repairs have been made and we and the Nuclear 22 Regulatory Commission are satisfied it is safe to 23 operate.
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28 1 including customers of Southern California Edison, San 2 Diego Gas and Electric and the City of Riverside. We 3 are also concerned about the concerns that you have, 4 members of the public and also our neighbors.
5 So Southern California Edison understands 6 the significance of the unexpected tube-to-tube wear, 7 and we agree with the facts presented tonight by the 8 Nuclear Regulatory Commission.
9 We appreciate the NRC's insights into this 10 situation and we pledge to continue to work with the 11 NRC to assure any remaining or additional questions are 12 answered promptly.
13 Early on, we recognized the seriousness of 14 the situation. As a result of the complex technical 15 nature of the wear, we recognized that we needed to 16 assemble the very best team to augment our resources 17 and the resources of the steam generator designer and 18 manufacturer, Mitsubishi Heavy Industries.
19 As a result, we have brought together 20 experts in thermal hydraulics and steam generator design 21 from around the world to help us gain an understanding 22 of the causes of this unexpected tube-to-tube wear and 23 potential corrective actions to address it.
24 The experts include such subject matter 25 experts from companies such as AREVA, Westinghouse and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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29 1 B&W Canada. We have used this assembled team, as well 2 as other industry experts and consultants, to review 3 the progress of our work and challenge the thoroughness 4 and adequacy of our conclusions. And we will continue 5 to do so.
6 With that, I'd like to turn it over to Doug 7 to discuss the current status of the units and our 8 response to the tube leak.
9 MR. BAUDER: Thank you, Pete. I would like 10 to cover the current status of the San Onofre units.
11 Unit 2 remains shut down since January the 9th when we 12 started our planned refueling outage, an outage that 13 included a reactor vessel head replacement and planned, 14 full-scope testing of our Unit 2 steam generator tubes.
15 On January 31st, the San Onofre operators 16 shut down Unit 3 in accordance with plant procedures 17 after detection of a very small tube leak on that unit.
18 Their actions demonstrated the right, 19 conservative decision-making and focus on protecting 20 the health and safety of plant personnel and the public.
21 I observed from the Control Room our 22 operators' response, and I was pleased with their calm, 23 deliberate approach to properly quantifying the leak 24 and the execution of our plant procedures to safely shut 25 down the plant.
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30 1 In fact, in my discussions with the 2 operators after the event, they told me the plant 3 response lined up with their experience and training 4 on our simulator where they frequently train --
5 (Sound system interference) 6 MR. BAUDER: I'm going to switch mics.
7 Everything okay over there? That would be a no.
8 (Off-mic discussion) 9 MR. BAUDER: Thank you. So yes, to catch 10 us back up. In my discussions with the operators 11 following the shut down on January 31st, they confirmed 12 with me the planned response matched what they were 13 trained for and evaluated for in our plant simulator.
14 And that evaluation is frequently done before our 15 operators for steam generator tube leaks.
16 As a learning operation -- organization, 17 we have reviewed our plant equipment, our procedures 18 and our operator training programs as a result of the 19 shut down on January 31st.
20 We have improved our leak detection 21 capability. We have enhanced our operator training 22 programs and built the lessons learned from this event 23 into our plant simulator training activities.
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31 1 that tied the post-shutdown critique process to any plant 2 trip.
3 Also, we have shared this information with 4 the industry. As Pete indicated, we are a learning 5 operation. We are all about learning, building things 6 back into our processes and sharing them with the 7 industry.
8 In conclusion, our operators took prompt, 9 conservative actions to shut down Unit 3, placing the 10 very highest priority on protecting the health and safety 11 of the public.
12 At this point I would like to turn the 13 presentation over to Tom Palmisano to talk through 14 insights and perspectives on open items, as well as 15 Southern California Edison's technical work so far on 16 our steam generators. Tom.
17 MR. PALMISANO: Okay. Thank you, Doug.
18 Can you hear me okay in the back? Great. Thank you.
19 What I would like to do is provide an update on the 20 technical work to date on our investigations, and talk 21 about some of the upcoming actions that we have in place.
22 And as Pete Dietrich has said and the NRC 23 has said, we have more work to do. We realize that.
24 And we're being very deliberate and conservative in our 25 approach to our work.
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32 1 So first, Mr. Warnick did a good job of 2 giving you an overview of the steam generator's function 3 of the plant design and the steam generator design 4 itself. I just want to point out a couple of things.
5 Tom, if you highlight the steam generator.
6 Two key functions we're talking about tonight. One 7 is the transfer heat from the radioactive primary system 8 to the secondary side to boil water to make steam that 9 ultimately turns the turbine and generates electricity.
10 The other key function, and particularly 11 from a safety standpoint, is the function of the steam 12 generator tubes to prevent radioactive primary water 13 from leaking to the secondary side. So, those are the 14 two key functions we are focused on in this discussion 15 and in our current work. Next slide please.
16 In this slide, a cutaway of the steam 17 generator, we have already explained, or the NRC has 18 already explained the flow path. Just let me reiterate 19 it.
20 The hot radioactive water comes in through 21 what's called the hot leg at the bottom, flows up through 22 the steam generator tubes, around the U-tube bend, the 23 top of the tubes, and down through the remaining straight 24 portion and out the cold leg.
25 The heat from that water is transferred to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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33 1 the secondary side to boil the water to make the steam 2 that exits the top of the steam generator. Of particular 3 importance tonight is what's labeled the U-bend section.
4 This is where the tube-to-tube wear has occurred that 5 caused the tube leak in one of the tubes, and also caused 6 the damage in the other tubes that caused us to do the 7 in situ pressure test and caused the test failures.
8 So it's the very top of the U-bend that we're 9 going to be talking about where the tube-to-tube wear 10 has occurred. Thank you, Tom. Next slide, please.
11 So, let me kind of summarize the actions 12 to date at this point. Following the Unit 3 shutdown 13 on January 31st, we performed a comprehensive and 14 rigorous inspection of all 19,454 steam generator tubes 15 in the two Unit 3 steam generators. Each steam generator 16 has 9,727 tubes, roughly 10,000 tubes per steam 17 generator. So we did a comprehensive inspection of all 18 of them.
19 We've reviewed these inspection results 20 with industry experts and identified the cause of the 21 tube leak as unexpected tube-to-tube wear. This wear 22 caused one tube to leak and caused the other eight 23 tubes -- there were eight tubes that we talked about 24 -- to fail the in situ pressure testing.
25 Further inspection showed wear on 326 of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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34 1 the these 19,454 tubes. So I'd like you to have that 2 perspective with those numbers. The wear is in a very 3 localized root area of that upper tube bundle we saw 4 on the previous slide, and based on the finding of this 5 unexpected tube-to-tube wear, we elected not to restart 6 Unit 2. Unit 2 was in the process of completing a 7 refueling outage, had already had all of its tubes 8 inspected, and was in satisfactory condition to operate.
9 We elected not to restart Unit 2 at that time.
10 We wanted to make sure, given the unusual 11 nature of this tube-to-tube wear in Unit 3, that we took 12 every opportunity to inspect and test Unit 2 to help 13 us understand what was going on with the Unit 3 steam 14 generator tubes. We felt that was very important.
15 Recognizing the significance of this 16 unexpected tube-to-tube wear, we assembled a team of 17 experts to assist Southern California Edison and 18 Mitsubishi, the steam generator manufacturer.
19 You have heard this discussed by the NRC 20 and by Pete Dietrich, and in a minute, I'll talk more 21 about that panel.
22 To date we have now completed extensive 23 tests and analysis. We have done over 60,000 tests on 24 steam generator tubes in both Units 2 and Unit 3 and 25 have performed significant analysis of the test results NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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35 1 to understand the cause of the tube-to-tube wear.
2 As has been pointed out by the NRC, it's 3 significant to note there are differences between the 4 two units. Unit 3, which experienced the tube leak, 5 had 326 tubes damaged by this tube-to-tube wear. Unit 6 2 had only two tubes which showed minor indications of 7 tube-to-tube wear, so small it was almost undetectable.
8 It was our rigorous re-testing that identified two tubes 9 that had minor indications.
10 So Unit 2 is in much better condition than 11 Unit 3. The comments that Mr. Werner had about the 12 differences in the manufacturing tolerances between the 13 units explains partially why Unit 2 is in much better 14 condition than Unit 3 is with respect to tube-to-tube 15 wear.
16 Next slide. The expert panel. This is 17 significant. You know, in any outage, we start with 18 our own expertise. We start with the manufacturer, 19 Mitsubishi Heavy Industries.
20 And as we realized the significance and 21 usual nature of this tube-to-tube wear, we stopped and 22 we formed a group of experts to assist us both onsite 23 and off-site and in expert panels.
24 We have brought in Areva, Westinghouse and 25 B&W Canada. All of those firms design, manufacture and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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36 1 test steam generators. They are competitors to 2 Mitsubishi.
3 (Off-mic question) 4 MR. PALMISANO: Babcock & Wilcox, Canada.
5 Yes. B&W, Canada. We brought in MPR Associates, which 6 is a leading problem-solving firm, both in the nuclear 7 and non-nuclear industry, renowned for their ability 8 to deal with difficult, technical issues.
9 We immobilized EPRI, the Electric Power 10 Research Institute. This is the electric utilities 11 industry's research group where we do cutting-edge 12 research across the board in the electric utility 13 industry, including nuclear. This is where we share 14 technical information, and in the nuclear side, we 15 maintain some technical standards that we operate and 16 maintain our plants to, particularly for steam 17 generators.
18 We also brought in other industry personnel 19 from sister utilities with similar steam generators with 20 good expertise to assist us, and as has been mentioned, 21 some recognized academics and consultants who do serious 22 research in thermal hydraulic analysis, vibration 23 analysis, and steam generator testing.
24 So, we have assembled a team, and I think 25 it has been alluded to, this is virtually an unparalleled NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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37 1 effort in the industry. The sharing, the cooperation, 2 the critical nature of this work has been the best I 3 have seen, and I think Mr. Werner's comments have echoed 4 that.
5 Now, the team was established not just to 6 assist us, but to also challenge our work. We wanted 7 to make sure that we put in place not just getting good, 8 solid technical assistance, but a good critical 9 challenge.
10 We used an expert panel board process. The 11 team forms up on site every three to four weeks, and 12 we spend one to two days reviewing the result of our 13 work to date, making presentations, getting critical 14 comments and getting some redirection, if you will, on 15 things that they feel we should investigate more fully.
16 They have turned out to be quite valuable 17 and we are continuing their use through our remaining 18 technical work and our restart decisions as we formulate 19 our final plans.
20 Next slide. So what have we determined in 21 terms of cause? The specific mechanism -- you have heard 22 the NRC discuss this, and I'll use the term -- it's called 23 fluid-elastic instability.
24 Basically, that is causing some of these 25 tubes, these selected tubes, to vibrate excessively to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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38 1 where they are contacting adjacent tubes. That is not 2 the way these steam generators are designed to operate.
3 It's a vibration mechanism that should not be occurring.
4 We see this. This is causing the excessive 5 wear and it's in this limited area of the Unit 3 steam 6 generators. It is caused, this fluid-elastic 7 instability or tube vibration, is caused by high steam 8 flow velocities -- and this has already been alluded 9 to -- very dry steam, in other words, very localized 10 areas where there is very dry steam, very little liquid 11 as the water is boiled to steam, and inadequate tube 12 support structure, that anti-vibration bar structure, 13 in the U-bend region around these tubes that are 14 experiencing wear. The tube support structure is not 15 providing sufficient restraint.
16 So a combination -- high stream flow 17 velocities, very dry steam and the interaction with this 18 tube support structure in the Unit 3 steam generators.
19 Again, we do not see much evidence of this phenomenon 20 in Unit 2 because Unit 2 clearly has a tighter tube 21 support structure than Unit 3 does.
22 Our findings correlate very well with the 23 NRC's comments on the thermal hydraulic analysis. These 24 conditions were not predicted clearly during the design 25 phase to be as severe as they are. We are in agreement NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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39 1 with the NRC's conclusions on that. And also, the 2 differences between Unit 3 and Unit 2, likely due to 3 manufacturing tolerance differences and manufacturing 4 process differences, seem to explain the difference 5 between Unit 2 and Unit 3, and we are in agreement with 6 the NRC's Augmented Inspection Team on those.
7 Now, we have a good understanding of the 8 cause of the tube vibration which causes the tube-to-tube 9 wear. Our expert panel has reviewed this several times.
10 They have challenged us and they are in concurrence 11 with our conclusion as far as what is causing the 12 tube-to-tube wear.
13 Next slide, please. So, the next steps.
14 And again, I'd like to emphasize something you have heard 15 Pete be very clear on and the NRC say, we are taking 16 as much time as necessary to ensure this is understood 17 and that this is properly corrected. So that has been 18 a theme from the start of this investigation.
19 So, we are following up with the Augmented 20 Inspection Team's additional request. Two of their open 21 items clearly are related to the cause. They have 22 legitimate needs for more information on the other open 23 items and our team is supplying that information as it 24 becomes available and working with the inspection team.
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40 1 corrective actions to prevent this tube vibration from 2 occurring, based on our understanding of the mechanism.
3 We are developing additional information 4 as stated in the Confirmatory Action Letter which we 5 committed to prior to restart that we know we need to 6 submit, and we are continuing to work to develop 7 intermediate and longer term solutions to this problem.
8 As Pete said, we are disappointed in this 9 and we are working on longer term solutions. And those 10 longer term solutions will require extensive analysis, 11 mock-up and testing prior to being implemented.
12 In summary, we have identified the cause 13 of the unexpected tube-to-tube wear. We are in 14 agreement with the comments as discussed by the NRC 15 tonight.
16 We continue to take a rigorous, deliberate 17 and conservative approach to completing our remaining 18 actions, and we are taking as much time as necessary 19 to insure safety.
20 With that, let me turn it back to Pete 21 Dietrich.
22 MR. DIETRICH: Thank you. By bringing 23 together experts in thermal hydraulics and steam 24 generator design and --
25 (Sound system interference)
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41 1 MR. DIETRICH: tests and analysis mentioned 2 by Tom Palmisano, we have determined the cause of the 3 unexpected tube-to-tube wear.
4 We are working on different options and 5 solutions for the future. We have 6 (No audio) 7 MR. BLOUNT: Thank you, Pete. We 8 appreciate those comments. Looking at our path forward, 9 it's important to note that the NRC still has much more 10 information to review. The cause evaluation has been 11 completed by SONGS and they are working on additional 12 actions to prevent the tube-to-tube wear from occurring 13 again.
14 We currently do not know what the final 15 actions will be. So for the NRC to speculate on what 16 is going to occur would not be appropriate. However, 17 I will tell you what we do know.
18 We continue to review information as it 19 becomes available, and as the Augmented Inspection Team 20 continues to review information, we ask SONGS additional 21 questions, and we request additional information, as 22 you have heard.
23 Our inspection will continue until we are 24 satisfied we have sufficient or enough information to 25 make a determination. Based on the Confirmatory Action NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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42 1 Letter, we will have to complete additional inspections 2 once SONGS informs us that they --
3 (No audio) 4 MR. DIETRICH: letter before we will go out 5 and do those inspections.
6 Portions of our AIT team will be called upon 7 to go out and do follow-up inspections on the 10 items 8 that we discussed earlier that were identified as part 9 of this inspection.
10 The NRC does plan to have additional public 11 meetings to keep you informed of our activities. As 12 part of our plans, we will have meetings with SONGS 13 designed to present their readiness plan associated in 14 response to the Confirmatory Action Letter.
15 After we have completed our inspection, we 16 will have another meeting to discuss the results of that 17 inspection. In addition, there are some type of public 18 meeting and press conference that will be held by the 19 senior management, NRC senior management, to discuss 20 any future NRC decision about the acceptability of 21 resumption of power operations. That decision will be 22 based on discussions with both the Region 4 and NRC 23 headquarter senior management.
24 And finally, as part of our normal process, 25 and how the NRC does business, we look back at our NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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43 1 inspection program and we look to see, are there things 2 out of this event that we should have seen earlier?
3 Are there processes that we should have been engaged 4 in, to help us learn how to get better at what it is 5 that we do? Is there something that we could have been 6 doing do better, or looking at, prior to this event 7 occurring, that would have precluded that event? That 8 is also to help our inspection efforts going forward.
9 So with that, I'd like to turn it over to 10 Elmo Collins for closing remarks. Elmo?
11 MR. COLLINS: Well, thank you, Tom. To 12 conclude the business portion of the meeting, I will 13 say thank you to the residents of California for being 14 here tonight and thank you for listening attentively.
15 I have been quite 16 (No audio) 17 MR. COLLINS: how polite and how patient 18 you have been as we move through a lot of information 19 tonight. So I thank you for that.
20 I want to thank this Augmented Inspection 21 Team that we have talked about. A lot of hours of work 22 has gone on of people with high expertise. And so I 23 am glad we were able to hear the results of their 24 inspection and I hope it was informative for you.
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44 1 your presentation and response to the information you 2 shared with us. And lastly, I probably would be remiss, 3 if we didn't all express our appreciation to the 4 representatives from the Orange County Sheriff's Office 5 who are here looking out after our safety. So give them 6 a round of applause.
7 (Applause) 8 MR. COLLINS: I know --
9 (No audio) 10 FACILITATOR DANIEL: Thank you Elmo. you, 11 Elmo. Thank you Southern California Edison and NRC.
12 Thank you audience, ladies and gentlemen, for being so 13 attentive, as Elmo --
14 (No audio) 15 FACILITATOR DANIEL: We are going to take 16 a --
17 (No audio) 18 FACILITATOR DANIEL: We are going to start 19 back at 7:20 sharp with a question and comment period.
20 In the meantime, Mr. Collins is going to be doing a 21 media interview, I believe --
22 (No audio) 23 FACILITATOR DANIEL: Enjoy the break. We 24 will see you at 7:20. Thank you.
25 (Whereupon, at 11:17 a.m., DVD 1 ended)
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