ML20236P585
| ML20236P585 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/09/1987 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| References | |
| REF-10CFR9.7 NUDOCS 8711180054 | |
| Download: ML20236P585 (80) | |
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION I
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Title:
Briefing on North Anna-1 Steani Generator Tube Rupture Event Location: Washington, D. C.
Date: Monday, November 9, 1987 s
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I Pages: 1 - 56 j
I Ann Riley & Associates Court Reporters l 1825 i Street, N.W., Suite 921 l
- " Washington, D.C. 20006 1 l
'(202) 293-3950
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6 This' 'is an. unofficial tran'cript.ofiaLmeeting:of;the s
7 United. States Nuclear. Regulatory Commission held on' S 11/09/87 .. In the Commission's office at' 3717 44 s t r e e t ',.
9 4. W . , . Wash i ng t on , D.C. The meeting was open toLpublic- Y 10 attendance and observat'lon. This1 transcript has<not been 11 reviewed, corrected, or edited, and it may contain' 3
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d 12 inaccuracies.
13 The transcript is inte'hdad solely for general 14 informational purposes. As provided byL10-CFR 9.1034 it is
. .l 15 not part of the formal or informal record of decision offthe l
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16 matters discussed. E.wpressions of opinion in this$ transcript j <
17 do not necessarily reflect final' determination or beliefs. No- i 18 pleading or other paper may be filed with the-Commission-In.
19 any proceeding as the result of or addressed,to any statement a
20 or argument contained herein, except.as.the Commissl'on may-21 authorize.
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' UNITED' STATES OF AMERICA.
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3 NUCLEAR REGUIATORY COMMISSION R
.4 w .l 5 BRIEFING-ON NORTH ANNA-1 STEAM GENERATOR'
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'6 TUBE RUPTURE EVENT' 7
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l l 9 Public-Meeting .
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12 MONDAY,l NOVEMBER 9, 1987; 13 , -1717-H Street, N.W.
14 Washington, D.C.- ,
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-1 16 The Commission met in Open Session, pursuant'to '
17 Notice, at 9:30 a.m., the Honorable Lando W. Zech, Chairman'of ,
18 the Commission presiding. !
19 .
20 COMMISSIONERS PRESENT: -
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21 LANDO W. ZECH, JR., Chairman of..the Commission 22 THOMAS M. ROBERTS, Commissioner i
23 KENNETH M. CARR,' Commissioner.
24 KENNETH C. ROGERS, Commissioner.. 4 al 25
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- y 2- U 1 NRC.' STAFF'AND PRESENTERS SEATED AT' COMMISSION. TABLE
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3 .S. Chilk W. Parler 4 T. Murley~ L. Reyes' 5 J. Caldwell J. Richardsoni 6 :j i
7 .NRC' STAFF.(Continued): '
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9 L.-Engle 'E. Rossi <
ll 10 R. Starostecki -'
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12 AUDIENCE SPEAKERS:
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- 14 M. Bowling j
15 16 17 ,
18 *****
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PROCEEDINGS .
2 CHAIRMAN 2ECH: Good morning, ladies and gentlemen.
3 Commissioner Bernthal will not be with us today, he is on 4 travel overseas.
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5 The purpose of today's meeting is.for the NRC Staff 6 to brief the Commission concerning the-steam generator tube 7 rupture event that occurred at Virginia Power Company's North 8 Anna Unit on the 15th of July, 1987. The staff should focus 9
their presentation on the safety implications of the event, 10 including the radiation releases to the atacaphere and off-site-11 consequences-if any, and what lessons may be learned from the-l 12 event.
, l 13 During the course of,your presentation, I'd like'the
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14 staff to specifically address the initial response to-the event 15 by both the Licensee and the NRC; the adequacy of the new 16 symptom-oriented emergency off-normal procedures in mitigating 17 such an event; and any generic implications concerning 18 Westinghouse steam generators or in-service inspection programs 19 that may have resulted from the review of this event.
20 I understand that copies of the slides that.will be 21 used in this morning's presentation'are available in the.back 22 of the' room. Do any of my' fellow Commissioners have opening 23 comments to make before we begin?
24 (No response.]
25 If not, Dr. Murley, would you proceed,.please?
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... 4 1- MR..MURLEY: Yes. Thpnk you, Mr. Chairman. I have.
2 with me staff:en my left, Jim Richardson and Leon Engle whol:is 3 the Project Manager for North Anna, and on my right from the 4 region, Luis Reyes and Jim Caldwell, and they'll.be making 5 parts of the presentation.
6 The staff has given a good deal'of attention-to. steam 7 generator tube. integrity for many years. It has been j 8 designated-as an unresolved safety issue'and in fact,.would.
9 have been resolved by now but we're goingito take into account 10 the North Anna event, so we'll have to update'a draft report 11 that we had put out'for comment some months ago.
12 There have been'four previous steam generator tube 13 rupture events -- 1975, 1976, 1979 and 1982 -- so'now-the.fifth 14 one is in 1987. And as you can tell, with more pressurized' 15 water reactors oparating, one can see that the frequency-of.
16 this event is decreasing. H 17 There have been a number of studies done, to resolve.
18 the.USI that concluded that th's overall public risk is' small
! 19 from steam generator tube failures. Nonetheless, there are two 20 major safety implications of a steam generator tube leak or i' 21 rupture.
22 The first implication is that the tubes, of course, 23 L
are part of the primary system boundary so that any leak 24 provides a path for the primary coolant water to the secondary-t 25 system, and.it thereby can overpressuriza the secondary system, 1
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5 l' and if steam' generator safety l valves were to open'there is'a 2 direct path for radioactivity to,the environment. In'this case-3 it would be an unmonitored path and one could'have an 4 unmonitored release.- Did not happen in this case at-North' 5 Anna; in fact, the. releases were less than one percent of the' 6 Tech Spec limits.
7 A second safety. implication of such-an event is that j 8 it's a difficult transient for the operators to handle.. It11s q
9 a loss of coolant' accident,-of course, with the potential.for' l j
10 extended loss of primary coolant water.outside' containment.
11 o The operators must contain that loss of coolant and they~must- -1 1
1 12 also cool down rapidly the primary system and the secondary
, 13 without over-cooling the pressure vessel.
14 The. operators at North Anna, as you will he,ar,'
15 handled the tube rupture skillfully and professionally, Land in 16 this event it was not a significant safety concern.
17 Nonetheless, we have learned some lessons and we will go over 18 those with you in a few moments..
19 Mr. Caldwell will describe the event and the Licensee 20 response to that. Mr. Ernie Rossi from my staff willLdescribe 21 the NRC response. Jim Richardson will talk about the lessons-
-22 learned and particul'arly the mechanical design aspects of the 23 generator, and also, generic implications and the~NRC actions 24 with regard to those generic implications. _.
( j. 25 So with that introduction, Mr. Chairman, let me turn.
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l' to Mr. Caldwell who is the Senior Resident-Inspector at North 2 Anna. '
3 CHAIRMAN ZECH: Before you do that, lat me just mAke 4 -sure that I understand your referenc'e to the release itself.
5 Did you say it was less than one percent'of the Tech Spec '
6 allowance?
7 MR. MURLEY: .Yes.
8 CHAIRMAN ZECH: So.I presume that.ifTit's.that small. i 9 that you would consider'the off-site-consequences what?
10 MR. MURLEY: Well, they're wellEwithin our' Tech Spec' 11 limits, and in this particular event'they were quite 12 negligible. .
13 CHAIRMAN ZECH: Negligible.
All right. You agree' I 14 with that, t.co?
15 MR. REYES: Correct. They're difficult to measure at 16 low levels.
1 17 CHAIRMAN ZECH: All right, fine.
18 MR. MURLEY: And there will be some reasons for that l' 19 as we go through, that you will see why.they were so' low.
20 CHAIRMAN ZECH: Fine, let's proceed.
21 MR. CALDWELL: My name is Jim.Caldwell, I'm the l 22 Senior Resident Inspector at North Anna. I've been asked to 23 i
address the sequence of events for the tube rupture event that 24
- occurred on July.15th. I'll do it in basically three segments. !
25 I will discuss the initial plant conditions prior to the start .;
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'l of the event, a. discussion of the operator actions from'the 'l 2 initial indication of a. problem to theJreactor trip, and then .l u
3 following the reactor' trip to termination of the event -- I 4 sequence of events.- i t
5 (Slide.)
6 The' initial conditions on ther15th,,just. priori.to1the-
.l 7 event, the' reactor was at 100 percent power, it hadLach:leved 8 100 percent power on the 14th,~ the day before, for the'first 9 time.since.the refueling outage commenced'in April of.i.thatL 10 year. So the core was relatively clean, which againe 11 attributed to.the low release. RCS pressure was approximately 12 2235 pounds, and the pressurizer level was ap' proximately 65' J 1
13 percent. '
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14 I'd also like to mention a couple:of instruments that 1 15 were out of service that contributed to this event or.that- 0 16 complicated the event. The condenser. air ejector. rad' monitor 17 had been declared inoperable on the 14th,.it hadLfailed low.> 1 18 That monitor monitors the radiation ~ release from the condenser-19 through the air ejector up to the atmosphere. It also has'an 20 automatic function which will cause it to divert to containment. J 21 on a-high/high level. With the monitor being' failed low, that 22 automatic function was defeated.
a 23 on the steam generator blowdown monitors, the-24 blowdown monitor rad levels or radiation monitorsL-- the rad .
( 25 Levels, the background levels, were basically. pretty hight The i <
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q l' alarm setpoints>had been adjusted prior'to the.out'ge a because.
2 they did have some-leakage prior to-the outage, and~the alarms
'3 had been adjusted up so they.did not get the alarms during.this-4 event.
1 5 operator actions'from the initial indication'of.the-6 tube rupture to1the' manual reactor. scram - - ;
1 7 CHAIRMAN ZECH: Excuse me,:should they have gotten' 8 the alarms or not?
9 MR. CALDWELL: Well,the way the background levelsL i 10 were on the monitors themselves, the counts'were up-in'th's. I 11 thousand counts; normally you would expect to get steam, d 12 generator blowdown radiation'at high level on~a tube rupture, .,
13 7 but the activity.of the reactor coolant was low, the rupture 14 was in the upper portion of the steam. generator:and'the 15 majority of the activity was carried.out.through'the'--'with .
16 the steam out of the generator. So in this case; lt think.it' 17 complicated the issue.
They.did not.get the-alarms. ,If the
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18 alarm setpoints had been adjusted back,1: don't know if they 19 would have gotten them or not.
20 CHAIRMAN ZECH: But it was low enough so that-[it 21-didn't set off the alarm; that's'what you're saying..
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MR. CALDWELL: 'It.did not set off the alarm.
23 MR. REYES: I was just goingcto add that on the 24 training'for the operators on the simulators, the blowdown' 25 radiation monitors are an indicator.that would help them do
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1 that. In this c'ase, it did not' alarm because of the- ,
2 background, the location of the break,.the cleanliness;of the 3 primary system. So even without that alarm,Jthe operators H l
4 reacted well.
5 ' CHAIRMAN ZECH: My. experience would beIthatithat is 6 one thing that the operators would be looking.for to' assist?
l 7 them.
8 MR. REYES: :That's'right.- 1 9 COMMISSIONER CARR: Let me make sure I understand it.
10 They were set higher-pre-outa'ge because?they had.known leakage.
11 MR. CALDWELL: The setpoints vere.up because'they:ldid -
12 have some leakage and the activity was higher prior to the
, 13 outages. ,
i 14 COMMISSIONER CARR: And they corrected the leakage -
15 during the outage?
16 MR. CALDWELL: Yes.
17 COMMISSIONER CARR: So why didn't they' set them back?- .
18 MR. CALDWELL: Well, their policy-at'the time was to 19 wait until the plant had reached the stable condition at 100 20 percent power and then adjust them back. That is not-the 21 present policy. Now they are adjusting the.alarmsLasLthey go 22 up in power.
23 MR. REYES: In.particular, the-C steam generator?had 24 the highest background of all'three, so'that one.was set at the- -
- ) 25 highest. '
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MR. MURLEY: Let me just interject here to point out- 4 2 as w's go through.this scenario ~, keep'in mind that one of:ou::
3 resident inspectors, not.Mr. Caldwell but tho'other inspectus.
4 at the site, was in the control room four minutes after the j 5 break, so we.'did have'someone observing what was' going on'most l
6 of this time.
7 CHAIRMAN ZECH: Before we g'o 'off this. point, .does 8 this procedure that they used as regards. setting-tho' 9 instruments, does that meet our regulations?. Was that within~ l
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- j. 10 their authority to make those adjustments to those instruments? i l !
11 MR. CALDWELL: Yes. The alarm setpoints'were still .
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12 well within the release lim'its in the Tech. Specs. And with the 13 core being as clean as it was E- '
14 CHAIRMAN ZECH: All right. 'Let's proceed.
15 MR. CALDWELL: At 0630, the control room operators .
16 received an annunciator for the main steam radiation monitorc, 17 the A&B main steam line monitors were in alert, the C: monitor 18 was in the high alarm; it.was basically about 10 times.the 19 magnitude of the A&B.- This alarm came in approximately six 20 times and was reset between 0630 and 0636.
21 At 0631, the control room operator observed the~
22 pressurizer level decreasing. At 0632 they received a low 23 pressure alarm of 2135, which is approximately 100 pounds less 24 than normal eperating. The level was approximately 59 percent
-I 25 at that time. The control room operator took acti.on. He-took T O
4% 11' 11 manual.'controllof charging, opened the dischargelvalve wide 2 open to maximize charging to the vessel.
3 At 0633'the shift supervisor entered the control-room 4
and relieved the Unit 2 SRO. .He directed that the letdown bel 5 isolated and that they realign the charging system suction to 6 the refueling water. storage tank which'is the ECCS' suction 7 source, and requested they commence a turb'ine rampdown at 2 1
8 percent per minute.
9 CHAIRMAN ZECH:- Were these correct actions.in your 10 view?
l 11 COMMISSIONER CARR: Yes. They are the actions they 12 would take on abnormal conditions. .
13 CHAIRMAN ZECH: All right.
I, 14 MR. CALDWELL:- At 0634'the shift technical advisor i 15 and resident inspector arrived in the control room.
The I L
16 pressurizer pressure was at approximately'2109 and the level 17 was approximately 49 percent.
. At that time, the' Unit 2 SRO.was 18 in contact with the Superintendent of Operations;over the phone 19 and the Superintendent of Operations directed that the unit be 20 manually tripped.
21 At 0635, the shift supervisor directed the Unit 1 CRO ,
22 to trip the reactor, the turbine, and enter EP-0 which is the 23 reactor trip safety injection emergency procedure. The 'l 24 pressurizer level'was approximately 45' percent at that time, 25 still in the indicating range, and the pressure was 2100 9
.. .12' pounds; about 200 pounds above the trip setpoint.-
2 Now I'd likelto commence on the sequence of eventsf 3 commencing with the' reactor trip. Again, the-trip was~at 0635, 4 it was a manual trip. Approximately 17' seconds later.they.had 5 an automatic safety. injection on pressurizer low pressure, 1765' u 6 pounds. This safety injection' initiated the additional.
7 charging pump, low head safety injections, the diesels'and-the 8 aux feed pumps. Starting of the~ aux feed' pumps created an i 9 additional release path --'the s, team-driven Terry turbine. aux. )
10 feed pump exhausts to atmosphere and it receives' steam from all 11 three steam generators. This safety injection:also initiated.a..,
12 Phase A isolation which-isolated tho' condensate. air injector
. 13 which was previously a release, path. .It' isolated that release 14 path. Also, the steam generator blowdown. monitors or steam 15 generator blowdown was isolated due to Phase A. i 1
16 At 0639, the Unit 2 SRO became the interin station 17 emergency manager and he declared a notification ot an unusual-18 l
avant and that was due to having a safety injection. . Also at.
19 0639 the C steam generator level began to recover. . It was-20 leading the A generator which is unusual because the A 21 generator is fed by the steam-driven aux feed pump which has 22 twice the capkcity of a motor-driven aux feed pump,-indicating 23 that the C steam generator'was also.being fed from some other 24 source other than the aux feed pump.
25 At 0640, the Licenses transition # from EP-0 into EP-3 d
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s 13 1 'which 'isLa steam generator tube rupture.. Basically, the.first 2- two steps of that procedure _wers done. -They entered _ Step'3.
3 Step'3 asks the operator to' identify which steam generator'
- 4 contained'the rupture and'isclate.it. At that: point, there
-5 were four questions asked.- Two of the.four could.haveLbeen
, 6 responded to in the affirmative for the c steam generator;'one' _
7- an unexplained increase in level,.and two, the main steda line' 8 rad monitor and alarm. '
9 The shift' supervisor chose not to choose the C steam 10 -generator at'that point because he felt he didn't have enough i
11 information and he wanted to -- he did not want to isolate the
- 12. wrong generator and complicate the' recovery actions'later. His l I
-7 13 reasoning -- the level was about 18 percent.in the.c steam 14 generator so it was still low in the indicating range, and 15 earlier the Tavg had dropped below 54.7, so the steam dumps had 16 closed which had basically stopped all steam flow. So the rad 17 nonitors were no longer in alarm at that point.
l 18 The operator chose the " response notobtained" l 19 section which allowed him to go on and perform' steps'6 through
'20 13.
21 At 0641 Tavg dropped below 543 which interlock closed-22 the steam dumps. At 0644, the operations staff was: performing 1 .
23 the Steps 6 through 13, one of which was to reset: safety: ,
2 24 injection.
The next was to reset Phase A isolation. When they [
. (' 25 reset Phase A isolation they unisolated the air ejector so it.-
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4 1 became a release path'again;1however, there was noLateam' flow to the condenser at.that' time.
2 3 . This particular question-came up and the Licensme-has.
4 corrected that now. 'Their procedure now requires them.to.
5 manually divert the air ejector to; containment prior <to- i
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6 resetting Phase A isolation. Consequently, the release will 7 not.go to atmosphere; it will go to inside the containment.- '
8 The low ~ head safety' injection pumps were also-9 secured. The inspecti'ontstaff had a problem'with thatibecause.
10 they were securing the ECCS~ pumps. prior'to. identifying and' 11 isolating the. leak.' It turns out that the emergency response-12 guidelines -- the emergency. procedures, apparently some plants.
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( have minimal recirc on their low head safety injection pumps 1 14 and there is fear of overheating the pumps.
. Inithe case of <
15 North Anna they have , adequate recirc so they have moved that 16 step now further on in the procedure after SI termination 17 criteria have been met. So that has'been corrected.
18 At 0646 the shift supervisor stil1Lwas unable to 19 determine the affected steam generator. He suspected it was C 20 so he isolated aux feed, and the level continued 'to rise so run . j 21 confirmed that was the generator with-the ruptureditube. They 1 22 shut'the C main steam trip valve,. directed'an operator to the-23 1 main steam valve house and he shut the steam supply:from the'C 24 steam generator to the Terry turbine, isolating that release ..
25- path.
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At 0649,-they-commenced a-rapid-cooldown using the"A j
[ 2 and B steam generators andIthe steam _ dumps.. TheyLbypassed-the 9 1 3 low Tavg interlock in the: steam' pressure mode. . .9 1
4 At 0654 the interim station emergency.manarJerL '
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f 5 declared an alert because the leak wan.estimatedLit greater; 6 than 50 gpm and it was determined to be'a steam generator tuba-V ,
7 rupture. -
8 At 07'4, 0 the steam generator level increase'had' M' .,
R 9 stopped, pressurizer level ~was about 60 percent.t,They metLSIl ,y(~~~} "
j i:'- J h 10 termination criteria, they secured the rechargi'ng pump, they. #
l 11 initiated isolation'of the bit flew path and then establishe'd ;'4 {.f; 12 ,, J " .( a normail charging flow path and' then several niinutes later they.
13 established normal letdown.
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14 At 0723 the NRC Region II Instant Response Cent s 'wasf1 <
1 15 activated in standby. At0726:NRC.HeadquartersResponsakanter.
., yu 16 was activated in standby. . . \.
17 T)}Q(, ;
At 0727 the Licensee began.the RCS cooldown usint,{ ~
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procedure ES-3.1, post-steam generator- tube rupture 1cooldowriR l '
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using the backfill method, which essentially isIthey ma'inta'in' '
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20 the primary plant at a pressure sliglit'ly :less- than.,' th'etsteam 21 generator,theycooltheprimaryplant*down,thehallch.lthe, K 22 steamgeneratorto'flowtotheprimary?,plantLandthey,ref{ Nit- L 23 %;, . ,
using aux feed with ambient temperature water, They'bringiboth..
i p 14 'the generator and the primarysplant down together. . ,
25 .
At 0730, the a:nargency diese?. generators were e
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- secured.- This was approximately 55 minutes after_they hadl 'i
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started whichLueant they"were running' unloaded for'that f 2- 1 1
3 timeframe. The vendor recommends'that1.lt:beEno more than 15 . !
4 minutes'.
% $?[ .i The Licensee hapiphanged.the proce.. dure to pince the
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5 securing of the'didsels ik EK.O which:is1the ihitial emergency; j q; ,
6 procedure, and:it is dode in the at'tachsent whichJisiassociatedL l
,Vh G ll 7 with Phase A' isolation. They will/dh one'at a4 time; pla'ce thel j
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1 1 ir 8 ene they securs inIauto and th'en do the nextIone.. That'way.
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'j they will alwayn"either have ond runn,ingforicne in automatic to 9
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/,' u 10 be able.to pick up the bush i f ' ,l 7; ', # '
s3s n l g 11 At 0745 the NRCfResponse Team was; formed and.
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12 dispatched fremLRegion'II. (
At 07t\5l thaicondensar ~ air ' ejector.'l l 7 <
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13 was: manually diverted to containment. .- -
( Again,.that.has.been. j -
14 corrected. The' air ejector will be.. manuallyTdiverted
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,s 15 containment regardless of;x<tho' radiation [ level _ prior to .;
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16 resetting Phase A.
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J f s.9 :$ Y 17 At1108theye'ntiredMode4,whichl[ij' (, '
a lass tha'n 350-18 degrees Fahrenheit. u.a s. ,
At'12L3 they pIaced the RERruystem in 3
19 my r 1 service to continue the co'ldown o The RHR syNt'em can be placed
\_ e 20 4 in at less than dSO pounde, at .'.ess than 350 dsgraes. .At 1330-s .
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1 they entered Mode;5,' desnithan 200 d grees Fahrenheit, cold 1 3 %e ,
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22 shutdown. Terminated the emergency.at 133% ;
23 MR. MURLEY:
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'z That.,is a summary,JMr. Chairman,lof_the l 24 \;
s events. 'Maybe this.,is the time to pausehand ask if thereJare
' i-25 any_ questions o that. I think we can' conclude that the H
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17 1 operators did' handle it well, professionally, skillfully. That i
2 was one reason -- you had asked about the off-site releases.
i 3 That was one reason, clearly. A second reason was that they 4 had just returned to power the day before-so that the decay. '
5 heat load was low, and also, the primary system was clean. l 6 I think a fourth reason might have been that the 7 condenser air ejector was diverted back to containment. I 1
8 understand not all plants have that feature, but they do have ,
! 9 t'his feature at North Anna and it was done. -
10 CHAIRMAN ZECH: I think we can go ahead and proceed.
11 MR. MURLEY: Ernie Rossi is the Director of Operating i 12 Events Evaluation in NRR and he'll talk briefly on NRC j 13 response. ,
14 MR. ROSSI: The NRC was in standby throughout the .
15 event from about 10 minutes after the initial notification was 16 made to the NRC operations Center, and we maintained open 17 communications with the Licensee starting at the time the .
18 initial notification was met.
19 This issue is being discussed today primarily because '
20 in a briefing for industry representatives on August 28th, the 1
21 Licensee indicated a concern regarding the burden placed on the 22 plant staff by NRC requests for information during the event.
23 I've talked to the Resident Inspector, Larry ~ King, who was in s 24 the control room at the time of the initial NRC notification "
25 and he tells me that he saw no indication that NRC requests for 5
18 1- information interfered with.the Licensee's handling of the l r *
(. 2 event.
4 3
I have also discussed the statement that was made 4 with senior VEPCO management, and I have been told that the 5 intent of that comment made by VEPCO in their August 28th .
6 presentation was primarily to reiterate to the industry-the >
7 importance of planning and being prepared for communications 8 with the NRC during an emergency. They consider that to be a i
9 lesson learned from the event. ,
10 In the discussion that I had with one senior VEPCO 11 official, he indicated, however, that the NRC needed to be
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12 disciplined in their questions to a plant during an'avent to 13 minimize the burden on plant p'erso'nnel, and we would certainly ;
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agree with that and make every effort to be disciplined in our '
15 requests to plants during any emergency. We do_however have a -
16 clear responsibility to monitor plant status to insure that 17 appropriate protective action recommendations are made offsite.
18 CHAIRMAN ZECH:
Do we take that to mean-that the '
19 utility comment was meant to be one of general caution rather 20 than a specific complaint?
21 MR. ROSSI: That's what I've been told by VEPCO 22 mant.gement.
23 CHAIRMAN ZECH: Because it's the age-old problem of 24 getting enough information but not bothering the operators. ;
(_) 25 It's one that will' continue to be with us, but as far as I'm 1 I v
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\
i u =19 i 1~ ..concetnad it's the utility's responsibility and a requirement-2 to keep NRC informe.b '
3 MR. ROSSI: That is indeed correct, and that. guidance 4 is contained'in NUREG-0654 which is. endorsed'by the Regulatory-5 Cuide on Emergency Planning, and we have issued.a couple ~of 6 Information' Notices on the subject, and it's currently.our plan 1
7 to issue an Information Notice on this particular situation i
8 here'to reiterate our responsibility during an emergency and- i i- 9 the Licensee's responsibilities to.have' people available to 10 communicate with us without interfering with the response to an i 11 event.
12 COMMISSIONER CARR: Do you know if that:was al general J
13 comment throughout the whole seven hours or was it in'the first
/. .;
14 15 minutes? ,
15 MR. ROSSI: That I don't know. There are people from j i
16 VEPCO here in the room. I don't know.whether you would want to 17 ask them to comment on that or not.
18 COMMISSIONER CARR: Well, it makes a difference ,
19 because --
20 CHAIRMAN ZECH: Why don't.we ask them?. Let's.ask the 21 VEPCO representative to come to.the microphone if you would and 22 identify yourself.
23 MR. BOWLING: Marty Bowling, Assistant Station 24 Manager of the North Anna Power Station. I gave the industry- .,
l' /
L s 25 briefing which is the subject of this conversation. Let me try.
t e
- - -.______ __m_ _ _ ,.d
.o , .
.. 20e ,
- l 1 to put.this in the' proper. con, text. It was not in the iformal-
~
- 2 remarks but it was in response:to a question. 'The question ..
3 was, what were the lessons learned from the, Surrey incident 4 that we were able to-apply at North Anna.. And one of-the 5 principal lessons we'1 earned was how to improve our 6 communications, particularly with.the'NRC.
7 At that time of the Surrey incident we ware'using an-8 unlicensed operator as a communicator. .We used a single ;
L 9 operator and he wasn't pre-desi,gnated but he would'be.a spare 10 operator. As a result, the communications after.the Surrey i 11 incident were somewhat slowed'down although'they were very !
l 12 adequate but they could have been improved.'
13 t, As a result, attNorth Anna we implemented,'after.the 14 Surrey incident as well as at the Surrey. Station itself, l
a new ,
15 concept where each shift pre-designated two senior -- that is, 16 top staff -- unlicensed operators - as the NRC- communicator and ' ~
l 1
17 as the communicator for the state and local! government I 18 agencies. They were pre-designated, and again,~we have'two.
19 So the communicators, once'this incident started 20 developing, had already started preparing their communications..
21 They were ready to go when the emergency was' declared.
22 What I wanted to pass on to the other' utilities'that!
23 were attending the industry briefing was the need to have that.
24 type of dedicated resources available because of the' demands 25 that.would be placed upon thum, although w-(")i
~
and I think.this.is' .i l
4 "'
s_ . . .
u 21' 1 the p' art that'got' misconstrued - clearly,;since we're using-2 very well-qualified, unlicensed l operators, they're not 3 available to assist the shift in responding-to the emergency 4- because it's a full-time job to do the, communications. _ So that i 5 if you're on a back shift with'no relief operators on site, i
6 then that's a resource that's not available..
7 CHAIRMAN ZECH: How about the shift technical 8 advisor?
9 MR. BOWLING: Well, the shift. technical 1advisorrin- ,
.I 10 our organization'is not authorized to be a: communicator. 'His 11 responsibilities .re to provideLthe technical.and engineering 12 assistance to the shift supervisor in mitigating the accident, _
13 and if he were to become a communicator he_certainly could not 14 perform that.
- 15 CHAIRMAN,ZECH: .Who is your communicator nowJthen?
)
16 KR. BOWLING: Generally, on-our watch station:
j' 17 structure, our safeguards area which is:all'of the ECCS-18 equipment which requires the highest level of unlicensed 19 operator, they're generally the ones pre-designated to be the 20 communicators. All of that equipment automatically responds to j
21 an emergency and doesn't require an operatorfin theLfield. So 22 they're generally available. On'the other hand,'they arefthe.
a 23 most experienced unlicensed operators on the shift.
24 CHAIRMAN ZECH: And where is he positioned during an
~
'( ;
~
25 emergency?
a.
4
_ i._________----- A---
t.
22-1 -MR. BOWLING:- Our procedures' require,.in:the' event of.
- 2 'an emergency, that all unlicensed operator's on the shift' return:
3 to the control room. .
4 CHAIRMAN ZECH: So is he under the direct supervision 5
'and direction of a qualified operator when he's communicating?.
6 MR. BOWLING: Yes. H
- e reports directly!to the --
7 well, we call it the Interim Station Emergency Manager,. which-8 is one of the SRO's on the shift.
9 There was another question I believed you asked,;how 10 long did this resource --
11 COMMISSIONER CARR: My real question.was did the 12 communications load go up or did.it go down after the first 15-13 minutes to an hour. ,
14 .MR.' BOWLING:
4 The requirements were about the same, 15 once the communications were established'because the technical 16 data that the NRC was asking -- they were requesting updates 17 avery 10 or 15 minutes or so. As a' result, that' load stayed 18 pretty constant for the first couple hours. 'About 0730 or so -
19
- the accident was at 0630, so about an hour later.we were able 20 to activate the Technical Support Center and shift the 21 communications from the control room.to the Technical Support 22 Center. And of course, that burden-of communications was no: 3 23 longer on the shift.
24 COMMISSIONER CARR: . But if you have -- if you're
(}[ 25 taking two of your operators to be the communicators onLthe w
R
?
23 1 back shift and the shift supervisor needsithose people to 2 operate, do they drop their phones and'go operate, I: hope?f 3 MR.-BOWLING:: No, they're' pre-designated. They'are 1 4 communicators.
5
~
COMMISSIONER CARR: So.it really cuts two of his 6 people out of helping in the emergency.
7 MR. BOWLING: Right. Our shifts are manned at.a.
8 higher level'than the minimum required by the Tech Specs so 9 that there are an adequate number of personnel to respond to 10 the emergency.
11 COMMISSIONER CARR: Yours are but we don't require 12 them to be. '
13 MR. BOWLING: That's.right.
7 14 CHAIRMAN ZECH: Any other questions?
15 [No response.)
16 All right, thank you very.much.
17 MR. MURLEY: Mr. Chairman,.you hadfasked about the -- -
18 CHAIRMAN ZECH: I presume this is something we're 19 going to look at, Dr. Murley, as a result of this lessons 20 learned from this event.
21 MR. MURLEY: Yes.
22 COMMISSIONER CARR: Before we drop this, did we have 23 two resident inspectors at the site?
24 MR. REYES: Yes.
( 25 -
COMMISSIONER CARR: Did the other one show up?
e t
24' 1- MR. REYES: Yes.-
U '2 MR.fCALDWELL: I got'there at around '0730.
3 COMMISSIONER CARR: Can you' relieve'some of that 4 communications responsibility?
5 MR. CALDWELL: We have been directed'not to-take the 6 communications' responsibility mainly because it' essentially 7 takes us out'of_the monitoring. We'would be unable to-observeL 8 what's going on.
9 MR. MURLEY: Mr. Commissioner,'we had an experience 10 at San Onofre_where the main communication was the resident 11 inspector and it was not the best experience. JWe believe it's 12 the responsibility of the licensee to correctly assess the-
,- 13 situation and keep us'inforted.
14 COMMISSIONER CARR: Bu,t- my' concern is if we ' don't 15 require him to have enough people.on shift to do that, --
t I'.
16 want him to take care of the casualt'y before he worries about 17 keeping us informed.
18 MR. MURLEY: Yes.
19 MR. REYES: Mr. Commissioner, I would.just relate two 20 things. One is I have been a senior resident-inspector in a- i 21 control room where I have been on-the red. phone,: and.it's very 22 difficult to provide any monitoring or assessment impression's 23 to your management when you're just. passing on information.
4 24 COMMISSIONER CARR: I. agree with-that..
25 MR. REYES: The other. thing is that having been on'-
.C s
25 1 the phone through all this. event and many others, ws:have had 2 occasions where the person at the other and'in the control' room:
3 finds a need to do something and he will say, I have to do-4 this, I will return to the phone in a few minutes, I just need 5 to do something. And we have no problems with that. So the
- 6. safety of the plant and taking care of the equipment is 7 priority.
8 CHAIRMAN ZECH: I presume this'is one of our lessons 9 learned, though, again, Dr. Murley. We're going.to pursue it.
10 MR. MURLEY: I don't know that it's a problem but we 11 will look into it. Clearly at North Anna they had adequate 12 people, we think.
13 CHAIRMAN ZECH: Right, and it sounds like it worked 14 out very satisfactorily here. But on the other hand, I think .
]
15 it's something that we ought to look into.
16 MR. MURLEY: Right.
17 Mr. Chairman, you had asked about the adequacy of the 'l 18 '
procedures nationwide to deal with steam generator tube 19 ruptures, and Rich Starostacki, Associate Director of NRR, has
. 20 looked into that.
1 21 CHAIRMAN ZECHk Proceed, please.
22 MR. STAROSTECKI: The procedures that were used for 23 steam generator tube ruptures are patterned after generic 24 guidelines that we, the staff, have reviewed and approved.
The
~s 25 utilities that individually generate for us call them the
- h a
e
i 26 i
1- Procedures. Generation Package which says here is how1they 2 implement'the owners' guidelines. .
3 The individual owners group guidelines that'are used )
4 by the utility to develop the procedure we've reviewed and j 5 w
'e've written safety evaluation reports. -In fact, the issue-6 then becomes one of how do we follow up and make sure that the 7 specific procedures in use at the plants have been properly
. ? \
8 implemented. And by that we mean translating.the guidelines 1 9 into the specific language for the operators to use. The !
10 audits that we've done over time have indicated that there has j 11 been a weakness here in the industry and in fact, we've worked 12 with about 16 utilities in doing audits and-inspections and' 13 have found that there is a n'eed for an iterative process to go 14 in and improve these procedures.
15 ,
North Anna's procedures'were reviewed by the NRC in .
16 May 1986, and at.the time, we found anJawful lot of !
17 deficiencies, to the point-that subsequently in August of '86 18 we issued an Information Notice cautioning the industry to 19 improve themselves in this very area. The North Anna 20 procedures were updated, as a matter of fact, in June of 1987 21 and obviously, as we know, the event occurred in July of '87.
22 Symptom-oriented procedures.I think are very 23 difficult for a lot'of people to understand because the' steps.
24 in them don't necessarily require.the' traditional verbatim 25 compliance.
If an operator hits a certain step, he generally t #
'T i
. _ j
.27- l 1 has* choices; he can proceed:to another stop or the procedure i -
2 allows him to make a. judgment,'and infthis-case, as was 3 mentioned earlier, the operator decided'not to~ isolate a-bad!
4 . steam generator. That's allowed for in these. symptom-oriented 'i; 5 procedures and I think that's a strength of the procedures.
4 6 So I'm not surprised.that we aren't having to take an 7 iterative process to get these procedures to where we really 8 vant them, and I.think it has been a healthy situation for the; 9 last four years where wa have been ide~ntifying these problems, i 10 and we need to be doing more post-implementation audits to^make 11 sure that the other stations.have these. kinds of procedures. H 12 We have,'in fact, recently been.looking at all the 13 plants that have these kinds of problems.tliat North Anna had ---
14 denting and high flows -- and have satisfied ourselves that the. 1 15 procedures they have in place are state-of-the-art and are 16 acceptable.
17 MR. MURLEY: Rich, did you mention that-operators I 18 routinely get trained on this event on simulators. I believe 19 they do, don't they?
20 MR. STAROSTECKI: They routinely get' trained,.and 21 that's part of the process. When you revise these symptom-- ;
I 22 orianted procedures, not only are the operators required to be 23 trained on them, we found that that has been a' failure in.the 24 past of the industry that they would use the simulator training i (j 25 on the operators to verify whether the procedure. worked'or not.- -
n
{
28 1 !And from.the last two. years ,of work,'in fact,'this fault has-
'. 2 been corrected.
J The simulators are used-to validate.the' 3 procedures,.then_the operators are trained'on tham'before the-4 procedures are implemented.
5 CHAIRMAN ZECH: I think it might be' helpful to'give j 6 us a layman's definition of symptom-oriented procedures,.
7 especially as they relate to the previous event-oriented 8 procedures that were used some years ago. If you could.put h) 9 that in plain language I think it might.be very helpful because 10 it's a different way of-looking at casualties and I'm familiar ,
11 with both areas, and I think'it's rather a significant step- !
12 that'has been taken in order to keep the plant under control at.
13 all times rather than trying tp diagnose' exactly what.the,
~
7 14 problem was.
Especially in this case, it was,a pretty. good, as
.i
-1 15 far as I could see, example of when the alarm'didn't.go off, if 1 16 they had had to diagnose completely the event'and'where.it' was )
17 it might have been much more difficult than_using'the 18 diagnostic or symptom-oriented procedures. 1 19 So if you.could give us a brief clarification perhaps 20 of the difference I think it might be helpful.
21 MR. STAROSTECKI: The difference, obviously is in 22 avant-oriented procedures one predisposes that one has complete '
23 knowledge as to the accident scenario and-how it's going.to 24 progress. And one then bases -- .
'i 25 CHAIRMAN ZECH:
Even of what a'ctually happened.-
.s i
i l
')
,.29" 1- MR. STAROSTECKI: -Versus'what actually happened: 1 e
'i- 2 because sometimes'what'actually happened'may impose additional. !
l 3 failures and problems, as itLwas11n=this case:that you;didn't- !
.i 4 have all the monitors. . So an event-oriented procedure is, 5 quite frankly, lacking in'some.regards because offits inab'ility l 15 to accommodate-further transients.
I 7 Symptom-oriented procedures, on the other hand,. form 8 8 an interesting basis. They.are reflective of. multiple failures )
0 9 so they allow the operator to deal with the available '
i 10 indicat'on, irrespective of what the scenario involves. "And in
.R 11 fact, you can have complex scenarios and'these procedures will 12 .therefore guide the operator to deal with the more important 13 indications.first. And the. symptom-oriented procedures give-14 l the operator a;1ot more flexibility to exercise jydgments,,and 15 without making a judgment of'a catastrophic failure. i 16 As in this case, the: operator'was hesitant to shut a 17 main steam isolation valve if, in his mind, he isolated the i 18 wrong stream generator because you just: don't' reopen-the-(
19 valves. And the procedure has this capability built.right into '
20 it so he could satisfy himself going through a few more' steps j 21 that what he was doing was correct, i r
22 The Westinghouse guidelines in fact marry bothi 23 event-oriented and symptom-oriented procedures. And the i
24 industry's reaction I think has been very. good'in' allowing .
g 25 s avant-oriented procedures eventually to.come into play whenlthe 4
30 1 operator has dealt with all the indications.
.f 2 That's a very lengthy discussion, but the thrust of 3 it is we're asking the operators to think based on what.
4 information is being presented to them, rather than having them 5 fulfill a scenario that somebody thought out at an engineering 6 office and in fact that is not what the operators are being 7 faced with at the time. ,
8 CHAIRMAN ZECH: It's my impression that in the ,
9 symptom-oriented, the diagnostic, though, each procedure has 10 the purpose of keeping the plant under control, and you don't 11 necessarily have to know what the casualty was right off the 12 bat because everything you do has a tendency to keep the plant 13 under control. Is that correct?
14 MR. STAROSTECKI: That is correct and there is a lot I 15 more cautions and notes in symptom-oriented procedures that ^
1 16 provide additional data to the operator. And again, it's that 17 reliance on giving the operator the best indications and the 18 best information and our interpretation or the utility's 19 interpretation of what's happening to him.
l 20 l
CHAIRMAN ZECH: It's been my personal experience that 21 'ie were all originally trained in the event-oriented 22 casualties, and I'm rather impressed by the newer system'of 23 diagnostic, symptom-oriented because you don't have to know 24 exactly what happened. I'm not sure if it's perhaps an example .
25 that would be the perfect example or not, but for example the k
._---._n--..., - - . -
1 4
- 31
.i 1 . casualty at Three Mile" Island,: if wo had had ' diagnostic f[. 2 procedures in place at that. casualty when'thatLpressurizer:
3 valve was giving an. improper. indication, perhaps if we'd had 4 diagnostic or symptom-oriented the. operators.would have'had a 5 procedure'to close that. blocking valve before theyldid. ' Is.
6 that a fair evaluation?
7 .ER. STAROSTECKI:. My own personal opinion'is yes, and 8 we could all ask a large number'of the staff for their opinions 9 but.it's clear to me that the focus on looking at'a variety of-10 indications, not just one, to establish ~what's' happening in1the 11 plant is critical. And I think.in.the case of the PORV,cthat's 12 a demand signal that the operators at:TMI had and it's really 13 knowing what actually the posi, tion of the valve'is'. And these 14 cautions and notes in these symptom-oriented procedures I would 15 presume today would lead one to look at te11taleLtemperatures 16 on the drain pipe and establish whether or not the valve is-17 shut, irrespective of what the little light is saying. .
'18 CHAIRMAN ZECH: Dr. Murley, would.you care to comment 19 on that? Would you agree with that?
20 MR. MURLEY: My general impression'is.that that would 21 have improved the situation'at TMI, but I don't know that'we've 22 really actually gone back and looked specifically..
23 CHAIRMAN ZECH: No, I'm not sure and that's why I say 24 it may not be a perfect example at.all. -But in, general,.:it' 25 .
seems to me that if we'd had those kind of procedures it would v
_ _ _ m..__ -.___ . _ _ _ _ _ _ _____mE
4__
32 1 have'been of. assistance to the' operators..
( 2 MR..MURLEY: Oh, yes. .The staff is'I think unanimous.
3 in'their view that these procedures-:are better. 'l i
4 CHAIRMAN ZECH: Yes.'When I first' heard aboutLthe 5 diagnostic I wasn't so sure about them'myself, but the. logic of ;
6 assisting the operator in keeping the plant under. control withL 7 avery step-you take, and eventually.he's-going to correctLthe-
. . a 8 casualty, seems to me from the operator's standpoint to be.a'
~
9 better way of handling the casualty.
10 I would agree,- too, that right off if you can.see the 11 event and it's very clear what it is, then.certainly you should-12 be able to do what you think is -- take the proper course of' 13 .i action. But if you're not-sur,e:of the casualty.and'sometimes.
14 we're not, the operators are not, it seems to meLthat'the-15 purpose of the symptom-oriented procedures'is to keep the ,
16 casualty under control, keep the plant under control -- is that 17 how you look at it, Mr. Starostocki?
18 MR. STAROSTECKI: I clearly look at it'as keep the.
19 l casualty under control and stop things'from progressing.to a 20 worse situation and stabilizing.what you can~in a very 7 '1 21 structured manner. 1 So that I thia:t it's very important to- 1 22 emphasize that all'the other utilities that are dealing with 23 these kinds of procedures should take the: time that the 24 Virginia Power people have in terms of revising theirJ 25 procedures, shaking them outL on the simulator and the
-J, 9
33
-1 retraining ~their people on them.' ,
I^ 2 CHAIRMAN ZECH: Anybody else at the table care'to 3 comment on that?
4 MR. REYES: ' I just want to add that. this particular 4
5 example supports your statement in that in the typical training I
6 you expect to have the blowdown radiation monitor come on, and 7 in fact it didn't, but the fact that the symptom procedure led 8 them there is a good example.
9 CHAIRMAN ZECH: Thank you very much.. Anybody else?
10 [No response.)
11 All right, let's proceed.
l 12 MR. MURLEY: Next, Jim Richardson will discuss the i
13 lessons learned about the generator itself. ;
14 MR. RICHARDSON: Thank you, Mr. Chairman. I'm Jim .
15 I Richardson, I'm the Assistant Director for Engineering at NRR.
16 Could I have the next slide, please?
17 [ Slide.]
18 '
Just to give you an idea of what we're talking about 1
19 and where we're talking about, I have a graphic of this model 20 l
l of steam generator that is used.at North Anna, and I direct 21 1
your attention at the top support plate. There are seven 22 support plates, the horizontal lines going around the bundles.
23 The failure occurred at that seventh support bundle, and that's 24 I where the focus of our attention will be.
[
25 CHAIRMAN ZECH:
N/
That's where the arrow is, right?
s
a f
' ii'
'34 - ,
i 1 MR. RICHARDSON: Yes. . No, it'will.be'below the arrow I 2 right at the. support plate.
'3 CHAIRMAN'ZECH: The support plate be2ow the' arrow, 4 all right. !
5 (slide.)
s 6 MR. RICHARDSON:'~Another arrangement;that you'.need-to-7 understand is the anti-vibration bars that are placed in the.U-
~
8
. bend portion'to prevent vibration from crossflow. EIf you'can.
9 imagine the flow going into.the viewgraph, since you have a. ;
10 bunch of cantilevered beams they would.become rather.floppyfin i 11 resisting the flow. These. anti-vibration; bars areJinsertedhto 12 resist that vibratory motion.
13 However, notice t' hat the' anti-vibration' bars do not-14 go in all the way to the center of' the tube -bundle', and that is 15 an important point.that I'll. touch on. .
16 (slide.)
17 I'd like to just very quickly take you throughi a -
18 little bit of the history of this steam generator that we might 19 4 understand what the failure-mechanism was, and particularly-20 a since this is a new failure mechanism. I'll'go throughLvery 1 21 quickly a little bit of history of this generator. ,.
I will then 22 talk about the root cause of'the failure, what. corrective' 23 actions have been taken, what lessons we have learned'and the' 24 basis of why we have allowed the plant tofcontinue operation, j
j 25 and.then finally,fthe generic' implications.- .
M y . .. .. . .
< T :. 'i m . _ . - ._.-_.m.
_ .m_--_i_._.i_
. .j
- 35' :
1 First of all, the. tubes are made of Inconel'-600. 'The 1
r .
2 support plates are made of carbon' steel. ,.That's an~important 3 point that I will.get'to'in.just a minute. The steam generator-4 was started in 1978.- From the very start,,the secondary water:
5 chemistry.was an all-volatile treatment, and we believe'they-6 have had good water chemistry in that plant.'and have. maintained-7 it well except for one instance that happenadLin the'first 8 cy'cle. There was an intrusion of some resins into the' l 9 secondary side. This then caused the secondary water to.become:
10 acidic and in fact, there was some corrosionLbuildup.in the )
11 crevices between the tubes'and the support plates which caused 12 denting. As you get corrosion you get buildup'of magnetite ini :)
i 13 the crevice; that starts squeezing the tube into an'. hourglass j
. 1 14 shape, commonly called tube denting. That is a vary. critical 15 part of the failure scenario. .
1 16 Early in the history of this steam generator, there .
17 was cracking in the bottom tube sheet and there had been- ~!
18 various indications of denting in the tubes early in'its first'-
19 cycle.
20 I point out that this is a new failure mechanism; we 21 have not seen this before. And it's also important to point 22 out that traditional, non-destructive examination techniques, 23 eddy current testing, woul,d not have picked this failure up. l 24 If they had examined this tube just prior to its' failure you. .j
, l
( _j
. 25 probably'would not have seen the crack there. And'I'll get e
O -_-a--__--
a, ,
36; 1
- i 1
- into,that in just a moment. '
- 1
[ 2 .[ Slide.')
3 Westinghouse has-performed an, extensive l root cause 4 analysis and we believe it_to be correct, and it seems to make 5 sense. The scenario goes something-like this. That the4 upper 6 support plate denting cau' sed-the damping coefficient to go-7 down. The' reason being that as you fill up that crevica';with' 8 magnetite you are essentially changing the and conditions,_
l 9 where if there was a' gap there and the' flow-induced vibration 10 would cause the bar to rattle in the support' plate, that would 1 11 tend to absorb-energy and have a higher damping-ratio.- ]
ji 12 Here is a diagram of denting,.and as youcan see,fthe- -
13 magnetite buildup around the tube prevents itJfrom' rattling l
( . .
1 14 against the support plate and essentially _ lowers the damping.
15 l It also increases the mean stress.in the tube. . That,. coupled 16 then with flow-induced vibration -- that is, cross flow across 17 those -- caused high local peak stresses to occur at-that '
18 denting location. So the combination'of the high mean stress,.
19 the lower damping and the flow-induced vibration then caused a 20 fatigue failure.
21 Tho'particular thing to note.here is that.although it
.22 would take many, many cycles-to initiate the crack, it doesn't -
23 take many cycles for that crack to propagateLto: failure.- So 1' 1
24 that's why it lea'ds us to believe that'a traditional inspection-
~
)
, 25 by addy current would not have picked thisLcrack up. . There-was v
4 4
- --_-__.u_-_--. _ _ _ _ , _ _ _
=
g 1
, ' 37 s
1 a fairly short time from crack' initiation to? failure.-
)
"f' 2 MR. MURI2Y: =Is ~that clear? That..the eddy-currenti 1 3 technique, to.be effective to detect alcrack, depends on having L >
j 1
4 a crack growth rate that -is relatively slow 'so:that you trouldt ,
l 5 see it over a cycle or.two. cycles or something like_that. In' ]
1 6 this' case, the crack initiates and grows very: rapidly relative-7 to a cycle,'so it's.likely that you would miss it using eddy- I 8 current techniques. ,
9 [ Slide.]
10 MR. RICHARDSON: So we' conclude then that therelare.
11 certain conditions required for this: type of failure mechanism. r.
12 , Number one, you must have tube denting near the top support 13 plate that would provide high mean stresses and loweridamping r 14 ratios. -
I 15 A second condition is that~the~ anti-vibration bar j 16 does not contact the tube, and as I' pointed'out'in the cartoon .l
'j i
.17 showing the anti-vibration bar it does'not'go all the vay'into .
18 the center.
The reason it doesn't is it was felt it.was not 19 needed because the very center tubes have a very sharp or small 20 radius and they are much stiffer than the outer rows ~and so-21 have a higher natural frequency. It turns out that'there are a 22 couple rows that seem to be critical'and that's around rows:7,-
23 8 and 9, that are in this regime wheraithey,have a natural 24 frequency that would cause problems and'were not. supported:by
'25 the anti-vibration bar. So the second condition-then would be-9
.~___________'_________________-___ ____.._____.__.I-..'..__.l..i_._________ _ _ _ . _ _ - . _ _ _ _ . . . _ . __ _ __ 1 _ . . _ . _ _ . . _ _ - ._... -_-_U
4 . i i
.r.
- -\ '
38 1 no anti-vibration support.
2 And finally, you need.to have sufficient crossflow .
-3 either in a gross sense 1 or..locali crossflows to cause;the flow-i 4 induced vibration. l l S (Slide.) , l1 6 The following steps were taken~by. Virginia Power to 3 7 4 correct the situation. Number one, they installed a downcomer
]
8 flow resistance plate which' cut down the flow.- When.they'do i
! 9 that, they cut down this. critical: velocity or cut down the. flow
{
, i 10 below the critical velocity such that:you-don't.get flow- l 11' induced vibration. Interesting to note here:thatithis steam 12 generator had originally installed a flow-resisting plate but' l
1 13 the decision was made.to.take that plate out to provide higher '
14 flow to, keep the crud from building up. Thisiwas'also done'at4 -
15 a number of other steam generators.
At Ginna.in particular, 16 when they. removed the support plate to get the higher. flows ~in 17 fact part of the plate was dropped into the steam. generator'and 18 became a loose part and eventually led to a. tube ruptureffrom
~
19 that11oose part impacting on the plate.
20 But installing the resistance plate does~have --~is~
21 effective in reducing the flow well below critical levels.- In 22 fact, it's calculated that this reduces the critical' flow ratio 23 which is the ratio of the critical. velocity.to the full flow 24 velocity, by more.than 15 percent. .
.( 25 Secondly, the failed tube'was removed for examination .
9 e
39 1 and a' dummy' tube was' ired nstalled'to take up'the place'of the 2
empty' space where the tube was cut out to provide stability-and 3 to prevent further damage. All the surrounding tubes around 4 the tube that was removed and failed were plugged-just in case-5 this replacement spear that was put in would come loose and 6 start banging around; it would only hit the plugged tube.' So 7 as a precautionary measure, all the surrounding tub'es were
- 8. plugged.
9 In addition, there was some other preventive plugging 10 in rows 8 through 10 where the-anti-vibration bar did not ~
11 contact and around tubes that were deemed to have high local 12 crossflows. Those tubes were preventatively plugged in-all .
13 three steam generators. ~
And all 150 tubes in.the three steam 14 generators were preventatively plugged.
s 15 Then there was an augmented leak detection procedure "
16 put in place. 1 Number one, a new. device that monitors the '
17 isotope N-16 was placed in the steam header and will be '
18 monitored,every four hours. This device is unique to North -
19 Anna and the Zion plant, are the only two plants that have this 20 device. It is very sensitive to the radioisotope N-16.
21 In addition, the condenser air ejector radiation 22 monitor will be monitored every four hours. There is an air 23 ejector grab sample that will be taken every eight hours, and 24 the blowdown' isotopic samples will be monitored every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.- .
25 '
With those monitors in place and thatLfrequency of t
e
... 40 l 1 inspection, the following procedures then have been
/' 2 implemented.- '
3 The N-16 and. air ejector monitors 'are alarmed to .
')
)
4 detect 10 to 20-gallon per day' increases in leak rate. The N16 .
U 5
monitors also are alarmed for 60 and 100-gallon per day l 6
increases, and then th's following procedures have been put in 7 place to react to those. !
If they detect 100-gallon per. day. j 8
leakage rate they will reduce t$ 50 percent power. If'a 60- 1 9
gallon per day leak rate increase is detected with four hours',.
1 l
10 they will reduce to 50 percent power. And' finally, if there is' 11 a trending analysis that shows that more than 100 gallons.per 12 day leakage rate would be accomplished within 90 minutes- they ,
13 will reduce to 50 percent power. These are put'in to take'into~
14 i ai:: count the fact that this is a fatigue crack rupture and we
{
15 may not have much time between crack initiation and failur,s. I 16 The data. indicates, from this rupture and from
{ 17 analysis, that we do have several hours, in excess of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> 18 and maybe a few days, from crack initiation to rupture,'so we.
l
- )
19 believe that these leak-monitoring procedures are fine enough 20 that we would pick up an increase in leak and be able to. shut 21 down before we get a tube rupture.
22 COMMISSIONER CARR: That 50 percent power reduction, 23 is that the first step?
24 MR. RICHARDSON: That would be a first step but it 25 ..
would, reduce the flow where you should'not"get the failure at
p 41-1 all.'
'2
, COMMISSIONER.CARR But is'the intent.to. keep running-3 at 50 percent power until the next . outage, or is that -just the -
4 first step before you go ahead and analyze where you've got a e
5 problem or not?
6 MR. RICHARDSON: We would certainly want to analyze 7~ it. There is no requirement at the tim'a to go;on down to. )
8 shutdown. We have removed the. primary force that would drive-9 the; crack to failure; that is, the high velocity' crossflow.
( 10 MR. MURLEY: I don't know if that's clear. We're 11 confident that it could run for-a long period of time..at 50 .!
12 percent power because you would not get.the flow-induced-13 vibration that those power and flow levels.- '
So the' intent 14 :
would be to take it down to that power'and figure out whether, j 15 it's safe to go back up. l 16 MR. RICHARDSON: .Next slide, please.
{ 17 CHAIRMAN ZECH: Before~you go off that'one could you 18 talk just very briefly on the plugging? You mentioned a number '!
19 of tubes to be plugged. What percentage is that, and is that '
20 within our tolerancers for the number of tubes that we permit-21 plugged? .
22 MR. RICHARDSON: .Oh, yes, it's well withi'n that 23 tolerance. Could I have backup slide B-6, please.
24
[ Slide.)
25 g This is the tube-plugging summary.
- f I ,
y
- 42 1 CHAIRMAN ZECH: How many tubes ers there all 2 together?
3 MR. RICHARDSON: In one steam generator a little over 4 3000 tubes in each generator. And these are the total 5
population in all three generators which would be about 10,000 6
tubes, and prior to May of '87 they had plugged almost 400 7 tubes. In May of 1987 they have plugged an additional 263 8 tubes. And of course we had the ruptured tube which'was 9
removed. After the incident, there was a re-examination of all 10 the tubes and an additional 84 were plugged by re-interpreting 11 some of the indications.j and there were 150 tubes that were 12 preventatively plugged.that I talked about earlier.
13 CHAIRMAN ZECH:
I And those numbers relate to a total 14 of 10,000 tubes?
15 MR. RICHARDSON: Yes. About 8 percent of all the 16 tubes in the three steam generators have been plugged.
I
{ 17 MR. KURLEY: What's the design margin, Jim, do you 18 know?
19 MR. RICHARDSON: I believe we allow up to 15 percent 20 can be plugged.
21 CHAIRMAN ZECH: All right, fine.
22 MR. MURLEY: So it's well within the margin.
23 CHAIRMAN ZECH: Proceed, please.
24 MR. RICHARDSON: We believe that the mechanism has 25
, N.) been adequately identified and the causal factors, and they
.m
?
i 43 1 have taken acceptable corrective actions in monitoring, and'on f , 2 that basic we.have allowed the plant to go back to 100 percent 3 power.
4 (Slide.)
5 So what have we learned from this, what are the
{
6 lessons to be learned? We believe there are a number. Number 7 one, this is a unique failure mechanism, it's new. We had not 8 anticipated it. It points out that tube denting can lead to 9 fatigue failures other than just den' ting itself. That the
(_' 10 denting can lead to something else.
11 The location of the ant.t-vibration bar is very 12 important as to how far in it penetrates. We also need to pay 13 close attention to local flow velocities. As you stick this 14 anti-vibration bar into the flow, you can create local flow 15 velocities that may be inducing high vibration on individual 16 tubes. Have to be careful with that. And the existing leak 17
{i detection programs that are in place may not be effective in 18 detecting rapid fatigue failures, and we have to be careful 19 with this.
20 MR. MURIEY:
I l
Jim, should that be the existing crack {
21 detection program, or did you mean leak detection?
22 MR. RICHARDSON: No. Existing leak detection 23 sensitive enough to pick up a crack in time.
24
[ Slide.] j l
25 l MR. RICHARDSON: So what are the generic l
l l
l l
\
~44 1 ' implications?
Westinghouse'went back and reviewed tho' designs
~
'; 2 of steam' generators.that.are in-the field.- Using the criteria
- 3. of denting and stability ratio they identified five plants that 4 may be susceptible to a. failure similar to North Anna.~ The 5 degree of that susceptibility, though, is. highly uncertain.
6 There's a lot of uncertainty in the calculations. And there' 7
may be other plants'beyond these five that are susceptible.to 8 this. -
9 CHAIRMAN ZECH: Are you going to tell us about those C: 10 five?
11 MR. RICHARDSON: Yes. The next slide --
12 CHAIRMAN ZECH: Before you go.on to that one, does 13 our in-service testing requirement for steam generators.--
14 would it be adequate now to detect similar' leaks before. steam 15 generator tubes would rupture?
16 MR. RICHARDSON: I want to make it clear, the addy
(_ 17 current testing.that we do would not pick thi,s up.
18 CHAIRMAN ZECH: That's what I understand.
19 MR. RICHARDSON: That would not pick it up. What we 20 have to rely.on is leak detection in picking up leaks that may 21 develop.
22 CHAIRMAN ZECH: Well, how good is the leak detection?
23 MR. RICHARDSON:
We're not'sure that it's:adequa'e t 24 yet.
We're looking into that at the other plants. But I think ..
25-what is more important is what are the necessary environmental.
^
s
45 1 conditions that set up the potential for this. Do you, in 2 fact, have high enough flow velocities and do you have the 3
presence of denting that would lower the damping to give you 4
the environment that woL11d lead to thia.
5 CHAIRMAN ZEC : So this is an open item is what ,
6 you're telling us.
7 MR. RICHARDSON: Yes, it is. -
8 CRAIRMAN ZECH: That's important I think for us to 9 recognize that.
10 MR. MURLEY: The first step is to determine the 11 susceptibility of plants to this and we found that there are l
12 ,
five plants potentially susceptible. Why don't we get on to e 13 those on the next chart. .
14 (Slide.) '
15 MR. RICHARDSON:
The next chart are the five plants 16 that were identified by Westinghouse as being susceptible.
(i 17 Four of the five plants are currently shut down, and one plant, 18 Indian Point 3, is operating.
We have met with Indian Point 3 19 and Point Beach. We will be meeting with the other three 20 plants over the next two weeks to discuss the problem.
21 Both Point Beach and Indian Point are challenging the 22 Westinghouse calculations. They believe that -- they have done 23 some independent calculations and believe that the Westinghouse 24 calculations are too conservative, and they believe that their 25 flow velocities are well below the critical velocity and that
46 1 they do not have this problem. We are examining their 2
/
calculations; we have not yet arrived at a point of agreement 3 with them yet, but they believe that they should not be in this 4 critical list of five.
5 In addition, Indian Point 3 has very sensitive leak 6 monitoring capabilities. Their air ejector rad monitor has the 7
capability of detecting something in the vicinity of 10 gallons 8
per minute flow -- I'm sorry, 10 gallons per day, which is 9 very, very sensitive. They have committed to monitor this at 10 least once per shift, and when they get a substantial increase ,
11 in leakage they will shut down. So we believe until we have 12 satisfied ourselves that that is good enough, there is not '
13 undue danger in allowing them to continue to operate.
1 14 COMMISSIONER ROBERTS: Do all of these plants -- do ,
15 the licensees know with accuracy their water chemistry history I 16 on the secondary side?
(j 17 MR. RICHARDSON: I'm not sure I can answer that yet.
18 These are the types of --
19 COMMISSIONER ROBERTS: Is it terribly important?
20 MR. RICHARDSON: Yes, I think it is, in that the 21 '
plants that were identified as the.five being most critical 22 were plants that were susceptible to tube denting, which would 23 reflect water chemistry. But I'm not sure we have identified 24 all of them yet. We want to go back and taka a look at water ,
25 *\
( ,
chemistry history of the other plants to see if we should take 4
47 1 a closer look at other plants.
f 2 MR. MURLEY: Jim, just to clarify, don't we think we 3
have relatively good information on tube denting from 4 measurements?
i 5 MR. RICHARDSON: Yes. That's how these five plants 6
got identified, is that they had indications of tube denting 7 7 and they had high crossflow velocities. '
i 8 MR. MURLEY: So it's not absolutely necessary, 9
Commissioner, that we know the water chemistry history; we can
(~ 10 detect denting.
And if we know that and that is one of the 11 conditions, then it's a calculation as to whether you've got 12 the sufficient crossflow to cause the vibration.
13 MR. RICHARDSON: My last slide, a'ain, g I think just 14 continues with what I -- '
15 COMMISSIONER CARR: Before you leave that one, you 16 mentioned that one plant had the. capability of detecting a 10-( 17 gallon per day leak. Does everybody?
- 18 MR. RICHARDSON: I don't know yet. As we talk to 19 these plants that are susceptible --
20 COMMISSIONER CARR: Just the radiation detector 21 you're talking about.
22 MR. RICHARDSON: Yes.
23 COMMISSIONER CARR: It's a matter of setting the 24 setpoint.
( 25 - MR. MURLEY:
N/ That, Commissioner, is one of the things.
P b
. l i
48 1 that we're going to be looking at. If we conclude -- we're
(* 2 going to approach this conservatively, like we usually do, and
'I 3
if we conclude that some of these plants are susceptible, then 4
that's one of the fixes that we'll be looking at, is increased 5 sensitivity leak detection.
6 COMMISSIONER CARR: It's not a fix; that's a 7 procedural solution. . I I
W 8 MR. MURLEY: That's correct, yes.
9 COMMISSIONER ROGERS: Excuse me, is there any reason (
10 not to ask these plants to install that kind of sensitivity?
11 Is that a big problem for them to get something like this 12 Nitrogen 16 detector in place on all of these?
13
, MR. MURLEY: I don't,think it's a big problem but 14 until we look at it I can't say for sure. 1 15 ,
COMMISSIONER ROGERS:
, Regardless of what your 16 1 analysis of their susceptibility says, wouldn't it be advisable
{ 17 to at least have a detection scheme in place, a detection 18 system in place?
19 MR. MURLEY: Yes, we're looking at that.
20 CHAIRMAN ZECH: Let's proceed.
21 (Slide.)
22 MR. RICHARDSON: My last slide is merely a 23 continuation of the basis of why we believe that continued 24 operation in the near term is justified. We believe multiple 25 (V .
1 tube ruptures are highly unlikely and that the single tube 9
_ - _ _ - _ _ _ _ - _ _ _ _ . _ _ _ _ . _ - _ _ _ _ _ . - - - - - _ _ _ _ . _ _ _ _ _ . _ _ _ _ - _ - . _ _ . - _ _ . - _ - - . _ - . - - - _ . - - _ _ _ _ - . _ _ _ _ _ _ _ - . _ ---____-_______a
l .-
49 11 rupture is a design basis, and their emergency operating
(' 2 procedures --
3 CHAIRMAN ZECH: Tell us what you mean by design' basis 4 accident; I'think it might be useful.
5 MR. RICHARDSON: The single-tube rupture has been l 6 assumed in the Safety Analysis Report and thoroughly reviewed 7
by the staff.and we believe that it is a controllable event, as-8 demonstrated by North Anna 1.
9 MR. MURLEY: And that any; radioactivity releases 10 would be.within our limits. '
11 MR. RICHARDSON: And that there are emergency 12 operating procedures in place. We have' verified with these 13 ~
five plants that those emergency procedures are in place and' 14 the operators have been trained. -
15 CHAIRMAN ZECH: All right.
16 MR. MURLEY: Mr. Chairman, that concludes our
( 17 prepared presentation. We are still, of course, as Jim 18 Richardson mentioned, talking with the utilities of the plants 19 that might be susceptible to this. - We are going to take 'a 20 careful, conservative approach to this problem, and that's our 21 conclusion.
22' CHAIRMAN ZECH:
1' Thank you very much. . Questions from 23 my-fellow Commissioners? .
24 COMMISSIONER CARR: I've got no questions but I've
~ [, 25 got a couple of comments.
%j I think-the operators did a '
e 4 6
' 50'
, l'. . fantastic job in{this particular casa.. We handicapped'them by
(' 2 not doing' post-maintenance testing.like ws should'have; they
\..
1 3 would have had a confirming alarm and might have saved .]
4 themselves'a few minutes on deciding which generator lit is. ;;
5 But I'm back on my maintenance kick of doing it right and ]
6 making sure you've done it right,.and then restoring those 7 conditions. If they had reset those'setpoints they would have had a heads up.
9 8
s 9
If they had -- it worries me that they reset that 3
' {- '
- 9 10 alarm five times. It's okay to reset the alarm but you've got' 11 to believe it the first time. If we get in the habit of-living 12 with those kinds of conditions we've trapped the operators. As I 13 the man said, we're not giving,them a full deck to play'with if
14 ,
they can't believe those things that are going on-in the plant l
15 and depend on them to work.
16 COMMISSIONER ROGERS: I have just a ' couple of
{ 17 questions. Were there any special technical. features of this
.t i
18
~
event that if they hadn't gone that way it would have been much 19 more serious?
l The operators clearly behaved very well and I i
20 s understand that the training that went on was very important'in 21 ' enabling them to be prepared to deal with that. And I think 22 i
that while the word training was mentioned very briefly here, I 23 think that really should be reiterated. If it was so important 24
-- it's my understanding that it was very important, that the r
25 j
V; licensee feels that training really equipped those operators to l
\
q
'.]
\
51 1.
deal so well'with it; they undoubtedly were good people buti
( 2 they were weli trained. AndIthinkthatthetrain$.ngaspects 3 of this performance should be emphasized i-f indeed that is 4 believed to be an important aspect of why they behaved so well.
5 But were there any technical features of the event 6 that just happened to go the right way so that it 'did turn out '
7 as well, and if they hadn't gone the right way we would have.-
8 'had a much more serious problem? Have you really looked at 9 that?
(I '
10 MR. MURLEY: Let me ask Mr. Reyes. !
11 MR. REYES: From the releases point of view, the i 12 primary system was very clean. If there would have been the 13 limit by Tech Specs, higher activity, the release would have 14 been of higher magnitude.. But again, Tech Spec limit is part 15 of the basis for the steam generator tube rupture that's 16 analyzed for the unit before it gets licensed, so it still 17
{i would have been below Part 100. But it would have been more 18 1 significant releases with higher activity in the primary 19 system. l 20 MR. CALDWELL: The plant itself behaved very well.
21 It essentially isolated its own steam flow path with the I 22 turbine tripped and then the steam dumps going closed, so that.
23 helped minimize the release itself. Had they continued to drag 24 steam, that would have contributed to the event. - i 25 MR. MURLEY:
I guess one point, Commissioner, I 4
$ _ . . _ . _ _ _ _ _ _ _ A
52 l'
mentioned earlier, that it only had one. day's operation so'the 2
( decay heat load was low, which meant that the~ primary system ,
3- came down in power and' temperature and pressure quicker than 4 ctherwise, and that made it easier to handle. But I don't. i 5 think that would be a fundamental. change. I think the way:they 6 approached it --
7 I COMMISSIONER CARR: Suppose they were just one day )
8 short of an outage -- how would that have looked then?
9 MR. MURLEY: It would have made it a~little more C. 10 i
difficult to equalize pressures and. temperatures andfso forth, l 11 but I think the way they handled it, it would have been --
12 MR. REYES: It would have been a longer cooldown and
, 13 perhaps slightly higher releases. I 14 CHAIRMAN ZECH: 'Let me just say I'd like to thank the 15 staff for this very informative briefing and also your 16 recognition that there are some events here that we have to-
{; 17 look into, some issues to look into, regarding follow-up 18 actions. I think it's important to' point out that in this 19 particular case, although the release was less than one percent 20 of the limits that we allow in our Technical Specifications and 21 that your evaluation was that the consequences of that release-22 were -- I believe you used the term -- insignificant; is that 23 right?
24 MR. NURLEY: Yes.
25 CHAIRMAN ZECH: Even so, I think we can see that the P j
- '1 53 'f t 1
cvent as it'certainly would apply to'other plants does require 4
-(
2 continued evaluation. I,.too, would like to' command,'though, l 3
the Virginia Power Company for the way they' handled this event. '
)
j 4 l I think our residents should be commended,.also, and'the Region 5
for the way they.-- and Headquarters staff -- in the response 6 they took to this event. Even though it was, as.it turned out, 7 an event of not' great consequence,.the potential is there. j 8
always, and it's something that I think Virginia Power handled i l
9 responsibly as did the NRC people handle responsibly.
( 10 I am particularly impressed that at 6:30 in the-11 morning one of our residents arrived on.the scene in four ;
12 minutes. That's very good.
13 I just recognize.that the: staff recognizes,.too,.that 14 this is an important issue to follow through on. Even though, 15 as we all know, the many steam generator tubes.-- one tube with 16 that water flowing through the reactor, in this case the.
{ 17 reactor history or power history was not great, therefore, the 18 radiation potential was not high. There are other times when 19 it could have been high, and I think even though we all know.
20 one tube does meet the design basis considerations, still we 21
(
don't want any releases if we can possibly help it. So I think 22 there are lessons to be learned here, and I think we should 23 continually strive to minimize any releases to the' atmosphere.
24 l That is, of course, our job, to protect the public health and l
i 25 safety.
k
e
~
54 1
So anything we~can.do, and I.think to follow through
( 2' the lessons ~ learned -- the. commission will be' anxious to hear
.\
3 your follow-through views and some kind of a report to the i 4' l commission in due course I think would be appropriate because' '
5 we do want to assure that from the regulatory side we're taking-6 every action we can.to protect the public.
7 Are there any other comments from my fellow 8 commissioners before we adjourn? 1 9
l COMMISSIONER ROGERS: Just along those lines, the: I
(- 10 continued advisability of operating at 50 percent power after.
11 there has been a detection of a crack is something that I think 12 ,
needs to be really documented as well as can be done, and I
- 13 would hope that a future report -- i 14 'MR. MURLEY: We have a Safety Evaluation Report on 50 -
15 percent power, commissioner.
, We'll be glad to send that down.
16 COMMISSIONER ROGERS: Good.
17 (i CHAIRMAN ZECH: Let me emphasize that remark, too.
18 It seems to me that is a very important issue and I would urge 19 the staff to take a very conservative approach to that because 20 if there's any doubt about it we should, as far as I'm 21 concerned, go to a much lower power level or certainly consider 22 aven shutting them down if there's any potential problem there.
23 So I think that is an important point to emphasize.
24 COMMISSIONER CARR: That was 50 percent power with a .
( 25 100-gallon per hour leak, right?
s.s e
W 9
a 55 1 MR. CALDWELL: If they get a 100-gallon per hour' leak 1 2
or per day, 100 gpd per day. leak on one steam generator,:they i 3 will shut down. They've already established the criteria to do 4 that. And they'll notify the NRC and confer with us prior to 1 5 restart.
)
6 CHAIRMAN ZECH: Does that apply to everyone else?
7 COMMISSIONER CARR: What's all this 50 percent power 8 stuff?
9 l MR. CALDWELL: Well, at 60 gpd they drop to 50 l h 10 percent power. If it looks like they're going to go to 100 gpd 1
11 in the next 90 minutes, they drop to 50 percent, and then in 12 the next six hours go down to Mode 3.
13 MR. STAROSTECKI: If.I could add'something, I share 14 the concern you have. We allow power plants in this country'to 15 operate with a 500-gallon per day leakage in each steam 16 generator. That's what is allowed today. And the concern is
(, 17 discriminating; once you have a high leakage, when you find -
18 more leakage that's not identified. So when people were 19 talking about sensitive devices they were talking about given 20 that you already have a high leakage, how are you going to find 21 that new leakage that is going to add that incremental.
22 COMMISSIONER CARR: That's why the sotpoints get 23 moved up.
2k MR. STAROSTECKI: So we're looking at that 500 as why .
( 25 is that even acceptable.
56 1 CHAIRMAN ZECH: I hope we're'looking at that again.
! 2 . Is that what you're telling us we're doing?
3 MR. STAROSTECKI: That's what we're looking at.
4 CHAIRMAN ZECH: All right, fine. Any other comments l 5 from my fellow Commissioners?
6 (No response.]
7 All right, thank you very much again. We stand 8 adjourned.
9 [Whereupon, at 10:55 a.m., the Commission meeting was 10 adjourned.)
11 12 13 .
14
- 15 16 C 17 18 19 20 21 22 23 24
(.- 25 e
i l
l
=,.
et 1
2 REPORTER'S CERTIFICATE 3
4 This is to certify that the attached events of a'-
5 meeting of the U.S. Nuclear Regulatory Commission entitled:
6 7 TITLE OF MEETING: Briefing on North Annael Steam Generator Tube Rupture Event 8 PLACE OF MEETING: Washington,-D.C.
9 DATE OF MEETING: Monday, November 9, 1987 .
10 ,
11 were held as herein appears, and that'this is the original 12 transcript thereof' for the file of the Commission taken ~
13 f stenographically by me, thereafter reduced to typewriting by 14 ne or under the direction of the court reporting company,~and 15 that the transcript is a.true and accurate record of the 16 foregoing events.
17 18 -
guzirfne B odng
~~~~~
19 20 4
21 ,
22 Ann Riley & Associates, Ltd.
23 24 25
- - - - - - - - - - . _ - - _ _ _ _ _ , . _ _ _ _ - _ _ _ _ - . _ - - _. f - - _ _ _ _ - _ _ . _ . _ _ - . _ _ - - _ _ .
A.
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ArBOA -
I. IhTRUDUCTirw II DESCRIPTION OF PENT
.* '\
III. STEAM GENERATOR TUBE FAILURE ASSES 90.T AND 00RRECTIVE ACTIONS' .
e e
t IV. GENERIC IMPLICATIONS AND ACTIONS ,
6 9
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. . H 9 )
A.- )
. 1 1
I 1
l STEAM GENERATOR TUBE RUPTURE EVENT l
JULY 15, 1987 1
- Initial Plant Conditions j
- Discussion on Operator Actions From -
l Initial Indication to Reactor Trip
!
- Sequence of Events ,
0 l
l L
e
OPERATOR ACTIORS FROM INITIAL INDICAT'!ON OF THE TUBE RUPTURE UNTIL REACTOR SCRAM
-4 DATE - JULY 15, 1987 0630 Main Steam (High Range) Radiation Monitor Alarm.
- "A" and "B" monitors in " ALERT"
- "C" monitor was in "HIGH ALARM" 0631 Pressurizer level decreasing 0632 Pressurizer low pressure alam - 2135 psig, CR0placedcharhingcontrolsinmanualand and maximized f ow to the ACS 0633 Shift Supervisor entered the control Room and directed the following:
- Isolate letdown i
- Realign Charging suction to RWST
- Commence Turbine ramp down at 25 per minute 0634 STA and Resident inspector' arrived in the Control Room. -
. . Pressurizer Pressure 2109 psig.
Superintendent of Operations was notified and directed the Unit to be manually tripped.
0635 Shift Supervisor directed the CR0 to manually trip the Unit and Turbine and enter EP-0 " REACTOR TRIP OR SAFETY INJECTION".
~
ayauss WP waum 4k '
DATE . JULY 15, 1987 0635 Shift Supervisor directed the U-1 CR0 to manually trip the reactor and turbine and initiate-EP-0.
- Pressurizer level - 45%
- Pressurizer pressure - 2100 psig.
0635:17 SAFETYINJECTIONautoinitiated(PZRLOW PRESSURE - 1765 psig) 0639 Notification of Unusual Event declared.
"C" SG 1evel begins to recover followed by "A" and "B" SG 1evels.
a 0640 Entered EP-3 " STEAM GENERATOR TUBE RUPTURE".
0641 Steam Dumps closed - Tavg less than 543 degrees F. P-12 interlock set.
i 06.44 SAFETY INJECTION and PHASE A ISOLATION reset.
LHS! PUMPS "A" and "B" SECURED i
. 0646 AUX FEED to "C" SG isolated and level still increases (Tube Rupture confirmed in "C" SG)
"C" MAIN STEAM TRIP VALVE closed.
0648 Steam supply from "C" $/G to steam driven Aux Feed Pump isolated.
0649 Commenced rapid cooldown on "A" and "8" SGs via steam dump valves.
9 b
0 a
... [
0654 " ALERT" DECLARED.
0704 "C" S/G level increase stopped and SAFETY INJECTION reduction criteria met.
- "B" Charging Pump secured.
- Initiated isolation of BIT flowpath.
- Established Nonnal charging flowpath, i
0723 NRC R11 Incident Response Center activated l and in standby ,
l 0726 NRC Headquarters Response Ceriter activated and in standby 0727 Began RCS cooldown .ES 3.1 " POST-SG TUBE RUPTURE C00LDOWN USING BACKFILL".
0730 Emergency Diesel Generators secured l J
0745 NRC Response Team formed and dispatched
! from Region II .
1 :.
0756 Condenser Air Ejector manually diverted to containment, 1
1108 Entered Mode 4, 1219 Placed RHR System in service to continue RCS cooldown, 1330 Entered Mode 5. .
1335 Emergency terminated. ,
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NITH ANNA 1 STFAM GENERATOR C
TUBE RUPERE EVEFT N M MBER 9, 1987 4
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Document Control Desk, 016 Phillips TRANSM1TTAL T0:
ADVANCED COPY TO: The Public Document Room
! DATE: #,/45 87 SECY Correspondence & Records Branch j FROM:
hl 2
! Attached are copies of a Commission meeting transcript and related meeting M l-;
[
document (s). They are being forwarded for entry on the Daily Accession List and placement in the Public Document Room.
required.
No other. distribution is requested or hl A
l Meeting Title. A DM w b-,*_/
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! Meeting Date: //,/9/f 7 Open N Closed 5
5 Item Description *: Copies '
Advanced DCS 5 Copy '8 to PDR E d$
1 1
- 1. TRANSCRIPT h)b!uLw.cu fb
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- PDR is advanced one copy of each document, two of each SECY paper.
C&R Branch files the original transcript, with attachments, without SECY papers.
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