ML20118D274

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Summary of 670719 ACRS & Regulatory Staff Meeting W/Reactor Vendors Re Accessibility for Insp of Reactor Pressure Vessels.List of Attendees Encl
ML20118D274
Person / Time
Issue date: 07/26/1967
From: Libarkin M
Advisory Committee on Reactor Safeguards
To:
Advisory Committee on Reactor Safeguards
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ML093631134 List: ... further results
References
ACRS-GENERAL, NUDOCS 9210120060
Download: ML20118D274 (21)
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(July 26, 1967)

To ACRS Members OFlGINAL SIC;Q BT-

g. ',i LIDAFX1H Trom M. W. Libarkin Staff Assistant Subjects IE3 TING TO DISCUSS CRITERION ON ACCESSIBILITY FOR INSPECTION OF REACTOR PRESSURE VISSELS, JULY 19, 1967 Enclosed for your information is a record of the subject meeting.

Coaumente cre iavited from those who attanded.

Encicoures Notes of Meeting to Discuse Criterion on

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Accessibility for Inspection of Reactor Pressure Vessele i

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REG./ ACES !SETING WITH REACTOR VENDORS 10 LISCUSS ACCESSIBILITY FOR INSPECTICII 0F react 0R PRESSURE VESSELS July 19, 1967 The meeting was held to discuss with the power reactor vendors, the proposed criteria on accessibility of pressure vessels.

Attendeest Westinsbouse Babcock & Wilcox GE-APED C. Landonnan J. H. MacMillan W. Schultheis L. Kats D. K. Davies W. R. Smith, Jr.

E. S. Beckjord J. B. Graham H. D..-Greenberg (R&DC)

A H. Hubbard O. H. Creager Combustion Engineerinn_

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R. E. Lorents, Jr.

d. G. Casa P. Morris J. M. Wes t A. B. Holt S. S. Pawlic4A C. Givone R. R. :taccary D. Thompson M

Ccanpliance AEC-REG F. R. Cook C. W. Reinmuth C. Beck L. E. Alsogar L. Kornblith H. H. Mann l-J. L. Norshon l

T. G. Schleitar l

l-I. E. Jackson M. Booth ACRS i

H. J. Palladino l

D. Okrent l

H. 2therington i

S. H. Bush H. W. Libarkin, Staff l

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& Committee mesabers and members of the Regulatory Staff met in executive sessive to discuss the proceduras for the meeting. Mr. Case noted that a tentatin agenda had been distributed to each of the companies invited.in.

dicating what matters would be dealt with. In answer to Mr. }kaselsdorf, l'.r. Case commented on some of r.he reactions which he has received to the criteria for accessibility. 3 3 has indicated that they have already est the critsrian in their design for the Lake Power Company. He felt that General Electric would probably offer some resistence since in the CE designs it is most difficult to remove the core internels and the company sees no gain in terms of relaxad requirements elsewhere.

Mr. Case also noted that the letter had indicated that a emeting in private could be arranged if any of the vendors so wished, Thus far, Mr. McWhorter has indicated that Cs might want to have such a private discussion.

Mr. Case thought that it was possible that representatives of one or more utilities might aPpaar since the meeting had been announced in Nucleonics Week.

It was agreed by those present that utility representatives would not be in-vited to attend this meeting. Mr. Case also commented tht.- representatives of Nuelsonics Weak had been told they would not be invited but that he had agreed to inform thou as to what had taken place.

l The discussion then turned to anticipation of questions which might arise and of suggested approaches to these.

It was agraed that if the degree of inspec-tion which is being considered came into question the document now under preparation which is to form part of the AEC requireswnts for quality assurance of reestor pressurs vessels, could be discussed in a general way. Mr. Case added j

that while access to the entire vessel is being required a more frequent inspec-tion of so callet critical areas would probably be in order in his opinion.

i Pr. Cass noted that if the question arose em to what standard would be used to l

validate the inspection it might prova embarrassing since none is presently l

available. Mr. Etherington suggested, howevar, that what was being requested I

at this time was the capability of performing inspections in anticipation of l

the developenent of apprepriate techniques.

1 Mr. Fa11 adios suggested that those present might also consider that the vendors would suggast that designing for inspectability could lead to reduced safety stase compromises would then be made on the strength of core internals, etc.

Other somments included one by Dr. Okrent to the effect that there might be seen reason for performing mere inspection than is thought strictly necessary la order to establish how such 4 indeed sufficient. Perhaps some emers could perform 1001 inspections and if expectatians are confirmed future progrees could be reduced.

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Mr. Retamuth commented that when ultrasonic tests are performed during fabrication there are some flawe which are considered recordable but which are not necessari19 repaired. The Regulatory Staff has been pressing for good desumentation af tmos so that future in service inspections could reveal growth, etc.

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Mr. Case opened the meeting by observing that the Commission is presently con-sidering the establistmanat of the criteria listed in Mr. price's letter and it was thought desirable to get eene feeling for the problems which might be raised by these criteria in terms of redesign, etc.

Mr. Case suggested that the-first of the two criteria be discussed initially:

"The interior of the reactor pressure vessel, including the bottom head, should be accessible for visual obser-vations at appropriate intervals. Such observations would have as their objective detection of mechanical damage or structural failure of the reactor vessel and its internels."

Mr. Meccary them listed the objectives uf the visual inspection criterion.

1.

E==t-tions of vessel interior surfaces to discover evidence of mechanical demage, unanticipated erosion in local areas, corrosive effects of long-term esposure to reactor coolant, grose creaking at areas subject to complex thermal gradients or shock.

2.

Detection of any mejor structural damage of core support attachemata to the vessel free unexpected vibratory or i

dynamis lands imposed during extended service periods.

3.

E==intium of the reaetor internals to uncover any evidence og damsgo induced by flow and hydraulis loadings during operation, disassembly or distortion of core components from sucessivs thermal loads, wear and breakage of festeners in l-the core structure caused by vibrations.

Mr. Massary stressed throughout this list that long-term effecca were of Laterest and-edded to the list toeg-tors surface changes, that is changes to the eladding from presently unaanticlyste GMeets.

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Mr. Case noted that there was also interest is dete mining the existense of damags er changes to other compements within the vessel such as parts of the ECCS.

Mr. Esta replied that the Westinghouse Corp has gives careful consideration l

La their destys se that it possible to inspect the followings 1.

The entire surfase of the reestor vessel 2.

h Laner and outer surfaces of the vessel closure head i

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The vessel stude, nuts and washers 4.

N field welds conaesting the vessel and primary piping i

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N roaster internals i

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N vessel and closure head, flange and gasket sealing j

surfaces, fuel assendily and control rod clusters i

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The following provistens have been made to allow these inspections.

P All internals are completely removable during refueling tools l

and storage spese are provided at each facility.

'Tha cThat s&osasd head eas.be>storodsdry on the reestor operating deck.

Vessel stude, nuts and weehers are stored dry during refueling operations.

Removable plugs sre.provided in the shield concrete above the coelaat pipikg-to-vessel weld.

Assess botes in the lower interest barrel flange allow 1.nspection of loost internal strusture without removal of the core barrel.

A removable plug is leested in the lower core suoport plate to allow assess to the betten head inner surface with the core support plate in place.

The sentrol rod eluster changoest statica design allows visual inspection of fuel assenh11es and associated contro1 rod clusters.

Mr. Esta seestuded that the present Westingbouse desips provide ensimum l

flamibility and assassibility for inspestion and that no desip changes would i

he mesessary to allow these designs to mest the proposed criterios.

Mr. Case asbed how mesh time would be nosessary for. remeral and insta11 tion of core

'antaessis to allas seseos to the entire inner ve ssel surface.

Mr. Kats suggestae that it might require one week for res ~al and one week for reinstalla-ties based oc past esperiense.

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Mr. Case asked if present inspection teshaiques were thought to be adequate.

Mr. Eats replied that Westinghouse has had considerable success with bere.-

esope and underweger TV inspections.

In addities, he noted that a satis-factiery inspectiesecan be perienmed,using strong light and bimeculare.

Dr. Seek asked if the enternet surface of the vessel was accessible as well.

Mr. Esta replied that presently there is not necess to the esternal surface of the roaster vessel in the area of the primary concrete stase the insulla--

ties is intimately atteshed to the vessel. The botten head and flange area aus assessible, however.

Mr. Falladise asked if the inspection would be done with the vessel wet or dry.

Mr. Esta noted that the core internals would be submerged unlese obey were re-moved but the top of the core would be under only about one foot c f water.

It is presently thought to be.impeesible to inspect a dry vessel visually because of the radiation problem even with..them..intasmats removed and in storage.

Mr. Ethertagten asked if it would be possible to-sum up by saying that the present design already complies with criterios 1.

Mr. Kats thought this _would be a fair statement.

Mr. Falladine noted that Mr. Kata had referred to past experience and asked

, hat the results of past visual inspeetions had been. Mr. Kata answeres a

w that slaan, bridt surfases had been seen on all encept horisontal parallel surfases of platesand on aosa parts of the bettom head. No special crud cleaning techniques hate been necessary. Dr. Maan aaked what resolution was possible with the visual inspeetica techniques now available. Mr. Kata thought that the inspections whiah had been performed by Westinghouse person-met would uncover groes cladding cracks,- that-Le -arose approximately three inehee in diameter, but would not discover hairline cracks. He= suggested th.s a 1/4-inch cladding crash would represent a marginal situation in terms of the resolution possible.

Mr. Etherington sammented that his experience has been that while positioning and li$ ting might be difficult, if a borescope is properly positioned one can get a elese view of a 1/2-insk machine screw including surface scratches.

Dr. Bush agreed and suggested that Mr. Kats was perhaps being overly conserv-stive.

Mr. Esta commented that be slee agreed if one knew before hand what one wee leeking for but if one is observing a-rough spot. for surzyle, adjacent to a weld deposit area se part of a scan of surface the situation would not be se steer.-

ter. MmeM111am them stated that in his opinion the situation with respect ta the Babseek and Wileau desips was similar to that of the Westinghouse Corp.

in terme of eempliance with the criterion on accessibility for visual. inspec-time.

The sapability exists for meeting the criterion although it would be time consuming in terms of removal of all vessel'internale. There is ready

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. 1, assaas to the vosoel flange and seal area and 54W eustomere are encouraged to perfesa careful inspections of these and of the reactor vessel stude at each refceling. hre is eseese to the taside of the vessel closure head when it is removed for refueling.

He core support barrel and the upper core strus-ture are readily accessible and the'inside surface of the wesel is sise accessible without removal of oore internale through the check valves in the upper sore banel.

N lower vessel head could be inspected through a vacant fuel element pceition with a device ne more than 1/2 inch in diameter.

If a more estensive inspeeties than is possible with tbs above capability to thought desirable, the fuel assemblias and core internals could be ramoved.

A water level would be necessary in thgpasel to keep the radiation level dous and inspostions would be carried /thrwugh the water.

At present there are plugs in the shkid ring for access to the inlet and outlet noestes and the core flooding nosales which inserr directly into the vessel _in B6W designs.

Nro is acanes with some diffir-Ity to the entire eaterior surface by the-removal of insulation. N bioL eical shtolding, which is removable in sostions, would also have to be removed to allow access to the lower sections of the roaster vossoa.

High radiation levels would exist in this area, of the order of several R/hr, se that inspection of the entire eaterior vessel surfaea would be difficult although possible.

Mr. MeeKillas concluded that 34W had attempted to provide flexibility in accommodating inspection of both the inside end-the outside surfaces of the roastor wesel if this is indicated.

Mr. Case asked about the time involved in-performing such inspections.

MasM111aa replied that this had not been considered in detail although removal Mr.

of the sleeure head, the fuel assemblies, the vessel internals and the teinstal-laties might take several acathe not instuding tha inspection procedare itself.

If this is considered is conjunction with a normal refueltas operacian, the increment of. time over and above that for normal reiue1 Lag would, of course, be somewhat less.

asked Mr. palladine/how difficult it would be to inapest the entire wesel outside surfase.

Mr. MacMillan replied that a three-foot annulus would be available after removal of the fienge seal plate and shield plugs.

H is would also be a hida radLation sene.

Be noted that 54W is now working on a program of in-specties but details are not yet available.

He pointed out, however, that assess has been provided se that/siNrior wesel surface would be inspectable ti at became meesseary. Dr. Bush asked if the noasta transition weLde were essessible and if more of the primary pipios could be seen.

Mr. MacM111am asted that some room has been lef t around the primary coolant pipe below the transities weld but agata this is not an easily accessible. area.

It wuld met be necessary to chip concrete to view this section of the piping but other-wise it woeld rapresent a diffieult job.

g,c In answer to Mr. Case Mr. MacMill.an couseented that he could saa no significant

'n"stuts possible for acer.%.ibility to the inner vessel surf aces.

Dr. Okrant asked if B&W designs also included a remover. 31ng in the wre supprt plats so that the bottom heed of the rnactor y Sed would be v.swabia.

Mrs Poe.r'illan roted that the botton head of the vessel -:otid be approached c1<

  • eough the intemd vent valves in the upper cute barrel or through s

%.eeably locat. tan but that no tueevabic plug in :w cora suppert t-s sN ro

  • sea ineluded. If it bw ans necessary *,o inspecc the botton st each refueling some m/.ification of the design would be y

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N11adino asked.whetherni presently available lighting was

. r any developoest. proarse on light sources was being undsrtaken.

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replied that liphting woe, of course, the key to good visual.

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ine; v-W W. that this might present difficulties if the bottom head of the

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s he inspected through a 1/2-inch hole. He noted that 56W ad, e

present t.as a detsloposat progre=, !L lighting sources. Mr. Kats answered that Martinsmuse personnel have used five-watt sealed besec. laws which hcve 1.fik jj work 9 quite successfully and in additfon the borescopes contain their own

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11gM seurses for toeni illumination. He suggested that lighting would not represent a matar problem, int termir.bf' visual' inspection.

1 Dr. Okrent asked if any undesirabia 1 tea could be sees 6: performing such a vestyval of core internals as has ben.

iscussed ard in nesG.ag the vessel inner surfaces other than tbs cost in a.1ss of c.ime.

Mr. h t> could not see any contraetud2.sations although Mr. MacMillan raggested & ' i snite of the careful design, of hem 1 *rq equipment scuas uegree of risk P.Ms wt anever i

If any mishandling occurred, however, it would be e

heavy equipocat is. p 4

in the no m of bro, c t.shles, ste., and would he readily detectable.

Mr. Ithern dten asked if thare wa any reluctanse to pull!, tt.c rasctor vessel studs each year. Mr. h.sMillas replied that call reactor vessel ends were removed at each refueltag altuough it was not yet determined what percentage

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of thm would be inspected each time.

Mr. !bebard noted that in terme el virual inspections of General Electric toester desiges the vessel head and seal surfaces are raadily accessible as is the upper area of the reestor vessel and some sections of the 1 mar area.

Wre are,-however, some areas of tha vessel internal surface,such as those sections which are located behind thermal sleeves in nossles,which are noe meseecilsle.

A Mr. Babbard vuagosted representative sampling as an answer to continued in-servise integrity assurance ro.her tha 1901 accusibility. He noted that he has slee had considerable experience with the use of television and underwar photography in conjunction with voice recordint of des 6riptions of the asetions being viawed, hse are later reproducible for an audience.

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la terms of outside surfane inspostions this saa be done in the area of l

noesles and it is thought that-the condition of the vressel can aure readily l

be assessed from these areas than from a 1001 inspection. Dr. Bush asked if the bottom head of the vessel could be viewed with TV cameras and a boressepov Mf. Hubbard replied the this was possible by looking at a sac 11 ~

saatiuA et a time but that bre weeld be some blind spots sush as-those noted above. He resoluties is of casrae a fumation of the 11pt svailable t

and the angle at whish the lidt.is directed onto the surface as well'as har elose one saa effectively

- piece one's eye to the surfase.and thel spe d of the traverse. Dr. Bush asked it the situaties was at all different from that represented during the Quad Cities review in terms of removal of ~

core interrsis. Mr. Hubbard replied that it was as different and that approximats.y sia reaths would be necessary to remove core-internals to per-l ferie a visual inspection of the vessel inner surface and replace the reactor sors.

l Mr. Falladinotasked what could be viewed if this six-month period were svailable. ler. Bubbard replied that approvisutely 801 of the vessel inurior sould be inspostes and these aestions ofithe core internalswhich.would be left behind. Dr. Okrent asked if the tien period had-been on the esme basis as those given prevAously, that is the increment ad/od to normal! refueling dauntime not including the time necessary for inspection. Itc. Hubbard L

replied that wf thout inspeettaa time he would guess that it would' take approni.

mately one.se enroe manths in the special handling and removal of the _raneinir4, part of the fuel.- Mr. Smith suggested that replesoment of-core interna.is -with th. same assurasse of integrity as the original-installation would require u

l approximately four months stase there is a very rest problem with underweter resssembly eveu when compeaamts een be: approached as closely ss could be done i

byta diver.wiWhthemenethahdhektag the situation would be even worse.~ Mr.

Hubbard noted that what was being suspassed was really two conflicting require-smaata. Assess means removability of core components but these must then be 1

restored. G3 has tried in its design te eliminate mechanical festeness and use all walded construction to avoid the problems such fastenere can pose and to assure ths assessary integrity. There seemed in Mr. Hubbard's view to be i

a eenflist betu _inspestability, that is ascessibility, requirements and -

l assessary integrity:assuranea. =Mr. Falladine asked.if there were any nians for psovistem of additicsal est.eesibility or for re-emaniastion of tho'whole.

questian is 3 design. Mr. Bubberd replied that to his knowleder there were as seek piens.

gr. Okreat asked with referesse to the blind spets noted amound' thermal l

sleeves whether the two previeue speakere s.ould comment on 'this' potat. Mr.

Eats replied that Westinrbeuse desiges, with all of the internals -removed, puweide 10'4 assess to tLe sladding surface and that as thennat sleeves are 1:asluded in vessel nessles. Mr. MacMillan replied that 940 designs. include thermal sleeves withis sees noseles and these would therefore not be. in-spostable free inside.

There are, howent, other ways to inspect these u

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anestes. Dr. Okreet asked if Westind ouse and h4N felt the same reassembly -

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asestanse preless existed.. Mr. data replied that Westinghouse-designed l

roastere have no sush. belting problems ctan sors' internals find their position by gravity and promeshined, slots ased t:ey way.sy. Mr. MasMillas

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replied that the situaties with 54M devips was essentially the_ saan and -

i that me festeners were used, i

I Mr. Case asked dat s's seurse would be if the ABC lease toward the require-mest of elimination of blind spots in vessel is.;wities., Mr M bard replied that he sould not answer that quest 1r's immediately, that the s e uation _wes --

being Jmoked at but that mora time would be necessary. L Dr. Okreat asked if a plug in the cosa support plate-would be feasible.and would provide better l

visibility of tM bottom head. : Mr. - Smith noted that this would not help; l

visibility much because of the multiplitity of control rod guide tubes i

penetrating the botton vessel head.

Mr. Case asked if he could i.um up the a position on the criterico for

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assoas for visual inspection as follows:

la oresent GE designs access is possible to about 801 of l

1-Laterior of the reaster pressure vessel.The time ia-l cr asst over and above normal refueling dish would be j

nosessary is approximately four months at a ininimum.

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Mr. Subbard and Mr. Smith thought this was a fair.statsaant. -- Mr. Hubbard '

added that in terms of resciutim one would expect ta see a cMck approxiessly l

1/22 of as fach wide. 'dernA*23 on the angle _ af the -lighting, sensitiviry and j

resolving power em that order would is espected, however.-

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Mr. West then opete for Combur?.ima Et g nearing Co. - The _ situation with regard

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te visual inspection of the vsesel in erior. La similar to that for the j=

Westinghouse and 34W designs._ That as, thel core barrel and reactor internals are removable with some diffievity so that' the total vessel-interior can.be i

inspected. The bottom head la aise vi,ually inspectable with some difficulty as is the juostion between the large nossles and the vessel proper. Mr. West l'

emphasised that the total inner surface:of the reester vessel including all j_

aossles, ete., would be inspectable. Es expressed same reluctance to die-suas the time required to propero the vessel' for svah an. inepeatisa

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tsinee he felt this to be properly the provians of the _ utility operators.

gr. Garant asked for some. clarification' of the -carm Swith difficulty".

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L Weeg sehd that very large sections, that is 12 feat in diameter by 30 feet l

leeg, would he involved and these are inserted with weJains to restrain them t

-assitast vibratian and only small clearances are therefors' allowed. In addi-ties, the. work on these large sections would of necessity be done from a.

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.distanse se that the initial installation would be a seach simpitr-problem

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them removal and reinstailaties subsequent to s'eme period of reactor operation.

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l Dr. Okreat asked if the-desip might be changed if it were clear that interns 1s-

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would have to be removed some number of times greater than one throughout the reaeter lifetims. Mr. West replied that off hand he doubted whether it s ould be prudent to looses the clearances but the question would have to be recon-sidered La detail.ia order to 4etermLne whether some modification wee possi' 4 -

bid such that the desip would edD be adequate in terms of operation but i

l would allow easier escoes.

l Mr. West noted that G designs inshje plugs in the core pupport structure

& laryst of which is so-sral inches in diameter, with many_ others one to two inches in diameter. Probes could therefore be inserted and the botton l=

head inspected. The largest 'of the holes' in the core support structure, app i

approximately-sia inches in dimenter, has a bolted closure plugg bolts rather_

l tham' welding being used to allow access.

Me.-West noted that while.it to rare i

to drop camponents in reactor vessels there may aria.a the need to_ remove small_-

l artiales se that fairly. easy access was thought to be necessary. Usually M has no responsibility.outside of the reactor vessell the biologir.a1 shielding i

desip being the responsibility of the architect magineer with some Cs advice.

Thes far all a reactors have allowed a few taches of clearcace around t.he vessel se that a borescope could be inserted to view the esternal surf ace.

Typisally, insultation has not been included around the bottom head. From the nor,sla area deva to the core the vessel is insulated and this. insulation sa diffisult to remove. la the region of thenossles G generally advises the architeet ougineer to provide assess to the outside of the piping. Around the pressure vessel itself; however, such access would not be available.

Mr. West observed that he mes ins 11aed more toward the G3 estimate of the time insressas inesived in readyias a vessel for such a complete it.spection, that is, two months at a minismes leaks like an optimistie estiasta. Dr.fSeek asked how mesh ef the inner surfose of the vessel would be accessible without removal cf the iz; tarsals. Mr. West replied that the. bottom head could be viewed through _the grid phte but that the cylindrical portien of the vessel l

could not be inspeeted because of the cera barceJ. The main coolant nossles

- could also be inspected. ~ Mr. Case asked what the G reaction would be to a requiremsat se inspeet appresiastely 25% of the vessel's surface et each refusitat. Mr. West noted that after the top and Lottom head were inspected.

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the anst ineremset of surfase would represent approximately a'100fr exposure l'

nisse the sore barre 1would here. to be reseoved in any case.

Dr. Chrent asked if the two-month estimate was for the removal of fuel over and above that reserved during a no aaA refueling, removal' of the core bat ;el, replasement e~ the core bau.wl and: additk%1 fuel.- Mr. West replied that that had been the basis of his estimate and'

. sated that he thought this to be an-J

_ eptimistia smeas for the insromental uses addition and that the utilities l

shoold really be asked to comment ce this potat. Mr. geheringtem asked whether any fasteners were used on the bolts holding down the core support structure assess plate. Mr. West replisd that both welder and crimped locking devices -

.ase used ta'.various places within G reactor vessels. In this application he suggasted that a crimped looking fevice'would be more satisfactory.

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them asked how Westinghouse affected such elesures. Mr. Kats replied that en the smaller plants the weight of the core structure _ itself is sufficient for holddeus of such assess plate. Da the larger plante whink have a higher pressure esop through the core and consequently greater lif ting forces, crisped looking devises se holddeum belts are used. N ee locking devices are deformed by tarkbgi; and can be lifted off by the toet used to - reene them.

The discussion them turned to the second of the two criteria, that soocarning accessih111ty for volumstris inspection of the vessel plata. -

Trastical means of assass to the surface of the reactor i

pressure vessel should be provided so as to permit inspec-tion of essentially 100h of the volume of pressure vos.

set material, either from the inside or outside of the vessel er a combination thereof. N purpose cf this assess is to permit thorough inspectica of the vessel at appropriate intervals by visual tasaas and ultrasonic or oth'ar suitabla anthods."

a Dr. Bush listed the objectives of this criterica.

1.

Detestion of fatigua creek developennt in critical stana of the vissel such as at nossia a shall intersections, bolting flange - stull and betting flange - head junctions, closure stude, and flange areas surroundtag the stude.

2.

Det sstian of the growth of manuf acturing flave within the alls of vessel materials, which may have escapod detection during fabrication.--

3. - Eamadaation oi eladding matertal of the vessel for cvidence. of suriace or sub-surfase smisre-fissuring and its progress into= the vessel wall.

4.

Examinaties of weld inter-1.ty, (tacluo u n id octal'and welddvessel-waterial ir.tsrfase) af ps! mtipal strength joince in the vessel proper, at noastas and the cc.itrel rod housings canaattion to the vessel head, and at transition sections between vessel nossles _ and connected piping.

E. Devias of 54N led off. With respect to-reactor vessel; design he would -

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see as differende betwece provisinar for visual si.rface inepection and inspea-tiam of the material volums. _ Be _wst, also not sesre of appropriate and signi-fiaast shaages in design which would allow easier essess for such inspections.

Es theeght that for the future ultrasonis inspection offered h*J4 possibilities few develegnant but that its presticability in terms of-in-sers '.se inspection-had yet to be demonstrated. He did not care to predhe the rewats of present developeastal programa en infrared and acoustia emission techniques. Mr.

Davies thought that essentially the same etepe would be taken to ready a ves-set for a veluantric inspection as for a visual ~ surface i spection. N capability esists to inspect the same ' sections of tho vessel in either way

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\\J without removal at internals and felt that the areas which could be se inspected represented the week links in terms of tha vessel integrity and should be those dich were concear, rated on most heavily.

In his opinion the need for a 1001 volumatria inspection had not been demon-strated. To illwatrate he suggested that if a reactor vessel were decontami--

nated af ter use end was to be certified for reuse in a second f acility a com-plate volumetrie inspection would not be performed. Instead a dye check for surfase flaws wovid be performed as would an ultrasoais inspection of welds but the types of failures of concern,in Mr. Davies opintaa, do no occur sub-surfase, Mr. Case asked why an ultrasonic test of the complete vessel would not be done in such a esse. Mr. Davies thought that needless problems would be raised consarming the interpretation from the findings. If an initial ultrasoais inspection of the complete vessel had been performed as a refer, ease datum it would be some help but it was not clear how much. He noted that the techa*. ques,equipmes: _and standards keep changing making as interpre-tation of subsequent inspections extremely difficult.

Mr. Davies suggested, and Dr. Bush agreed, that the most likely area in which s

a failure would be initiated by many or3ers of eagnitude was the heat affeccad some or weld in an aret of high restraint. Therefore, if flave can be elimi-nated by ultrasoais inspection of welds and heat affected sones, the proba-bility of a failure initiated in the bulk metal is extremely-low, are Dr. Oktaat pointed out that there/ sections of the vessel in which the existence of a crack might be of much higher concern than a similar crack in other areas.

These sections mi$t aise be inspected even though probabilitp off a; failure initiated in sea areas is low.

Mr. MasM111am noted as a plant designer the access for wiaust inspe.ction in BW plaats is thought to be adequate for volueetric inspections as well. He also felt that it is not clear what technique would be appropriate _so that the dreign requirements are not clear. BW has been conc.erned. only with pro-viding suffisiaat access. Mr. MacMillan added that it was e n tful whether a 1001 vchumstris inspection was necessary or desirable.from an economic stand standpoint.

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Dr. Bush disagreed that only economics were involved. He sugaested that there si$t be risks in-a 1001 inspection since inevitably the scanning rate would be Lassessed with a concomitant decrsaae in sensitivity so that significant flaus-sould be missed. If only the critical 101 of a vessel were being inspec-ted see weald he were likely to scan slowly at higher sensitivity and less liksty, therefers, to mise significant flaws. Mr. Crochrs agreed and suggested that wkCS discontinuities in the base piste are tolerated the welss are gemorally defeat free. - As inspection which included the piste as well as wetAs and heat affected seems taight tend to < worlook flaws in the weld areas which usu14 he datasted if only those areas wre f>eing examined. Kr. Green-berg alee pointed out that his inclinatica would be to inspect the critical areas tse or even three tinse before inspecting the base plata.

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bre was also some discussion of the extreme difficulty experienced in gettinc j

reproduc&bility between ultrasonic inspections even when perfor1ned soon af ter j

one another and by the same operators using the same equipment.

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Mr. Smith of GE then spoke concerning the programs now being carried out to improve the volumstric inspection techniques. He discussed programa now be-ing carried out ucder the auspices of the PVRC and the. Edison Electric Insti-aimed at the design and development of mechanised inspection-tute

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techniques particularly in critical areas of pressure -vessels. The programs wil'. be aiand both at modification of existing techniques ad the development of new techniques such as the use of installed transducers. Mr. Smith was<of the opinion that a really satisfactory in-service inspection approach might be i

available within five years but noted that accessability to the critical areas would be necessary in order to utilise it and suggested that this was being f

provided in present GE designs. Access is available to the areas which are considered of most concern,mainly the nossle areas and the flange - shell connection.

Mr. Case asked if an A access for visualj inspection was equivalent to the capability cf impeccing 80% of the vessel volume in GE designs. Mr. Smith-replied that it was not. He noted that it was not clear that a volumetric inspection from the inside of the vessel would be adequate because of the j

high noise level resulting frou 'ha cladding. He suggested that an outside l

based inspection would.be bett.ex. h re will therefore be accass to the out-side surface of noasles and the flange.

Mr.' Smith noted that in the material now in use for reactor pressure vessels the heat affected sones have the best impact properties of the vessel and the lowest transition temperature.

A siseable mechanised ultrasonic inspection device could probably. be placed around all of the big nossles, the vessel head, the vessel. shell' flange -and the control rod drive connectione. This would probably include about 10% of the total vessel material volume and approximately 25% of tbe total weld footags and h me affected zone'volues.

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Dr. Bush asked if it were possible to eliminate the noise resulting-from the

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%1 adding serface roughness-and if - the internaiss could ~be removed how much of the inner surface would be accessible for volumetric inspection. Mr. Smith replied that in any case it would not be possible to get below the core support plate.so that only 50% of the inner surface area would be accessible.

Nte is some space between the shroud and vessel wall to that with appropri-see fixtures about 2/3 of the vessel barrel section and about 1/2 the core regias could be - inspected. (

.:sil about 70 - 80% of' the vessel' material volume would be inspectable... if core internals were' removed. Not much ie addition to this could be inspected by approaching the vessel from the out-side since the surface will be -inaulated and there will not be sufficient space to remove to insulation.

In response to a question by Dr. Okrent the CE representatives pointed out that the vessel in the vertical area le insulaced on CE designs but that-the insulation is af txed to the shield rather than the vessel at the botton he' 4.

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B&W representatives noted that insulation is included on the vessel vertical sections but is. independently supported on the upper head. Hewever, they noted also the insuistion will be radioactive and must, therefore, be stored.

Mr. MacMillan concluded that for B4W designs access to the vessel material volume from As outside verses on being marginal.

Mr. Kats and Mr. Lorents2 agreed that in terme of the noise level resulting from cladding surf ace roughness problems associated with ultrasonic tr.'ac-tion from within the vessa,1 vtre not ituuperable. A defect apprortmately 107.

of the wall thickness could be readily found.

Mr. Lorants added that with materials such as are presently in use these are the defects which are of interest.

Mr. Kats of Westinghouse cocamented that with respect to a volsetric inspec-tion he agreed with Mr. Smith that it might taka as long as five yees.s to develop an adequate technique. It is now necessary to decide waat should be provided so that the techniques not presently available could be utilized in future. He added that in his opinion ultrasonic inspection would provide the basis for these yet to be developed methods. Westinghouse has, therefore, tried to allow accessibility for in-service ultrasonic inspection.

In addi-tion, Westinghouse is now investigating with.the vessel manufacturers the performance of ultrasonic inspections of completed vasels to provide t.

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reference base for future tests. Such a base is necessary in order to detect any changes which may occur. Westinghouse agrees with the other spokesmen so far, however, that the tests should prcperly be of selected areas rather than 1007, of the ves Plans include the incorporation of the PVRC Sub-commit tee /ifilS"yl volums.fulure Westinghouse designs.

l Mr. Etherington asked if the reference mapa being made would be of 1007 of l

the vessel volume.

Mr. Kats replied that this had not yet been decided, nor had the response to any unexpected indications resulting frcus this reference i

mcyping. He noted that at the time of this overall inspection the v essel will already have seat all code renuirements and t.his last test will not be a l

code required test.

Any indications would certainly be recorded but repairs might not be effected..

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Thers followed some discussion of the need for performance of reference-base l

tests in a manner sunilar to future tests to be made. Some of the vendor representatives present felt that in order to be meaningful future taats and reference-easet tests must be performad in the same manner with the same orientation and equip 6,sut and if possible by the same technicians. Evan in such an extreme case the utility and reproducibility of the tests might be doubtful.

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Mr. Civons of Combustion Engineering noted that many of the points which he l

had to.aake Lad already been made but that he intanded to repeat them. A 1007, volumetric inspectico is not new feasible for C2 designs. He felt that selected areas only should be examined. Ultrasonic inspectior. has net yet been demonstaated as an effective in-service test on an irradiated vossel but l

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a that he personally was _ looking to the WRC program to develop this capability.

Access from the interior of. the vessel is now considered adequate for large defects and ultrasonic inspection should be confined to a search for such si nificant defects only sad the technique shou 1J not be pressed to the limit I

d of its capability. To get_an effer.tive ultrasonic inspection. competent and qualified personnel are absolutely necessary. A baseline inspection 'using the same techniques and equipment as are to be used in the in-service inspections must be performed. Mr. Givons reiterated that in his opinion the baseline and in-service tests must be really identidal.

Dr. Okrent asked why this was-

.necessary if only grass defects were being sought. Mr. Civons replied _ that changing ever minor conditions of the test mignt produce spurious signals 4 and wuld make the-detection of changes very difficult. 13. Givons coocluded that -

the definition of the mapitude, frequency and locat185/ defects !;a be considered unaccaptable was necessary as was a correlation of defect - growth with service conditions _ including radiation. He noted that' the PVRC program was again being loosed to to provide these.

Prior to the luncheon break Dr. Okrent posed the following questions:

1.

What are the relative merits of-periodic hydrotesting at some preesure above design pressure and 2.

How does this compare with periodic careful inspection?

Following lunch the meeting reconvened. Mr. Smith opened the discussicn; he felt that hydrosta:ic testing sud periodic inspection could not substitute for one auocher. He cited as an example the f ailuru of a large vessel on its fourth hydrostatic tast. This vessel had incorporated in it a large flaw and had been pressurised at about 1008 below its transition temperature. - Mr.

Smith also cited a recent international meeting at _which this question was discussed. The conclusion of those present was _ that repeated overpressure testing is not indiceed.with the materials presently available. -Mr.-Smith agreed in answer to'a question by Mr. Etherington that there would be a dis-

- tinction between a P.est as twice design pressure and one at 101 above design pressure. The test at twice design pressure would produce.significant strain in many areas of the vessel and indications are-that at approximately 1%

strata strain aging of the material now being used.for reactor pressure ves-seis becomes a significant factor. The--130% design pressure test would strain only saml1 areas by comparison and would do relatively little damage.. The con-alusions of the international conference cited above actually centered on not easeeding 110 --120%

of desip pteseure.

i Mr. Beekjord commented-that Westinghouse sould also answer that hydrostatic t

testing and volunutric inspection-cannot substitute for one another.

Mr. Is) rents noted that his personal experience with hydrostatic testing is that not all defects present are discovered.

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A 4-e 2,b Dr. Okreat pointed out that since the vendors as a groupcare proposing only partial ultrasonic inspection one could also conclude that the nondestruc-tive test procedure will also not caveal every fisw. Mr. Lorents and Mr.

Creenberg, however, noted there is some e Lance uhich indicates that hydrostatic testing can in fact damage / '

eave them in a les desirable condition.

Mr. Davies commented for Babcock and Wilcou. The initial hydrostatic test' does more good than harm because it reduces the subsequent strain range with-in which the veasel operatest that it high stress areas will yield during the test' and redistribute their stressee.

Subsequent hydrostatic tes ts,- how-ever, are considered to-be good only as leak tests.

Dr. Suah thought it was worth r.cting, without personal cocsaant, that at the iAEA meeting held in the Fall of 1966 the opinion of the group concerned with this question was that repetitive hydrostatic testing was a desirable pro-cedure.- This position was -strongly supported by the German and Swedish delegations to the meeting so-that the overall nituation is apparently not one of complete agreement among the experts.

Following this the vendors met in private with the repree.ntatives of the regulatory group.

C.

@ COCK AND W11rOI COR1 Dr. har asked what the reaction of the BW representatives would be to the prosul ation of critaria of the sort discussed in Mr. Price's letter.

t Mr. MacMillan replied that he had already stated'BW's position during the opening session. The acce sability of the interior c4 the reactor vessc111s not a probica but would represent a matter of time and inconvenience. He noted that the accessibility now being considered would require the vessel to be flooded and if dry access was desired some design modification vauld be-necessary.. Be could, however, see no advantage to dry access at 'this time.

On volutatrie inspection be did not understand what techniques were being anticipated and noted that BW had tried to retain flexibility by providing access,althcugh difficult and only marginally practical. He also repeated that in his opinion a 1001 volumetric in.pection was not usedful and that cri-tical areas of the vessel should be concentrated on.

Dr. Mann asked what his opinica wee concerning preoperational mapping by nondestructive test methods.

Mr. MeeMillan replied that he thought it had been well learned that 'one must inspect in the same way with the same equipment and.under the same conditions as would be done subag.ce,ly in order to get reproducible results. This was true even though sized 4n crecks were being sought.

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J Mr. Pallodino asked what normal practice = was on non-nuclear vessels.

Mr.

l Daviss replied that procedures on stem drums vary, tha ths. surface is _ sen-srally inepected in a somewhat cursory =aamar and then the areas of l

attachment of penetrations, ste., ' are closely -inspected.- This represents in some way a combinacias of both the critical area ~ and general i. spection.

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Mr. Case pointed out taat one should not necessarily equate accorsihtlity for a.1001 volumetric inspestion wit's inspection of 100% of the material volume I

each time.

Mr. Mangelsdorf asked what.asthod of inspection has been found to be roost Mr. Davies replied that in his opinion visual inspection and-I offattive.

surface inspection by magnafluming were most effective. He added that the criterion concerning accessibility was not of concern but the question cf j-concern vould be how much inspection and how of ten.

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COMBUSTION ENGINEERING.

Dr. Mann asked what CE's position would be with respect to promulgation of criteria 'such as were proposed in Mr. Price's lac ~.or.

Mr. West replied'that l

it is now feasible to visus 11y inspect ard ultrasonically test CE.essels.

l The internals are completely removabis. ; As te.;he advisability of such-inspectione he thought them unnecessary and expensive. It was. not clear. to I-j-

him _what the utility.of a_ visual-inspection would be except-to discove'.

l unenticipated events such as loose componente within the vessel.- _ In view

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of the large snount of money involved in pertorming such a' test, should ultr aspection he considered necessary,he suggested:a heavily support-ed /t peby de a nondercruetive test which wou',d be meaningful.

Mr. Etherington-asked if CE would take-the same view of -hydrostatic testing-_

on conventional-Section I vessels-as they had'taken on nuclear vsssels.

That is, that a hydrostatic test' above design pressure is not necessary.

Mr. Lorents replied that it 'is now a code = requirement' to perfo:n a hydrostatic

. test periodically and that these are done but are considered leak t,4sts only.-

' Mr. Falladiso asked for some clarification of ife. Wst'sitatement that inspec-tions ere-not necessary. Mr. West rsplied that of course this depends on = the L.

-prise tag. Inspection of nossla areas w:tJ.d be acceptable ae-would a _ bore-

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scoping of the bottom of ths reactor vussel. _ However. - removal of _ the core -

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' barrel representa a step fuu:t. ton in the prise tag-and therefore is ' con-L sidered unnecessary. Mr. Falladino pointed out. that the excellent history.

of operation of-pressure vessels has. generally been' conoidered to be' associ-ated with the widespread use of visual inspection. Mr. Lorenta replied that conversely w'una a f ailure has occurred it is almost always due to soosthias

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groes and is _ preceded by warnings of one kind or another.

Dr. Mana noted that the point _at issue now was the reaction.of _ CE-to the cri-teria for accessibility. Mr. West replied that CE's 1:eaction would not be -

3-l' adverse since-thetr _ vessels are accessible as a matter of simple prudence.

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WESTINGHOUSE EMCTRIC CORP.

l Mr. Case asked what Westinghouse's position would be on criteria such as were i

described in Mr. Price's letter. Mr. Beckjord replied that he felt that i

Westinghouse wee already complying vjth,MS.the criterie and had done so-starting with the San Onofre sad Connecticut / bin There have also been plans; in i

i effect begiming with the Rochester and Indian Point 2 plants-to provide a

- reference base ultrasonic test of approximately 701 of the vesest volums l

j tithough a 1001 inspection would be fossible. Mr. Beckjord also noted that a-I hydrostatic tcc. was not considerid equivalent to nondestructive test methods.

Mr. Beckjord seded that while _ West 2.aishouse intended-to carry through its plans on volumetric inspection details will have to follow the development work now going on on ultrasonic, test methrds. No schedule is yet available for periodic ratesting in Westinghouse pinues although he believed that such a progrant would be effected.1, Dr. Okrent asked if the two-week time incremsnt suggested for tna performance of ouch an in-service inspection of the vessel surface was really _ considered i

a realistic estimate. Mr. Kats replied that -it was _ based 'on the removal of -

l the lower core support structure several timas at the San Onofre plant. The difficulty of fit at the radial eupport member was not tound to be a problem, j

He suggested that the estimatea made by the other-vendors present at the i-meeting might tu.ve been based on'the lack of experience or earlier ' adverse j

experience. He did not feel.that the Westinghouse estimate would be: changed i

by radiation since fuel handiing type equipment had been used.

Mr. Kats-repeated that the two-week figure cited was above and beyond the time required for normal refueling operations and did not include the time required -for_ the inspection itself.-

F.

GENERAL EMCTRIC CORP.

it, Case asked whacGEh position was concerning criteria of the type suggested -

in Mr. Price's letter. Dr. Greager replied that it was now-felt necessary to I

know more about the specific nondestructive test methods posed before these could 1= u.es as bases. for criterie. Dr. Mann pointed out that -what was now being discussed was the crite. son for accessibility itself.

Dr. Greager noted that. it.was difficult to determine what access provisions to allow if 11 was not clede what would be necessary. He repeated that;it was first-l necesaary to develop techniques.-

1er. Case thought that-a distinction had been ut de by the Regulatory Staff' whiah l

separatad the development of' the 'techniquea from making space-available so thet the, techniques could be-used when they h:d beec. developed.

- Dr. Okrent em that -it was still not clear. to him what the practicality was of the eccess y the outside of too vessel which had been discuss 3d.

Mr.

Hubbard replied, that there is easy access to the major;nossle areas and that the question arose in connection with' access to the barrel areas. Feasibility-e e

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%%w at this location would be associated with moving the shield dell back and it ves not now clear how far back the shield wall would have to be moved.

Gg's position in general is that there now exists an adequate test program for the present generation of reactor vessel withou;. modification.

bre was a great deal of d*scussion concerning the possibility of various modifications which wuld allow an increase in the annular space between the biological shield and the reactor vassel insulation. N Westinghouse person-I nel repas*ed the dif ficulty of providing such an inusase without at the same 7.ime tact.asing the total contniament voltana, etc. Mr. Palladino noted that it is presently anticipated that the vessels;now under construction would If access is provided any techniques deloped would be useable.

last 40 years.

Dn Greager replied that in his opinico Gg use now providing the access necessary to perform inroect' a as required to assure the vessels would per-form na designed. Ar.y addition in accessibility and testing are apparently based on the assuaption that if these are not provided one is takin$ the risk of a catastrophic event.

Dr. Creaper felt it more likely that 15 years of development effort would indicate that the vesselm sa they are presently being fabricated with the techniques available would fail, L' at all,through slow leale and without risk to the public haalth and safety. Mr. Palladino agreed that the endarlying premise was indeed that if such inspectiens are not per-Its noted also that formed a significant risk of catastrophic f ailure exists.

tne reason most of fered tor the high degree of success of pressure vessels in non-nuclear service is periodic inspectiors. Tue c&ndancy, howevar, has been j

to bu7 reactor vessels af ter construction.

bre was additional discussion of the problems associated with providing an increase in the space availabla around the outside of CC reactor vessein.

Dr. Greager pointed out that any approach to increasedaccessibility calls for some penalties and felt that a more substantial reason should be available than tha supposition that there will be a meaningful inspection tr.chnique availabis in the future.

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Mr. Case asked bow long it would tue.:o perfo m the naco aary design changes if the Commoission decided to premulgate criteria calling for incraased accessi-Mr.

bil.ity.

Dr. Creager did rot feel that he could answer that question.

Smith asked again wny it was considered unnecessary to inspect more than just the so called critical areas of the vasteis. Mr. Case replied that accessi-bility was necessaiy to allow one to accommodate a new dafinition of critical arose should one arise.

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"*g SECRETARIAT August 12, 1968' j.

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APPARENT DEFICIENCIES IN ASME BOILER AND PRESSURE VESSEL CODE, SECTION III " NUCLEAR VESSELS"

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Note by the Seemtary s.N The General Managdr has requested that the attached memorandum of August 6,g-1968 from the Director of Reactor Development and Technology be circulated for the information s

of the Commission.

a F. T. Hobbs

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Acting SJcretary 1

NO. OF NO. OF DISTRIBUTION COPIES DISTRIBUTION COPIES "

Secretary 7

Exec. Asst. to GM 1

Chairman Seaborg 2

Asst. GM for Admin.

1 Commissioner Ramey 1

Asst. GM for Operaticns 1

Commissioner Tape 1

Asst. GM for Reactors 1

Commissioner Jonnson 1

General Counsel 1

Commissioner 1

Congr. Relations 2

General Manager 2

Controller 1

Deputy Gen. Mgr.

1 Inspection 1

Dir.

'f Regulation 1

Naval Reactors 1

Deputy Dir. of Regulation 1

Operational Safety 1

Aust.Dir.of Reg.for Admin.

1 Reactor Dev. & Tech.

10 Aust.Dir.of Reg.for Reactors 1

Reactor Licensing 1

Asst.Dir.of Reg.for SP 1

Rec.ctor Standards 1

Asst. Gen. Mgr, 1

Chairman, AS&LBP 1 l C

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