ML19262A345

Event Rept 76-12/1T:on 760304,during Attempt to Remove Surveillance Capsule from Holder Tube,Damage to Holder Tube Observed.Cause of Observed Tube Wear Due to flow-induced Motion Between Surveillance Capsule Train & Holder Tube

ML19262A345
Person / Time
Site:	Crane
Issue date:	03/18/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
ER-76-12-1T, GQL-0378, GQL-378, NUDOCS 7910260668
Download: ML19262A345 (6)

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naa ~ ~xnss ME JROPOLII AN EDISON COMPANY POST OFFICE BOX $42 RE ADING, PENNSYLVANI A 19603 TELEPHONE 215 - 929-3601 3,6'

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l-Director of Nuclear Reactor Regulation

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Dear Sirs:

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Operating License No. DPR-50

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Event Report 76-12/IT On March 4, 1976 while attempting to remove a suneillance capsule from its holder tube, damage to the holder tube was observed. At that time we did not recognize, as we now do, that the damage to the tubes constituted a reportable occurrence as defined by Technical Specification 6.9.2.A(9); however, NRC Region 1 inspector Mr. Kellogg was informed of this problem on March 5, 1976 at the SSIP meeting held at TMI, and Dr.

Don Bridges of NRC Operating Reactors Branch No. 4 was notified of this situation on March 8, 1976 in a telephone conversation with Mr. Smyth of my office. The above mentioned notifications, although not given in the context of reportability, were responsive to the need for 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> verbal notification required for prompt notification type occurrences. We do recognize that no confirming follow-up telegram to these notifications was forwarded. This letter is intended to serve as the confirming telegram as well as the required 14-day written follow-up report.

1485 148 290:

The attached Surveillance Holder Tul'e Report provides a complete explanation of this event including the cause, circumstances surrounding the event, the corrective actions, and the appropriate component failure data.

Please note that a Technical Specification Change Request pertaining to this matter will be forwarded in the very near future.

Should you have any further questions on this matter, please contact me.

Sincerely, l)f'/

i R. C./ rnold Vice President RCA:CWS:rk

Attachment:

Surveillance Holder Tube Report 1485 147

THREE MILE ISLAND-UMIT 1 SURVEILLANCE HOLDER TUBE REPCRT IUTRODUCTION Metropolitan Edison has discovered during the current refueling outage at TIC-1, da= age to the reactor vessel surveillance holder tubes. As a result of this danage, T!H-1 =ust be operated during Cycle 2 with the surveillance speci=en capsules and holder tubes removed. This report de=enstrates the acceptability of these actions.

SURVEILLANCE CAPSULE HOLDER ARRANGE!ENT The design 9 )the surveillance capsule holder tube is described in B&W Tcpical Report f

BAW-10006A.ll The survillance capsules are attached to and secured within the holder tube by a spring-loaded push rod asse=bly as shown in figure 2-8 of Reference 2.

The a- - "'--- eWreves the push rod asse=bly spring as the plenu: is lovered into the core support shield. The spring-locded push red asse=bly has four spacers

=cunted along it s axial length to provide lateral positiening of the push rod.

The top two of these 3-piece spacers, are shown in Figure 2-10 of' Reference 2, and are locatM N the prtinn of the holder tube which is within the shroud tube. The third spacer is axially located in a portica of the holder tube with a thicher vall and within a journal bearing =ounted to the core support shield. The fourth spacer is approxi=ately in the center orthe ogee bend in t.he holder tube..._... - 1

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.w A fe= ale fitting on the lover end of the push rod =ates with the tcp end fitting -

of the ;.pper surveillance. capsule in a =anner si=ilar to the between capsule ccupling

-shown in figure 2-6 of reference 2.

The bottc= en

• fitting of the lover surveillence capsule =ates with a special fitting in the base of tha holder tube which prevents ca'psule rotation.

I SURVEILLANCE TUBE INSPECTICN During speci=en capsule re= oval, two of the three holder tubes were found to be severed at the axial location of the second push rod spacer from the top, thus separating the top approxi=ately six feet of the holder tube. One of these two tubes was also severely vorn at the axial location of the first push rod spacer and beca=e separated at that locatien during capsule re= oval. The third holder tube was intact following capsule removal.

Remote video techniques were used to inspect for further evidence of wear on the internal surfaces of two of the holder tubes, (the intact tube and one severed tube).

In general, the results of these inspections shoved evidence of vear at each of the axial locations of the push rod spacer, at the axial 1ccatien of the holddown spring, and at the axial locations of the surveillance capsule rings.

The wear sites on the holder tube are attributed to contact and relative =ction between the push rod spacers, the holddown spring, and the surveillance capsules and the holder tube.

1485 150 CORRECTIVE ACTIOII B&W has concluded that the most likely cause of the observed tube wear is flow-induced relative =ction between the surveillance capsule train and the holder tube.

To prevent the possibility of loose parts occurring during Cycle 2, the surveillance capsules and holder tubes vill be re=oved, prior to Cycle 2 operatien.

- CORRFGOIVE ACTION can't Engineering of the holder tube and push red assembly design codificaticns and material procure =ent vill be ec=pleted during Cycle 2 to allev installation of the revised design prior to the start of Cycle 3 Re= oval of the specimens frc= the reactor vessel for one cycle vill not adversely affect the results of future testing of these specimens or the overall results of the surveillance progra=.

SA, T EVALUATION Thi TMI-l Technical Specifications provide the operating pressure and te=perature limitations applicable up to the end of two EFPY of operation. One speci=en capsule was removed at the e td of Cycle 1 and these speci= ens vill be tested during Cycle 2.

Cycle 1 has accu =ulated approxi=stely 13 EFPY of actual exposure to the reactor vessel vall at 1/h wall thickness (1/ht).

The neutron fluence at the center of the surveillance specimens is reported in Reference 1 to be approxi=ately 1 7 ti=es the maxi =u: fluence at the reactor vessel vall. A =cre recent calculation using i= proved methods reported in Reference 2 for the Cconce class reactors indicates that the neutron flux (E > 1Mev) is 2.h times greater at the specimen : location than the reactor vessel 1/ht location. Thus, the capsules in,TE-1 have reedved-the; equivalent. irradiation-in-exce_ss of the first- ~

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three cycles of operation.-

Cycle 2 is planned for 296 EFFD (0.8 EFPY) and Cfeles 3 and h are cach planned for 270 EFFD (0 7) EFPY) of operation. A revision to the technical specificatica limits vill be requested prior to the beginning of Cycle 3 and vill be based on the results of testing of the specimens from the surveillance capsule eithdrawn at the end of Cycle 1.

This revision vill be applicable up through the end of at least the first 5 EFPY* of operation and vill provide additional assurance that adequate fracture toughness properties are retained through the period of the next surveillance capsule withdrawal and testing.

A revised surveillance capsule withdrawal schedule based on the results of the specimen testing pl anca during Cycic 2 vill be submitted for URC approval in accordance with Appendix H to 10 CFR 50.

• 5 EFPY Reactor Vessel Exposure

)k CONCLUSION It is concluded that operation of TMI-l with the surveillance specimen capsules and the surveillance speci=en capsule holder tubes rencved is acceptable during Cycle 2.

This change vill not result in:

1.

An increased probability of cecurrence of any accident previously analyzed, or 2.

An increase in the censequences of any accident previcusly analyzed, or 3

An increased probability of =alfunction of any equipment important to safety previously analyzed, or k.

An increase in the consequences of the calfunction of any equipment i=portant to safety previously analyzed, or

. 3.* The creation of the possibility of an accident of a different type than previcusly analyzed, or 6.

The creation of the possibility of a malfunction of a different type than previcusly analyzed, er 7

A reductica in the =argin of safety in the basis of any technical specificatien.

REFE.w.EUCES 1.

Reacter Vessel Material Surveillance Procras, BAW-10006A, Revision 3, Babecek

& Wilcox, January 1975 2.

Reacter Vescel Material Surveillance Procran - Cc=pliance with 10 CFR 50, Appendix H, for,.g snee Class Reacters, 3AW-10100A, Babcock & Wilecx, February 1975 r r... ~.- -

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1485 152