IR 05000344/1992034

Meeting Rept 50-344/92-34 on 921201.Areas Discussed:Sg Tube Leak & Licensees Subsequent Insp of SGs

ML20127F070
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	12/31/1992
From:	Johnson P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
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ML20127F031	List: IR 05000344/1992034 ML20127F028
References
50-344-92-34-MM, NUDOCS 9301200131
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i U. S. NUCLEAR REGULATORY COMMISSION

REGION V

Report No.: 50-344/92-34 Docket No.: No. 50-344 License No.: NPF-1 Licensee: Portland General Electric Company 121 S. W. Salmon Street Portland, Oregon 97204 Facility Name: Trojan Nuclear Power Plant Meeting at: Trojan Site, Prescott, Oregon Report Prepared by: J. F. Helfi, Resident Inspector Approved by: ta&M /!Tk P.Hffohnson, Chief

. Date Signed Reactp Projects Section 1 Summary:

Meetino on December 1. 1992 (Report No. 50-344/92-34)

A public meeting was held at the Trojan site to discuss the November 9,1992 steam generator tube leak, and the licensee's subsequent inspection of the steam generators. At the conclusion of the licensee meeting, an opportunity was also provided for public and news media comments and question PDR ADOCK 05000344

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DETAILS Meetina Att?,ndati Ep_t11and General Electric (PGE)

K. E. Harrison, Chairman and Chief Executive Officer J. E. Cross, Vice President and Chief Nuclear Officer W. R. Robinson, Vice President, Nuclear C. K. Seaman, General Manager, Nuclear Plant Engineering G. D. Hicks, General Manager, Plant Support R. D. Machon, Plant General Manager D. L. Nordstrom, General Manager Nuclear Oversight T. D. Walt, General Manager, Technical Functions C. P. Yundt, Project Manager, Special Projects L. K. Houghtby, Manager, Security H. K. Chernoff, Manager, Licensing .

I W. J. Williams, Manager, Nuclear Compliance G. J. Kent, Inservice inspection (ISI) Supervisor J. H. Pedro, Compliance Specialist J. F. Henke, ISI Engineer

' Nuclear Reaulatory Commission (NRC)

J. B. Martin, Regional Administrator, Region V K. E. Perkins, Director, Division of Reactor Safety & Projects, Region V J. E. Richardson, Director, Division of Engineering Technology, NRR L. E. Kokajko, Senior Project Manager, NRR R. C. Barr, Trojan Senior Resident Inspector G. C. Cook, Public Affairs Officer, Region V J. F. Helfi, Trojan Resident inspector Oreoon Department of Enerav (0 DOE)

H. Grainey, Deputy Director D. Stewart-Smith, Administrator, Facilities Regulation Division A. Bless, Resident Safety Manager V. Sarte, Resident Inspector Enerav Facilities Sitina Council-(EFSC)

R. Weil EFSC Member T. Hayes, EFSC Member C. Beatty EFSC Member Allen Nuclear Associates (ANA)

B. L. Curtis, President, ANA C. Brown, ANA

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, . _ _ _ . . . - ___ __ . . _ _ _ . _ _ .. _ _ . - ____ . '. . Westinahouse Corporation T. A. Pitterle, Nuclear Service Division Babcock and Wilcox (B&W)

John Helmey, Manager, Steam Generator Process Engineering Sandy Hellman, General Manager, Steam Generator Services The meeting was also attended by the plant staff, media representatives, and members of the publi . Details Mr. Martin opened the meeting by providing a historical perspective of the steam generator issue. He stated that axial cracking (microcracks)

were found at the tube support plate (TSP) intersections in 1991, and that this cracking was discussed at a December 1991 meeting. He noted that at the December 1991 meeting, the NRC and the licensee had diseassed revised tube plugging criteria, which were subsequently reflected in an amendment to Trojan's Technical Specifications, f

Mr. Martin stated that the purpose of this meeting was to understand the November 9, 1992, steam generator tube leak. This included a need to understand: (1) the cause of the tube leak, (2) whether the tube leak affects the NRC's understanding of the microcracking, as discussed in December 1991, (3) the licensee's request for an emergency Technical Specifications change, and (4) other relevant fact Mr. Martin recognized Mr. Grainey, who introduced the ODOE and EFSC members at the meeting. He then asked PGE to make their presentatio Mr. Robinson began the discussion on the steam generator tube leak. He said the cause of the leak was a failure to properly perform a stress relief on one tube after installation of a tube sleeve, and that it was an isolated case. This failure was the result of not fully inserting a heating element into the sleeve to properly stress relieve the tube after the sleeve was kinetically welded. The heatirg element did not fully insert because it was bent, and the technician made a personal error in concluding that it was properly interted. He noted that the failed tube was in the B steam generator, row 25, column 17 (R25C17) at the first tube suaport plate (TSP). Mr. Robinson described the event and actions PGE too( to mitigate this event. He then described the sleeving process, the fault, and the cause for the failur Mr. Robinson noted that recent eddy current testing had shown that there was a permeability change in the tube material below the sleeve in the R25C17 tube. Eddy current inspection had subsequently indicated no permeability change below the sleeve in any other tube. Mr. Richardson asked why a permeability check was not done when the tube was originally installed. Mr. Curtis_ replied that the parent tube was Inconel 600 material, while the sleeve was Inconel 690. Since inconel 690 would not show a permeability change, it was not previously believed possible to see the permeability change through the Inconel 690 to the Inconel 60 .

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Hr. Richardson then asked if PGE has been able to verify these permea-  !

bility changes in the other sleeved tubes (see handout, page 7). M Robinson replied that there was indication of a permeability change, in the weld region, in all other sleeved tubes. lir. Martin summarized the discussion, noting that the failed tube showed a permeability change below the sleeve, but not at the weld area, as was the case for all the other sleeves. He noted that there had been no independent Quality . ,

Assurance (QA) check at the time the failed tube was stress relieve Hr. Perkins asked if these results were reproducible in a lab. M Robinson replied that they wer Mr. Robinson noted that if one heater had not been inserted properly into the R25C17 tube, it raised a question as to whether other heaters were properly placed within the sleeve. Placement of the heater is critical to assute that the welds are stress relieved properly. He stated that his staff had developed other criteria to verify that the heater was properly placed in all other sleeves. These criteria involved (1) hard stop pressure (HSP), (2) heat affected zone (HAZ), and (3) heater profile (HP).

Mr. Kokajke asked what the operator did after the heater was bent. M Robinson replied that he tried to straighten it and went to another two tubes. Based on the HSP indications, the operator felt that the streo relieving was satisfactory. Mr. Barr then asked Mr. Robinson to explain the procedure and process for inserting the heater. Mr. Robinson explained that there should be two pressure drops (see page 13 of the handout), which the technician monitors by procedure. However, in the case of this tube, the technician did not follow the procedure. No Quality Control individual observed this process. Mr. Richardson asked if this was a weakness in the procedure, and Mr. Robinson agreed that the procedure could be improve Mr. Robinson continued, explaining that these different criteria would assure that the heater was pro)erly placed for the other sleeves. In summary, if the HSP was less t1an 5 psig, the sleeve was properly inserted. For tubes on which the a HSP was not recorded or was greater than 5 psig, the licensee used the HAZ or HP criteria. The HAZ criterion looked at the recent eddy current trace and verified that the permeabi-lity line was greater than 1.65-inches from the sleeve weld centerlin The HP criterion was a check on the differential temperature between the upper and lower heaters. This criterion would show if the heater was mispositioned. For the HP criterion, lab testing demonstrated that a 1/4-inch difference from the heater's previous relative position in a sleeve would increase the differential temperature (between the u)per and lower heater coils) by 30 degrees. Therefore, by assuring that tie differential temperature did not significantly change from sleeve to sleeve, this showed that the heater was placed properl Mr. Robinson concluded that, based on these criteria, the re n of the sleeves were properly stress relieved in the steam gesrators. He further noted that R25C17 was an isolated occurrenc Mr. Robinson then described other conditions identified during their investigation. Four sleeves had a slight decrease in their tube

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diamete This was due to water ingress (into the annulus between the tube and the sleeve) during cold shutdown, followed by innility of the '

water to egress during plant heatup. These tubes had been plugge Mr. Perkins asked if this could happen to other tubes. Mr. Robinson told him that the conditions needed to be uniqu Mr. Robinson also noted that one tube had a bobbin voltage at one TSP indication greater than one volt and that tube was plugged. He further noted that this indication's projected growth rate (based on a voltage increase) was within the range of expected growth rates for cycle 1 Mr. Perkins inquired about the corrective actions to correct the sic n ing problem. Mr. Robinson stated that they will verify that there is a permeability change in the tube material for future sleeve installation The NRC asked if PGE considers this sleeve installation process problem a generic industry issue. Mr. Cross responded affirmatively, and stated that it would be identified as such in the licensee event report on this event. Mr. Richardson said that NRR intends to issue an Information Notice on this even Mr. Robinson's presentation ended and Mr. Martin invited ODOE comment Mr. Stewart-Smith asked about the nature of the proposed Technical Specification change versus other Technical Specifications change Mr. Martin replied that Mr. Kokajko would address this shortl Mr. Grainey asked why the steam generators were closed on November 24, and Mr. Robinson replied that this was duo PGE's desire to minimize the time spent in a reduced inventory conditio Mr. Martin summarized the presentation by noting that this tube failure was not related to the microcracking previously identified, that additional tube inspections would be performed during the next refueling outage, and that this appeared to be an isolated personal erro Mr. Kokajko explained some relevant features of the licensing process, in that the licensee's amendment request was being considered as an emergency technical specification relief request. It met the definition of an emergency technical specification relief request in that it was not foreseeable ano the technical specification did not adequately address this circumstanc He noted, accordingly, that opportunity for a public hearing would occur af ter the technical specification change was implemented. He further noted that there were at least two letters to the Commission requesting a hearing. Mr. Kokajko explained the emergency and normal technical specification change )rocesses. He commented that the amendment would need a no-significant-lazards determination to be made before it could be issue Mr. Martin then referred to other issues, including press reports noting a differing professional opinion (DPO) among the NRC staff regarding steam generators and plugging criteria for Trojan and other plants. He invited public comment Several members of the public questioned the NRC regarding newspaper articles which discussed apparent dissension within the NRC on the subject of steam generator tube ,

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Mr. Richardson responded to the questions, discussing the alternative Llegging criteria, which the NRC was addressing as a generic issue. He noted that the NRC was considering the concerns expressed by Drs. Muscara nod Hopenfeld as they relate to the alternative plugging criteri Teilowing completion of the meeting, members of the public and the press asked questions and made statements to the NRC, PGE, and ODO The focus of their questions generally did not relate to this technical specifica-tion change, but to the technical specification change 1: sued in Fehn tary 199 These issues included:

• The February 1992 tennnical specification change included proprietary information. How could the public be asked to comment on that technical specification change without a review of all the informati,m?

• Some individuals 2tated that they did not receive tha information for this technical specification change until the meeting, even though they had previously asked for it. Therefore, they could not comment on it since they had'not had time to review i * Dr. Hopenfeld and Dr. Muscara should have come to this meeting so that the public could present questions directly to them and see if they hcVe any concerns with Troja * Some members of the public requested an adjudicatory hearing to independently consider questions on this issue prior to Trojan -

restar * The public raised other previous issues involving Trojan, including the Cascadia Subduction Zone, earthquakes, waste disposal and economic Acetisations were made that NRC, ODOE and PGE were not giving adequate consideration to public concerns regarding this issu '

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NRC PUBLIC MEETING l Steam Generator Tube Leak Event December 1,1992

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Agenda e introduction

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* Steam generator tube leak event description

• Cause investigation

• Additional evaluations

• A'ctions for other conditions identified

• Conclusions

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Introduction .

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• Cause of the leak has been determined

• Determined to be an isolated case

• No additional examinations are warranted at this time

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Event Description

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i * Initial plant conditions

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• Indications l- > N-16 monitors

>- Off-gas monitors

• Operator actions

• Event termination

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Cause Investigation .

• Location identified -

• "B" Steam Generator R25C17

> 1st Tube Support Plate sleeve

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• Fault identified

• Multiple indications at lower weld area by eddy current testing

4 * Cause identified

> No other faults identified in this tube

! > Permeability change indicated below sleeve

> No permeability change in the sleeve area

> Lack of stress relief can cause failure within one cycle

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e Conclusion

> The leak was caused by failure to properly stress relieve the tube after the sleeve was kinetically welded S

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EDDY CURRENT TRACE OF PARENT TUBES  :

BELOW SLEEVE  !

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B" S/G Fow 17-Column 6 11" S/G Row 25-Column 17 '

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Bottom ofSleeve Area

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EDDY CURRENT TRACE WITIIIN SLEEVE AREA

"i," S/G Row 17-Column 6 "B" S/G Row 25-Column 17

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Additional Evaluations ~

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e Demonstrate stress relief was accomplished within the sleeves

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! > Eddy current tests showed no stress relief outside the sleeve l area in each of the remaining sleeved tubes

! * Eddy current tests showed stress relief in the sleeve area for i each of the remaining sleeved tubes

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• Conclusion

• This was an isolated case of the stress relief heater being I

positioned outside the sleeve area.

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Additional Evaluations (Cont.) -

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* Demonstrate the heater was positioned properly -

within .the sleeve .

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> Stress ~ relief process

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>- Data review

Operator logbooks

>- independent criteria for heater position established

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Hard Stop Pressure (HSP)

Heat Affected Zones.(HAZ)

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Heater-Profile

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. TYPICAL TUBE SUPPORT PLATE SLEEVE INSTALLATION AFTER WELDING WITH HEATER PROBE COILS POSITIONED A

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Stress Relief Process

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• Remote tooling is designed to place the heater coils within 1/8" of the weld centerline e I-eater coils are designed to achieve required temperatures in the weld if placed within 1/4" of the weld centerline

• Heat the weld area to specified temperature (1275 F) for 5 - 12 minutes a

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! Hard Stop Pressure (HSP) ~

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e Defined pressure profile for coil heaters I i

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Testing confirmed heater mispositioning of 21"

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will abort' cycle on temperature  :

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a e : Proper' heater placement is confirmed if -

L HSP <; 5 psi 1

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e ; Heater could be positioned properly and' exhibit a

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HSP > 5' psi due to:- ,

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• Sleeve dimensional tolerances i ,- * Heater' dimensional tolerances

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> Sleeve end tolerances '

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Typical HardFtop Prersure Distribution

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Distance from Heater Hardstop to Bottom of Sleeve (in)

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UPPER C0ll ENTERS 14WER EXPANDED AREA C GRNMumM x, Ax l

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Soununnnq =_ 5 num pun g p UPPER COOLING PORT ENTERS UNEXPANDED SLEEVE l Osivimninh- _ ~~i i\munumu d [* @ E ,

E _E LOWERC0_tL ENTERS SLEEVE ENT l ERamewmi x1 t

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Typical Hardstop Pressure Distribution 8 i E7 ,R 3N . .s  ;

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0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.000 .

. Distance from Heater Hardstop to Bottom of sleeve (in)

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Heat Affected Zone JHAZ) .

• Heat Affected Zone definition

The area in which the heater coil causes a change in the

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permeability in the parent tube

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• Permeability Line

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Distance from the weld centerline where the parent tube permeability starts to change i > Permeability line location can be measured by eddy current testing

• Proper heater placement is confirmed if the distance from the HAZ to the lower joint is 1.65" or greater

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) Heat Affected Zone (Cont.) J '

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• Heater could be positioned. properly and ex7ibit a

HAZ < 1.65" due to: .

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> Sleeve positioning relative to the tube support plate

* Variation in heat transfer conditions within the tube

> Heater coil' temperature differences

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> Total heater cycle time differences

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Heater Profile .

• Heater Profile de"inition -

• The relative temperature difference between the upper and lower coils from one sleeve to the next, and

• The relative temperature difference between the lower coil and the norm for-that coil e Heater Profile is an indicator of proper heater position to within 1/4"

• The temperature of the lower coil will increase by 30 F for

. each 1/4" of heater mispositioning

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Heater Profile 4 Cont.)

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• Heater per"ormance was recorcec curing the sleeve installation process

• . Heater position is confirmed if:

• The lower heater coil temperature did not increase by more I

than 30 F relative to the upper coil from the previous sleeve; and

• The temperature of the lower coil does not deviate from the norm for the heater by more than 30 F

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Conclusion .

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• With the exception of the sleeve installed in R25C17 in the "B" -

Steam Generator, it was demonstrated that the heater probes used in the stress relief process were properly positioned within the sleeve e in conjunction with the records documenting the proper ,

temperatures and duration of the stress relief process, it has been determined that the sleeves which remain in service were adequately stress relieve * Based on this additional testing and analysis, it has been shown that the failure to properly stress relieve the tube sleeve installed in "B" Steam Generator tube R25C17 was an isolated occurrence.

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Testing and analysis have verified that similar problems did not occur during the' installation of the remaining tube sleeves in the

"B", "C", and "D" Steam Generator .

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Actions for Other Conditions Identified -

e Four sleeves were found with a slight decrease in sleeve ciameter

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These sleeves were evaluated as acceptable to remain in service

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To be conservative, two of the tubes containing these sleeves were plugged

Technical Specifications require Reactor Coolant System flow rate to be verified acceptable once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> ensuring adequate flow through the steam generators

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• Greater than 1 voit bobbin coil voltage indicated in

"C." steam generator R29C24 at the 2nd tube support plate

The tube was removed from service by plugging The observed growth rate is within the range of expected growth rates predicted for Cycle 14

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Conclusions -

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o Cause of the leak has been determined e Determined to be an isolated case o No additional examinations are warranted at this time L

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