ML19210E149

LER 79-017/01T-0:on 791103,testing Revealed 131 Defective Tubes in a & B Steam Generators.Cause Under Investigation. Tubes Welded & Plugged

ML19210E149
Person / Time
Site:	Point Beach
Issue date:	11/16/1979
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19210E147	List: ML19210E145 ML19210E149
References
LER-79-017-01T, LER-79-17-1T, NUDOCS 7911300555
Download: ML19210E149 (7)

Text

NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION 87-7 M LICENSEE EVENT REPORT CONTROL BLOCK; l 6

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(PLE ASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 l Steam generator tube eddy current testing during refueling seven l gl and completed 11-3-79 revealed 69 defective tubes in the "A" steam l o A l generator and 62 defactive tubes in the "B". All but five of the l n s I defects were in the tubesheet crevice region and all were on the inlet l 1016l side. 100% of the inlet sides of the tubes in both generators were l l0 l7l j examined up to the first support by multifrequency eddy current l o a;; techniques. This event is reportable per T.S. 15.6.9.2.A.3 and similar to 7 8 9 prev 10uS Lt.KS . 80 SYSTEM CAUSE CAUSE COMP. VAtyg CODE CODE SU8 CODE COMPON ENT CODE SUSCODE SU8 CODE

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43 lWl1l2l0lg 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i o l Three inlet tubesheet samples of tubing were removed for metallurgical li til l evaluation. Plugs were welded in the three tubesheet holes. The

, 7 l defective tubes were explosively plugged. Also explosively plugged i 3 l after leak testing were two dripping tubes in the "B" steam generator ml and one in the "A" steam generator. l 7 8 9 80 SA S  % POWER OTHER STATUS DIS O RY DISCOVERY DESCRIPTION i s

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NAME OF PREPARER Sol Burstein PHONE:

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i ATTACHMENT TO LICENSEE EVENT REPORT NO. 79-017/OlT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 1 Docket 50-266 Steam generator tube eddy current testing was conducted in both steam generators on October 16 and 18, 1979, for further evaluation of certain tubes examined during an outage in August 1979. A post outage review of the August 100% eddy current inspec-tion, a 400 KHz program, had raised questicus on a number of tubes which it was felt should be verified by an additional multifrequency inspection. Thirty-eight (38) tubes were inspected in the hot legs of both steam generators.

Of the 38 tubes inspected in the "A" steam generator, 12 tubes were found defective. Of the tubes inspected in the "B" steam generator, six tubes were found defective. All defects found were located in the tubesheet region.

The tube at position R15C45, one of the defective tubes in the "A" steam generator, was chosen to be removed for metallur-gical evaluation.

While doing profilometry inspections of the tubes adjacent to R15C45 prior to its removal, a defect was found in a tube which had not been part of the original sample program. Discovery of this additional defective tube required an expanded inspection program in accordance with Technical Specification Table 15.4.2-1.

Prior to commencing the expanded eddy current inspection, the tube at position R15C45 in the "A" hot leg was cut just below the second support plate and removal procedures began on October 20.

With pulling pressures up to 25,380 pounds and several equipment failures, five pieces of tube totalling approximately 21 inches in length were removed on October 21 and 22.

An examination of the tube portions, plus a later eddy current probe verification, indicated that the pulling operation had broken off the tube at a known defect, approximatel; one inch below the top of the tubesheet.

Following completion of the removal of the sections of tube from R15C45, a 2S (approximately 199) tube sample eddy current inspection was commenced in the "A" hot leg on October 23. The analysis of the 199 tubes determined that 28 of the tubes were defective. All defects in the tubes were located within the tube-sheet. The inspection program was again expanded in accordance with Technical Specification Table 15.4.2-1 to 100% of the tubes in the "A" inlet. This also required that an eddy current program be conducted in the "B" steam generator.

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The 100% multifrecuency eddy current inspection in the "A" inlet commenced on Octcaer 24 and was completed on October 27.

The analysis of the eddy current data showed 69 tubes with defects

>40% which would require plugging of the tubes. See Table 1 for details.

Following completion of eddy current testing in the "A" steam generator inlet, a decision was made to remove two additional tube samples from the generator. The first of the two tubes was chosen as a good tube from an area where no deep crevice tubesheet defects were evident. The tube at position R20C73 was cut just below the second support plate on October 28 and four pieces of tube totalling over 140 inches were removed on October 29. The breaking force for this tube was 10,400 pounds, the pulling force varied between 3,000 and 1,500 pounds.

The final tube to be removed was chosen as a good tube with no previous defects located in an area of the tube bundle where numerous deep crevice defects have been found. This tube at position R22C37 was cut just below the first support plate on October 29. The tube broke loose at a loading of 25,380 pounds on October 30 and three sections totalling 74 inches were removed on October 31. After breaking loose, the pulling force varied between 4,400 and 10,000 pounds during this operation.

The holes from which the three tubes were removed from the "A" inlet were weld repaired on November 2 and 3. Prior to the weld plugging of the hole at R15C45, a stabilizing rod was inserted 132 inches up into the tube to tie the tube which was cut just below the second support plate, but broken off one inch below the tubesheet top, to form a single member with the original tube and tubesheet hole.

The 2S (approximately 199 tube) multifrequency eddy current inspection of the "B" hot leg was commenced on October 29 and was completed on November 3. The analysis of the eddy current data showed 62 tubes with defects greater than 40%, which would reauire the tubes to be plugged. See Table 2 for details.

Prior to explosive plugging, an 800 psi secondary side leak test was performed on the "B" steam generator on November 5 to determine if any of the 90% (plus) defective tubes would leak or if other leaks could be generated by the test. Seven leaks were identified. Four of the leaks were leaking plugs in previously explosively plugged tubes, the other three being tube leaks. Of the tubes identified as leaking, one was previously identified as defective during the eddy current program; two tubes with extremely small leaks, in the range of one drip every ten seconds, were not identified as defective by the eddy current program.

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The four leaking plugs were weld repaired in the "B" inlet during the week of November 5. The defective tubes totalling 67 were explosively plugged during the period between November 6 and 8.

In summary, a total of 68 tubes were plugged in the "B" steam generator on the above dates: 62 tubes had defects greater than 40%; three tubes had defects less than 40%, but were plugged as a conservative measure; two tubes were found leaking during the leak test; and one tube, a sound tube, was plugged by mistake. See Table 2 for details.

An 800 psi secondary side leak test was scheduled to be performed in the "A" steam generator on November 7. Preparations for the leak test were terminated abruptly during the initial filling of the generator when water was found to be issuing from a tube directly over the cold leg manway and out the manway. It was immediately recognized that a scheduling error had been made in that the "A" steam generator should not have been filled prior to explosive plugging the outlet side of the tubes opened up ta the cold leg side by removal of the three sample tube lengths on the hot leg side. For further details, reference Licensee Event Report No. 79-019/0lT-0, " Inadvertent Reactor Coolant System Dilution During Refueling Shutdown". The outlet tube ends were explosively plugged on November 8.

The 800 psi secondary side leak test was performed in the "A" steam generator on November 9 prior to explosive plugging of the defective tubes. One leaking tube (R24C32) was noted which had been previously identified as having a 92% defect by eddy current testing.

Explosive plugging of the defective tubes in the "A" steam generator on November 12 revealed one additional leaking tube (one drip every 20 seconds), R29C25, with 0% defect indicated during the eddy current program. This final tube was plugged on November 12.

In summary, a total of 77 tubes were explosively plugged in the "A" steam generator: 69 tubes had defects greater than 40%;

three tubes had defects less than 40%, but were plugged as a conser-vative measure; two tubee were plugged by mistake; one tube was identified as a leaker. Two good tubes were plugged because of the dbove described tube removal program. See Table 1 for details.

This event is reportable per Technical Specification 15.6.9.2.A.3.

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TABLE 1 Plugged Tubes with Defects $40%

Tube  % Defect Location R18C24 84% 18" above tube end R24C32 91% 5" above tube end R09C24 93% 11" above tube end R10C41 94% 18" above tube end R10C42 95% 21" above tube end R22C41 87% 21", 15" and 5" above tube end R15C45 89% 20" above tube end R23C62 89% 7" above tube end R19C54 83% 20" above tube end R19C53 92% 20" above tube end R12C54 92% 20" above tube end R12C55 93% 18" above tube end R08C53 93% 20" above tube end R12C53 71% 17" above tube end R13C53 75% 20" above tube end R09C51 89% 20" above tube end R13C50 95% 20" above tube end R05C50 90% 11" above tube end R13C49 92% 20" above tube end R15C49 88% 21" above tube end R19C49 91% 20" above tube end R15C47 92% 20" above tube end R10C46 96% 20" above tube end R10C45 93% 20" above tube end R17C45 92% 20" above tube end R19C45 90%-81% 20", 21" above tube end R15C44 97% 21" above tube end R12C44 84% 12" above tube end R23C41 80% 6" above tube end R27C40 81% 20" above tube end R24C40 93% 4" to 12" above tube end R23C39 65% 5" above tube end R27C39 59% 21" above tube end R23C37 87% 10" above tube end R24C36 82% 6" above tube end R22C36 76% 11" above tube end R27C35 90% 21" above tube end R23C33 89% 3" to 8" above tube end R20C32 42% 20" above tube end R08C43 82% 15" above tube end RllC37 88% 17" above tube end R03C36 91% 10" above tube end R13C26 95% 16" above tube end RllC26 58% 19" above tube end R20C25 92% 17" above tube end R21C45 79% 21" above tube and R22C46 55% Top of tubesheet R29C46 84% 21" above tube end j437 320 Table 1 Page 2 Tube  % Defect Location R20C40 99% 19" to 21" above tube end R30C53 65% 14" above tube end R17C53 73% 15" above tube end R15C51 81% 20" above tube end R05C56 87% 10" above tube end R30C57 80% Top of tubesheet R17C57 76% 8" above tube end R09C57 71% 20" above tube end R15C58 85% 18" above tube end R05C59 97% 10" above tube end R15C61 73% 17" above tube end R13C61 94% 19" above tube end R13062 81% 21" above tube end R14C62 95% 15" above tube end R13C63 96% 21" above tube end R12C63 76% 21" above tube end R13C64 91% 17" above tube end R23C64 72% 19" above tube end R13C65 92% 19" above tube end R05C76 85% 8" above tube end R15C62 94% 20" above tube end Tubes Plugged as Conservative Measure "A" Steam Generator R19C38 34% 8" above tube end R28C25 26% 14" above tube end R24C54 37% 21" above tube end Tubes Plugged by Mistake "A" St< tam Generator R24C30 R23C63 Tube Plugged - Leaker R29C25 i437 329

rY TABLE 2 Plugged Tubes with Defects >40%

Tube  % Defect Location R14C61 86% 20" above tube end R14C48 86% 21" above tube end R23C43 63% 16" above tube end R24C30 90% 8", 14", 16" above tube end R06C39 90% 11" above tube end -

R06C35 87% 12" above tube end R22C31 90% 5" above tube end R20C32 89% 17" above tube end R23C32 94% 10" above tube end R22C33 78% 20" above tube end R25C38 90% 6" above tube end R23C41 87% 3" to 11" above tube end R12C43 91% 21" above tube end R24C45 84% 6" above tube end R23C45 73% 6" to 8" above tube end R22C45 92% 15" above tube end R14C46 93% 21" above tube end R24C46 75% 13" above tube end R26C54 93% 20" above tube end R09C16 83% 3" to 8" above tube end RllC18 83%, 92% 15" and 18" above tube end R04C19 77% 8" above tube end R11C24 73% 20" above tube end R17C27 78% 11" above tube end R12C27 72% 20" above tube end R06C27 64% 20" above tube end R11C29 85% 21" above tube end RllC30 92% 21" above tube end R13C30 53% 21" above tube end R13C31 92% 19" above tube end R04C32 76% 6" above tube end R09C33 86% 14" above tube end R27C36 95% 5" above tube end R04C37 90% 4" above tube end ..

R28C38 45% Top of tubesheet R09C39 62% 19" above tube end R08C39 95% 8" to 13" above tube end R32C42 61% " above tubesheet R29C44 65%, 50%, 20", 10", 5" above tube end 90%

R30C44 83% Top of tubesheet R31C44 90% 3" to 13" above tube end R29C45 77% 11" above tube end R10C46 87% 20" above tube end R27C50 89% 3" to 15" above tube end R22C56 91% 10" to 15" above tube end R20C57 82% 17" above tube end R21C57 83% 6" above tube end 1437 330

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Table 2 Page 2 Tube  % Defect Location R20C58 93% 14" to 21" above tube end R03C58 90% 3" above tube end R06C59 90% 15" above tube end R15C59 84% 20" above tube end R08C60 89% 10" above tube end R21C61 94% 5" to 10" above tube end R23C62 96% 5" above tube end R13C62 61% 20" above tube end R03C62 48% 15" above tube end R21C64 76% 7" above tube end R08C65 64% 12" above tube end R10C66 40% 13" above tube end R01C68 95% 11" above tube end R24C71 93% 5" above tube end R02C77 95% 3" above tube end Tubes Plugged as Conservative Measure "B" Steam Generator R25C36 32% 21" above tube end R13C39 36% 15" above tube end R13C59 36% 20" above tube end Tube Plugged by Mistake "B" Steam Generator R09C32 Tubes Plugged - Leakers R23C47 R20C39 Leaking Plugs Weld Repaired "B" Steam Generator (Inlet) -.

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(RE: These plugs inserted during previous outages.)

R22C41 R23C31 R23C50 R21C26 1437 331