ML20126B618

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Forwards Updated once-through Steam Generator Repair Briefing,Dtd 831116.Encl 1 Addresses Sequences of Major Events Current to Date.History Updated to Reflect Insps Performed in Early 1984
ML20126B618
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 05/16/1984
From: Young F
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To: Conte R
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
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ML20126B295 List: ... further results
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FOIA-84-897 NUDOCS 8506140155
Download: ML20126B618 (9)
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r ENCLOSURE 4

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NUCLEAR REGULATORY COMMISSION g g REGION I y lg E 631 PARK AVENUE o, KING OF PRUSSIA, PENNSYt.VANIA 19408

          • May 16, 1984 R.Conteg ,

TO:

FRON: F. Young

SUBJECT:

0TSG Repair Briefing Attached is an updated copy of the OTSG Repair Briefing dated November 16, 1983, with Enclosure 1 addressing the sequences of major events made current as of this date. In addition, the history has been updated to reflect inspections performed in early 1984.

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2 ENCLOSURE 1 SEQUENCE OF MAJOR EVENTS TMI-1 OTSG REPAIRS j t.

In late November 1981, while increasing RCS pressure to 45 psig for testing, primary to secondary system leakage was detected. The RCS was -

' then depressurized and partially drained to conduct OTSG 1eakage tests.

In early December 1981, approximately 130 OTSG tubes were determined to be leaking and non-destructive examination of the OTSG tubes was commenced using eddy current testing (ECT) techniques. ,The initial ECT

, examination indicated that there were thousands of potentially defec'tive tubes. As a result, GPU Nuclear established internal task groups to investigate the mechanism and cause of the tube failures, the extent of-the problem and acceptable methods of repair. .

. Subsequently, as a result of metallographic examination of portions of  !

' removed tubes, it was confirmed that the cause.of the tube failures was ' -

intergranular attack initiated from the primary side of the tubes resulting in the formation of stress assisted intergranular cracks. The active chemical impurity causing the corrosion was sulfur in " reduced Initial ECT results, conducted in January and February,,1982,

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indicated approximately 8-10,000 tubes contained defects with the vast majority (approximately 95%) of the defects occurring withir. the top 2-3 inches of the 24 inch upper tubesheet. Subsequent ECT using special probes and techniques verified that many more defects existed at the very top of the tubes (top i inch).

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To repair the tubes which have defects within the upper tubesheet, the licensee decided (July,1982) to perform an explosive expansion repair

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technique which expanded and tightly sealed the tubes within the tubesheet, thereby establishing a new leak limiting / load carrying mechanical seal. The explosive expansion repair technique was applied to

' all tubes in both .0TSGs, except those tubes already plugged.

Implementation of the repair technique occurred between September 1982 and February 1983. The repair. technique consisted of inserting a n -

polyethelene sheath into each tube. The polyethelene sheath contains a prima cord which, when ignited, expands the polyethlene sheath against the tube and the resultant force expands the tube. The polyethelene sheath prima cord and a booster cap was called a candle. Each candle was.

connected by an individual ordinance transfer cord. The transfer cord

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4 connected the candle in the tube to the blast box located'outside the OTSG. The transfer cord ends were bundled together and connected to a

-standard type blasting cap. The candles were detonated via the transfer cord by the. blasting cap which is ignited electrically by a licensed

-blaster.

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.During the expansion, a problem was noted with the kinetic expansion process which caused metal pieces from these stubs to. break free from the -

tube. Tube stubs are tube sections that protrude approximately 1/8 inch above the primary side of the tube sheet with welds between the tube and the tube sheet. These' stubs, which have circumferential cracks, are not a part of the reactor coolant system boundary. Licensee evaluated the need to mill (grind) down the tube stubs to prevent loose pieces from breaking away during power operations and decided to mi'11 down all tube stubs in March 1983.

In May 1983, after completion of kinet.ic expansion, a final bubble test was performed to document the "As Left condition of the OTSGs. .The test

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was conducted with primary water. level approximately 5% above the Upper

.Tubesheets(UTS)ofeachOTSG. Secondary. water level, after the N pressure was applied, was approximately 480" in the A OTSG and 560"2in the B OTSG. The secondary side was pressurized via the Plant Nitrogen System to approximately 150 psig. No indications of leaks were noted in the B OTSG. Ten indications of leaks were identified in the A OTSG. '

Bubbles were noted emitting from a B&W welded plug. This plug was reworked prior to final closeout. The r'emaining nine bubble indications !

were from six Westinghouse style temporary plugs and three unobstructed -

tubes. All of the leak indications were very fine streams of minute bubbles. _The licensee has decided to leave these tubes'in service to aide in tube'. leak identifications.

r The licensee's laboratory tests on sulfur contaminated tubes from the TMI-l steam generators demonstrated that the peroxide treatment could-remove-50% to 80% of'the sulfur. Tests have shown that the

.desulfur'ization process will be slowed in the kinetically expanded portion of the steam generator tubes because the expansion process leaves a thin polypropylene film on the tube surface. Sulfur removal on the remainder of the RCS can be anticipated to be more effective than for the OTSG tubes because the polypropylene film does not exist outside of the

- OTSG. ~ For this reason, prior to kinetic expansion, the primary side of 4 .the OTSG's was coated with immunol to alleviate this problem.

In July 1983, the licensee - desulfurized Reactor Coolant System (RCS) surfaces using a dilute' oxidizing solution of hydrogen peroxide (H,;0,,) to p reduce'the likelihood of corrosion problems from the sulfur remaining on '

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.the . RCS ~ pressure boundary component and piping surfaces. In order to

. - enhance the cleanup boron concentration, ph, lithium ion concentration, RCS temperature and pressure were maintained in specific range as stated in the. licensee. Test Procedure (TP) 600/4. Actual removal rate was less than expected and sulfur continues to " leech out" in the RCS during cold shutdown conditions. This is removed by ion exchange.

The final step in the recovery process was Hot Functional Testing (HFT) ,

in. September 1983. The OTSG HFT was designed to include transients which will stress the OTSG tubes, open up any cracks which are on the threshold l of propagation or open up any undetected cracks further. Leak detection a

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of 0TSG primary to secondary leakrate was calculated using a tracer gas

. Krypton (Kr-85). The testing sequence and subsequent heatups and cooldowns were designed "to simulate most of the same conditions in which the original

- cracking was initiated. . Results of the OTSG HF1 indicated no significant increase in RCS leakrate (0.0 to 0.2 gpm). As a revalidation of the first OTSG HFT, the. licensee is planning to conduct an additional HFT during May 1984. This HFT is primarily to complete the required testing of modifica-tions to the plant other than OTSG repair work. However, the licensee is planning on repeating the primary to secondary leakrate calculation (using Krypton tracer gas).

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5 ENCLOSURE 2 REGION I ACTIVITIES TMI-1 OTSG REPAIRS Summary Direct inspection of the License'e OTSG Repair Program totaled approximately 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br /> by tegion based and resident inspectors (See Table 1). These inspections hours represent a period o'! November 1981 to May 1984. During the review of the inspection, several unresolved items arosewhichdealtwith(a)adequacyoftheWestinghouseplug,andthe adequacy of the ALARA program used during the recovery process. There were no major violations noted except during HFT. To date, all violations dealing with OTSG Repair have been adequately addressed except for OTSG HFT violations. Most technical concerns by the resident and/or region based inspectors were directed to (and discussed with) NRR. T:1e

. Office of_NRR incorporated these concerns into previously identified concerns of their consultants or the staff. Due to the frequent meetings (see Table 2 for specific meetings) and discussions with the licensee, most issues were resolved quickly.

Conclusions One concern of the inspectors was that the licensee should have-

. determined the exact cause of the sulfur intrusion. Due to many possibilities, the licensee was never able to determine the specific causal event leading to this problem. The concern was noted to NRR and was addressed in the staff's SER.

The adequacy of the Westinghouse Temporary plugs from NRR point of view has been adequately addressed. From the region point of view, the final evaluatipn and testing on mechanical temporary plugs, however, could have been better documented..

Additionally, the licensee is to submit to the NRC their final management review of the data generated during HFT and this will be reviewed by Region I. The review of NUREG 1019 and Supp. 1 (Staff's SER addressing TMI .1 OTSG Repair Program) is essentially complete. Several inspector followup items from NUREG 1019 still require closecut' but have no safety significance in the evaluation of the total OTSG repair process. From the review of these documents, several action items are expected to develop. Two other inspection findings remain open and they are the review of both the licensee's response to notice of violations from OTSG

, -HFT and 0TSG Man Rem Exposure program.

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-ENCLOSURE 2 TABLE 1 ,

0TSG INSPECTION PROGRAM -

IMPLEMENTATION Inspection--

-Report Dates Inspector Hours Area of Review 81-32 11/81-1/82 Young 40 Initial Review of severity of problem Eddy Current, Bubble Test 82-01 1/82-2/82' Young 45 Eddy Current, Tube-Sam-ples, Licensee's preparation for RCS internal inspection ,

.82-02 2/82-3/82 Young 50 Plugging / Eddy Current  !

ALARA Review /19 tubes .

removed-82 3/82-4/82 Young 30 Review of Task Group Organization 82-06 4/82-5/82 Young 50 RCS Inspection Review /

Gray 30 Jacobs Witnessing RCS Inspection Eddy current Testing Materials Lab Visit '

82-07 5/82-6/82 Young 45 Tube stabilization

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82-09 6/82-7/82 Young -30 Tube stabilization Kinetic expansion 82-10 7/82-8/82 Young , 26 Kinetic Expansion

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3. . stabilization

'82-14 8/82-9/82 Young 20 Flushing and drying th'e cracks 82-20 9/82-10/82 Young 40 Witnessing Kinetic.

Expansion

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82-21 -10/82-11/82 Young -80 Witnessing Kinetic Expansion 82-22 10/12/82- 0'Neil, 120 HP aspects o' OTSG

'10/28/82 Barr. ,

Repair - ALARA

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, Inspection Report Dates Inspector Hours Area of Review 82-24 11/82f12/82 ,

Young 42 Kinetic Expansion.

82-26 11/12/82- ~ Gray 40 Records review i i

12/31/82 28 12/82-1/83 Young 30 Kinetic Expansion, Eddy Current .

. Candle Debris removal 83-01 1/83-2/83 Young 40 Debris removal Tube End Milling 83-02 1/83-2/83 Young 45 Final steps of kinetic Gray expansion

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83-05 2/83-3/83 Young 85 Tube end milling

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83-06 2/83-3/83 Gray 39 QA/ Welding 83-07 3/21-24/83 Gray /Reynolds 60 Kinetic Expansion r- (WeldingAspects) 83-08 2/83-3/29/83 Young 85 Man Rem tracking

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83-09 3/83-4/8/8'3 Gregg 10 PORY Inspection 83-11 3/83-5/83 Young 60 OTSG Quality Assurafice

, Conte Review Internal Inspection of-Pressurizer 83-12 5/83-6/83 Nicholas 40 OTSG HFT Procedure Review

. . '83-14 6/83-7/83 Young 60' Tube plugging Desulphurization 83 7/83-8/83 Young 50 TP(600/4) 83-22 7/83-8/83 Young 35 Desulphurization RCS cleanup

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83-25 8/83.10/83 Young 60 HFT Conte Nicholas

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8 Inspection Report Dates Inspector Hours Area of Review 84-01 1/84-2/84 Nicholas. 20 Preoperational test-Young results 84-07 2/84-3/84 Conte 30 Verification of NUREG l Young 1019 comitments L

84-11 4/84-5/84 Conte 10 NUREG 1019 open item Young closeout e

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. 9 L TABLE 2 e . REGION I SUPPORT TO NRR Topic '

Location Date Bethesda, MD -'

OTSG Meeting. 1/24/82 '

Status' Licensee Approach to problem

. Chemical Analysis / Columbus, OH 2/9/82 Destruction Analysis

- ' performed Status'OTSG work- Parrsippany, NJ 3/8/82

Status of th~e work Bethesda, MD 4/6/82

.of each of its task -

groups- _,

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Status OTSG' Parrsippany, NJ _

6/15/82 .

  • work Task RC Inspection Parrsippany,.NJ 6/21/82~

Kinetic Expansion Mount Vernon, IN. 8/5/82 Kinetic Expan.sion Parrsippany, NJ 8/25/82

-QA Control of Explosives. Mount Top, PA 10/13/82

[ ' Status OTSG Work Bethesda, MD 10/19/82

.. Third Party Review Parrsippany, NJ 12/9/82 b

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