IR 05000255/1989032
| ML18054B388 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 01/10/1990 |
| From: | Danielson D, Schapker J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML18054B385 | List: |
| References | |
| 50-255-89-32, NUDOCS 9001240194 | |
| Download: ML18054B388 (10) | |
Text
U. S. NUCLEAR REGULATORY COMMISSION REGION I I I Report No.: 50-255/89032(DRS)
Docket No.: 50-255 Lice~see: Consumers Power Company 1945 West Parnall Road Jackson, MI 49201 Facility Name:
Palisades Nuclear Generating Plant Inspection At:
Palisades Site~ Covert, MI 49043 License No.: DPR-20 Inspection Conducted:
October 19-20, Dec.ember 6-7, 14, and 20, 1989 Inspector:: J/JY'-d,_(.,___,"'~.... ---
~J. F. Schapker
.
Approved By:
~~t'~u..,,~.
D. H. Danielson, Chief Materials & Processes Section Inspection Summary Ins ection on October 19-20, December 6-7, 14, and 20, 1989 (Re art N..,o 90 2 R Area~ Inspected:
Routine announced inspection of eddy current examination (ET) of steam generator tubing (73753), review of ET procedures, data review and evaluation (73755) and licensee action in response to previously identified inspection findings (92702).
.
Results:
No violations or deviations were identified within the areas inspected. The inspector noted the following:
0 Eddy current examination detected significant increases in circumferential cracking of steam generator tubin Due to the status of degradation of the steam generator tubes, the licensee is planning steam generator replacement at the next refueling outage (Fall of 1990).
The licensee's corrective action in reply to a previous NRC find~
(Violation 50-255/88022-01) was incomplete. Further action by*the licensee is required to resolve this findin PDR ADOCK 05000255 Q
PDC l
- DETAILS Persons Contacted Consumers Power Company (CPCo)
- J. G. Lewis, Technical Director
- D. J. Malone, Licensing Analyst
- L. V. Vanwagner, iSI Supervisor
- W. E. Nummerdor, Senior QA Consultant
- C. S. Kozup, Technical Engineer K. V. Cedarquist, Senior Engineer S. R. Wellman, NDT Project Supervisor R. D. Orosz, Engineering and Maintenance Manager
/1 l lEr. r;uclear P.ssc,c*iates (NM}
B. L. Curtis, President, ECT-Level III U. S. Nuclear Regulatory Commission (U. S. NRC)
- J. K. Heller, Resident Inspector Other rn~mbers of the plant staff and contractors were also contacte *Penotes those present at the exit intervie.
Licensee Action on Previously Identified Inspection Findings (0 en) Violation (255/88004):
re~ L'. t 1 r. g in rr. 1 s p I u g g E * or e Background verification Numerous discrepancies with respect to tube plugging have been identified since 198 Included are misplugged tubes, defective plug welds and incomplete plug weld The licensee's quality verification process appeared inadequate to assure that these deficiencies were identified and corrected. As part of the licensee's commitment to assure that all misplugged tubes had been identified and corrected, the licensee connnitted to review existing video tapes of the tube sheet. If the video tape review was inadequate to assure that the tube plugging was performed correctly, a 100% tube sheet verification via video camera in both 11A 11 and 118
steam g~nerators would be conducte Inspection The NRC inspector reviewed corrective action documents concerning inadequate quality verification of steam generator tube plugging
(E-PAL-89-00lE).
Corrective actions taken in response to this violation were deemed adequate for future steam generator tube pluggin However, corrective actions taken to assure that all previously plugged tubes were correct were not apparen During the current 6u"tog<:. a tube: shEft scan was µerformeci c, A 11 and 11 [)' ;,i.eam gt:nE:1atu1 hot leg The results of this examination disclosed no discrepancies for misplugged tubes but identification of a dr9wing error disclosed that two tubes were incorrectly 1r1dicated as being plugge Review of the plugged tube list indicated the tubes were not required to be plugge The drawing was subsequently corrected. Cold leg visual scans for leakage only were performed, but did not involve inspection for misplugged tubes since entry into the cold leg side was not planned for the current eddy current inspectio "'.""!.c licensec-'s ISI supervisor informed the NRC inspector that CPCo had performed a review of the cold leg side via video tapes from previous outages and confirmed that no misplugged tubes exist in the cold leg However, no documentation was produced to verify that this action was completed and the corrective action documents did not reference this revie The licensee indicated the proper documentation is available and would be retrieved and furnished for the NRC inspector's revie This violation will remain open pending review by the NRC of the licensee's corrective action documentation for verification of correct plugging in the cold leg tube sheets of the 11A 11 and 118 11 stear generator (Closed) Open Item (255/88022-02):
Control Rod Drive Mechanism CY'ackinq Background In December 1986, with the plant in a hot shutdown condition (i.e.,
530°F, 2150 psia), engineering walkdowns identified control rod drive mechanism (CROM) Number 101 (head position 25) to be exhibiting primary coolant system leakage of approximately o. 12 gallons per minut The CRD seal housing (SEAL AA) was removed from the reactor head and, during bench testing, exhibited leakage from the drive shaft tube penetration. Subsequently, on December 16, 1986, dye penetrant inspections identified positive circumferential indications around the inner diameter of the motor tube sleev On December 17, 1986, due to positive dye penetrant indications on CRD seal housing 101, an additional six seal housings were dye penetrant tested per ASME Section X No similar positive indications were noted *
On D~cember 19, 1986, CRD seal housing 101 was sent to Combustion Engineering to determine the primary failure mechanism via destructive and metallurgic examination A records search initiated by both the licensee and the vendor indicated that CRD seal housing iOl was one of three spare CRD seal housings procured from Combustion Engineering in 1977.. Also indicated was that the seal housings were manufactured f1u1., the same hec.t uf materials and compri~ed the entire manufaciurillSJ lot. The remaining seal housings were determined to be on the reactor head in positions 23 ahd 28. *
On January 7, 1987, CRD seal housings 102 and 103 (head positions 23 and 28 respectively) were removed and dye penetrant tested. Both seal housings exhibited positive indications similar to CRD seal housing 10 Subsequently, both seal housings were sent to Combustion Erigine~ring for further examinatio On January 9, 196;, due to the additional findings on seal housings 103 and 102, and per ASME Section XI, five additional CRD seal housings were removed and dye penetrant teste No similar positive irdications were note The Combustion Engineering destructive and metallurgical analyses indicated that the axial and circumferential cracking existing on thP inner diameter of the motor tube sleeve was a result of transgranular stress corrosion crackin During the refueling outage of 1988, as part of the long term corrective actions taken in response to the indications noted above, six additional CRD seal housings (Serial Numbers 2966-02, 09, 34~ 35, 36, 44 and 45) were removed and dye penetrant teste On September 21, 1988, test results revealed that five of the six CRD seal housings exhibited positive indications similar to those found in 198 Seal housing 35 did not exhibit unacceptable indications, while seal housing 02 contained a positive 360 degree indicatio Due to the positive indications noted in the 1988 sample, the remaining 39 CRD seal housings on the reactor head were removed and dye penetrant tested (PT).
As a result of these inspections, six additional CRD seal housings (Serial Numbers 2966-11, 14, 27, 30, 41, and 50) were found to exhibit positive indications. Therefore, a total of 11 out of the 45 CRD seal housings tested in 1988 failed the PT examination. Between the identification of the 1986 and 1988 positive, dye penetrant indications, 13 CRD seal housings were inspected with no evidence of indications. Ten of these 13 housings were again inspected in 1988 and again, no evidence of indications were note The remaining three housings not reinspected are spares that were not in service. These spare housings had been rebuilt and inspected in March 198 Repair of the CRD se~l housings was pursued in accordance with ASM Section XI via a honing proces As a result of this process, the indications were characterized to typically be 0.003 to 0.004 inches in dept The maximum indication depth has been determined to be 0.012 inche In addition to these repair efforts, CRD seal housing 02 was s~nt to Combustion Engineering for destructive examination anti testin ln order to provide assurance that the honing prGcess was completely removing the existing indications, a fluorescent dye penetrant test (FPT) procedure was develope The nine previously repaired CRD seal housings were again removed from the reactor head and the FPT performed. This testing reveaied that indications remained within several seal housings. A review of previous standard dye penetrant tests revealed a good correlation between remaining indications and those originally identified. These remaining indications were t~en removed by localized grinding efforts and the seal housings reexamined using the FPT. This further testing revealed no remaining indications. The total maximum depth of material removed to eliminate these indications was 0.015 inche The NRC inspector observed the FPT and mechanical processing to remove the defect The cause of the indications identified in 1986 has been attributed to transgranular stress corrosion crackin However, the initiating factor of the transgranular stress corrosion cracking could not be determine There is evidence of a contaminant being present on the fracture surf ace; however, the specific contaminant could not be determine Metallurgical analyses of the housing indicate that the prin1ary elements identified ere consistent with thofe found in Type 304 stainless steel and dye penetrant fluid and developer. Additional elements were identified which are known to promote transgranular stres~ corrosion cracking (i.e., potassium) in stainless steel; however, no explanation for their presence could be determine Nor could an exact correlation be derived between their existence and the crackin The presence of the contaminant and evidence of transg~anular stress corrosion cracking originally appeared to be an isolated case, associated with the manufacturing lot comprised of CRD seal housings 101, 102 and 10 The positive dye penetrant indications exhibited on the 11 CRD seal housings discovered in September 1988 have again been attributed to transgranular stress corrosion cracking. This conclusion was primarily derived from data taken and analyses performed by Combustion Engineering during destructive testing of CRD seal housing 10 These*efforts focused on evaluating stresses imposed by shrink fitting and welding processes during manufacturing, and operating stresses normally impose Analyses concluded that there is no evidence of fatigue cracking and that the indications are transgranular in nature. Although no traces of corrosive contaminant were identified in the 1988 sampling, it is assumed that the crack initiation and subsequent growth was accelerated by the presence of a contaminan This was due to the fact that the steady stresses computed would not otherwise be anticipated to result in the cracking exhibite All 45 CRD seal housings currently installed on the reactor head were PT examine Inspecticn The NRC inspector reviewed the licensee's augmented inspection plan*
fer exarr.inc~.icn of thE CF.C seal hou~ings. Each refueling outage tlK licensee wi11 examine the previously cracked housings and replace if cracks are presen In addition, all of the previously cracked housings will be repl~ced at a rate of three housings per outag The remaining CRD seal housings will_be inspected in accordance with the ASME Code Section XI requirement The licensee's corrective action was adequate.to assure that all.of the cracked CRD seal housings were identified. Root cause analyses, repair, and planned replacement of the cracked CRD housings will assure the safety objectives of regulatory requirements and the ASME Code are being met~ Inspection of Steam Generator Tubing Background Following plant startup on March 1, 1989, primary to secondary leakage was detected. Operation of the plant with an average calculated leak rate of.015 gallons per minute continued until October 1, 1989,*when Palisades was shut down to repair suspect Westinghouse mechanical tube plugs, and perform eddy current (ET) examinations as previous*1y committed to the NR During the operations of the plant since March 1: 1989, the licensee reduced power (to 80%) to maintain leakage below levels as required by the administrative controls committed to the NR The licensee has experienced rapid degradation of steam generator (SG)
tubing over the last two years. Leaks due to circumferentially cracked tubes in SG_"B" hot leg at tube support plates 3 and 13 have occurred, causing forced outages and extensive repair and evaluatio The.licensee employed the services of MPR Associates to perform a support plate stress evaluation. The purpose of the evaluation was to identify tubes within the SG which are most susceptible to circumferential stress corrosion cracking. Stress and deflection analyses of the support plates, the location of tube support plate flow circulation holes *and the recent history with respect to tube leaks and tube cracking were taken into considerat-1~::J:il in completing the evaluatio The MPR Associates evaluation concluded that the high probability stress areas for inducing circumferential corrosion cracking was in the hot leg at support plates 3 and 1 Consequently, the licensee committed to provide the NRC with the final eddy current.inspection scope for this mid-cycle outage. Previous discussions with the NRC's NRR staff concluded that the licensee would inspect all of the tubes recommended by MPR Associates in their support plate stress evaluation report (MPR-1125 Palisades Steam Generator Proposed* Eddy Current Inspection Plan~ May 1989).
.
- The scope consisted of inspecting 1006 tubes in 11A 11 stearn generator hot leg and 783 tubes in 118" steam generator hot leg. All of these tubes were inspected with the 8 x 1 probe. A subset of these tubes which are 1ocattu near previous leakers were inspected with the motorized rotating pancake coil (MRPC) at support plates 3 or 1 The MRPC was used to inspect 239 tubes in 11A 11 hot leg and 94 tubes in 118 11 hot le The 8 x 1 probe is qualified for the detection of circumferential crack It is not, however, qualified to size intergranular attack (IGA) or wastage type def~cts. During_ the inspection, based on past experience with the 8 x 1 probe, a large number of 11 noncrack 11 indications were expected to be identified with the 8 x 1 probe in regions of IGA or wastag In order to ensure these indications do not represent true degradation growth or exceed the plugging criteria, the licensee inspected 10% of the tubes which contain 11 noncrack 11 indications (minimum of 100 tubes) with a bobbin prob Any indication which exceeded the Palisades Techr:ical Specification for p1ugging we.s plugge Tlit: 540 SFW bobbin probe with the MIZ-12 tester was use~ in lieu of the MIZ-18/580 bobbin to obtain a comparison with previous ET result The licensee recently aualified the Zetec MIZ-18 to perform the SC tubing examination, which was utilized for the 8 x 1 and MRPC examination Initial ET examination as described above detected seven crack-like -
irdications, including two leakers which were identified by leak tests previous i_y* in the 118 11 S Each tube with crack-1ike indications was plugged and bounded by ET examination of two rings of tub~s adjacent to i No tubes were found in 11A 11 SG hot leg which contained crack indication The MIZ-12 540 SFW bobbin inspection for 11 non-crack 11 defects did not detect any further degradation in the sample of 100 tubes selected for.examinatio Sut,scqurnt to the hot leg ET examination, the licensee performed tubcsheet visual scans (for leakage only) of 11A" and 116 11 SG cold leg "A" SG cold leg visual examination revealed a region of wetness close to the divider plate. Fifteen tubes adjacent to the wet area of the tubesheet were examined using the 8 x 1 prob Five tubes were identified with possible crack-like indication ET with the MRPC probe of these five tubes confirmed three crack indication Each of these tubes had been last inspected in August 1983 with no apparent degradation present at the third support plat The licensee expanded the ET examination to include all tubes located within three rings of the degraded tubes in 11A 11 SG cold leg (77 tubes) and all tubes in rows 12 -
~'~: Jdjacent to the divider plate, in quadrants l and 4 of SG 11A" cold leg. *rhe results from this ET sample detected 17 additional crack-like indications using the 8 x 1 probe. With the three previous indications, 19 were located at support plate 3 and one at support p1ate Of these indications, nine were dispositioned with the MRPC ET probe as satisfactory, with 11 crack-like indications confirmed as defects. Further expansion of the examination included: all tubes in rows 15 - 16 in SG 11A 11 cold leg and in rows 12 - 14 in 11A 11 hot le One potential crack-like indication was found in rows 15 - 16 in quadrant 4; the inspection scope was expanded to rows 17 - 18 in that quadran No further crack indications were foun The licensee employed MPR Associates
to perform further review to provide a crack mechanism assessment using the eddy current dat The assessment, performed by MPR Associates, determined two probable mechanisms responsible for the cracking found in the cold legs; in-plane loads due to severe denting and out-of-plane loads due to thermal expansion stresse The average denting values for the third support plate.based on December 1987 profilometry inspection indicates significantly high dentin The third support plate does not have flow circulation holes, which provides some stress relief, ahd the tubes adjacent to the areas of plugged are subjected to higher thermal expansion stresses, particularly the short *radius tubes which have the hottest primary water at the cold leg tube sheet. Most of the tubes in rows 1 - 12 are plugged causing the unplugged tubes close to the divider plate to see the highest out-of-plane
_loads due to thermal expansio The secqnd most probable areB of high stress was determined to be the tubes located in the lug regions of the tube support plates. The restraining force of the lug, in addition to thermal expansion stresses between the_
11cold 11 lug and a hot tube make it a high suspect are t*iPR Associates recommended further ET samples at the lug regions of support plate 3. The licensee performed ET of six tubes at each of the five lug regions at support plate 3 of SG 11A 11 *
No crack-like indications were found in these inspection In summary, the 11A 11 SG hot leg inspection had covered 1,017 tubes specifically targeted by the original MPR inspection plan plus 130 tubes along the divider plate, plus a five percent random sample for a total of 22.7 percent of the tubes inspected with no cracks identified. The 11A 11 SG cold leg inspection had covered 360 tubes along the divider plate,
. 2: tubE.::.
"-~ the lugs ar:c t;. f*ive percent random sampl A totc:..1 of 12 crack-like indications were detected in the cold leg (one leaker) primarily at support plate The licensee also expanded the scope of the ET in the 11B 11 SG cold le Initial ET detected 24 crack-like indications in rows 12 - 1 The sample was expanded into rows 15 - 16 in which 10 additional crack-like indications were foun Further ET was performed in rows 17 - 18 of quadrants 1 and 4 where an additional 16 crack-like indications were found causing ET. scope expansion to rows 19 - 2 No indications were found in these two row A total of 50 crack-like indications were found in rows 12 - 18. The licensee subsequently performed a five percent random inspection in "B 11 SG cold leg and rows 12 - 14 in "B" SG hot l~~.
No additional indications were found in 118 11 SG hot le The "B 11 SG ~old leg ET detected five additional crack-like indications. Four of these indications were located at tube support plate 4 and one at support plate Each of these tubes had been ET examined during August of 1988 with no defects detected at that tim The licensee performed ET of the tubes' two rings surrounding these 5 defective tubes; no additional indications were found in this sampl The licensee made the decision to ET an additional six percent random sample in the 118 11 SG cold le No additional crack-like indications were found in this sampl Following recommendations from the NRC made during ongoing status briefings, the "B" cold leg examination was expanded to further bound the five tubes with crack-like indications found in the original five percent r~n~om sample (189 tubes).
- ET crack-like indications*were'detected in seven tubes in support plate 3 lus rE;1on, The sample was ~~panded to incluae t~o rings of tubes surrounding the defective tube No additional crack-like indications were detecte No additional ET examinations were mad A total of 27 tubes were plug~ed in the "A" SG of which 11 contain crack indication In the "B" SG, 118 tubes were plugged, of which 69 contained crack indications. Tubes adjacent to the leakers or containing cracks in excess of 80 degrees circumferentially were also plugge The licensee contacted NRR (EMTB) through the NRR Project Manager and reported the resu~ts of the above examinatior1s throughout the inspectio Through conference calls with NRR, inspection results and engineering submittals, the licensee's eddy current examirtation was judged adequate to assure reliability for safe operation to the next refueling outage where the replacement of the Palisades SG's are planned (Fall of 1990).
Inspection The NRC inspector observed eddy current examinations in progress, reviewed the ET inspection program, ET inspectors* certifications, data analysis guidelines for the ET at Palisades, and certification/calibration of ET equipmen The NRC inspector did not observe the ET performed throughout the outage due to other commitment However, the inspector co~tacteci NRR (EMTB) and site personnel throughout this period to keep current on the ET examination results at* Palisades. Subsequently, the NRC inspector reviewed t~e ET data and concurred with reported result A total of 1,473 tubes (22.7 percent) were examined in SG "A" hot leg, 714 tubes (11 percent) in the cold leg, 939 tubes (15 percent} in the
"B" $G hot leg, and 1,425 tubes (23 percent) in the cold le The licensee plans to limit plant operation to a maximum of 80 percent of rated power until SG replacement in the Fall of 199 The Palisades Technical Specifications (TS) limits primary to secondary system leakage to 0.3 gallons per minut However, the licensee has committed to an administrative limit of 0.05 gallons per minute during plant operation Based on the licensee's adherence to the administrative primary to secondary 1 eakage limits and reduced power ope rat ion, ti:, safety significance of possible cracking in additional tubes not inspected is reduced. Analysis performed by the licensee (CPCo to NRC submittal dated April 19, 1984 and MPR analyses of May 1989) indicated throughwall cracking will develop leakage and be detected by install~d plant equipment prior to a crack reaching a critical circumferential length. Therefore, the safety significance of possible cracked tubing is conservative in that leakage will preclude the tube failure by a safe margin (leak before break analyses).
The 1icensee 1 s ET was performed in accordance with-approved procedures which comply with ASME Section XI requirements, ET inspectors'
qualifications, and certifications complied with ASNT TC-lA requirement No violations or deviations were identifie The inspector met with licensee representatives (denoted in Paragraph l) on December 7, 1989, and during a subsequent telecon with Mr. B. V. Vanwagner on December 14, 1989, and at the conclusion of the inspection via telephone with
~-Is,. K. V. Cedarquist on December 20, 198 The inspector summarized
.the scope and findings of the inspection activities. The licensee acknowledged the inspection finding The inspector also disc~ssed the likely informational content of the inspection report with regard to documents or processes reviewed by the inspector. The licensee did not idt;!nt if.Y any such dccun,ents/µrocesses as proprietar