View source for A830019, Forwards Info Re Intergranular Stress Corrosion Cracking Observed in Core Spray & Reactor Water Cleanup Sys,Per 830822 Request.Weld Overlay Repairs Meet Safety Margins of App X to Section IX of ASME Code

{{Adams
| number = ML20080E193
| issue date = 08/23/1983
| title = Forwards Info Re Intergranular Stress Corrosion Cracking Observed in Core Spray & Reactor Water Cleanup Sys,Per 830822 Request.Weld Overlay Repairs Meet Safety Margins of App X to Section IX of ASME Code
| author name = Pilant J
| author affiliation = NEBRASKA PUBLIC POWER DISTRICT
| addressee name = Vassallo D
| addressee affiliation = NRC OFFICE OF NUCLEAR REACTOR REGULATION (NRR)
| docket = 05000298
| license number = 
| contact person = 
| document report number = LQA8300199, TAC-46657, TAC-51699, TAC-52037, NUDOCS 8308300783
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE, UTILITY TO NRC
| page count = 1
| project = TAC:46657, TAC:51699, TAC:52037
| stage = Other
}}

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GENERAL OFFICE Nebraska Public Power District
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4 LQA8300199 August 23, 1983 i
Director of Nuclear Reactor Regulation Attention: Mr. Domenic B. Vassallo, Chief Operating Reactors Branch No. 2 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 205$5 Subj ect : Core Spray and Reactor Water Cleanup System IGSCC                                                                          l Cooper Nuclear Station NRC Docket No. 50-298, DPR-46

==Dear bk. Vassallo:==

On August 22, 1983 our NRC Project Manager requested information relating to the IGSCC observed in the CNS Core Spray and Reactor Water Cleanup Systems and the resulting repairs. The requested information is attached in the form of two Licensee Event Reports dated July 8, 1983 and July 20, 1983. All weld overlay repairs meet the safety margins of Appendix X to Section XI of .ne ASME code. It should be noted that weld CSA-BJ-4 was also repaired by veld overlay on the Core Spray System and not reported in the LER submitted July 20.
If you require additional information, please contact me.
Sincerely, b 4 A. V m
((ayM.Pilant           b Technical Staff Manager                                                                                                               l Nuclear Power Group JDW:cmk Attachment 0\
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60           61             DOCKET NUMBER                     69       EVENT DA TE              I4       7b      RE PORT D ATE         BD EVENT DESCniPTION AND PROBABLE CONSEQUENCES h Lo L2.J LD_urirjg_Lnsulation removal on 6" RWCU suction line in containment. pin hole leaks were 1 0 3         I found in the heat affected zone of CWA-BJ-2 (Reference CNS ISI 'Drawine 73). Subsequent 1 I IOI4I l examinations of other velds in the line revealed IGSCC in CWA-BJ-4.5.7.8.9.10.12.23.25 I I O I 5 l Iand 27.                     The reactor was in the refuelinn node of operation when_the event occurred.                                                                   I l a 161 LThis event is renetitive. There were no adverse effects on the public health and                                                                                            1 0 7          [ Safety.                                                                                                                                                            I I Ola } l                                                                                                                                                                            l SYSTEM             CAUSE           CAU$E                                                      COMP.          VALVE CODE               CODE         SUSCODE                COVPONE,.T CC::E                   suBCODE          SueCODE lo_Lej 7        8 I c i c l@ LyJ@ LcJ@ I r l 1 l r i r I x ix l@ LB_J@ ILJ O 9         10          13              12             13                          13             19              20
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: e. %a CNSS830430 July 8, 1983 Mr. John T. Collins, Regional Administrator U. S. Nuclear Regulatory Con: mission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

==Dear Sir:==

This report is submitted in accordance with Section 6.5.2.A of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occur-rence that was discovered and promptly reported on June 29, 1983. Written notification was submitted on June 30, 1983. A licensee event report form is also enclosed.
Report No.:           50-298-83-09 y                      Report Date:          July 8, 1983
(           -
Occurrence Date:      June 29, 1983 Facility:             Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:
A condition was discovered which. indicated an abnormal degradation of the Class ~IN Reactor Water Clean-up (RWCU) System pressure boundary inside ,
primary centainment.
Conditions Prior to Occurrence:
The reactor was in the refueling mode of operation.
(
Description ot Occurrence:
During recoval of insulation from the six inch RWCU pump suction line for other work in the drywell, two pin-hole leaks were visually discovered.in the Heat Aftected Zone (HAZ) of weld CUA-BJ-2 (reference CNS ISI Drawing
                                  #3). Subsequent examination of six inch welds on the RWCU line produced rejectable indications in welds BJ-4,5,7,8,9,10,11,12,23,25 and 27.
Additional pin-hole leaks were found in the HAZ of BJ-25. No indications were found'in welds BJ-1 and 28. Welds BJ-13,15,16,19,20,21 and 22 were not examined because these welds were associated with RWCU piping re-placement in 1982 (Reference Report No. 50-298-82-14-1), and had seen less than ten months of operating service. Weld BJ-19 was, however, examined at a later time to provide additional justification for not examining the subject group of replacement welds. No rejectable                indica-(,.
tions were found as a result of the BJ-19 examination.
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Mr. John T. Collins July 8, 1983 Page 2
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t Designation of Apparent Cause of Occurreace:
The mode of failure in welds BJ-4,5,7,8,9,10,11,12,23 and 27 is Inter-granular Stress Corrosion Cracking (ICSCC).
Analysis of Occurrence:
The RWCU System provides a neans of purifying the prinary coolant                                   water by continuously removing a portion of the Reactor Recirculation (RR)
System flow f rom RR "A" Loop via a 20" Residual Heat Removal (RHR) System suction line.
l All examinations were conducted with an ultrasonic (UT) procedure qual-ified at the Electric Power Research Institute (EPRI) Non-Destructive Examination (NDE) Center in Charlotte, NC in accordance with IEB 83-02.
All examiners were qualified either at the EPRI NDE Center or at Cooper Nuclear Station with Nine Mile Point recirculation piping specimens exhibiting IGSCC.
The subject six inch RWCU welds had not initially been scheduled for IGSCC examination due to the fact that 100% IGSCC inspection had been performed during the previous refueling outage with subsequent partial system piping replacement. Had the pin-hole leaks gone unnoticed at this time, leakage could have been detected by drywell radiation monitors or by drywell floor drain sump monitoring. The limiting conditions for C                 plant operation with respect to unidentified drywell leakage are now being changed in Technical Specifications to reflect the concern about -
operation of the plant with the existence of shallow IGSCC indications in several large bore RR System piping welds. Fracture rechanics analysis was performed on these large bore welds to justify operation without veld overlay repair. Consequently, no further Technical Specification change will be necessary as a result of additional 1GSCC found in RWCU piping.                                   .
The reactor was in the refueling mode of operation when this event occurred.                                 This occurrence presented no adverse consequences concerning public health and safety.
Corrective Action:
All welds with rejectable indications are currently being prepared for veld overlay repair.                                     RWCU piping will be replaced in conjunction with RR System piping replacement.
Also, as a result of the findings in the RWCU piping, susceptible welds in Core Spray piping vill be examined for possible IGSCC.
Sincerely,
               /([ $l 4CL/ 4 - -
f          P. V. Thomason 1      i Acting Station Superintendent                                                                                     l Cooper Nuclear Station PVT:SSF:cg Attach.

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  ?              O                         60             El                DOCKET NUMSER                 68    69       EVE NT DATE              34      2S      REPORT DATE EVENT DESCRIPTION AND PROB ABLE CONSEouENCES h 1012 l l In preparation for ultrasonic examination (UT), weld crowns were being ground off of ten l l0 l3 j l inch Core Spray piping. 'During such grinding, welds CSA-BJ-5 and 6 (ref. CNS ISI Dwgs. l
[o l4 l l1 & 2) were reported ~to be leaking.                                                       Subsequent liquid penetrant exams on these welds                                          l loisl 1were negative. UT cxamination was performed and (IGSCC) crack indica: ions were sized atl l IOl_s] l'50% through wall and near through wall in welds BJ-6 and 5, respective N.
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; l o l 7 l l Jectable IGSCC indications were found in welds CSA-BJ-2, 9,10, 12; CSB-BJ-2, 3, 4, 5,                                                                                               l l
0 a           1 6, 9, 10 & 12.                         There were no adverse effects on public h'ealth and safety.                                                                       I i              ae                                                                                                                                                                           80
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l i l 0 l l All rejectable indications found in subject 10" C'S piping are due t'o Intergranular                                                                                               I i i            l Stress Corrosion Cracking (IGSCC). Affected welds will be repaired by weld overlay                                                                                       l li]2l Inethods. Pipins; will be replaced in conjunction with recirculation and reactor water                                                                                                   l
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CNSS830452 July 20, 1983 Mr. John T. Collins, Regional Administrator                 ~
U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

==Dear Sir:==

This report is submitted in accordance with Section 6.5.2.A of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occur-rence that was discovered and promptly reported on July 10, 1983. This letter                     i provides follow-up information to the written notification which was submitted on July 11, 1983. A licensee event report form is also enclosed.
Report No.:              50-298-83-11 Report Date:             July 20, 1983 Occurrence Date:         July 10, 1983 Facility:               Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:
A condition was discovered which indicated an abnormal degradation of the Class IN Core Spray (CS) system pressure boundary inside primary contain-ment.
Conditions Prior to Occurrence:
The reactor was in the refueling mode of operation.
Description of Occurrence:
Ultrasonic testing (UT) of welds in the ten inch Type 304 ~ stainless steel' CS piping for potential Intergranular Stress Corrosion Cracking (IGSCC) was conducted following the discovery of extensive IGSCC in Reactor Water Cleanup piping at Cooper Nuclear Station (reference Report 50-298-83-09).
As a result of the UT performed, rejectable indications were found in welds CSA-BJ-2, 5, 6, 9, 10, 12; CSB-BJ-2, 3, 4, 5, 6, 9, 10, 12' (reference CNS ISI Dwgs. 1 & 2). Welds CSA-BJ-5 and 6 were initially
                                                                                                      ~
reported to be leaking.
Designation of Apparent Cause of Occurrence:                                           -
The mode of failure in welds CSA-BJ-2, 5, 6, 9, 10, 12; CSB-BJ-2, 3, 4, 5, 6, 9,.10 and 12 is IGSCC.
c                     .

           ,.'. Mr. John T. Collinn July 20, 1983 Page 2 Analysis of Occurrence:
The function of the Core Spray system is to provide a redundant means for the removal of decay heat from the core following a loss of coolant 1
accident. This system also operates in conjunction with the Low Pressure Coolant Injection system.
                                                                                                          \
All examinations were conducted with a UT procedore qualified at the Electric Power Research Institute (EPRI) Non-Destructive Examination                l (NDE) Center in Charlotte, NC in accordance with IEB 83-02. All examiners and equipment were qualified either at the EPRI NDE Center or at Cooper Nuclear Station with Nine Mile Point recirculation piping specimens exhibiting IGSCC.
The subject ten inch CS welds were scheduled for examination after finding ICSCC in RWCU piping. Welds CSA-BJ-5 and 6 were visually observed to be leaking by maintenance personnel who were grinding the veld crowns off in preparation for UT inspection. Bowever, the
       ~              subsequent UT inspection showed that the cracks were 50% through wall and near through wall in welds CSA-BJ-6 and 5, respectively. These UT results were verified by two independent UT inspection teams. Subsequent liquid penetrant exams of each veld failed to reveal the presence of                I cracks. It is recognized that the grinding performed on the BJ-5 weld               '
crown could have sealed an existing through wall crack. It is questionable, however, whether or not weld BJ-6 was actually leaking.
For stress and weld overlay analysis purposes, the actual as found UT data vil1 be used.
The reactor was in the refueling mode of operation when this event occurred. This occurrence presented no adverse consequences concerning public health and safety.
Corrective Action:
All welds with rejectable indications are currently being prepared for veld cverlay repair. Core Spray piping will be replaced in conjunction with Reacter Recirculation and Peactor Water Cleanup piping replacement, during a future outage.
Sincerely, 1
6M' P. V. Thomason Division Manager of
  ,              Nuclear Operations Cooper Nuclear Station PVT:SSF:lb Attach.                                                                             -
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