ML20150D338
| ML20150D338 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/11/1988 |
| From: | NRC OFFICE OF SPECIAL PROJECTS |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8803230360 | |
| Download: ML20150D338 (5) | |
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UNITED STATES o,
NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20655 g
l s...../
SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS NRC WELDING CATEGORY - WELD DESIGN AND CONFIGURATION TENNESSEE VALLEY AUTHORITY SEQUOYAH' NUCLEAR POWER PLANT, UNITS 1 AND 2 o
DOCKET NOS. 50-327 AND 50-328 1.0
SUBJECT:
NRC Welding Category "Weld Design and Configuration" TVA Category:
WELDING TVA Subcategories:
EN 22201 EN 22202, WE 50915 WE 50999, IH 60300, WE 50899 The employee concerns were evaluated by TVA a3 potentially safety-related and applicable to the Sequoyah site or ac potentially applicable to the Sequoyah site on a generic basis.
TVA established the Welding Project to formulate a program for each nuclear plant site to address the employee concerns related to TVA's welding program. -Many of the concerns which originated at the Watts Bar Nuclear Plant were determined by TVA as possibly being generic, and therefore applicable to all of the TVA nuclear plant sites.
For the Sequoyah site, the TVA Welding Project is divided into two chases.
Phase 1 is a review of the records to detemine if there are any problem indicators. Most of the final element reports which are TVA's evaltation of employee concerns with a common issue (s) were written on the basis of the Phase 1 efforts.
Phase 2 involved a review of ISI and LER records, an audit by Bechtel of the welding program records, and a physical reinspection of specific weldment populations whose samples were selected on an engineering and logic
- basis, The NRC staff fomed a Welding Task Group with representatives from the Offices of Nuclear Reactor Regulation (NRR), Inspection and Enforcement (I&E), and Region II.
The Task Group established an Expert Welding Team through an NRR Technical Assistance contract with Brookhaven National Laboratory (BNL).
BNL provided a Technical Evaluation Report (TER) which summarized the opinions of the Expert Welding Team concerning the various welding issues and the actions taken by TVA as addressed in TVA's Element Report drafts of mid-1986.
The NRC Welding Task Group also performed independent visual, surface and volumetric reinspections of weldments at the Sequoyah site with help of Region I personnel i
operating out of the NDE van.
The TER and the Inspection Reports were incorporated in the initial Welding SER issued to TVA on November 11,1986.
This SER is being provided to address, in more detail, the individual employee concerns and the changes made of the indivicual employee con: erns declared generic to the Sequoyah facility since the initial staft Welding SER.
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8803230360 eso311 PDR ADOCK 05000328 P
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. The staff believes that there are five essential elements which must be functioning for a welding program to be viable.
The staff placed each of the individual empisjee concerns into one of these essential elemenc categories.
A miscellaneous category was established to cover those aspects which are not directly related to the welding program.
These program essential element categories are as follows:
Welding Procedures Welder Qualification / Training Welding Inspection Weld Design and Configuration Filler Material Control Miscellaneous /One of a Kind The staff's approach has been to group similar employee concerns within an essential element to establish an "issue" or "issues".
.'he staff reasons that the particular issue (s), if valid, and significant, would generate an adverse condition in the hardware.
As part of the overall program for reassessing the TVA welding program implemented during plant construction and operations, TVA and the NRC staff conducted reinspeccions at the Sequoyah site to determine 1),
that the licensee's corrective actions for resolving the issues raised by the employee concerns were being satisfactorily implemented, and 2), that the hardware was suitable for service.
NRC staff inspections and evaluations were performed on TVA's record audits program, personnel performing TVA's audits and reinspections, and TVA's records.
The employee concerns considered in NRC Essential Element "Weld Desig.1 and Configuration' are as follows:
TVA FINAL ELEMENT EMPLOYEE REPORT RESPONDING CONCERN NO.
TO CONCERN BRIEF DESCRIPTION OF CONCERN EX-85-039-003 WP-15-SQN WATTS BAR: DESIGN DEFICIENCY:
WRONG WELD ON B0X ANCHOR IN-85-405-001 WP-15-SQN POSSIBILITY OF METAL FATIGUE /
IN-SERVICE FAILURE IN CIRCUM.
WELOS CONNECTING SS PIPE TO BOX HANGERS...
IN-85-613-001 WP-15-SQN THERMAL STRESS CAUSED BY 1/2" - 1" CIRC WELD ON PIPE TO INSTALL BOX HANGER (GENERIC CONCERN)
- WBP-6-007-001 WP-15-SON B0X ANCHORS ARE IMPROPERLY DESIGNED PLANT WIDE XX-85-086-003 I-85-560-SQN DESIGN DEFICIENCY ON B0X HANGERS WHICH WILL WELD HANGER TO P1PE AND RESTRICT PIPE MOVEMEhT t
, TVA FINAL ELEMENT EMPLOYEE REPORT RESPONDING CONCERN NO.
TO CONCERN BRIEF DESCRIPTION OF CONCERN XX-85-068-007 I-85-636-SQN TVA MANUFACTURED SPOOL PIECE REPLACED DRAVO CODE STAMPED SP0OL PIECE i
i XX-85-200-001 ERT XX-85-100-001 IMPROPER REPAIR OF AN UNDETERMINED NUMBER OF WELDS.
The employee concern XX 85-086-002 was originally listed as being applicable to Sequoyah, and was subsequently judged by TVA's Welding Project as not being applicable to Sequoyah.
The staff has reviewed this concern and has determined that this concern is a duplicate of other concerns already applicable to Sequoyah, and that its removal does not significantly change the distribution of concerns / issues within the five NRC essential element categories. This concern is further discussed in the NRC Miscellaneous /One of a Kind category.
2.0
SUMMARY
OF ISSVES The welding issues involved with the four employee concerns covered in WP-15-SQN and the one concern covered in I-85-560-SQN are sunr.arized as follows:
Box anchor drawings have a typical detail that show a weld configuration which limits pice movement because a box anchor weld would fuse to the pipe.
Restriction of movement during pipe expansion due to box anchor weld fusing to piping could cause fatigue in service.
There is a possibility of fatigue in service and material degradation due to continuous welding using large diameter electrodes and excessive amperage.
Thermal stresses could possibly degrade piping where large fillet welds on box anchors attach to process piping.
, The issue involved with the employee concern covered in I-85-636-SQN is summarized as follows:
TVA manufactured a spool piece, substituted it for a Dravo ASME Code stamped spool piece, and then removed the nameplate (including the ASME stamp) from the Cravo piece and placed the nameplate on the TVA manufactured piece.
The issue involved with employee concern XX-85
>0-001 covered by the ERT Report of the same number is sumarized as follows:
An undetemined number of welds may have been improperly repaired. This issue is based upon a Watts Bar Steamfitter General Foreman having instructed steam fitter welders to repair welds contrary to the requirements of a weld procedure.
This foreman was employed at one time as foreman of the Sequoyah Hanger Fabrication Shop. However, there was no direct knowledge of this foreman giving instructions for improper weld repairs at Sequoyah.
3.0. EVALUATION The four employee concerns addressed in WP-15-SQN and the employee concern in NSRS Investigation Report I-85-560-SQN relate to a box anchor weld touching and fusing to the pipe.
The issue of the weld limiting the pipe's motion, and imposing fatigue loads on the pipe was solved in the field for one instance by special steps to allow the plate to move along the pipe.
The remai,ing seven of eight instances where this particular anchor design was used at Seouoyah have been addressed by having the drawings revised to prevent the box anchor weld from fusing to the pipe.
Accordingly, the issues of restriction of movement and fatigue are not valid because the conditions that causes the issues had been corrected in the installation or design.
The TVA Office of Engineering's evaluation and acceptance of the tests (Hodges mema o."
April 22, 1983 to Cox) of welding lugs to thin wall, small diameter stainless steel pipe with relatively large fillets found that there were no adverse effects on similar weldments at Bellafonte. The staff considers these results applic-able to Sequoyah.
The heat affected zone in the pipe at the interior surface of the pipe of such a weld may be sensitized, and conceivably be susceptible to stress corrosion cracking in an aggressive environment.
However, the primary water control of a pressurized water reactor steam supply system reduces the oxygen content such that the heat affected zoncs of stainless steel welds, even though sensitized to an extreme degree, is not expected to result in stress corrosion cracking.
Accordingly, this concern does nnt appear justified for a PWR.
In WP-15-SQN, TVA stated that analyses (CEB-CAS-173) took into account restraint, themal stresses and fatigue were perfomed for the box anchor designs used.
Based on the stated results of the analysis, the staff concurs with the conclusion of WP-15-SQN that the concern regarding themal stresses has been adequately addressed.
The employee concern XX-85-068-007 addressed in I-66-636-SQN had as an issue that TVA manufactured a spool piece and then substituted it for a Dravo manufactured spool piece by transferring the Dravo nameplate including the code stamp to the TVA spool piece. This sequence of events was demonstrated by TVA as highly unlikely to have occurred.
There were no records of Dravo spool pieces being delivered to Sequoyah and Dravo had no record of having shipped spool pieces to Sequoyah.
Sequoyah is not a "Code" plant, and stamps are not applied to spool pieces which are basically pieces of pipe, but are applied to pressure vessels and other pressure retaining devices. TVA provided a possible circumstance for an observer to believe that an ASME "stamp" on a nameplate could have been transferred when the observer witnessed the transfer of a heat number from the original stock pipe matteial to a piece cut from stock to i
maintain traceability. We believe TVA adequately demonstrated that there was no issue of substance in this concern.
f The issue of employee concern.XX-85-100-001 addressed in an ERT Report of the same number is of a foreman, while working at Sequoyah, instructing workers to weld contrary to procedures.
The concern was not substantiated at Sequoyah.
However, the same foreman had instructed workers to repair welds contrary to requirements in a weld repair procedure at Watts Bar.
The reinspections performed by TVA and NRC of many weldments from the Hanger Fabrication Shop where this foreman had worked did not find any weldments which were unsatisfactory for service.
4.0 CONCLUSION
S The staff has concluded that concerns addressed in TVA element report WP-15-SQN,
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I-85-560-SQN and I-85-636-SQN have been adequately addressed.
The concern addressed in in ERT XX-85-100-001 could not be substantiated.
- However, inspections by TVA and NRC did not identify any weldment in hangers unsatis-factory for service.
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