ML20150C816
| ML20150C816 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/11/1988 |
| From: | NRC OFFICE OF SPECIAL PROJECTS |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8803220328 | |
| Download: ML20150C816 (2) | |
Text
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[o.* ugg'o, UNITED STATES
~j NUCLEAR REGULATORY COMMISSION
,j WASHING TON, O. C. 20S$5
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SAFETL EVALUATION REPORT BY THE OFFICE OF SPECIAL PROJECTS f.MPLOYEE CONCERN ELEMENT REPORT 222.6(B)
"AISC MINIMUM WELD CRITERIA" l
1C9FSSEE VALLEY AUTHORITY SEOUOYAH NtfCLEAR POWER PLANT, UNITS 1 AND 2 DOCXET N05. 50-327 AND 50-328 1.
SUBJECT Category:
Engineering (20000)
Subcategory:
Pipe Support Weld Design (22200)
Element:
AISC Minimum Weld Criteria (22206)
The basis for Element Report 222.6(B) Revision 1, dated January 14. 1987 is Element Concern IN-85-109-003 which states:
s "AISC minimum weld criteria is violated by Memo E44011-01.
Names are known."
This concern was evaluated by the licensee as potentially nuclear safety-related and potentially applicable to Sequoyah (generic).
II.
SUMMARY
OFISSlg The licensee identified the issue as "American Institute of Steel Construction (A!SC) minimum weld criteria were not always followed.
III. EVALUATION The basis for the employee concer.. is paragrarb one of an internal licensee letter dated January 20,1984, "Watts Bar Nuclear Plant - Clarification of Welding Requirements" which states:
"TVA has performed Qualification tests to the recuirements of Feference 2, which serve to cualify the use of fillet welds smaller than the minir,cm sizes as given in Table 2.7 of Pcference 2.
On the basis of this cualification, fillet welds of
)
any size necessary to carry calculated loads may be used for
,ioining materials listed in Group i Table a.1.1 of Peference 2 when such welds are rade by the shielded metal are welding (SMAW) process. using Icw hydrogen electrodes '
$$03 soc @ $$o N 2a p
1 l Reference 2 is the Structural Welding Code published by the American Welding Society which is incorporated into the design through the seventh edition of AISC in par. 1.17.1.
Provisions for the qualification of fillet welds are contained in par.1.17.2, "Qualification of Weld and Joint Details." These provisions permit the qualification of welds smaller than those listed in par.
1.17.5, "Minimum Size of Fillet Welds."
The licensee remains responsible for assuring that these smaller velds are capable of carrying the design loads.
According to the licensee's evaluation team, the qualification tests are documented in memorandun no. NEB-840120-275 dated January 20, 1984, "Clarificatinn of Welding Requirement."
The evaluation tean did not show that these small-weld qualification tests were performed prior to their ure in the 1970's.
The FSAR commitrent in par. 3.8.4.5.2, "Structural Steel" is to design in accordance with the seventh edition of the AISC rules.
The licensee reviewed 34 pipe supports selected from the safety-related plant systems and found 4 in Unit 1 and 8 in Unit 2 with welds detailed smaller than AISC requirements of par. 1.17.5.
The difference varied from 20'; to 40% of fillet weld leg size.
In addition, the calculations for the discrepant supports could not be found.
The evaluation team introduced an American Society of Mechanical Engineering nuclear code case into the discussion, but it is irrelevant.
The 1Icensee calculated the minimum weld size for the Unit 2 supports using the original AISC design criteria supplerented by the licensee's factors of safety.
Seven were satisfactory and the eighth met MSC criteria and the licensee's short term criteria, but not their long tern criteria and it will be replaced after restart.
The licensee committed in post restart corrective action plans to revise the FSAR and design criteria and perfonn analytical verification for the 4 supports in Unit 1.
The qualification tests performed by the licensee in 1984 showed that the smaller sizes used earlier will be adequate for the design criteria.
The resolution of the employee concern is acceptable to the NPC staff.
IV.
CONCLUSIONS The employee concern is substantiated and it does not appear that the licensee cualified the small welds until long after they were completed.
The NRC staff has reviewed the licensee's element report 222.6(B) ravision 1 dated January 14, 1987 "AISC llinimum Weld Criteria" and the conclusions and corrective actions are acceptable.
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