ML20024C068
| ML20024C068 | |
| Person / Time | |
|---|---|
| Issue date: | 06/13/1983 |
| From: | Barnes I, Hamilton J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20024C060 | List: |
| References | |
| REF-QA-99900707 NUDOCS 8307120226 | |
| Download: ML20024C068 (7) | |
Text
,
ORGANIZATION:
NELSON ELECTRIC A UNIT OF GENERAL SIGNAL TULSA, OKLAHOMA Ktruni ANSFtbl10N INbFLL11UN N0.:
99900707/83-01 DATE(S) 4/25-27/83 DN-SITE HOURS:
16 CORRESPONDENCE ADDRESS:
Nelson Electric ATTN: Mr. B. R, Karr Director of Quality Assurance P. O. Box 726 Tulsa, Oklahoma 74101 ORGANIZATIONAL CONTACT: Mr. B. R. Karr, Director of Quality Assurance TELEPHONE NUMBER:
(918) 627-5530 PRINCIPAL PRODUCT: Mineral insulated (MI) heating cable assemblies, heat trace panels, and motor control centers.
NUCLEAR INDUSTRY ACTIVITY:
Currently 5% of the work at Nelson Electric is for nuclear power plants.
iMN T)
ASSIGNED INSPECTOR:
A l6N1 W. hamilton, Reactive and Component Program gate Section (R& CPS)
OTHER INSPECTOR (S):
APPROVED BY:
8-4 - < 3 -i 3 I. Barnes, Chief, R& CPS Date INSPECTION BASES AND SCOPE:
A.
BASES:
10 CFR Part 50, Appendix B and 10 CFR Part 21.
B.
SCOPE: This inspection was made as a result of:
(1) a 10 CFR Part 21 report by Nelson Electric which identified a defective hot-cold electrical splice in MI heating cable assemblies supplied to St. Lucie Plant, Unit 2, and Susquehanna Steam Electric Station, Unit 2; and (2) a (cont. on next page)
PLANT SITE APPLICABILITY:
Defective MI heating cable assemblies, 50-389, 50-388; broken insulators in heat trace panels, 50-389.
db 8307120226 830617 Cortifica 27 PDR GA999 ENVNELE 99900707 PDR
r ORGANIZATION: NELSON ELECTRIC A UNIT OF GENERAL SIGNAL TULSA, OKLAH0MA REPORT INSPECTION NO.:
99900707/83-01 RESULTS:
) AGE 2 of 4 SCOPE:
(Cont.) potential construction deficiency report filed by Florida Power and Light :ompany concerning broken insulators in heat trace panels at St. Lucie Plant, Unit 2.
A.
VIOLATIONS:
None B.
NONCONFORMANCES:
None C.
UNRESOLVED ITEMS:
None D.
OTHER FINDINGS OR COMMENTS:
1.
10 CFR Part 21 Report: The 10 CFR Part 21 report filed by Nelson Electric identified a failure of the hot-cold sleeve in MI heating cable assemblies.
Cracks occurred in the Inconel 600 splice sleeve which houses the electrical splice between the heating section and the power carrying cold lead.
This deficiency applies to Underwriters Laboratory (U. L.) Classes 307 and 308 MI heater cable assemblies manufactured between August 2 and December 6, 1982.
Failures were detected on U. L. Classes 307 and 308 heater cable during insulation resistance (IR) testing after a customer specified 5 atmospheres water pressure leak testing.
Leak testing is normall performed at atmospheric pressure, but customer Purchase Order (P0)y ML 619 specified leak testing to be done at 5 atmospheres.
Two years earlier, a purchase order specified similar water pressure leak testing with no failures being detected in IR testing.
However, for P0 ML-619 a 20% rejection occurred.
l When Nelson Electric personnel were unable to detect the cause of failure, samples were sent to Midstates Analytical Laboratory (MAL) in Tulsa, Oklahoma.
MAL Report No. 82-32199 of December 17, 1982, states, in part:
... The failure of the... joints was attributed to cracking of the sleeve in the brazed area.
... The l
cracking was intergranular in nature and generally appeared to be filled with braze material....
e t
ORGANIZATION: NELSON ELECTRIC A UNIT OF GENERAL SIGNAL TULSA, OKLAHOMA REPORT INSPECTION NO.:
99900707/83-01 RESULTS:
) AGE 3 of 4 It is reported by Huntington Alloys, Inc., in their product bulletin 15M8-76T-2 " Joining" and also in the AWS handbook, Volume 4, seventh edition, page 264, that stress corrosion cracking can occur during silver brazing of nickel alloys if certain stress conditions, e.g., cold working stresses, fixturing induced stresses, or thermal stresses from differential heating, are present....
MAL conducted controlled tests in an electric oven using fittings, brazed wire, and flux obtained from Nelson Electric stock to test the validity of stress-corrosion cracking for the conditions at Nelson Electric. MAL reported, in part:
The fittings, flux and brazing wire were placed in an electric furnace preheated to 1800 F.
The fitting was observed in the furnace and when the braze turned liquid and flowed the fitting was removed. This brazing procedure consistently produced cracking like that found in the subject parts....
It was concluded that the cracking was caused by a stress corrosion (liquid-metal embrittlement) phenomenon of the Inconel 600 material and the braze 650 alloy during the brazing process.
MAL also performed evaluations of brazed splice sleeves where the Nelson Electric stock sleeves used were in an annealed condition.
The brazed annealed splice sleeves were found to be free from stress corrosion cracking.
(
The NRC inspector was informed that prototype evaluations were made l
using both work hardened and annealed splice sleeves.
After brazing, the assemblies were exposed to thermal shocks, atmospheric leak tested, and then microscopically examined for anomalies. No cracks were discovered in either the annealed or work hardened splice sleeves. The NRC inspector was also informed that it was originally decided to use annealed splice sleeves and this decision was based on less tooling wear and less of a tendency to flatten during the forming process. However, engineering did not specify I
the annealing requirement on Drawings GA-1213 and GA-1234 which resulted in the splice sleeves received on August 2, 1982, not being l
in an annealed condition.
Nelson Electric's letter of December 15, 1982, to the NRC which was written as a follow-up to the 10 CFR Part 21 report states, in part:
r ORGANIZATION: NELSON ELECTRIC A UNIT OF GENERAL SIGNAL TULSA, OXLAHOMA REPORT INSPECTION N0.:
99900707/83-01 RESULTS:
) AGE 4 of 4
... The individual cable assembler's techniques of preheating the fitting, fluxing and silvering the sleeve vary.
Hence many of the assemblies never received the right combination of time and temperature during the brazing operation to cause the stress crack to develop....
Nelson Electric stated that this was the reason why the prototype work hardened splice sleeves and the majority of the production between August and December 1982 did not not contain stress corrosion cracking. After review of this situation, the NRC inspector found no reason to dispute this position.
Corrective action by Nelson Electric was to change the drawings to require annealing of the splice sleeves. To further minimize the risk of future cracking problems, Nelson Electric has also changed from a silver brazing material to an Inconel brazing rod.
Documentation was presented to the NRC inspector which demonstrated what steps were taken to identify customers with safety-related applications. Documentation was also presented which pertained to field service trips that were made to conduct dye penetrant inspections at St. Lucie Plant, Unit 2, and Susquehanna Steam Electric Station, Unit 2, and the subsequent test results.
2.
Potential CDR:
Florida Power and Light filed a potential CDR concerning heat tracing control cabinets having cracked insulators.
The deficiency was observed in hardware supplied to St. Lucie Plant, Unit 2.
The cracked insulators retained their required position and the cracks did not prevent them from insulating the power panels from the bus.
The NRC inspector reviewed the field service report pertaining to the Nelson Electric examination of the defective power panels at site.
This examination revealed significant additional damage to the control cabinets.
The Nelson Electric field service engineer concluded that the cabinets had been subjected to gross mishandling which had most probably occurred during shipment of the units.
Necessary repairs l
were performed on the units with the exception of controllers which l
were returned to the vendor for repair.
From the information available, the NRC inspector concluded that the problem did not appear to be generic in nature and was attributable to mishandling i
during shipping or receiving.
PERSONS CONTACTED r#~{
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Dates 2.T-29 APS! T3 Company i
Docket / Report No.99900707 ff5-01 Inspector Teknkl.MAdiNtu s
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