ML20151Y806
| ML20151Y806 | |
| Person / Time | |
|---|---|
| Issue date: | 02/11/1986 |
| From: | Harper J, Merschoff E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML20151Y794 | List: |
| References | |
| REF-PT21-86, REF-QA-99900340 99901012-85-01, 99901012-85-1, NUDOCS 8602130164 | |
| Download: ML20151Y806 (3) | |
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O'<GANIZATION: YARWAY C0P.P0 RATION
. BLUE BELL, PENNSYLVANIA REPORT INSPECTION INSPECTION NO.: 99901012/85-01 DATE(S): -10/30/85 ON-SITE HOURS: 6 CORRESPONDENCE ADDRESS: Yarway Corporation ATTN: Mr. Richard Rose Vice President, Manufacturing Blue Bell, Pennsylvania 19422 ORGANIZATIONAL CONTACT: Mr. Frank Peszka TELEPHONE NUMBER: (215) 825-2100 PRINCIPAL PRODUCT: Valves NUCLEAR INDUSTRY ACTIVITY: Less than 5%.
ASSIGNED INSPECTOR: - h ,
') /a [g J. C ,. Harper, Reattive Inspection Section (RIS) D#te' OTHER INSPECTOR (S): P. Cortland APPROVED BY: .
2 i E. W. Merschoff, ief, RIS, Vendor Program Branch Date INSPECTION BASES AND SCOPE:
A. BASES: 10 CFR Part 21 B. SCOPE: To review the technical aspects of reported valve stem problems with Yarway valves.
PLANT SITE APPLICABILITY: Midland Plant, Units 1 & 2, 50-3294, 50-330; Grand Gulf Nuclear Station Units 1 & 2, 50-416 & 50-417; Susquehanna Units 1 & 2, 50-387 & 50-388; V. C. Summer Nuclear Station 50-395; Clinton Power Station Units 1 & 2, 50-461 & 50-462.
8602130164 860211 PDR OA999 EMVYAP 99901012 1
O ORGANIZATION: YARWAY CORPORATION BLUE BELL, PENNSYLVANIA REPORT INSPECTION N0.: 99901012/85-01 RESULTS: PAGE 2 of 3 A. Inspection Issues A Part 21 notification was made to the NRC on September 26, 1985 concerning cracked valve stems on 1/2 inch and 3/4 inch weldbond valves. Although the cracked stems were not involved in nuclear plant service, stems from the same heat were sold to multiple nuclear plants.
Yarway concluded that the stem cracking and subsequent leakage "...is caused by a void in the bar stock used to manufacture the stems...."
Therefore, they consider this incident an isolated case.
B. Background Information On September 26, 1985, Yarway Corporation issued a Part 21 notification concerning a cracked valve stem in 1/2 inch and 3/4 inch weldbond valves.
Specifically, a Houston Light & Power (HL&P) fossil power plant reported leakage of a newly installed valve to Yarway in July 85, and five other stems cracked during a non-ruclear hydrotest at Yarway. All stems were manufactured from the same heat of material. Yarway determined that additional stems from this heat were sold to Grand Gulf, Susquehanna, V. C. Summer, and Clinton. Yarway has notified these plants of the potential problem and has recommended replacement of the valves. As of December 1985, Yarway has not received any reports of stem leakage from the identified nuclear facilities.
The bar stock used to manufacture the stems was 5/8" round bar, martensitic stainless steel type 416, ASTM A582-75 condition T, heat number 93876. This grade contains a relatively high sulfur content in order to improve machinability. The bar stock originated from the Al Tech Specialty Steel Corporation where an oversize bar is heat treated (1850 F - I hr. - oil quenched) and tempered (1025 F - 6 hrs. -
air cool) according to ASTM 582-75, eddy current tested and ground down approximately 1/32 inch to size. Subsequently, the bar stock was supplied to P. A. Frasse and Co., Inc. , then to Yarway who threads and inspects the stems for surface finish.
The stem hardness was within specification at Brinell 302. Mr. Bill Toter of Yarway indicated that transverse microhardness testing across the cross section of the stem revealed uniform hardness properties which were within specification. The chemical analysis for carbon, manganese, sulphur, and silicon were all witnin specification. Both the carbon content and hardness were at the upper limit of the specification.
ORGANIZATION: YARWAY CORPORATION BLUE BELL, PENNSYLVANIA REPORT INSPECTION N0.: 99901012/85-01 RESULTS: PAGE 3 of 3 Conclusions Upon visual examinatian of the cracked stems, the NRC inspectors found a crack running the c , ire length of the stem. No bulk elongation was evident. Microscophic analysis of the stem transverse cross section at 50X and 100X revealed a martensitic grain structure with uniform randomly spaced spheriodized manganese sulfide inclusions. There was no apparent evidence that the cracks preferred initiation at the inclusions.
There was nn evidence of stringers or banding. Evaluation of the microstructure revealed that the heat treatment appeared to be adequate.
The cracks were viewed at 100X and generally appeared to be straight with little or no branching. The space between crack faces appeared very tight at the outside diameter and progressively wider at the inside diameter. Therefore, it appears that the crack initiation occurred internally.
From the given information, and assuming the heat treatment was carried out as certified, it appears that internal inherent flaws combined with severe internal residual stresses caused the cracks to initiate at the flaws and propagate. The source of these residual stresses may be from cold working such as thread machining (or excessive thread machining) and hydrotesting. As a' result of the crack appearance and the normal microstructure for this material and heat treatment, the failure appeared not to be a result of material selection or heat treatment. These conclusions are consistent with Yarway's determination of the problem.
E. Persons Contacted Roy G. Chew - Manager of Quality Assurance, Yarway Corp.
Frank Peszka - Manager of Quality Systems, Yarway Corp.
William F. Toter - Welding Engineer, Yarway Corp.
George Papson - Product Manager, Yarway Corp.
Jin Wiggin - Region I, US NRC Hal.Gregg - Region I, US NRC Ed Daily - Phone Contact-Al Tech Speciality Steel Corp.
F. Exit Interview At the conclusion of the inspection, the inspectors met with the persons identified in Section E (with the exception of Mr. E. Daily) and discussed the scope and findings of the inspection.
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