ML20054G408
| ML20054G408 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 06/15/1982 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-82 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8206210528 | |
| Download: ML20054G408 (3) | |
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June 15, 1982 BLED-50-438/82-38 BLRD-50-439/82-34 U.S. Nuclear Regulatory Commission Region II Attn: Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - INSTALLATION OF WRONG VALUED RESISTOR IN MODULES - BLRD-50-438/82-38, BLRD-50-439/82 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. V. Crlenjak on May 18, 1982 in accordance with 10 CFR 50.55(e) as NCR BLN EEB 8204. Enclosed is our final report. We consider 10 CFR Part 21 applicable to this deficiency.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Licensing Enclosure cc:
Mr. Richard C. DeYoung, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 i
8206210528 820615
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An Equal Opportunity Emptoyer b[
ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 INSTALLATION OF WRONG VALUED RESISTOR IN MODULES NCR BLN EEB 8204 BLRD-50-438/82-38, BLRD-50-439/82-34 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency Because of NCRs 1296 and 1309 the vendor, Consolidated Controls Corporation, Bethel, CT (CCC), was reworking the modules within the Solid State Control System (SSCS) located in the Bellefonte Nuclear Plant.
During the process of modifying the field buffer modules (CCC Part No.
6N193), a 3 6 ohm resistor was installed on some ~of the modules instead of the required 5.6 ohm tesisitor.
It was further determined that 108 field buffer modules were shipped in February and 220 in March 1982, for a total or 328 at the job site. Of the 104 field buffer modules modified during the first two weeks of April and still at CCC, 79 had the incorrect resistor. Of the 328 shipped to the site in February and March, approximately 250 modules will require replacement of this resistor.
The modules passed the functional test since the value between 3 and 5 ohms does not affect the functional operation of the circuitry; its purpose is to control current inrush when the board is plugged into a hot (online) ca?inet. One tenth (0.1) ohm protection is required per volt. Field buffer modules require 45V protection which is provided by the 5.6 ohm resistor. All markings on both resistors are identical with a single exception that the 3 6 ohm is marked V3R6 and the 5.6 ohm V5R6. To complicate matters the letter forms are similar, 3 and 5.
Detection of an incorrect resistor by visual inspection when mounted on board, is difficult because:
(1) as stated above, the resistors have practically identical markings and the resistors are the same size and same color; and (2) in bending the leads, the single identifying number is often on the bottom of the resistor and cannot be read. The responsible assembler was identified, and it was determined the problem began at the time of assignment in mid-February 1981. The problem was confined to only the field buffer modules (6N193). These components are not being used on any other TVA plants.
Safety Implications The subject resistors are intended to limit inrush current when the module is inserted into an energized panel. Analysis of the deficiency indicates that the modules' ability to perform their intended function would not be impaired by the lowered resistance value. However, when the modules containing the incorrect resistor were received at BLN and inserted into l
energized panela, one module experienced a loss-of-function failure. Since this failure has not been determined to be a random failure, TVA conservatively assumes that the cited deficiency was a contributing factor to the failure. Consequently, the deficiency cited could adversely affect the ability of the Solid State Control System to perform its intended safety function and thus adversely affect the safety of operations of the plant.
i E
O Pagb 2' Corrective Actions The 79 field buffer modules at CCC requiring replacement of the 3.6 ohm resistor have been reworked.
~
1.
The 3.6 ohm resistor was removed and replaced with the correct 5.6 ohm resistor.
2.
The resistance was verified electrically.
3 The workmanship was verified visually.
CCC dispatched a three (3) man team to' the site, two field service engineers, and one QA inspector to inspect all m6dified field buffer modules furnished to TVA to date by serial number. Modules requiring the replacement of the resistor were reworked as indicated above. A total of 838 modified field buffer modules have been returned since November 1981 and required inspection. To prevent the possibility of a recurrence, the responsible vendor personnel have been instructed to follow installation procedures more closely; and the inspection checklist will be amended to include visual verification of correct resistor value before and after installation. Selected personnel will be utilized to perform production rework and inspection functions, and rework of all remaining TVA modules (all types) will be performed in a segregated manufacturirg area at CCC.
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