ML20079K937
| ML20079K937 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/30/1991 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-88-021, TXX-91285, NUDOCS 9111050245 | |
| Download: ML20079K937 (2) | |
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Log # TXX-91285 File # 10110 (CP-88-21)
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903.9 71/EU!C7R/C Ref.#10CFR50.55(e) j OLober 30, 1991 wmiam J. c.hm, Jr.
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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
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SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 2 DOCKET NO.60-446 INSTRUMENT TUBING CLAMPS SOAR:
CP-88-021 (SUPPLEMENTAL REPORT) l i
REF:
- 1) TV Electric letter logged TXX-88140 from W. G. Counsil to NRC dated January 29, 1988
On January 21, 1988, 10 Electric orally notified the NRC of a deficiency In"olving the use of J. C. White single bolt instrument tube clamps (model NC-
< 05/500-3D) as 3 directional restraints. Reference 1 described the two 9;'lcations for the single bolt tube clamps as those attached to concrete i
w4 1 zing a Hilti Kwik Bolt (HKB) and those attached to Unistrut channels, ni erence 2 indicated that the Unit 2 corrective action would be completed t.ior to 'asel load.
This letter addresses the Unit 2 corrective and preventi,e actions for this deficiency.
DESCRIPTION The vendor-recommended torque value for J. C. White tube claap NC-2-375/500-30 mounted with ASTH-A307 bolts is 32-34 inch-lbs.
For attachments to concrete, an installation torque of 8 foot-lbs is required for a 1/4 inch diameter HKB to properly set the wedge in the concrete. When attached to a Unistrut channel, an installation torque of 6-7 foot-lbs is required for a 1/4 incn diameter bolt to set the spring nut.
Using con:ervative statically determinate methods, the calculated clamp stresses resulting from these torque values are in excess of 43 ksi which exceeds the allowable stress of 22,5 ksi for the tube clamp material at 100 degrees F.
These deficiencies were caused by the failure to recognize the individual torque requirements of the various components that comprise the restraint assembly.
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TXX-91285 Page 2 of 2 s
CORRECTIVLjND PREVENTIVE ACTIONS for Unit 1, a new three-bolt clamp was designed which met all installation requiraments.
Installation specifications and drawings were revised to clearly indicate the applicable tube clamps and corresponding torque values required for each application.
The tube clamps requiring replactment were identified and corrected during the Post Cinstruction Hardware Validation Program.
Consistent with thu Unit 1 program, the new three bolt clamp is being used in Unit 2 as a three directional restraint.
The installation drawing permits the three bolt clamp to be installed on structural steel members, Unistrut channels, or on concrete surfSces using HKBs.
For the single bolt clamp designs using Unistrut channels, additional test data obtained in late 1989 showed that tube clamp NC-2-375/500-30 can withstand a bolt torque of 7 foot-lbs with no material yielding. Accordingly, Unit 2 Engineering revised installation drawings to allow the use of this clamp on Unistrut channels for 3 dimensional restraint applications.
Unit 2 safety-related instrument tubing is being redesigned, replaced or verified to comply with the revised design drawings.
The validated design drawings, installation d'awings, and installation specifications serve as the basis for rework and O'ality Control inspection.
Unacceptable c, lamps will be replaced with suitabis tubing clamps and inspected by Quality Control. These actions will be completed prior to Unit 2 fuel load.
Sincerely,
/
at. w l. a h.'/
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// 6 William J. Cahill Jr.
CBC/rjb cc: Mr R. D. Martin Resident Inspectors, CPSES (2)-
Mr H. B. Fields. HRR 3
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