TXX-6735, Interim Deficiency Rept CP-87-68 Re Concrete Expansion Anchors Supplied by Hilti.Initially Reported on 870824.Spec Will Be Revised to Prohibit Further Use of Hilti Bolts.Next Rept Will Be Submitted by 871118
| ML20235S975 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/02/1987 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-68, TXX-6735, NUDOCS 8710090210 | |
| Download: ML20235S975 (2) | |
Text
l i
F Log # TXX-6735 File # 10110
__=
903.8' Ref # 10CFR50.55(e)
M# ELECTRIC wmiain c. counsa October 2, 1987 lims,iw he Pnnident U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 l
HILTI BOLT INADEQUACIES SDAR:
CP-87-68 (INTERIM REPORT) i Gentlemen:
OnAugust 24, 1987, we verbally notified your Mr. H. S. Phillips of several deficiencies involving concrete expansion anchors supplied by Hilti.
The specific issues include bottomed-out nuts and unacceptable torque for bolts in general, improper application for bolts installed on rotating equipment, and l
lack of installation documentation for bolts that are inaccessible due to grout.
These deficiencies were discovered during third-party investigations -
and are addressed in Corrective Action Request CAR 87-052.
A written report was due on September 23, 1987. On September 23, 1987, we verbally requested and received an extension from your Mr. R. F. Warnick until October 2, 1987.
This is an interim report of a potentially reportable item under the provisions of 10CFR50.55(e).
Hilti bolts used to install rotating equipment have been found with bottomed-out nuts.
Hilti bolts are designed to be installed such that the threads on the bolt shank extend below the concrete surface.
As the nut is tightened, expansion wedges below the concrete surface exert pressure on the walls of the hole in the concrete.
A bottomed-out nut could occur if an unthreaded portion of the bolt shank extends above the concrete surface creating a potential for the nut to be tightened against the unthreaded portion of the bolt shank.
This condition could lead to incorrect torque being applied to the bolt.
A preliminary analysis has also concluded that Hilti bolts may be unsuitable for rotating equipment installations.
In order to assess the significance of this deficiency, all rotating equipment anchored with Hilti bolts will be analyzed considering the vibration frequency of each piece of equipment. The j
results of this analysis will determine the acceptability or requirement to replace the anchor.
Design Basis Document CS-015 will be revised to provide engineering criteria necessary for this evaluation.
Specification 2323-MS-101, " Mechanical Erection Specification," will be revised to prohibit further use of Hilti bolts in this application.
F 8710090210 871002
- q DR ADOCK 0500 5
t 4W North Olive Street LR 81 Dallas, Texas 7320I
,6 TXX-6735 October 2,1987 Page 2 of.2-For Hilti bolt torque and bottomed-out nuts, Specification 2323-SS-30 was revised to include torque verification and inspection frequency requirements.
-Torquing requirements _will be. field validated in accordance with EC 9.04,.
" Post Construction Hardware Validation Program" using revised requirements noted per Specification 2323-SS-30 " Structural Embedments." The significance of these conditions will be determined upon evaluation of the verification results.
For inaccessible Hilti bolts for which no installation documents are available, we have determined that the inspection requirements at the time of installation, according to QI-QP-11.3-13, required torque' inspection of a.
minimum of ten bolts per shift and only unsatisfactory inspections be documented.
Therefore, no deficiency is associated with this item.
t We are continuing our evaluation.
Our next report on this issue will be submitted no later than Hovember 18, 1987.
Very truly yours, fM3v W. G. Counsil
~l CBC/gj c - Mr. R. D.
Martin, Region IV 1
Resident Inspectors, CPSES (3)
{
l i
l
.