ML19257B950
| ML19257B950 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/10/1979 |
| From: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 8001210310 | |
| Download: ML19257B950 (3) | |
Text
9 bec to DAC:ADM:
y CENTPAL FILES
- ng-Nebraska Public Power District
' ' fel'e'd STATE December 10, 1979 Mr. Karl V. Seyfrit, Director U.S. Nuclear Regulatory Cc= mission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011
Subject:
IE Sulletin No. 79-02 (Revision No. 2)
" Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts" Refe rence:
- 1) Letter from J. M. F11 ant to K. V. Seyfric Dated July 6, 1979, " Response to IE Bulletin No. 79-02 Revision No. 1"
Dear Mr. Seyfrit:
This letter is written in response to the subject bulletin and our commitment in Reference 1 to provide a su= mary program report.
Resoonse to Action Item 5 A review of the extent to which expansion anchor bol:s were used in concrete block (masonry) walls to attach piping suppor:s in Seismic Category I systems, as defined under the Cooper Nuclear Station FSAR, has resulted in our determination that there are no systa=s falling into this category at Cooper Nuclear Station.
Therefore, we wish to advise that with respect to the Seismic Category I Piping Systems at Cooper Nuclear Sta:1on this concern poses no risk to the health and safety of the public.
Resconse to Action Item 6 All supports, whether they consisted of base plates or strue: ural shapes for Seismic Category I Piping Systems utili:ing expansion anchor bolts, were included in our initial reviews and responses :o the subject bulletin.
Final evaluations and =odifications necessitated by the subject bulletin are presently underway, and all results will be incorporated within our final report upon completion of :he field modification efforts.
[f'( }/8 Resconse to Action Item 7 Under the present work effort, our architect-engineer has completed the analysis of all Seismic Category I piping wherein the modified factors 8001210j5/O($(
'e Karl V. Seyfrit December 10, 1979 Page 2 of safety taking plate flexibility into account were determined.
Those supports found to have a factor of safety inconsistent with the subject bulletin have been or are presently being field modified to assure their meeting the requirements of the bulletin.
The criteria followed to meet the bulletin was on the basis of the oper-ating basis earthquake which was the original criteria used in the design of Class 1S pipe hangers and supports.
Under this criteria a minimum factor of safety of five (5) is assured under the operating basis earth-quake plus other operating loads that form the design criteria (i.e. dead-weight,
- 5ermal, etc. ).
This approach is considered sufficient since very high fac;.rs of safety are normally used to account for uncertainities in design and installation, and these uncertainities have now been eliminated with our detailed computer analysis and our very detailed torque testing and inspection of Class 1S anchor bolts.
To date the following has been performed in response to the subject bulletin:
1.
Analytical work has been completed and recommended fixes for hangers with factors of safety less than five have been proposed.
(This amounted to approximately 115 of the 1530 hangers reviewed which fell into the subject bulletin category.)
2.
Approximately 50% of those hangers identified in Item #1 have now been modified.
The remainder are expected to be completed prior to March 1,1980.
3.
All Class 1S hangers supporting lines 2b" and larger in diameter were torque tested with very satisfactory results (less than.4%
defective in approximately 5600 anchor bolts tested).
All bolts reported as unacceptable have been immediately replaced with properly torqued wedge anchors.
4.
All Class IS hangers and supports supporting lines 2b" and larger and supported by walls or ceilings are currently being further inspected for additional assurance of parameters added in Revision 1 of the subject bulletin.
Further inspection involves removal of each anchor bolt and a check for:
embedment depth, thread engage-ment, plate hole size, bolt spacing, edge of concrete member, and full expansion of the concrete anchor. This inspection is approx-imately 65% complete and is being done in conjuncticn with the modifications noted in Item 2.
Anticipated completion is prior to March 1, 1980.
Our architect-engineer is currently reviewing the systems for 2" and under piping. A torque verification program of these supports will be performed after completion of all work on the large li as.
As discussed in Item 7 of the bulletin, we have completed the anchor bolt testing in inaccessible areas and are continuing testing in accessible 1774 279
Karl V. Seyfrit December 10, 1979 Page 3 areas as rapidly as possible. The following is a summary description of work remaining to achieve compliance with the subject bulletin:
1.
Modification prior to March 1, 1980 of all the supports noted as having a reported factor of safety less than 5.
2.
Completion prior to March 1, 1980 of the detailed inspections.
All of these supports have already been torque tested.
3.
Torque inspection of the small hangers and supports after com-pletion of all work on the 2b" and larger lines.
If you have any questions regarding these responses, please contact me.
Very truly yours, M
Pilant
~
Director of Licensing and Quality Assurance JDW/c~A cc:
U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, DC 20555 1774 280