ML17199U407
| ML17199U407 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, 05000000 |
| Issue date: | 02/24/1988 |
| From: | Johnson I COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| 4263K, NUDOCS 8803020160 | |
| Download: ML17199U407 (4) | |
Text
Common.,th Edison One First Nati-Plaza, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, lllinois*60690 - 0767 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 February 24, 1988
Subject:
Dresden Station Units 2 and 3 Quad Ci 1ties Stat~on Units 1. and 2.~
-"Embedment Plat~s 'Assessment Program" -
NRC Docket 50-237/249 and 50-254/265
Dear Mr. Murley:
During a November 23, 1987 conference call with members of your staff and NRC Region III, four questions were raised regarding the Executive Summary Report for our Embedment Plate Assessment Program.
The response to these questions can be found as an Attachment to this letter.
Please direct any questions regarding this transmittal to this
- office.
Very truly yours, Nuclear lm Attachment cc:
T. Ross - NRR
-M. Grotenhuis - NRR
~!<,
A. B. Davis RIII 4263K
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(r 4263K
-*.::.=- - - ---
ATTACHMENT 1 COMMONWEALTH EDISON'S RESPONSE TO EMBEDMENT PLATE ASSESSMENT PROGRAM
ATTACHMENT 1 Question 1: Why are 24" strap anchor spacing allowable loads greater than 18" spacing allowable loads?
Answer 1:
Some allowable loads for 24" spacing are larger than those for 18" spacing~ The acceptance criteria for computing the allowable loads for both spacings is the same and was described in the May 13, 1987 letter.
The 24" spacing allowable loads are larger since the computation utilized the full strain limits of 2, 4, and 10 times the yield strain value where as the 18" spacing allowable load computation did not.
- Therefore, the*" 24" -spacing,allowable. loads are higher in some cases.
Question 2: How were the allowable loads for 24" spacing calculated?
Answer.2:
As mentioned above, the acceptance criteria for computing allowable loads for both the 18" and 24" spacing is the same as that described in the May 13, 1987 letter.
Question 3: Concerning the statement "These 23 plates were assessed using appropriate allowable loads and determined Answer 3:
to be adequate" (found on second to last page of December 12, 1987 letter).
A. Were the plates determined to be adequate based on calculations or engineering judgement?
B. What were the allowable loads and what was the basis for these allowable loads?
A. The plates were determined to be adequate based on calculations.
B. For the plates with 18" spacing, allowable loads cdmputed for 18" spacing were utilized.
Similarily, for the plates with 24" spacing, allowable loads computed for 24" spacing were utilized.
Where needed, the embedment plates were assessed for
. specific a~tachments by running ~he APLAN program since these 23 plates were ultrasonically tested for strap anchor locations.
An example of such APLAN program analysis was provided in a May transmittal to the NRC.
Question 4: Have all the accessible embedment plates been examined to locate any with 24" spacing.
Answer 4:
As described in the December 12, 1987 letter, from the 296 plates ultrasonically tested at Dresden and Quad Cities.during the course of the program, only 12 plates were found to have 24" spacing.
These 12 plates were all located at elevation 517'-6" in the Dresden Unit 2 Reactor Building.
Based on a review of the shop drawings, these 12 plates were found to be part of 83 mark "A" plates for this el-evation.
Based on the UT results, the occurrence of 24" spacing plates was shown to be limited to these mark "A" plates.
A total of 11 other mark
-~A" plates were-tested during the course ~f the program and were found to have 18" spacing.
It was conserva-tively assumed that the remaining 60 mark "A" plates (83 minus 12 with 24" spacing minus 11 with 18" spacing) may have either the 18" or 24" spacing.
In lieu of ultrasonically testing these 60 plates for strap anchor spacing, they were assessed for both 18" and 24" spacing and determined to be adequate.
- Thus, ultrasonic testing of these 60 plates was not required and hence was not performed.