ML20037B237
| ML20037B237 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 05/01/1973 |
| From: | Brian Lee COMMONWEALTH EDISON CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20037B236 | List: |
| References | |
| NUDOCS 8009080631 | |
| Download: ML20037B237 (3) | |
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..IQ A :.. I V. l l CNC FIMST NATIONAL PLAZA CNICAGO.
ILLINOIS Mdress f es'y fa POST OF7 ACE SOX 747
- CHICACO. ItLINOl5 40690 May 1, 1973 I
Mr. Boyce H.
Grier Regional Director Directorate of Regulatory-Operations - Region III U.S. AtomOic Energy Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Grier:
Your letter of June 29, 1972 requested verification that valves important to safety installed or to be installed at our Zion, Quad-Cities and Dresden facilities meet minimum wall thick-ness requirements specified by applicable codes, standards and procurement specifications.
We responded on August 14, 1972.
On September 13, 1972, you requested.more information.
Following an industry meeting in Washington at which the subject was briefly discussed, we submitted a program for our Zion Station on Decenber 22, 1972.
This program was subsequently accepted by a letter of acknowledgement from your office.
This letter constitutes our response on our five operating units.at Dresden and Quad-Cities.
In our letter of August 14, 1972, we described a program based on ultrasonic measurement of a sample of the valves important to nuclear safety in our Quad-Cities Unit 2.
We believe this program gives reasonable assurance that required valve wall thicknesses have been maintained for such valves in both the Quad-Cities units and in Dresden Station Units 2 and 3.
We chose this program because we believe the benefits gained by field measurement of all valves in an operating plant were outweighed by the costs of obtaining this additional data.
We estimate at least 50 man-rem e::posure will be received by the people involved in obtaining data, on the average, for each of'the four 0009080 h }j
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bommonwealth Edison Company Er..Boyce'E.-Grier. -
May 1, 1973L
. units-involved.
We believe this exposure is inconsistent with i
rhe: policy'of keeping exposures as low as practicable.
Ue now~ propose'to undertake ultrasonic naasurement-of an expanded sample of valves.
We have determined that Dresden Units 2 and 3 each have 61 valves which meat the i
definition of "important. to nuclear - safety" laid down in your June 29, 1972 letter, i.e. valves within the reactor coolant pressure boundary.
Each unit at Quad-Cities has 58 such valves.
These 238 valves may be partitioned into 28 subsets, with all members of each subset identical-in terms of nominal size, pressure rating, base material, valve type and manufacturer.
We'willtndertake to test one valve from-each of these subsets, by an ultrasonic measurement method substantially the same as those used at Zion Station.
We would except from this program of additional measurement any subsets included in our previous program on Quad-Cities 2, in view of the fact that the original tests showed these valves to be
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acceptable.
It is our intent to minimize the radiation dose incurred by choosing the valve to be tested from among the four operating units based on accessibility and radiation level.
The work will be done during regularly scheduled outages,-and will be completed by June 29, 1975.
If deficiencies (in the sense of your June 29, 1972, letter) are found, we will undertake to measure all the remaining valves in the subset in which the deficiency is found.
The need for corrective action will be based on evaluation of each deficiency found.
Such a program for Dresden Unit 1 seems. unwarranted for.several reasons.
Fifteen years ago when the Unit 1 valves were designed and purchased, wall thicknesses were heavier than required by present codes and standards.
The radiation burden involved in doing the tests on this unit is estimated to be at least several times that for any one of our other four operating BWR units.
Using available data, we estimate the radiation dose involved in testing 27 of the 116 valves involved to be 143 man-rem of exposure.
In view of the above facts, we believe the costs far-outweigh.any benefit and see no reason for under-taking a program of valve wall measurement on Dresden Unit 1.
. Commonwealth Edison CompanyL Mr. Boyce H. Crier 3'-
May 1, 1973 This unit has operated for over 12 years without a valve vall failure.
It has withstood the initial start-up hydrostatic tests plus an operating pressure test (1000 psig) after each refueling outage.
In addition, six hydrostatic tests have been performed since 1967 at prbssures between 1175 and 1250.
psig at temperatures between 225 cnd 250 F.
The last of I
these tests was ccnducted on January 28, 1972.
All replacement valves for Unit 1 which are important to nuclear safety ill have adequate documentation on minimum wall thickness.
.u We hope this program will satisfy the Commission'c concerns, and we will be happy to discuss it with your representatives.
Very truly yours,
. 3-Dupan 04-i Byron Lee, Jr.
J Assistant to the President 6
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