ML20052B705
| ML20052B705 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/26/1982 |
| From: | Palladino N NRC COMMISSION (OCM) |
| To: | Scott S CALIFORNIA, STATE OF |
| Shared Package | |
| ML16340C523 | List: |
| References | |
| NUDOCS 8205030477 | |
| Download: ML20052B705 (3) | |
Text
'/
UNITED STATES o,,
[I' )*(
NUCLEAR REGULATORY COMMISSION g
g
- , g WASHINGTON, D. C. 20566
%[@Tl April 26, 1982
- -Q
' "7 CHAIRMAN Y
l l
Mr. Stanley Scott, Chairman California Seismic Safety Commission 1900 K Street, Suite 100
'[Z'-] g, g Sacramento, California 95814
Dear Mr. Scott:
D-333 This is in response to former Chairman Mader's October 28, 1981 letter and your followup letter of December 11, 1981 which expressed concern about the implications of the recent seismic design errors detected at the Diablo Canyon nuclear plant.
We share your concern and we assure you that the implications of these errors are under review by the NRC staff.
The timing of the detection of these errors, so soon after authoriza-tion for. low-power operation, was indeed unfortunate and it is quite understandable that the Congress', the State's and the public's percep-tion of our licensing process has been adversely affected.
Had this infonnation been known t'o us on or prior to September 22, 1981, the facility license would not have been issued until the questions raised by these disclosures had been resolved.
I trust that the information enclosed is responsive to your questions.
Sincerely, Od Nu adino
Enclosure:
a Responses to Specific Questions s
- co' e
i 1 add 2
~~
e
,932 s -e l
g "EShnt?;*'
g6 t
s 1
A o
D 1gl 820 sos o V7 7
- :.. a r.: 1 RESPONSES TO SpECXFfC OUESTIONS Ouestion 1:
Do you believe the process of independent review set up for Diablo Canyon was truly independent as delineated by Seismic Safety Comission policy for independent review?
We have reviewed the Seismic Safety Comission policy which you provided for our information.
Even though PG&E did engage the services of outside con-sultants, we make no claims that the review conducted by PG&E consultants
. was independent as described in the Seismic Safety Comission policy. We believe, however, that the NRC's reviews in the areas of geology, seismicity and seismic design were independent.
As you may be aware, the NRC hired consultants prior to issuance of a con-struction permit to evaluate, among other things, the acceptability of b-th the geological and seismological features of the site proposed for the c n-struction of Diablo Canyon, Units 1 & 2.
It is our view that the work per-formed by the NRC's geologic consultant, U.S. Geological Survey, constitutes s
an independent review.
Site inspections were made by the Survey to evaluate the extensive trenching down to bedrock and our consultants concluded that the geology of the site presented no unusual engineering problems for the construction of a nuclear power plant.
During the same time period, similar independent reviews were performed in the seismic area by the NRC's con-sultant, the U.S. Coast and Geodetic Survey. From the studies, the NRC staff concluded that PG&E's predicted maximum ground acceleration was acceptable.
In addition to the independent reviews of the geological and seismological aspects of the Diablo Canyon site, the NRC review also included an independent review of the seismic design by Dr. N. Newmark of the University of Illinois-Once the Hosgri Fault was identified, comprehensive reanalyses were conducted by both PG&E and its consultants and the NRC and its consultants.
Extensive public hearings were held before the Atomic Safety and Licensing Board (ASLB) over about a two month period (from December 1978 to early 1979). Moreover, additional public hearings were held before the Atomic Safety and Licensing Appeal Board (ASLAB) to obtain testimony related to a major earthquake which occurred in California's Imperial Valley in October 1979.
On June 16, 1981 the ASLAB issued a favorable finding on the seismic issue.
In sumary, based on the extensive review and the use of external consultants by the NRC staff, it.is our view that the review conducted is consistent with the provisions of the California Seismic Safety Comission policy.
It is to be noted that the nature of the NRC's review, while being independent, is still an audit type and would not necessarily extend into the level of detail to uncover the
.recent error in the use of incorrect diagrams for Unit 1.
l
' Question 2:
Since errors apparently arose, where in the process do you believe the weaknesses existed which allowed for such errors?
We believe the cause of these errors is directif attributable to the lack of formal effective design quality assurance procedures within the PG&E organization, especially in areas dealing with service related contracts, such as URS/Blume Associates, prior to the 1978 time-frame.
For example, a diagram incorrectly showing the location of certain frames of the vertical mathematical model used for the annulus area of the Unit I con-tainment was provided to URS/Blume Associates without receiving the required technical review of the development, use and transmittal of such information.
As a result of this error, incorrect vertical response spectra were developed and used in the design of restraints for certain equipment and in the analysis of certain piping systems.
By Comission Order dated November 19, 1981 we are requiring an independent review of all pre-June,1978 seismic-related service contracts.
In addition, the NRC staff is also requiring an independent review of all pre-June 1978 non-seismic service related contracts, PG&E internal design activities and all service-related contracts post-January 1,1978. Moreover, the Commission's Order requires PG&E to provide the following information:
1.
A technical report that fully assesses the basic cause of all design errors identified by this program, the significance of the errors found and their impact on facility design.
2.
PG&E's conclusions of the effectiveness of the design verification program in assuring the adequacy of facility design.
3.
A schedule for completing any modifications to the facility that are required as a result of the design verification program.
4.
A description and discussion of the corporate qualifications of the company or companies that PG&E would propose to carry out the independent design verification program, including information that demonstrates the independence of these companies.
5.
A detailed program plan for conducting the design verification program.
As you know, the Comission recently approved PG&E's selection of Teledyne Engineering Services as the independent au' itor.
d Question 3:
What, if any, steps have you taken thus far to correct the problems in your review process which would be applied to other facilities?
The Commission is developing an action plan that will result in improved NRC review of quality assurance programs at operating nuclear power plants and nuclear power plants under construction.
The details of the acti.on plan will be made available to the public upon its completion.
1