ML20236B737

From kanterella
Jump to navigation Jump to search
Responds to 760317 Note Requesting Views on Concern Expressed by E Jacobson in .Commission Evaluating FSAR for Plant.Plant Designed to Withstand Earthquake of Magnitude 8.5 Along San Andreas fault,48 Miles from Plant
ML20236B737
Person / Time
Site: Diablo Canyon, 05000000
Issue date: 04/16/1976
From: Dircks W
NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
To: Percy C
SENATE
Shared Package
ML20236A877 List: ... further results
References
FOIA-87-214 NUDOCS 8707290217
Download: ML20236B737 (6)
v • d • e


Text

lLL 3d# *%,k UNITED STA1ES

' g.

NUCLEAR REGULATORY COMMISSION y j WASHINGTON, D. C. 20555 April 16, 1976-s,

...../

Docket No.: 50-275 i

Honorable Charles H. Percy United States Senate

Dear Senator Percy:

This is in response to your note of March 17, 1976, requesting our views on a concern expressed by Mr. Eric Jacobson in his letter to you  ;

dated March 7, 1976. The Diablo Canyon Nuclear Power P3 ant is located on the coast about 12 miles from San Luis Obispo, California. Construc-tion is nearly completed for the first of the two units at this site.

The owner, Pacific Gas and Electric, (PC&E) applied for an operating license in 1973. The Commission's staff is currently evaluating the Final Safety Analysis Report for the plant. This evaluation is now nearing completion but has been delayed by considerations associated with the offshore Hosgri fault first reported '.r 1971.

Construction permits were first issued in 1968. Based on the investi-gations conducted at that time, the plant was designed to withstand the following earthquakes:

(1) A great earthquake of magnitude 8.5 along the San Andreas fault 48 miles from the plant.

(2) A major earthquake of magnitude 7.25 along the Nacimiento fault 20 miles from the plant.

(3) A major earthquake of magnitude 7.5 along the offshore extension of the Santa Ynez fault 50 miles from the plant.

(4) An aftershock of magnitude 6.75 not associated with a known fault six miles from the plant.

After the construction permits were issued, offshore seismic oil explor-ation conducted by.Shell 011 Company showed-the existence of a fault which had been previously unmapped. This is the Hosgri fault which runs offshore from the vicinity of Point Sal on the south to Point San Simeon on the north and passes within about 3 1/2 miles of-the Diablo Canyon Nuclear Power Plant at its closest approach.

s 8707290217 870721 i

-PDR FDIA PDR CONNDR87-214 ,

t. I
p. . % %.
  • Docket No.: 50-275 4

l I

Hono ble Charles H. Percy j United tates Senate

Dear Senato Percy:

The Diablo Cany Nuclear Power Plant is located on the coast about

12 miles from San uis Obispo, California. Construction is nearly I completed for the f e of the two units at this site. The owner,
Pacific Gas and Electr , applied for an operating license in 1973.

The Commission's staff i currently evaluating the operating license application. This evaluat is now nearing completion and has been delayed nearly two years by c siderations associated with the Hosgri fault, first reported offshore om the plant in 1971.

Construction permits were first iss d in 1968. Based on the investi-gations conducted at that time, the p nt was designed to withstand the following earthquakes:

(1) A great ea'thquake of magnitude 8.5 al g the San Andreas fault 48 miles from the plant.

(2) A major earthquake of magnitude 7.25 along e Nacimiento fault 20 miles from the plant.

l (3) A major earthquake of magnitude 7.5 along the off ' ore extension of the Santa Ynez fault 50 miles from the plant.

(4) An af tershock of magnitude 6.75 not associated with a own

\

fault six miles from the plant. -

)

After the construction permits were issued, offshore seismic oil e lor-ation conducted by Shell Oil Company showed the existance of a faul 1 which had been previously unmapped. This is the Hosgri fault which  !

runs offshore from the vicinity of Point Sal on the south to Point Sa j Simeon on the north and passes within about 3 1/2 miles of the Diablo l l Canyon Nuclear Power Plant at its closest approach. l

! l i i s

I 1

I

.j

e a ,.

Honorable Charles H. Percy 2 The Pacific Cas and Electric Company was asked to provide additional data concerning the offshore fault zone. Seismic surveys performed by PG&E and our advisor, the U. S. Geological Survey (USGS) indicated a discontintnus fracture zone near the surface which could be caused by

! a continuous fault at depth. The surveys indicated the center of the main fault zone to be 3 1/2 miles offshore from the plant with a smaller splinter fault within 2 1/2 miles.

Such a fault could produce higher levels of shaking than were considered in design of the plant. The Applicant and his consultants, ou' staff, the USGS, and our structural engineering consultant, Dr. Nathan Newmark of the University of Illinois, are considering potential ground motion at the site from an earthquake on the Hoegri fault and the capability of the plant to withstand such ground motion.

Nuclear power plants are designed to withstand the pressures and tem-peratures which would be generated by a large break in the primary cooling system. Because these design loads frequently far exceed the seismic loads, the seismic design generally contains a large margin of safety. These safety margins are now being assessed. If analysis of

) plant design indicates that an earthquake that is possible on the Hoegri fault could cause damage, the NRC will require PG6E to redesign and modify the plant to withstand the shaking.

I trust that the above information is sufficient for your responsa to l Mr. Jacobson. Please let me know if I can be of further assistance on j this matter. '

Sincerely,

Enclosure:

QSjuQ WAm J. Cads I Note transmitting ltr fron Willian L Direb DIST: Mr. Jacobson dtd 3fi//76 Assistant Exum n Director for Operations DOCKET FILES 50-275 RHeineman WRegan NRR Reading VStello GKnighton GSB Reading HDenton BYoungblood DBE Reading WGammill I&E (4)

EDO Reading RBofmann GErtter d ov/o/)

NRC-PDR JStepp l LOCAL-PDR CA (3)

BRusche MGroff (00101) ELD ECase JMiller ELD MJambor jn

4. 4/T .d/76 Nb RBoyd ,

DMuller I%n ,

' CA orrics

  • g.;1TjGAB,. DS : .. D S., /_ DO g,_,,,,. _ _

I

> ,,,,,,, plofmann/rw .g y....._.

DM r E e gg. .. HD n' -B 1e- A m,M.LZ/hp 6 _41[./.7 6., ,4] 4 /76 4/, _ 76 j ,

4/)N/76 -- 4/tf/76 0318 (Re.453) AECM 0240 W u. s. oovsnmusNT PRINTING OrF4CE61974 526186

j*** "ag UNITED ! - TES

., ,, f ,m 2 NUCLEAR REGULATORY COMMISSION 5,  ; /, W ASHINGTON, D. C. 20655

          • April 9, 1976 j L. V. Gossick, Executive Director of Operations The attached mamo was held an extra day by <

OELD thereby making it late for distribution.

M H. R. Denton, Director Division of Site Safety. s and Environmental Analysis Office of Nuclear Reactor Regulation l

t i

[

L

)\t .

.m o .,

.. K j w h. - e

[lfDtj

._. /'r

d' March 17, 1976

?Cnifeb Sfnics Sennie Mr. Eric Jacobson 3620 North Fre:nont Chicago, Illinois 60613 Respectfully referred to:

Nuclear Regulator / Comnission (please see last paragraph of letter)

Please reply to the attention of H. Wells.

Because of the desire of this office to be responsive to all inquiries and communications, ,

your consideration of the attached is requested. Your findings and views, in .

duplicate form, along with return of the enclosure, will be appreciated by gg*f, 0\\. 5T '

_ .r,lp s,,, . , ,P,9,r,ey, , , , , , , ,

Form #2 I'-

e ks 9

~:

L I

>aa

.c 7 74 A

" g as_%uw

- u e b

~

q L p k<gdL ds+g e M "-&Q k facauhlg L k fr  ;

e< 4 uA ,All 4e a n 7 .A ' '

% .6 n ud& w~ 6 a t us= A A.

i E

I

$OO~

~~ bS S'5I *L4Q W K f.hcrillk h

&Ts v ^A&

c-9 n v ed~

puu{ g a -( ashka -h-fta.!d E;

$th Ar m' ud & wee cat .

~M us zer- negge_ vo,< ue 1 ia[n ad r.ut..

ic S w k o'is O b iP o Et bhb 9veluu;a. Powev Red

--- vss imMWm% %zu c ov u+3 - c m as a h i

as .- ~ '

i

  • ognk. TA a mA u . .

3ee x+ x t

" ' * * * * = ~ T t \. a e, g , _

c_-_____- _ - . _ _ _ - _ _ _ _ - _ _ _ - _ - - _ . _ _ _ _ _ _ _ _ - _ _ - _

Retrieved from "https://kanterella.com/w/index.php?title=ML20236B737&oldid=3448287"