ML18116A182
| ML18116A182 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/19/1979 |
| From: | Gossick L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Trible P HOUSE OF REP. |
| Shared Package | |
| ML18116A184 | List: |
| References | |
| NUDOCS 7907230739 | |
| Download: ML18116A182 (6) | |
Text
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i JUN 1 9 1979 The Honorable Paul Trible United States House of Representatives Washington, D. c~
20515
Dear Congressman Trible:
This lettef is-in response to your memo of April 26. 1979 in which you requested a reply to the concerns of one of your.constituents regarcli ng the shutdown of the bto reactor units at the _Surry Power Station, operatec1 by the Vi rgi ni a El ecri c and PovJer Company (VEPCO).
The sequence of events which led to the Nuclear Regulatory Commission's Orders of March 13, 1979 to shut down five nuclear power reactors, incl~ding the t1:10-unit Surry Power Station, was delineated in the Federal Register, a copy of which *;s enclosed.
Our actions were not the res4Ttof*-a-- Senife-
. committee hearing or report.
As indicated in the enclosure, our actions to shut down the reactor were due to the discovery that safety system piping, essential to the safe shutdown of the reactors in the event of an earthquake, had been analyzed using an unacceptable computer technique.
An acceptable full reanalysis of all the affected systems \\'ias not available and a preliminary partial reanalysis indicated that, for at least some systems, calculated pipe stress
, levels would exceed the maximum allowable stress levels under earthquake conditions.
Likewise, the adequacy of the design of various pipe hangers and supports was questioned.
Thus, we determined that protection of public health and safety required that the reactors in que.stion be shut down until t,he results of reana lyses of all affected pipe systems and pipe supports.
were submitted for our review and until any necessary pipe system rnodifi-.
cations were implemented.
- Our order to* shut down the_ Surry Pov,er Stat i_on was not based on a nevv fhidi ng
- of a seismic fault in the Surry area.
In fact, there has been no such, ne~v finding.
Hm<1ever.* one important characteristic of the Surry site is that the facility rests on about 1300 feet of sediments which overlays rock. 'This condition, including the characteristics of overburden damping and ampliff-,l cation of vibrations from bedrock to the surface, was considered in estab-\\ l12.
lishing the seismic design basis for the facilityo However, the.1300 *feet\\ a{J of overburden at the Surry site masks the basement. rock so that faulting
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The Honorable Paul Trible cannot be i dent ifi ed in the area.- This is true for most of the eastern United States. Since th~ tectonic structures which give rise to earth~
quakes cannot be identified and localized, our practice is to assume tha:t
. earthquakes at 1 east as severe as regional hi stori ca 1 earthquakes could occur anyt1here in the region.
In addition, in establishing *the seismic
-- design bases for a nuclear power plant, we take into account the impacts on that plant of more distant earthquakesq For example, the Charleston, South Carolina earthquake of 1886 was felt in the region of the Surry site.
vie are aware of the energy concerns alluded to by your constituent.
Our actions were based~ however, on assuring public health and safety. \\rJhile we continue to meet with VEPCO and Stone and Webster representatives to discuss preliminary results of their reana.fvs~'§,~we are at this time a\\,1aiting submittal of the results and analysis-justification by VEPCO for staff evaluation.
Following the staff evaluation of the VEPCO submittals for each reactor unit, we will be in a position to reconsider whether continued suspension of operations at that unit remains necessary or appro-priate. The staff's recommendation concerning possible resumption of operation will be considered by the Commission before a final decision is made.
Enclosure:
11Federal Register Notice 11 Sincerely, -
{Signed) Lee V. Gossick lee V. Gossick
- Executive Ditedor for Operations DISTRIBTUION *
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Honorable Paul Trible House of Representatives Washing n, D. C.
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This 1 etter is 1 response' to your memo of April 6, 1979 in who:ch you.
requested a reply the c;oncerns of one of you constituents regarding the shutdown of the
- r-10 reactor units at the rri Power Station, operated by the Virginia Electr* and Power Company EPCO).
The sequence of events whi led to the uclear Regulatory Commission's orders of March 13, 1979 to ut down ive nuclear power reactors; including the two-unit Surry Power Stati, is elineated in the enclosure to this letter. Our actions were not th
- r. sult of a Senate committee hearing or report.
As indicated in the enclosure, our act ns to shtit down the reactors were due to the discovery that sa ty system iping, essential to the safe shutdown of the reactors in the event of a earthquake, had*been analyzed using an unacceptable com ter technique.
acceptable full reanalysis of all the a'ffected system was not available an a preliminary partial reanalysis indicated tat, for at least some sy terns, calculated pipe stress levels would exceed* e maximum allowable stress evels under earthquake conditions.
Li k'ew
- e, the adequacy of the design f various pipe hangers and supports was,uestioned. Thus we determined tha protection of public health a a safety required that the reactors i question be shut down until th results of reanalyses of all affected pie systems and pipe supports weYJ submitted for our review and until any nee sary pipe system modificati ns were implemented.
Our or
- r to shut down the Surry Power Station was not based a new finding of a ei smi c fault in the Surry area.
In fact, there has been o such new fi ing.
However, one important characteristic of the Surry sit is that e facility rests on about 1300 feet 9f sediments which overlays ock. This condition, including the characteristics of overburden damping and plifi-cation of vibrations from bedrock to the surface, was considered in establishing the seismic design basis for the facility. However, the 1300 feet of overburden at the Surry site masks the basement rock so that faulting 1
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Honorable Paul Trible cannot be identified in the area. This is true for most of the eastern U_nited States. Since the tectonic structures *which give rise to earth-quakes cannot be identified ahd localized~ our pra ice is to assum~
that earthquakes at *1east as severe as regional 1storical earthquakes could occur anywli re in the region.
In addition, i establishi.ng the_ seismic design bases for a nuclear power plant, we ake into account the impacts on that plant of ore distant earthquakes.
or example, the Charleston, Sout,h*
Carolina earthq. ke of 1886 was felt in he region of the Surry site.
We are aware of the nergy concerns luded to by your constituent. Our actions were based, n 11ever, on as iring public health and safety. While we continue to meet wi VEPCO an Stone and Webster reoresentatives to discuss preliminary resu s of eir reananlyses, we are at this time
- awaiting *submittal of the *. esu s and analysis justification by VEPCO for staff evaluation. Followin e staff evaluation of the VEPCO submittals for each reactor-unit, we will b *jn a position to reconsider whether continued suspension of operations a tha unit remains necessary or appropriate. The staff's recommendation co ernin possible resumption of operation will be considered by the commi s ion be for a f ina 1 dee is ion*. is made.
Enclosure:
11Facts Related o the Shutdown of F"ve Plants 11 Sincerely,
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e The Honorable Paul Trible United States House of Representatives Washington, D. C.
20515
Dear Congressman Trible:
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\\ LRubenstein This letter is in response to your memo of April 26, 1979 in which you requested a reply to the concerns of one of your constituents regarding the shut down of the two reactor units at the Surry Power Sta ti on, op3;_r_9.,,ted by the Virginia Electric and Power ~~any (VEPCO) :,-p;,,,~:J*a ~f:.~~:~~-'J...,,.~~
The sequence of events \\'Jhich led ~~ne Nuclear RCi~mmission 1s orders of March 13, 1979 to shut qown five nuclearp~r reactsrs, including the two-unit Surry Power Station, '.i,?delineated in thel\\enclos~*to tAis-1-~ Our actions were not the result of a Senate committee hearing or report.
As indicated in the enclosure, our actions to shut down the reactors were due to the discovery that safety system piping, essential to the safe shutdown of the reactors in the event of an earthquake, had been analyzed using an unacceptable computer technique.
An acceptable full reanalysis of all the affected systems was not available and a preliminary partial reanalysis indicated that, for at least some systems, calculated pipe stress levels would exceed the maximum allowable stress levels under earthquake conditions.
Likewise, the adequacy of the design of various pipe hangers and supports was questioned.
Thus we determined that protection of public health and safety required that the reactors in question be shut do\\'m until the results of reanalyses of all affected pipe systems and pipe supports
\\'/ere submitted for our review and until any necessary pipe system modifi-cations were implemented.
~
- Our order to shut down the Surry Power Station was not based on a new finding of a seismic fault in the Surry area.
In fact, there has been no such new finding.
However, one important characteristic of the Surry site is that the facility rests on about 1300 feet of sediments which overlays rock.
This
_condition, including the characteristics of overburden damping and amplifi-cation of vibrations from bedrock to the surface, was considered in estab-lishing the seismic design basis for the facility.
However, the 1300 feet of overburden at the Surry site masks the basement rock so that faulting
... *-,~-*.,.
The' Honorable Paul Trible e. cannot be identified in the area. This is true for most of the eastern United States. Since the tectonic structures which give rise to earth-quakes cannot be identified and localized, our practice is to assume that earthquakes at least as severe as regional historical earthquakes could occur anywhere in the region.
In addition, in establishing the seismic design bases for a nuclear power plant, we take into account the impacts on that plant of more distant earthquakes.
For example, the Charleston, South Carolina earthquake of 1886 was felt in the region of the Surry site.
We are aware of the energy concerns alluded to by your constituent.
Our actions were based, however, on assuring public health and safety.
While we continue to meet with VEPCO and Stone and Webster representatives to discuss preliminary results of t,hejr reanalyses, we are at this time a\\vaiting submittal of the results 'and analysis justification by VEPCO for staff evalaution.
Following the staff evaluation of the VEPCO submittals for each reactor unit, we will be in a position to reconsider whether conti.nued suspension of operations at that unit remains necessary or appro-priate.
The sta,ff's recommendation concerning possible resumption of operation wi 11 be considered by the commission before a fi.nal decision is ma.de.
Enc1 osure:
11 Facts Related to the Shutdown of Fi. ye Pl a.nts 11 Sincerely,
- SEE ATTACHED YELLOW COPY FOR CONCURRENCES NRR:PSS*
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