ML20052H505
| ML20052H505 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/11/1982 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Alicia Dixon SENATE |
| Shared Package | |
| ML20052H506 | List: |
| References | |
| NUDOCS 8205210150 | |
| Download: ML20052H505 (14) | |
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Dear Senator Dixon:
This is in response to Mr. Buchner's letter to you dated February 12, 1982, in which he expressed concern regarding the possibility of a steam generator tube rupture at the Zion Station near Chicago similar to that which occurred at the Ginna iluclear Power Plant in New York.
In addition, he commented on the high population density around the Zion Station and evacuation in the event of an accident.
Experience has shown that ste n generator tube leakage between the primary (tube)sideandthesecondary(shell)sideoccurringduringoperation is usually very small and can only be accurately measured by radiological techniques. Very small leak rates do not constitute a safety problem and the periodic inspection programs of the tubes themselves are used to confirm tube structural integrity.
During the past several years, the Zion Station has experienced some tube degradation. This degradation has resulted la tube leaks which were detected during operation by radiological techniques.
In recognition of the potential for the tube leaks, the Zion Station operating license contains provisions which limit the amount of leakage and radioactivity in the reactor coolant and process steam.
If the plant exceeds these limits, the condition must be corrected within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or the plant shutdown for repairs. These operational limits assure that no signifi-cant radiological releases or hazards to the public will occur should a steam generator tube rupture and result in release of steam to the atmosphere. The tube degradation at Zion has also been detected in the steam generator tube inspection program. This inspection program also required by the operating license is performed during each refueling outage. Those tubes found to be leaking or degraded beyond acceptable j
inspection limits are removed from service.
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e The Honorable Alan J. Dixon g ;, g While the measures discussed above are intended to make likelihood of a steam generator tube rupture small, that possibility cannot be eliminated totally.
Therefore, we have required, as a design basis for nuclear power plants, that plant design be such that the public is adequately protected against a tube rupture event. The design of the safety and mitigating features of nuclear power plants and the conservative assumptions used in our analyses of a tube-rupture event are such that consequences to the public health and safety would not be significant. The four steam generator tube rupture events in the U.S.
to date have confirmed our licensing assumptions and predictions in that the actual releases, as expected, hcve been very low and have not resulted in any significant offsite doses.
Although I believe that our restrictions and limitations on steam generator operating parameters are such that adequate protection to the health and safety of the public is provided, I want to assure you and Mr. Buchner that significant regulatory and industry effort has been and will continue to be applied to resolve steam generator problems.
Returring to Mr. Buchner's concern as to the feasibility of evacuation around the Zion Station, it should be remembered that evacuation is only one of the various protective action strategies that could be taken in the event of a serious accident.
In fact, for most of the serious low probability events, we envision that sheltering would be the more desirable action from a risk-p benefit viewpoint.
Even for the most serious type release, sheltering followed by a more leisurely relocation may be the optimum choice of pro-tective measures. Here again, as in most disaster situations, the actual measures to be taken at the time of the event will be influenced by the many variables that bear on the decision-making process.
In the case of a nuclear power plant, such factors would include the release characteristics, meteoro-logical conditi.ons, operational time constraints, and the physical protection factors of available shelter facilities.
Sioce the accident at Three Mile Island, the Nuclear Regulatory Commission has amended its regulations to require upgraded emergency preparedness capabilities around power reactor facilities. These new regulations require that emergency plans be extended to an area within a radius of about ten miles. This ten mile radius is referred to as the plume exposure pathway Emergency Planning Zone (EPZ) and applies to potential airborne exposure.
The size of the zone is based on an NRC/ Environmental Protection Agency Task Force conclusion that it would be unlikely that any protective actions would be required beyond the. plume exposure pathway EPZ. The results of the Task Force and review by the FEMA conclude that even most core melt accidents would not require individual protective action outside ten miles and that the ten mile plume exposure planning zone provides a response base for the worst case accidents. More recently, NRC siting policy has also emphasized the requirement of reasonable assurance that adequate protective measures can i
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and will be taken by the licensee and the state and local authorities ir the event of accidents more serious than design-basis accidents. This manifests itself in the utilities preparation of an emergency preparedness plan and the 4
review by the Feoeral Emergency lianagement Agency (FE!!A) for all offsite emergency plan provisions and requirements.
We trust this information will be helpful to you.
Sincerely, 7
(signed) T. A.adas i
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/WilliamJ.Dircks l
T Executive Director l
for Operations
Enclosure:
David E. Buchner letter dated February 12, 1982 l
DISTRIBUTION:
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Local PDR ED0 rdg ORB #1 Rdg 0 ELD OCA (3)
MBridgers (11678)
Program Support Staff, NRR M.*Jambor M. Stine t
D. Eisenhut J. Heltermes D. Wigginton (w/ encl) i C. Parrish R. DeYoung L. Underwood B. Snyder E. Case H. Denton S. Hanauer (Note: Emergency Preparedness words R. Mattson concurred in by F. Pagano.)
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e The Honorable Alan J. Dixon ;
Nevertheless, as you are aware, tube ruptures have occurred at facilities l
other than at Zion. While I believe that because of the measures discussed above, the likelihood of a steam generator tube rupture is small, these,-
3 measures are not expected to eliminate totally the possibility of a tube
'/
l failure.
Because the possibility of a tube rupture does exist, we have required, as i
a design basis for nuclear power plants, that plant design,be such that i
the public is adequately protected against a tube rupture event. The design of the safety and mitigating features of nuclear power, plants and the conservative assumptions used in our analyses of a tube-rupture event cre such that consequences to the public health and safety would not be signif-icant. The four steam generator tube rupture events in the U. S. to date have confimed our licensing assumptions and predictions in that the actual releases, as expected, have been very low and have not resulted in any i
significant offsite doses.
i Although I believe. that our restriction's and limitations on steam generator operating parameters are such that adequate protection to the health and safety of the public is provided,'I want to assure you and Mr. Buchner that significant regulatory and industry effort has been and will continue to be applied to resolve steam generator problems.
l Returning to Mr. Buchner?s concern as to the feesibility of evacuation around i
the Zion Station, it should be remembered that evacuation is only one of the various protective action strategies that could be taken in the event of a serious accident. In fact, for most of the serious low probability events, we envision that, sheltering would be the more desirable action from a risk-benefit viewpoint. Even for the most serious type relea:e, sheltering followed by a more leisurely relocation may be the optimun choice of pm-tactive measures. Here again, as in most disaster situations, the actual measures to be takcn at the time of the event will be influenced by the many i
variables that bear on the decision-making process.
In the case of a nuclear
^
power plant, such factors would include the release characteristics, meteorolog-ical conditions, operational time constraints, and the physical protection factors of available shelter facilities.
/
Since the accident at Three Mile Island, the Nuclear Regulatory Comission
/has amended its regulations to require upgraded emergency preparedness
/ capabilities around power reactor facilities. These new regulations require that emergency plans be extended to an area within a radius of about 10 miles. This 10 mile radius is referred to as the plume exposure pathway Emergency Planning Zone (EPZ) and applies to potential airborne exposure.
i The size of the zone is based on an HRC/ Environmental Protection Agency Task Force conclusion that it would be unlikely that any protective actions would i
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c be required beyond the plume exposure pathway EPZ., The results of the Task Force and review by the FEMA conclude that even most core melt accidents would not require individual protective action outside ten miles and that the ten mile plume exposure planning zone provides a response base for the worst case accident. NRC studies also indicate-that no severe acute effects would be expected outside the 10 mile plume exposure planning zones elen for worst case accidents. More recently. NRC siting policy has also emphasized the requirement of reasonable assurance'that adequate protective measures can and will be taken by the licensee and the state and local authorities in the event of accidents more serious than design-basis accidents. This manifests itself in the utilities preparation of an emergency preparedness plan and the review by the Federal Emergency Management Agency (FEMA) for all o'ffsite emergency plan provisions' and requirements.
We trust this information will be helpful to you.
Sincerely,
/
/
William J. Dircks Executive Director for Operations
Enclosure:
David E. Buchner letter dated February 12. 1982 DISTRIBUTION:
Courtesy Copy E. Case Docket File /
H. Denton NRC PDR S. Hanauer Local PDR R. Mattson ED0 Rdg R. Vollmer ORB #1 Rdg H. Thompson OELD P. Check OCA (3)
R. Starostecki, RI MBridgers (11678)
SECY Program Support Staff, NRR M. Jambor M. Stine D. Eisenhut J. Heltermes DWigginton (w/ encl) p C. Parrish
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i Thlir Honorable Alan J. Dixon UnityStatesSenate Washington, D. C.
20510 i
Dear Se or Dixon:
N This is in response to Mr. Buchner's letter to you dated February 12, 1982, in which he ex'p(essed concern regarding the possibility of a steam generator 2
tube rupture at T.he Zion Station near Chicago similar to what occurred at l
the Ginna Nuclear' Power Plant in New York.
In addition, he consented on f
the high population \\ ensity around the Zion Station and evacuation in the d
event of an accident.
j Experience has shown thatNsteam generator tube leakage between the primary (tube) side and the secondary (shell) side where it occurs during operation, is usually very small and carbonly be accurately measured by radiological techniques. Very small leak rates do not constitute a safety problem and the periodic inspection progtams 'of the tubes themselves are used to confirm tube structural integrity.
l During the past several years, the Zion tation has experienced some tube l
degradation. This degradation has resultedsin tube leaks which were i
detected during operation by the radiologicaTNtechniques.
In recognition of the potential for the tube leaks, the Zion Station operating license contains provisions which limit the amount of lea'kage and radioactivity in the reactor coolant and process stcam.
If the plant exceeds these or the plant is limits, the condition must be corrected within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />'\\that no signifi-shutdown for repairs. These limits on operation assure 4
cant radiological releases or hazards to the public will' occur should a I
steam line and steam generator tube rupture and release steam to the atmosphere. The tube degradation at Zion has also been detected in the i
steam generator tube inspection program. This inspection program also required by the operating license is performed during each refueling outage. Those tubes found to be leaking or degraded beyond accephable l
inspection limits are removed from service.
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The Honorable Alan J. Dixon Nevertheless, as you are aware, tube ruptures have occurred at facilities other than at Zion. While I believe that because of the measures discussed above, the likelihood of a steam generator tube rupture will be reduced, these changes are not expected to eliminate totally the possibility of a tube failure.
Because the possibility of a tube rupture does exist, we have required, as a design basis for nuclear power plants, that plant design be such that the ublic is adequately protected against tube rupture events. The design of t safety and nitigating features of nuclear power plants and the conser tive assumptions used in our analyses of a tube-rupture event are such tha consequences to the public health and safety would be insignif-icant. Ttg four steam generator tube rupture events in the U. S. to date have confinhed our licensing assumptions and predictions in that the actual releases, as bpected, have been very low and have not resulted in any significant off ite doses.
Although I believeNthat our restrictions and limitations on steam generator operating parameters are such that adequate protection to the health and s
safety of the public is provided, I want to assure you and Mr. Buchner that significant regulatory and industry effort has been and will continue to be applied to resolve steam \\ enerator tube problems.
Returning to Mr. Buchner's concern as to the feasibility of evacuation around the Zion Station, it should be remembered that evacuation is only one of the various protective action strategies that could be taken in the event of a serious accident.
In fact, for%ost of the serious low probability events, we envision that sheltering woulebe the more desirable action from a risk-benefit viewpoint. Even for the mdst serious type release, sheltering followed by a more leisurely relocation may be the optimum choice of pro-tective measures. Here again, as in ritt disaster situations, the actual measures to be taken at the time of the elent will be influenced by the many variables that bear on the decision-making p}ocess.
In the case of a nuclear power plant, such factors would include the release characteristics, meteorolog-ical conditions, operational time constraints, an'd the physical protection factors of available shelter facilities.
Since the accident at Three flile Island, the Nuclear Regulatory Commission has amended its regulations to require upgraded emergency \\ preparedness capabilities around power reactor facilities. These new regulations require that emergency plans be extended to an area within a radius of about 10 miles. This 10 mile radius is referred to as the plume exposure pathway Emergency Planning Zone (EPZ) and applies to potential airborne' exposure.
The size of the zone is based on an NRC/ Environmental Protection Agency Task Force conclusion that it would be unlikely that any protective actions would omce) sunuur) om>
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Honorable Alan J. Dixon Un ed States Senate tlashington, D. C.
20510 Dear \\
Senator Dixon:
This is \\
irtxresponse to Mr. Buchner's letter to you dated February 12, 1982 in which heNxpressed concern regarding the possibility of a stear. generator tube rupture'ht the Zion Station near Chicago similar to what occurred at 4
i the Ginna Nucl'6er Power Plant in New York. In addition, he commented on the high populat' ion density around the Zion Station and evacuation in the i
event of an accidht.
Perhaps a bit of bac round on steam generator tube leakage and rupture would be helpful to pdt this concern in the proper context. Experience has shown that steam genera' tor tube leakage between the primary (tube) side and the secondary (shell) sid(where it occurs during operation is usually so small that it can only be Accurately measured by radiological techniques.
Leakage limits are establishhi by the NRC to provide appropriate corrective f
action.to minimize the potent for tube rupture. These very small and i
unchanging leak rates do not cons'titute a safety problem and the periodic inspection programs of the tubes themselves are used to confim tube structural integrity.
\\
However, over the past several years, s am generator tube degradation has been experienced in a number of steam gen rators due to a variety of causes, and increased inspection requirements and creasingly restrictive limits on leak rates and on changes in leak rate ha been imposed on these generators. These tube degradations, in gene 1, have manifested themselves in increased leak rates, in some cases exceedin established leakage limits.
In all such cases, steam generator inspections we required, and these i
inspections, while requiring corrective actions su as plugging degraded tubes before resuming operation, did not identify an tubes as being in iminent danger of rupture. This gives us a measure assurance that our added restrictions are in the right direction.
In addi on, the technical resolution of Unresolved Safety Issue A-3, 4, 5 " Steam ator Tube Failure," is in its final stages of development and includ consideration i
l of recommendations for improvements in inservice inspection, team generator secondary water chemistry monitoring and turbine condenser in tion.
These improvements when completed should lessen the overall pro em of tube t
corrosion.
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CATE) unc ronu sia cio.ao) nacu o24o OFFICIAL RECORD COPY uso,e is.>-azee
The Honorable Alan J. Dixon Nevertheless, as you are aware, tube ruptures have occurred. While I believe that because of the measures discussed above, the likelihood of a steam generator tube rupture will be reduced, these changes are not expected to eliminate totally the possibility of a tube failure at Zion. Our consideration of this event, however, goes much further. Regardless of the likelihood, because the possibility of a tube rupture does exist, we have required as aVesign basis for nuclear power plants, that they be acceptably protected against tube rupture events. The design of the safety and mitigating features s
of nuclear power plants and the conservative assumptions used in our analyses j
of a tube-rupture event are such that consequences to the public health and safety would be insignificant. The four steam generator tube rupture events in the U. Ato date have confirmed our licensing assumptions and predictions in that the actual releases, as expected, were even less than our conserva-tive calculatibns, and no significant offsite doses occurred.
Although I belie that our restrictions and limitations on steam generator operating parameters are such that adequate protection to the health and safety of the publi s provided I want to assure you and Mr. Buchner that significant regulato and industry effort has been and will continue to be applied to resolve ste generator tube problems.
Returning to Mr. Buchner oncern as to the feasibility of evacuation around the Zion Station, it shoul e remembered that evacuation is only one of the various protective action st egies that could be taken in the event of a serious accident.
In fact, fo st of the serious low probability events, we envision that sheltering woul be the more desirable action from a risk-benefit viewpoint. Even for the. st serious type release, sheltering followed by a more leisurely relocatlpn may be the optimum choice of pro-tective measures. Here again, as in thost disaster situations, the actual measures to be taken at the time of the% vent will be influenced by the many variables that bear on the decision-makin)kelease characteristics, meteorolog process.
In the case of a nuclear i
power plant such factors would include the ical conditions, operational time constraints and the physical protection factors of available shelter facilities.
Since the accident at Three Mile Island, the Nucle Regulatory Commission has amended its regulations to require upgraded eme ency preparedness cspabilities around power reactor facilities. These regulations require l.
that emergency plans be extended to an area within a ra us of about 10 miles. This 10 mile radius is referred to as the plume e sure pathway Emergency planning Zone (EPZ) and applies to potential airbirne exposure.
The size of the zone is based on an NRC/ Environmental Protech on Agency Task Force conclusion that it would be unlikely that any protective etions would l
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The Honorable Alan J. Dixon United States Senate Washington, D. C.
20510
/
Dear Senator Dixon:
o This is in response to Mr. Buchner's lettar to you dated !%bruary 12, 1982 in which he expressed concern regarding the possibility yf a steam generator tube rupture at the Zion Station near Chicago similar tef what occurred at the Ginna Nuclear Power Plant in New York.
In addition, he commented on
^
the high population density around the Zion Station ap'd evacuation in the event of an accident, f
f Regarding the possibility of a steam generator tulp rupture at Zion, I believe that, while unlikely, the possibility of such a rupture exists.
Perhaps a bit of background on steam generator talbe leakage and rupture would be helpful to put this concern in the proper context. Because of the nature of steam generator design and fabricatjen, a very small leakage between the primary (tube) side and the secordary (shell) side is usually present. This leakage is usually so small that it can only be accurately 4
measured by radiological techniques and leakage limits are established by the NRC to provide appropriate corrective, action to minimize the potential for tube rupture. These very small and unchanging leak rates do not constitute a safety problem and the periddic inspection programs of the tubes themselves are used to confirm this conclusion.
However, over the past several years steam generator tube degradation has been experienced in a number of steam generators due to a variety of causes, and increased inspection requiremeryts and increasingly restrictive limits on leak rates ar.d on changes in leak rate have been imposed on these i
generators. These tube degradations, in general, have manifested themselves in increased leak rates, in some/ cases exceeding established leakage limits.
In all such cases, steam generator inspections were required, and these inspections, while requiring cdrrective actions such as. plugging degraded tubes before resuming operatidn, did not identify any tubes as being in imminent danger of rupture. /This gives us a measure of assurance that our added restrictions are in t,.he right direction.
/
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p-The Honorable Alan J. Dixon Nevertheless, as you are aware, tube ruptures have occurred. While! I believe that because of the measures discussed above and because the number of ruptures that have occurred compared to the number of steam generator tube operating hours that have been accumulated, the likelihood of a steam generator tube rupture at Zion.is small, this in it/ elf is probably of cold comfort to Mr. Buchner. Our consideration of this event, however, goes much further. Regardless of the likelihood, because the possibility of a tube rupture does exist, we have requiredias a design basis for nuclear power plants, that they be acceptably protected against l
tubo rupture events. The design of the safety and mitigating features of nuclear power plants and the conservative assumptions used in our analyses of a tube-rupture event are such that consequences to the public health and l
safety would be insignificant. The four steam generator tube rupture events in the U. S. to date have confirmed our licensing assumptions and predictions i
in that the actual releases, as expected, were even less than our conserva-l tive calculations, and no significant offsite doses # occurred.
/
i Although I believe that our restrictions and limitations on steam generator i
operating parametars are such that adequate prot,5ction to the health and safety of the public is provided, I want to assdre you and Mr. Suchner j
that significant regulatory and industry efforif has been and will continue to be applied to resolve steam generator tube fproblems.
Returning to Mr. Buchner's concern as to the feasibility of evacuation around the Zion Station, it should be remembered that evacuation is only one of the various protective action strategies that /ould be taken in the event of a j
serious accident.
In fact, for most of the serious low probability events, we envision that sheltering would be thefmore desirable action from a risk-benefit viewpoint. Even for the most serious type release, sheltering followed by a more leisurely relocatiot may be the optimum choice of pro-i tective measures. Here again, as in clost disaster situations, the actual 1
measures to be taken at the time of the event will be influenced by the many variables that bear on the decision,saking process.
In the case of a nuclear power plant such factors would include the release characteristics, meteorolog-ical conditions, operational time donstraints, and the physical protection factors of available shelter facilities.
/
Since the accident at Three M11ef Island, the Nuclear Regulatory Commission has amended its regulations to require upgraded emergency preparedness l
capabilities around power reacdor facilities. These new regulations require that emergency plans be extended to an area within a radius of about 10 miles. This 10 mile radius.fs referred to as the plume exposure pathway Emergency Planning Zone (EP,Z) and applies to potential airborne exposure.
The size of the zone is based on an NRC/ Environmental Protection Agency Task Force conclusion that it w'ould be unlikely that any protective actions would i
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S. Hanauer MBridgers (#11678) R. Mattson The Honorable Alan J. Dixon Program Support Staff, United States Senate NRR
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Washington, D. C. 20510 M. Jambor /
R. Vollmer
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H. Thompson pear Senator Dixon:
D. Eisenhut P. Check
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r This is in response to Mr. Buchner's letter to you dated February 12, 1982 in which he expressed concern regarding the possibility of a steam generator tube rupture at the Zion Station near Chicago simitar to what occurred at the Ginna Nuclear Power Plant in New York. In ad# tion, he commented on the high population density around.theaZion Statjsn and evacuation in the event of an accident.
The design basis for assuring that plants are deceptably protected against steam generator (S.G.) tube rupture events infa postulated double-ended 4
rupture of a single S.G. tube coincident witW a main steam line break. This assumption provides a bounding leak rate foi a spectrum of rupture geometries ikra single steam generator. Primary to s'econdary loak rate limits are an extremely inportant requirement for ensuri'ng safe S.G. operation. Some forms of tube degradation have been observed to' degrade tubes beyond the prescribed plugging limit during the interval betwoen inspections. Technical Specifica-tion primary to secondary leak rate lirt ts requiring shutdown, inservice inspection (ISI), and corrective actioEs provide protection against unaccept-able levels of degradation. between inspections. Many seriouc conditions of tube degradation have been detected By monitoring of primary to secondary leakage and sbbsequent inspection. Arimary to secondary leak rate limits exist in each plant's technical spet:ifications. The bases for these limits are twofold. First, the leak rate'11mit ensures that the calculated dosage i
contribution from tube leakage will be limited to a small fraction of the allowable limits in the event of/a S.G. tube rupture coincident with main steam line break. Second, the a defect size that would not by}eak rate limit is intended to correspond to expected to result in tube rupture under normal or posutlated accident onditions.
In addition, degradation linds for tube plugging exist in the plant Technical Specifications. The criteri for establishing the tube plugging limits require that the plugging 1 it include margins for eddy current testing error and continued degradation tween inspections. Thus, it is important to have a good estimate of ths rate of degradation based on successive ISI i
results and an understanding of the degradation phenomena.
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l The Honorable Alan J. Dixon /
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The NRC approach to assuring S.G. tube integrity under all operating conditions is based on inservice inspection, primary to secondary leakage i
rate limits, and preventive tube plugging requirements. Tfplcal plant specifications require periodic inspections of 3% of the S.G. tubes in the
]
plant and augmented ISI in the event tube degradation 1sjdetected. Required i
frequency of inspection is generally flexible enough tof allow inspections to be performed concurrent with refueling outages.
Certain incidents such i
as tube leakage require unscheduled inspections.
Furthermore, many plants with extensive degradation problems have licensing amendments imposing higher frequency and larger size inspections. The;ISI requirements were developed largely through a combination of engineering judgment and operating experience. The purpose of the required inspection is to determine if tube i
degradation is occurring in the S.G., assess thefrate of tube degradation i
based on results of successive inspections, and.ridentify those tubes requiring j
plugging or repair. Thus, the primary focus of the current NRC philosophy is directed at the utility maintaining primary' system integrity. This is accomplished primarily through the requirements described above for ISI, j
leak rate monitoring, and tube plugging. The design of the plant and its mitigation features are such that the consef uences to a person at the exclusion l
i area boundary at the site would be extremely small in the event of a tube rupture accident. The four S.G. tube rupture events in the U.S. to date I
have confimed our licensing assumptions /and predictions in that the actual releases were even less than our conser/ative calculations and no significant j
offsite doses occurred.
/
/
Returning to Mr. Buchner's concern asito the feasibility of evacuation around the Zion Station, it should be remen! ered that evacuation is only one of the b
various protective action strategies that could be taken in the event of a serious accident.
In fact, for most of the serious low probability events, we envision that sheltering would be the more desirable action from a risk-j benefit viewpoint.
Even for the.most serious type release, sheltering followed by a more leisurely re16 cation may be the optimum choice of pro-tective measures. Here again, a's in most disaster situations, the actual measures to be taken at the tim'e of the event will be influenced by the many variables that bear on the decision-making process.
In the case of a nuclear power plant such factors woul.d include the release characteristics, meteorolog-factors of available shelter / time constraints, and the physical protection ical conditions, operational facilities.
As a matter of infomation;/evacuations are a relatively connon event in this country.
In fact, the records show, at least since 1960, that an evacuation takes place somewhere in.i;he U. S. on almost a weekly basis. The number of people evacuated u thost events has ranged from a few to hundreds of thousands and some have occurred in high density urban and suburban ~ areas. Two such events occu red in Batos Rouge, Louisiana in 1965 where 150,000 persons were evacuated in two hours /and in Wilkes-Barre, Pennsylvania in 1972 where 75,000 persons were evacuated in five hours. Also, the metropolitan business district of downtown Portland, Oregon with a population of 101,000 persons and a OFFICE) suname >
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The Honorable Alan J. Dixcn,/
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l population density approaching that of New York City, was evac [ated in l
less than one hour during a Civil Defense test exercise in 1955. One of the largest evacuations in our history rook place in 1961 as/a result of hurricane Carla where over 500,000 people were evacuated from the States of Texas and Louisiana.
Even though these are just a few examples, we j
consider that large scale evacuations are indeed feasible, and are a th'e actual conditions viable option depending on the constraints imposed by /
at the time of the emergency.
t Since the accident at Three Mile Island, the Nuclear [egulatory Commission has amended its regulations to require upgraded emergency preparedness capabilities around power reactor facilities. These new regulations require that emergency plans be extended to an area within'a radius of about 10 miles. This 10 mile radius is referred to as the plume exposure pathway Emergency Planning Zone (EPZ) and applies to potential airborne exposure.
The size of the zone is based on an NRC/Environriental Protection Agency Task Force conclusion that it would be unlikeli that any protective actions would be required beyond the plume exposure pathway EPZ. The results of the Task Force and review by the FEMA conclude that even most core melt accidents would not require individual prote'ctive action outside ten miles and that the ten mile plume exposure plannihg zone provides a response base for the worst case accident. NRC studies also indicate that no severe acute effects would be expected outside the 10 mile plume exposure planning zones even for worst case accidents. More recently, NRC siting policy has
~
also emphasized the requirement of reasonable assurance that adequate protective measures can and will be tak'en by the licensee and the state and local authorities in the event of accidents more serious than design-basis accidents. This manifests itself in emergency preparedness plan and the r,the utilities preparation of an eview by the Federal Emergency Management Agency (FEMA) for all offsite emergehcy plan provisions and requirements.
I We trust this information will be felpful to you.
/
/
Sincerely,
/
i William J. Dircks
,/
Executive Director for Operations
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Enclosure:
David E. Buchner letter
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dated February 12, 1982 OCA 04/ /82 ORB #1:DL ORB #:DL AD/0R:DL D/DL DD/.NRR.
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