ML20237G425
| ML20237G425 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 07/18/1986 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Andrews H WELD COUNTY, CO |
| References | |
| TAC-60400, NUDOCS 8708140062 | |
| Download: ML20237G425 (5) | |
Text
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>S Rigg UNITED STATES
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g NUCLEAR REGULATORY COMMISSION
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- l WASHINGTON, D. C. 20555 July 18, 1986 Docket No. 50-267
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60Y00 l
Mr. Harold L. Andrews-Sheriff, Weld County Greeley Office I
Post Office Box 759 Greeley, Colorado 80632
Dear Sheriff Andrews:
I am replying to your letter dated July 2,1986 to Chairman Lando W. Zech,
]
Jr., of the Nuclear Regulatory Connission, concerning the safety of the 1
Fort St. Vrain Nuclear Generating Station in light of the'recent accident
)
at the Chernobyl facility in the Soviet Union.
You expressed interest in two catastrophic accident scenarios:
- 1) complete destruction of the containment building with total release of all fission products, and 2) a major internal malfunction with containment of the radio-j activity. You also inquired about " entombment" of the plant, as is being done at Chernobyl.
The hazards relative to the operation of Fort St. Vrain were initially examined by the Division of Reactor Licensing of the U. S. Atomic Energy Commission in a S,afety Evaluation published on January 20, 1972.
In this
.j Safety Evaluation','the staff anticipated the scenarios discussed in your Pfr letter.
In particular, in Section 4.4 of this report, the staff reviewed i
the consequences of the radioactivity released in a rapid depressurization of the reactor vessel, designated as Design Basis Accident No. 2.
Enclosure 1 indicates the radiation doses that could result from this accident. These consequences, which are considered conservative, were found to be acceptable in accordance with the Commission's standards.
In the extremely unlikely event that this accident should occur, the utility would shut down the reactor and remove the remaining decay heat from the reactor cort. However, it is anticipated that no further specific actions would be required to prevent additional releases of radioactivity or provide protectwi to the public.
In Section 4.5 of the Safety Evaluation, the staff also examined the consequences of a major internal malfunction, i.e., permanent loss of forced circulation cooling (designated as Design Basis Accident No. 1). The staff found that the reactor vessel could effectively contain the radioactivity released from the fuel particles with acceptable consequences for the public health and safety. Using conservative assumptions, the staff's evaluation indicated that the radiation doses would be so low as to not require evacuation of the local residents (see Enclosure 2).
8708140062 060710 DR ADOCK 03000267 PDR
1 1
July 18, 1986
' Mr. Harold L. Andrews,
Since the massive reactor vessel serves as.an effective barrier to contain radioactive materials, " entombment" of the reactor is not. envisioned either as a necessary precaution, or as a remedial action in the event.of an accident.
Other public officials in Colorado have inquired recently about the safety of Fort St. Vrain relative to the Chernobyl accident. is a copy of a letter dated May 29, 1986 to Governor Lamm which provides a discussion of the NRC staff's post-Chernobyl reassessment of Fort St. Vrain.
Please note that all docketed materials concerning the safety of Fort St.
Vrain Nuclear Generating Station are available to you at the Greeley Public Library, City Complex Building in Greeley.
Sincerely, t
arold R. Denton, Dir ctor Office of Nuclear Reactor Regulation j
Enclosures:
As stated i
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July 18, 1986 Mr. Harold L. Andrews Since the massive reactor vessel serves as an effective barrier to contain radioactive materials, " entombment" of the reactor is not envisioned either as a necessary precaution, or as a remedial action-in the event of an accident.
Other public officials in Colorado have inquired recently about the safety of Fort St. Vrain relative to the Chernobyl accident. is a copy of a letter dated May 29, 1986 to Governor Lamm which provides a discussion of the NRC staff's post-Chernobyl reassessment of Fort St. Vrain.
Please note that all docketed materials concerning the safety of Fort St.
1
-Vrain Nuclear Generating Station are available to.you at the Greeley Public Library, City Complex Building in Greeley.
Sincerely, Original signed by Richard Vollmer for Harold R. Denton, Director Office of Nuclear Reactor Regulation
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Enclosures:
As stated DISTRIBUTION.
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i TABLE 4.2 ACCIDENT ASSUMPTIONS P.APID DEPRESSURIZATION ACCIDENT:
DBA-2 ITEM STAFF APPLICANT Coolant Fission Product Inventory Design Design Coolant Loat Unfiltered 100%
100%
)-
l
-4 3
~4 Inhalation Rate 3.47 x 10
/sec 3.47 x 10 m /sec Meterological Model Volume Source Area Source Pasquill Condition "F"
"G" Wind Speed 0.3m/sec 1 m/sec Dilution Factor:
-4 3
-4 3
X/Q (Exclusion Radius) 8.4 x 10 see m 4 x 10 sec/m X/Q (LPZ) 4 x 10-5sec/m 4 x 10-5sec/m3 Doses - (2 Hr. at exclusion radius) due to Coolant-Borne Activity Thyroid 11 rem 5 rem Whole Body
(
Bone
< 0.2 rem
< 0.1 rem Plateout Inventories - Source Calculated Allowable Design 1-131 'equival,ent 5000 Ci/ loop 5500 C1/ loop Sr-90 equivalent 140 C1/ loop 160 C1/ loop i
}
V:
Fraction of Plateout Inventory Released i
Iodine 0.06 0.0057 l
- 0. 0'5 0.01 j
i Doses (2 Hr. at exclusion radius) due to removed Plateout Activity i
Total Accident Doses at Exclusion Radius i
Thyroid 150 rem
.U. 4 rem Bone 75 rem 4.8 rem j
Whole Body
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' TABLE 4.3 V
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ACCIDF.MT ASSUMPTIONS y
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PERMANENT LOSS-0F-FORCED-CIRCULATION COOLING - DBA #1 STAFF APPLICANT.
ITEM I
Power Level 879 MWT 879 MWT Assumed duration of accident emissions used in dose calculations 180 days 180 days
)
50% of Core Halogens Re leased to PCRV inventory) 5.5%
(
2 Halogen Plateout Factor.
Halogens Available for Release from PCRV 25% (of Core inventory) 4.6%
Strontium Available for Release from PCRV 1% (of Core inventory) 0.026%
Noble Gases Available for Rolease from 100% (of Core i"
'PCRV inventory) 99%
Reactor Building Filter Efficiencies 90%
90%
Halogens Particulate 95%
95%
PCRV Leak Rate 0.2%/ day 0.2%/ day inhalation Rates 3.47 x 10'4m /sec 0-12 hrs 2.9 x 10 m /sec
~
Most unfavorable 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period
~4 Next most unfavorable 16' hours 1.75 x'10 m /sec Remainder of 180 day period 2.32 x 10 m /sec 2.32 x 10 'm /sec
~
Meteorological Dilution Factors Most unf avorable 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period 7.8 x 10-6,,cj,3
-6
~
Next most unfavorable 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> 3.9 x 10 sec/m 1-12 hrs 4,7 x 10 sec/m
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}
For the 1-4 day period 2.4 x 10-6,,cj,3
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~7
~9 3
l For the 4-30 day period 7.8 x 10 sec/m All others 9.5 x 10 sec/m For the 30-180 day period 4.6x 10 sec/m
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~7 Strontium Dose Conversion Factor 3.6 x 10 rem /C1 1.07 x 10 rem /C1 Course of Accident dose at Low Population Zone Thyroid
< 8 rem 66 mrem Bone
< 5 rem 1.9 mrem Whole Body
< 330 mrem 0.56 mrem l <
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'o, UNITED STATES Si)y
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NUCLEAR REGULATORY COMMISSION
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j WASHINGTON, D. C. 20555 k-),/
May 29, 1986
Dear Governor Lamm:
In view of the recent Soviet reactor accident at Chernobyl and because of questions that were beirg raised about possible design similarities of the Fort St. Vrain reactor, the Nuclear Regulatory Commission staff has reexamined our original licensing bases for this facility. We a Service Company of Colorado to investigate scenarios,1so asked the Public which could lead to rapid oxidation of the Fort St. Vrain graphite core and to assess the consequences of such an event.
On the basis of these evaluations and all other relevant information available to us at this time, we have concluded that continued operation of the Fort St. Vrain facility is justified and have so informed our management and Commission.
Because of your interest in this matter, I am enclosing for your da9W. ion a copy of the staff's evaluation and findings.
As a separate matter, the Fort St. Vrain reactor is presently authorized to operate at levels not to exceed 35 percent of full power until May 31, 1986, at which time it will be shutdown in order to complete environmental qualification-related equipment modifications. We anticipate that the plant-7~.
will not be ready to operate again before September 1986.
',7[
Should you have any questions, please feel free to contact me.
Sincerely,
/#7 M ar d R. Denton, recto ff ce of Nuclear eacto egulation I
Enclosure:
Memorandum for Victor Stello, Jr.
from Harold R. Denton dated May 9, 1986 cc: Richard F. Walker, President, PSC
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