ML19290F199
| ML19290F199 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/06/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Rich Smith VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| NUDOCS 8003180298 | |
| Download: ML19290F199 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION 3
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March 6, 1980 Docket No. 50-271 Vermont Yankee Nuclear Power Corporation ATTN:
Mr. Robert L. Smith Licensing Engineer 25 Research Drive
'dastborough, Massachusetts 01581 Gentlemen:
The enclosed IE Circular No. 80-03, " Protection from Toxic Gas Hazards", is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, Y/f/f L
Boyce H. Grier
~~~ Director
Enclosures:
1.
IE Circular No. 80-03 with Attachments 2.
List of Recently Issued IE Circulars CONTACT:
R. J. Bores (215-337-5260) cc w/encls:
W. F. Conway, Plant Superintendent Ms. J. Abbey, Technical Secretary Mr. J. E. Griffin, President 8003180878
ENCLOSURE 1 SSINS:
6830 Accession No.:
UNITED STATES 7912190685
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NUCLEAR REGULATORY COMMISSION IDN OFFICE OF INSPECTION AND ENFORCEMENT
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20555 IE Circular No. 80-03 Date:
March 6, 1980 Page 1 of 2 PROTECTION FROM T0XIC GAS HAZARDS Chlorine gas releases have been reported at two different reactor facilities in the past two years.
At Millstone, in March 1978, a leak of about 100 standard cubic feet of chlorine (about a gallon of liquid) occurred over a ten minute period, resulting in the hospitalization of 15 people.
The ventilation system carried the chlorine into the plant buildings, where personnel distress was noted.
No injuries occurred in the buildings due to the small size of the release.
At Browns Ferry, in June 1979, a small leak from a diaphragm on a chlorine reducing valve resulted in the hospitalization of five people, including a control room operator.
Chlorire is highly toxic, producing symptoms after several hours exposure in concentrations of only one ppm.
Concentrations of 50 ppm are dangerous for even short exposures and 1000 ppm is fatal for brief exposures.
- Chlorine, used at some power stations to control organisms in the circulating water, is normally supplied in one ton containers or in tank cars of up to 90 tons capacity.
Other potential sources of toxic gas that have been identified at nuclear power plants include:
Nearby industrial facilities.
At Waterford, in July 1979, construction forces had to be evacuated for two and a half hours due to a chlorine gas release from a nearby chemical plant.
Chlorine transportation on adjacent highways, railways and rivers.
Large tanks of aqueous ammonia stored near plant buildings.
Both acid and caustic storage tanks located in a common building near the control room.
At the Dresden site, in August 1977, accidental mixing of acid and caustic solutions resulted in toxic fumes that entered the control room via the ventilation system.
IE Circular No. 80-03 Date:
March 6, 1980 Page 2 of 2 Criterion 19 of Appendix A to 10 CFR 50 requires a control room from which action can be taken to maintain the reactor in a safe condition under accident conditions.
The control room designs in current license applications are reviewed for operator protection from toxic gases (as well as radiation), in accordance with Standard Review Plan (SRP) 6.4 (NUREG 75/087 dated 11/24/75).
Related information on the identification of potential hazards and the evalua-tion of potential accidents can be found in SRP sections 2.2.1-2.2.2 and 2.2.3 recpectively.
The SRP references Regulatory Guide 1.78 (dated June 1974) on control room habitability during chemical releases.
It also references Regula-tory Guide 1.95 en requirements for protection against chlorine releases specifically.
The majority of the plants currently operating, however, were built and licensed prior to the development and implementation of this guidance.
A review of some older plants, with respect to toxic gas hazards indicates that they do not have the degree of protection that would be required for present day plants.
Evaluation of the protection of control rooms from toxic gas releases is part of the systematic evaluation program currently being carried out on certain older plants.
Also, as older facilities submit requests for significant license amendments, their design features and controls for protection of control rooms are reviewed and, if appropriate, are required to be changed.
However, the recent history of frequent toxic gas release incidents appears to warrant a more rapid implementation of the newer toxic gas protection policies.
For the above reasons, it is strongly recommended that:
You evaluate your plant (s) against section 6.4 and applicable parts of sections 2.2.1-2.2.2 and 2.2.3 of the SRP with respect to toxic gas hazards.
Where the degree of protection against toxic gas hazards is found to be significantly less than that specified in the SRP, provide the controls or propose the design changes necessary to achieve an equivalent level of protection.
No written response to this circular is required.
If you desire additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
Attachments:
Sections 2.2.1-2.2.2; 2.2.3 and 6.4 of NUREG 75/087
Attachment to IE Circular No. 80-03 NU REG.75/087 gp aro,s u
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U.S. NUCLEAR REGULATORY COMMISSION D
STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTIONS 2.2.1 - 2.2.2 IDENTIFICATION OF POTENTIAL HAZARDS IN SITE VICINITY l
PEVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AA3)
Secondary - None I.
AREAS OF REVIEW Locations and separaticn distances from the site of industrial, military, and transport: tion facilities and routes in the vicinity of the site. Such facilities and routes include air, ground, and water traffic, pipelines, and fixed manufacturing, processing, and storage facilities. Potential external ha:ards or hazardous materials that are present or wnich may reasonably be expected to be present during the projected life time of the proposed plant. The purpose of this review is to establish the informati n concerning the presence of potential external ha:ards wnich is to be used in further review in Sections 2.2.3, 3.5.1.5, and 3.5.1.6.
II. ACCEPTANCE CRITERIA 1.
Data in the SAR adequately descrioes the locations and distances of 1.mustrial.
l military, and transportation facilities in the vicinity of the plant, and is in agreement with data obtained from other sources, wnen available.
2.
Descriptions of the nature and extent of activities conducted at nearoy facilities, including the products and materials likely to te processed 4tored, used, or trans-ported, are adequate to permit evaluations of possible hazards in Part 3 review sections dealing,with specific hazards.
J.
Where potentially hazarcous materials may be p"ocessed, stored, used, or transoorted in the vicinity of the plant, sufficient statistical data on such materials are l
provided to establish a basis for evaluating the potential hazard to the plant.
III. REVIEW POOCEDURES Selection and empnasis of varicus aspects of the areas c:vered by this review plan will be :rm.de by the reviewer on each case. The judgment of the areas to be given attention during the review is to be based on an inspection of the material presented, the similarity of the material to that recently reviewed on other plants, and wnether itens of special safety significance are involved. The following procedures are followed:
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NU R EG.75/087
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STANDARD REVIEW PLAN
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SE~TICN 2.2.3 EVAWATION OF POTENTIAL ACCIDENTS REVIEW RESP 0NSIBILITIES Primary - Accident Analysis Branch (AAB)
Secondary - Applied Statistics Branch (ASB/MPA) 1.
AREAS OF REVIEW The applicant's identification of potential accident situations in the vicinity of the plant is reviewed to deteriine the comoleteness of and the bases upon which these potential accidents were or were not accccr'odated in the design. (See Standard Review Plans 2.2.1 and 2.2.2.)
The applicant's prcbability analyses of potential accidents involving hazardous materials or activities in the vicinity of the plant, if sucn analyses have been perfor ed, are also reviewed by ASB/MPA on request by AAB to determine that approcriate data and analytical models have been utilized.
The analyses of the consecuences of accidents involving nearby industrial, military, and transportation facilities wnich have been identified as design basis events are reviewed.
II. ACCE?TANCE CRITERIA The identification of design basis events resulting from the presence of hazard 0us materials or acchities in the vicinity of the plant is acceptable if the design basis events include each post.ulated type of accident for wnich the expected rate of occurrence of otential exposur<,s in excess of the 10 CFR Part 100 guidelines is estimated to exceed the NRC staff objective of approximately 10 per year. Because of the difficulty of assigning accurate nwnerical values to the expected rate of unprecedented ;otential hazards generally con-sidered in this review plan, judgment must be used as to the acceptability of the overall risk presented.
The probability cf occurrence of the initiating events ?eading to potential consequences in excess of 10 CFR Part 100 exposure guidelines should be estimated using assumpticns that are as representative of the specific site as is practicable. In, addition. because of the low probabilities of the events under contidaration, data are of ten not available to permit accurate calculation of probabilities. Accordingly, the expected rate of cccur-rence of potential exposures in excess of the 10 CFR Part 100 guidelines of approximately 10 per year is acceptable if, when conbined with reasonable qualitative arguments, the realistic crobability can be shcwn to be lcwer.
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Attachment to IE Circular No. 80-03 The effects of design basis events have been adecuately considered if analyses of the l
effects of those accidents on the safety-related features of the plant have been perfomed g
and measures (e.g., hardening, fire protection) to mitigate the consequences of such events have been taken.
III. REVIEW PROCEDURES g
In some cases it may be necessary to consult with or obtain specific data from other branches, such as the Structural Engineering Branch (SEB) or Auxiliary Systems Branch l
(ASB), regarding possible effects of external events on plant structures or components.
The applicant's probability calculations are reviewed, and an independent probability analysis is performed by the staff if the potential hazard is considared significant enough to affect the licensability of the site or is important to the identification of design basis events.
All stochastic variables that affect the occurrence or severity of the postulated event are identified, and judged to be either independent or conditioned by other variables.
Probabilistic models should be tested, wnere possible, against all available information.
If the model or any portion of it, by simole extension, can be used to predict an observ-able accident rate, this test should be perfomed.
The design parameters (e.g., overpressure) and physical phenomena (e.g., gas concentration)
Selected by the applicant for each design basis event are reviewed to ascertain that the values are comparable to the values used in previous analyses and found to be acceptable by the staff.
Each design basis event is reviewed to determine that the effects of the event on the safety features of the plant have oeen adequately accorrnodated in the design.
If accidents involving release of smoke, flammable or nonflammable gases, or chemical bearing clouds are considered to be design basis events, an evaluation of the effects of these accideats on centrol room habitability should be made in SAR Section 6.4 and on the coeration of diesels and other safety-related equipment in SAR Chapter 9.
Special attention should be given to the review of standardized designs which propose criteria involving individual numerical probability criteria for individual classes of external man-made hazards. In such instances the reviewer should establish that the envelope also includes an overall criterion that limits the aggregate probability of exceed-ing design criteria associated with all of the identified external man-made hazards.
Similarly, special attention should be given to the review of a site where several man-made hazards are identified, but none of which, individually, has a probability exceeding the acceptance cc,iteria stated herein. The ofjective of this specia' review should be to assure that the aggregate probability of an outcome that may lead to unacceptacle plant damage meets the acceptance criteria of Part II of this SRP Section. (A hypothetical example is a situation where the probability of shock wave overpressure greater than design Rev. 1 2.2.3-2
Attachment to IE Circular No. 80-03 overpressure is about 10"I per reactor year from accidents at a nearby industrial facility, and approximately equal probabilities of exceeding design pressure frem railway accidents.
highway accidents and from shipping accidents. Individually each may be judged acceptably low; the aggreg6te probability may be judged sufficiently great that additional features of design are warranted.)
IV. EVALUATION FINDINGS If the reviewer verifies that sufficient infermation has been provided and that his evaluation is sufficiently complete and adequate to meet the acceptance criteria in Section II of this SRP, conclusions of the following type may be prepared for the staff's. safety evaluation report:
"The applicant has identified potential accidents which could occur in the vicinity of the plant, and from these has selected those which should be considered as design l
basis events and has provided analyses of the effects of these accidents on the safety-related features of the plant. The applicant has demonstrated that the plant is adequately protected and can be operated with an acceptable degree of safety with i
regard to potential accidents which may occur as the result of activities at nearby industrial, military, and transportation facilities."
V.
REFERENCES Regulatory Guide 1.70, " Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants " Revision 2.
I Affidavit of Jacques B. J. Read before the Atomic Safety and Licensing Boaro in the matter of Skagit Nuclear Power Project, Units 1 and 2. July 15,1976. Docket Nos. STN 50-522, 523.
Atomic Safety and Licensing Board, Supplemental Initial Decision in the Matter of Hope Creek Generating Station, Units 1 and 2, March 28,1977. Docket Nos. 50-354, 355.
Section 2 Supplement 2 to the Ficating Nuclear Plant Safety Evaluation Report, Docket No. STN 50-437, September 1976.
Rev. 1 2.2.3-3
Attachment to IE Circular No. 80-03 pnarc NUR EG.75/087
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STANDARD REV1EW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.4 HABITABILITY SYSTEMS REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAS)
Secondary - Hydrology-Meteorology Branen (HM8)
Auxiliary Systems Branch (A58)
Effluent Treatment Systems Branch (ETSB)
I.
AREAS OF REVIEW The control room ventilation system and control building layout and structures, as described in the applicant's safety analysis report (SAR). are reviewed with the objective of assuring that plant o;erators are adequately protected against the effects of accidental releases of toxic or radioactive gases. A further objective is to assure that the control room can be maintained as the center from which emergency teams can safely operate in the case of a design basis radiological release. To assure that these objectives are acccm-p11shed the following items are reviewed:
1.
The zone serviced by the control room emergency ventilation system is examined to ascertain that all critical areas requiring access in the event of an accident are included within the zone (control room, kitchen, sanitary facilities, etc.) and to
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assure that those areas not requiring access are generally excluded from the zone.
2.
The capacity of the control room in terms of the number of people it can accommodate for an extenced period of time is reviewed to confirm the adequacy of emergency food and medical supplies and self-contained breathing apparatus and to determine the length of time the control room can be isolated before CO levels become excessive.
2 3
The control room ventilation system layout and functional design is reviewed to determine flow rates and filter efficiencies for inout into the AA8 analyses of the buticup of radioactive or toxic gases inside the control room, assuming a design basis release. Basic deficiencies that might im; air the effectiveness of the system are examined. In addition, the system operation and procedures are reviewed. The ASB has primary responsibility in the system review area under Standard Review Plan (SRP) 9.4.1.
The AS8 is consulted when reviewing hardware and cperating procedures.
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