ML19290F191
| ML19290F191 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/06/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R Maine Yankee |
| References | |
| NUDOCS 8003180282 | |
| Download: ML19290F191 (1) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION E
REGION 1 0,
8 631 PARK AVENUE E
%, * * * * *,o KING OF PRUSSIA, PENNSYLVANIA 19406 March 6, 1980 Docket No. 50-309 Maine Yankee Atomic Power Company ATTN:
Mr. Robert H. Groce Senior Engineer - Licensing 25 Research Drive Westborough, 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, f
ayK k s-3 Boyce H. Grier
~~~0irector Enclosu: --
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:
E. Wood, Plant Superintendent E. W. Thurlow, President 8003I801E
ENCLOSURE 1 SSINS:
6830 Accession No.:
UNITED STATES 7912190685 NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT fj.hciB _'~l' WASHINGTON, D.C.
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IE Circular No. 80-03 Date:
M3rch 6, 1980 Page 1 of 2 PROTECTION FROM T0XIC GAS HAZARDS Chlorine gas releases h&ve 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 it 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.
Chlorine 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.tazards and the evalua-tion of potential accidents can be found in SRP sections 2.2.1-2.2.2 and 2.2.3 respectively.
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 ?n 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 i:4.' cates that they do not have the degree of protection that would be requireo 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 suomit 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 '.o 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 'E Circular No. 80-03 NUREG 75/087 a proo
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',g U.S. NUCLEAR REGULATORY COMMISSION i
1 STANDARD REVIEW PLAN
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OFFICE OF NUCLEAR REACTOR REGULATION SECTIONS 2.2.1 - 2.2.2 IDENTIFICATION OF POTENTIAL HAZAR05 IN SITE VICINITY l
REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAS)
Seccndary - None I.
AREAS OF REVIEW Locations and separation distances from the site of industrial, military, and transportation facilities and routes in the vi:inity of the site. Such facilities and routes include air, ground, and water traffic, pipelines, and fixed manufacturino e cessing, and storage facilities. Potential external hazards or hazardous mats.415 that are present or which 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 infor-ation concerning the presence of potential external hazards which 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 describes the locations and distances of iaustrial, I
military, and transportation facilities in the vicinity of the plant, and is in agreement with data obtained from other sources, when available.
2.
Descriptions of the nature and extent of activities conducted at nearby facilities, including the products and materials likely to be processed, stored, used, or tre.ns-ported, are adequate to pemit evaluations of possible hazards in Part 3 rev'ew sictions dealing,with s:ecific hazards.
3.
Where potentially hazardous materials may be processed, stored, used, or transported 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 PRCCEOURES Selection and empnasis of varicus aspects of the areas covered by this review plan will be made 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 whether iters of special safety significance are involved. The following procecures are followed:
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Attachment to IE Circular No. 80-03 lpn neog NUREG 75/087 o
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j' U.S. NUCLEAR REGULATORY COMMISSION V'
STANDARD REV3EY1 PLAN
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OFFICE OF AIUCLEAR REACTOR REGULATION SECTION 2.2.3 EVALUATION OF POTENTIAL ACCIDENTS REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAS)
Secondary - Applied Statistics Branch (ASB/MPA)
I.
AREAS OF REVIEW The applicant's identification of potential accident situations in the vicinity of the plant is reviewed to determine the comoleteness of and the bases upon which these potential accidents were or were not accommodated in the design. (See Standard Review Plans 2.2.1 and 2.2.2.)
The applicant's probability analyses of potential a idents involving hazardous materials or activities in the vicinity of the plant, if such analyses have been perfor ed are also reviewed by ASB/MPA on request by AAS to determine that appropriate data and analytical models have been utili:ed.
The analyses of the consequences of accidents involving nearby industrial, military, and transportation facilities which have been identi.'ied as design basis events are reviewed.
II. ACCEDTANCE CRITERIA The identification of design basis events resulting from the presence of hazardous raterials or activities in the vicinity of the plant is ac:eptable if the design basis events include l
eacn postulated type of accident for which the expected ratst of occurrence of potential exposures in excess of the 10 CFR Part 100 guidelines is estimated to exceed the NRC staff objective of approximately 10'I per year. Because of the difficulty of assigning accurate numerical 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 oresented.
The probability of occurrence of tne initiating events leading to potential consequences in excess cf 10 CFR Part 100 exposure guidelines should be estimated using assumptions that are as representative of the specific site as is practicable. In addition, because of the Icw probabilities of the events under consideration, data are of ten not available to permit accurate calculation of probabilities. A a rdingly, the expected rate of cc:ur-rence of potential exposures in excess of the 10 CFR Part 100 guidelines of apprcximately 10 per year is acceptable if, when combined with reasonable qualitative arguments, the realistic probability cai be shewn to be lower.
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Attachment to IE Circular No. 80-03 The effects of design basis events have been adecuately cr'sidered if analyses of the l
effects of those accidents on the safety-related features of the plant have been perfomed 3
and measures (e.g., hardening, fire protection) to mitigate the consequences of such events have been taken.
III. REVIEW PROCEDURES In some cases it may be necessary to consult with or obtain specific data from other brancho, such as the Structural Engineering Branch (SEB) or Auxiliery Systems Branch l
(ASB), regarding possible effects of external events on plant structures or components.
The applicant's probability calculations are reviewed, and an independaat probability analysis is perfomed by the staff if the potential hazard is considered significant enough to affect the licensability of the site or is important to the identification of design basis events.
All stocnastic 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 snould be tested, where possible, against all available information.
If the model or any portion of it, by simple extension, can be used to predict an observ-able accident rate. this test should be perfomed.
Tne design parameters (e.g., overpressure) and physical phenomena (w.g., gas concentration) selected by the applicant for each design basis event are reviewed to ascertain that the values are comcarable to the values used in previous analyses and found to be acceptable by the staff.
Each design basis event is rsviewed to determine that the effects of the event on the safety features of the plant have been adequately accomodated in the design.
If accidents involving release of smoke, flamable or nonflammable gases, or chemical bearing clouds are considered to be design batis events, an evaluation of the effects of these accidents on control room habitability should be made in SAR Section 6.4 and on the operation of diesels and other safety-related equipmert in SAR Chapter 9.
Special attention should be given to the review of standardized de:igns which propose criteria involving individual numerical nrobabi.ity criteria for individual classes of external man-made hazards. In such instances the reviewer should establisn 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 wnere several man-made hazards are identified, but 'Tne of which, individually, has a probability exceeding the acceptance cr,iteria stated herein. The objective of this special review should be to assure that tne aggregate probability of an outcome that may lead to unacceptable plant damage meets tne acceptance criteria of Part II of tnis SRp Section. (A hypothetical example is a situation where tne probability of snock wave overpressure greater than design Rey, 1 2.2.3-2
Attachment to IE Circular No. 80-03 overpressure is about 10'7 per reactor year from accidents at a nearby industrial facility,
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and approximately equal probabilities of exceeding design pressure from railway accidents, highway accidents and from shipping accidents. Individually each may be judged acceptably low; the aggregate probability may be judged sufficiently great that additional features of design are warranted.)
IV. EVALUATION FINDINGS If the reviewer verifies that sufficient information 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 tncse which should be ccncidered 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 t'ie plant is adequate'y protected and can be operated with an acceptable degree of safety with regard to a,cential accidents which may occur as the result of activities at nearby industrial, military, and transportation facilities."
V.
REFERENCES Regulatory Guide 1.70, " Standard For-nat and Content of Safety Analysis Reports for Nuclear Fower Plants," Revision 2.
I Affidavit of Jacques B. J. Read before the Atomic Safety and Licensing Board 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, 255.
Section 2. Supplement 2 to the Floating Nuclear Plant Safety Evaluation Report, Oceket No. STN 50-437, September 1976.
2.2.3-3 Rev. 1
Attachment to IE Circular No. 80-03 O Mag NUREG 75/087 f
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U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEY1 PLAN
%'%.*..j' 'j OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.4 HABITABILITY SYSTEMS REVIEW RESPONS!3ILITIES Primary - Acciden*, Analysis Branch (AAB)
Secondary - Hydrology-Meteorology Branch (hPB)
Auxiliary Systems Brarch (ASB)
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 operators are acequately protected against the effects of accidental releases of toxic or radioactive gases. A further oofective is to assure that the control room cari 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 accom-plished 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 1
assure that those areas not requiring access are generally excluded from the zene.
i 2.
The capacity of the control room in terms of the number of people it can accommodate for an extended period of time is reviewed to confirm the acequacy of emergency food and medical supplies and self-contained breathing apparatus and to determine the length of time the ccotrol room can be isolated before CO levels become excessive.
2 3.
The control room ventilatica system layout and functional design is reviewed to determine flow rates and filter efficiencies for input into the AA8 analyses of the ouildup of radioactive or toxic gases inside the control room, assuming a design basis release. Basic deficiencies that mignt imcair 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 Stancard Review Plan (SRP) 9.4.1.
The ASB is consulted when reviewing hareware and cperating procedures.
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