ML18044A767
| ML18044A767 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point, Palisades File:Consumers Energy icon.png |
| Issue date: | 04/02/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8004180040 | |
| Download: ML18044A767 (27) | |
Text
e e*
UNITED STATES NUCLEAR REGULATORY COMMISSION Docket No~~~S.:.
Docket~~0-25.,2_.....)
Consumers Power Company ATTN:
Mr. R. B. DeWitt Vice President Nuclear Operations 212 West Michigan Avenue Jackson, MI 49201 Gentlemen:
REGION Ill 799 ROOSEVELT ROAD GLEN Ell YN, ILLINOIS 60137 APR 2 1880 IE Circular No. 80-03 dated March 6, 1980, was inadvertently sent to you without the enclosed attachments.
We are sorry for any inconvenience this may have caused you.
Sincerely,
~-....a.1(-wL James G. Kepp e.
Director Attachments:
Sections 2.2.1-2.2.2; 2.2.3 and 6.4 of NUREG 75/087 cc w/attach:
Mr. D. P. Hoffman, Nuclear Licensing Administrator Mr. C. J. Hartman, Plant Superintendent Mr. J. G. Lewis, Manager Central Files Director, NRR/DPM Director, NRR/DOR PDR Local PDR NSIC TIC Ronald.Callen, Michigan Public Service Commission Myron M. Cherry, Chicago
.. __:., ___ 1.,. ___.*,
TJQJ1
- t
(
NUREG-75/087 U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTION 6.4 HABITABILITY SYSTEMS REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAB)
Secondary - Hydrology-Meteorology Branch {HMB)
Auxiliary Systems Branch (ASB)
Effluent Treatment Systems Branch {ETSB)
I.
AREAS OF REVIEW The contro 1 room vent i1 at ion system and contro 1 bui 1 ding 1 ayout and structures, as.described in the applicant's safety analysis report (SAR), are reviewed with the objective of assuring that plant operators are adequately protected against the effects of acci~ental 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 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 ~one (control room, kitchen, sanitary facilities, etc.) and to assure that those areas not requiring access are generally excluded from the zone.
- 2.
- 3.
The capacity of the control room in terms. of the number of people* it can acco11111odate for an extended period of time is reviewed to confirm the adequacy of emergency food and medi ca*l supplies and se 1 f-contai ned breathing apparatus and to determine the length of time the control room can be isolated before co2 levels become excessive..
The control room ventilation system layout and functional design is reviewed to determine flow rates and filter efficiencies for input into the AAB analyses of the buildup of radioactive or toxic gases inside the control room, assuming a design basis release. Bask deficiencies that 111ight impair 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 ASB is consulted when reviewing hardware and* operating procedures.
USNRC STANDARD REVIEW PLAN
-dard-..----tor-auidaftceo*-Officeoflllu-llNCtorli-lotionn.rt_.lbhoforttle-of llPPflcft'-**o-end
....,... nuc..., power,a.nu. TMM docul'Mftt8 en med*..,.....,.. 'tD dM,..buc
- pen of the Co111m6aion'* 'policy to infonn the n_.._ Munry end th*
_..,..bile of,..ulftory.,-u __...,.__..__ -
not -- for regulnery.- or-c-... -*a,...._ -
-..i-ce--*--ul,....TM __....., ___.,.clto-2of_l ___
C:--of-,,_.,.ll_rta
.. -**----*-~-plan.
....... -be.-~.-~** to--.---to -,_..,,_..... -......-...
fer~-----*-*tlleU.8.-ll...-,,C1**'11l1 o.-of--llelu-
-.---......D.c.-.
Rev. 1
...... e
--~---
- 4.
The flow rates and iodine removal efficiencies used in the analysis are obtained fro*
the ETSB (see SRP 6.5. 1).
- 5.
The physical location of the control room with respect to potential release po1nts of hazardous airborne materials (SAR Chapter 2 and other pertinent chapters) is reviewed to deter111ine the location and source strength of radioactive, toxic, or noxious materials.
The layout of the control building is reviewed to assure that airborne*
materials will not enter the control room from corridors or ventilation ducts, etc.
Estimates of dispersion of airborne contamination ar, made in conjunction with HMS.
- 6.
Radiation shielding provided by structural concrete is analyzed to dete,..ine the effectiveness of shielding and structure surrounding the control room.
The control building_ layouts are checked to see if radiation streaming through doors (or other apertures) or from equipment might be a problem.
- 7.
Independent analyses are performed to determine whether dose values or toxic gas con-centrations remain below recommended levels.
The HHB provides meteorological input and checks the X/Q values for the control. room location.
II.
ACCEPTANCE CRITERIA
- 1.
Control Room Emergency Zone See Section.III:l of this plan.
- 2.
Control Room Personnel Capacity
- Food, water, and medical supplies should be sufficient to maintain the emergency team I
(at least 5 men) for 5 *days.
I
- 3.
Ventilation System Criteria (See III.3 of this plan).
Rev. 1 The following criteria_*deal with the verification of acceptable system perfonaance and assurance of system availability:
- a.
Isolation Dampers - Dampers used to isolate the control zone from adjacent zones or the outside must be leaktight.. This may be accomplished by using low leakage dampers or valves.
The degree of leaktightness should be documented in the SAR.
- b.
Single Failure - A single failure of an active COIJIPOnent should not result in loss. of the system's functional performance. All the components of the eontrol roo* emergency filter train will be considered active co1111>onents.
See Appendix A
. for criteria regarding valve or damper repair.
- c.
- Pressurization Systems - Systems that will pressurize the control ro<>11 during a radiation emergency should meet the following requirements:
(l)* Those syste11s havi-ng pressurization rates of greater than or equal to 0.5 volume changes per hour will require periodic (every 18 110nths) verification that the 11akeup is ! lOI of design value. During plant construction or 5.4-2
-.r
- ..... \\
_,)
- v" f*
.)
- J
(
j
. i
~:** *,
- _ ~-.!...=----~-_..-::.
- e after any modifications to the control room that might significantly affect its capability to maintain a positive pressure, measurements should be taken to verify that the control room is pressurized to at least 1/8-inch water gauge relative to all surrounding air spaces (while applying the design makeup air rate).
(2) Those systems having pressurization rates of less than 0.5 and equal to or greater than 0.25 volume changes per hour will have identical testing requirements as indicated in (1), above.
In addition, at the CP stage an analysis *ust be provided (based on the planned leaktight design features) that ensures the feasibility of maintaining 1/8-inch water gauge differential with the design makeup air flow rate.
(3) Those systems having pressurization rates of less than 0.25 volume changes should meet all the requirements for (2), above, except that periodic
. verification of control room pressurization (every 18 months) will be required.
- 4.
Toxic Gas Protection Self-contained breathing apparatus for the emergency team (at least 5 men) should be on hand. A six-hour onsite bottled* air supply should be available* with unlimited offsite* replenislwent capability from nearby location(s). Refer to References 3 through 6, and see Section III.3*of this plan.
- 5.
Emergency Standby Filters See Standard Review Plan 6.5~1 for acceptance criteria for control room* ESF systems.
Credit for iodine removal efficiencies will be given in accordance with Regulatory Guide 1.52. Filter efficiencies for systems not covered by Regulatory Guide 1.52 will be detennined.on a.case-by-case basis by*ETSB.
- 6.
Relative Location of Source and Control Room In general, the ~ontrol room inlets *ust be so placed in relation to the location of potential release points as to *inimize control room contamination in the event of a release. Specific criteria as to radiation and toxic gas sources are as follows:
- a.
Radiation Sources
- b.
As a general rule the control roo11 ventilation inlet should be separated from the major potential release points by at least 100 feet laterally and by 50 feet vertically. However, the actual *inimum distances must be based on the dose analyses. Refer to Section II_I of this plan and Reference 7 for further information.
Toxic gases The minimum separation distance is dependent upon the.gas i'n question, the container size, and the available control room protection provisions. Refer to Regulatory Guide 1.78 (Ref. 3) for general guidance and to Regulatory Guide 1.95 (Ref. 4) for specific acceptable design provisions related to chlorine.
6.4-3 Rev. 1
. ~.*.
- -**---~-*. --~" ----............. ~... ;. __ _
- 7.
Radiation Shielding
- See discussion of General Design Criterion 19 below.
- 8.
Radioactive and Toxic Gas Hazards
- a.
Radiation Hazards The dose guidelines {see General Design Criterion 19, Appendix A of 10 CFR Part 50) used in* approving emergency zone radiation protection provisions are as.
follows:
(1) Whole body ganrna:
5 rem (2) Thyroid:
30 rem (3) Beta skin dose:
30 renrt The whole body ganrna dose consists of contributions from airborne radioactivity inside and outside the control room, as well as direct shine from fission products inside the reactor containment building.
- b.
Toxic Gases For acceptance purposes, three exposure categories are defined:. protective act.ion exposure. (2 minutes or less), short-term expos_ure (between 2 minutes and l hour), and long-term exposure (l hour or greater). Because the physiological effects can var)' widely from one toxic gas to another, the following general restrictions-should be used as guidance: there should be no chronic effects frOlli exposure, and acute effects, ff any, should be reversible within a short*
- period of time* (several minutes) without benefit of medication other than the use of self-contained breathing apparatus.
The allowable limits should be established on the basis that_the operators should be capable of carrying out their duties with a minimum of interference caused by the gas and subsequent protective measures.
The limits for the three categories normally are set as follows:.
(1) Long-term limit (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or greater):
exposure (40-hour week).
use a limit. assigned for occupational (2) Short-term limit (2 minutes to.l hour):
use a limit that will assure that the operator will not suffer incapacitating effects after.a 1-hour exposure.
- Credit for the beta radiat1on shielding afforded by special protective clothing and* eye pro-tection is allowed if the applicant conmits to their use during severe radiation releases.
However, even though protective clothing is used, the calculated unprotected skin dose is not to exceed 75 rem.
The skin and thyrotd dose levels are to be used only for judging the acceptability ol the design provisions for protecting control room operators under postulated design basis accident conditions. They are not to be interpreted as acceptable emergency doses.
The dose levels quoted here are derived for use in the controlled plant environment and
_)
_)
should not be confused with the conservative dose computa.tion assumptions used in evaluating exposures to the genera 1 pub 1i c for the purposes of comparf son with the guide 1i ne va 1 ues
')
of 10 CFR Part 100.
Rev. l 6.4-4
).
(
~ >
~~-
-~~~~~~~~~~~
__ ! ____ ~-,;__-.:- -;_,_!. --. ;*-~*::;_..L.;_-:~-~~:.:,_..:*-.:::.:.:;.._
(3) Protective actfon limit CZ 11in. or less) use a limit that will assure that the operator will quickly recover after breathing apparatus is in place.
In determining this limit, it should be assumed that the concentration increases linearly with tilne frOll zero to two minutes and that the limit is attained at two minutes.
The protective action limit is used to deteT'llline the acceptabflfty of emergency zone protection provisions during the ti11e personnel are fn the process of fitting themselves with self-contained breathing apparatus.
The other limits are used to determine whether the concentrations with breathing apparatus in place are applicable.
(They are also used in those cases where the toxic levels are such that emergency zone isolation without use of protective gear is suffi-cient.) As an example of appropriate limits, the following are the three levels for chlorine gas:
Long-tenn:
1 ppm by vo 1 ume:
Short-term:
4 Protective action:
15 (See Reference* 3 for protective action levels for other toxic* gases.)
III *. REVIEW PROCEDURES The reviewer selects and*emphasfzes aspects of the areas covered by this review* plan as may be appropriate*for a particular case.
The judgment on areas to be given attention and emphasis in the review is based on an inspection* of the material presented to see whether it is similar to that recently reviewed for other plants and whether items of special safety significance are involved.
- 1.
Control Room Emergency Zone The reviewer checks to see that the zone includes the following:*
- a.
Instrumentation and controls necessary for a safe shutdown of the plant, i.e.,
the control room, including the critical document reference file.
- b.
The COllputer roOll, if ft is used as an integral part* of the e11ergency response plan.
- c.
The shift supervisor's office.
d..
The operators' wash room and the kitchen.
The emergency *zone should be limited to those spaces requiring operator occupancy.
Spaces such as battery ro011s, cable spreading rooms, or any other spaces not requiring continuous or frequent occupancy after a desiQft basis accident (OBA) generally should 6.4-5 Rev.
- i j
J
- *- --**--* -i.***.
"...,:.. '~*.
.e be excluded fra11 the* emergency zone.
Inclusion of these.spaces may increase the probabiHty of smoke or hazardous gases entering the emergency zone.
They Ny also increase the possibility of infiltration into the emergency zone, thus dec~easing the effectiveness of the ventilation.system in excluding contamination. It is-advantageous to have the emergency zone located on one floor, with the areas included in the zone being contiguous *
- 2.
Control Room Personnel Capacity
- 3.
The reviewer checks to see that emergency food and water are provided.
Normally, a five-day supply for five men would be sufficient for land-based plants. A medical kit is also helpful. Specific requirements for these items have not been formulated.
The air inside a 100,000 cubic foot control room would support five persons for at least six days.
Thus, co2 buildup in an isolated emergency zone is not normally considered a limiting problem.
Ventilation System Layout and Functional Design This area is a major port ion of the review.
The procedures are as. fo 11 ows:
a..
The type of* system proposed is determined.
The following types of protection provisions are currently being employed for boiling water reactor (BWR) or pressurized water reactor (PWR) plants:
(1) Zone isolation, with the incoming air filtered and a positive pressure
-L *. '"'.
-.._1,...,,._~
--~
)
~...
i
~-
\\
i maintained by the ventilation. system fans.
This arrangement is often
__.)*
provided for.BWRs having high stacks. Air flow rates are between 400 and Rev. l 4000 cfm.
(2). Zone isolation, with filtered recirculated air. This arrangement is often provided for BWRs and PWRs with roof vents.
Recirculation rates range from 2,000 to 30,000 cfm.
(3) Zone isolation, with filtered recirculated air, and with a positive pressure maintained in the zone.
This arrangement is essentially the same as that in (2), with the addition of the positive pressure provision.
(4) Dual air inlets for the emergency zone.
In this arrangement, two widely spaced inlets are located outboard (on opposite sides) of potential toxic and radioactive gas sources.
The arrangement guarantees at least* one inlet being free of contamination (except under extreme no-wind conditions). It can be used in all types of plants.
Makeup air supplied from the contamination-free inlet provides a positive pressure in the emergency zone and thus *inimizes infiltration.
6.4-6
)
- ~
.I
(
. ____ __...!;..,.,.--*.~**'
- b.
(5) Bottled air supply for a limited time.
In this arrangement, a flow* rate of 400 to 600 cfm is provided from compressed air containers for about one hour, to prevent inleakage. It is used in systems having containments whose internal*atmospheric pressure becomes negative within an_~our after a OBA (subatmospheric containments).
The input paruieters to the radiological dose 110del are determined (see Item 5).
The parameters are emergency zone volume, filter efficiency, filtered *akeup air flow rate, unfiltered inleakage (infiltration), and filtered recirculated air.
flow rate.
- c.
The ventilation system components and the system layout diagrams are examined.
The responsible reviewer in the ASB should be consulted if there are questions pertaining to the system design.
He will determine if the system meets the single failure criterion as well as other safety requirements (see Standard Review Plan Section 9.4.1).
Damper failure and fan failure are especially important.
The review should confirm that the failure of isolation dampers on the upstream side of fans will not result in too much unfiltered air entering the control room.
The AAB dose analysis results are used to determine how much unfiltered air can be tolerated.
- d.
The following inforaation *ay be used in evaluating the specific system types (see Reference *7 for further discussion):
(1) Zone isolation, with filtered incoming air and positive pressure.
These systems may not be sufficiently effective in protecting against iodine, (2)
The staff allows an iodine protection factor (IPF), which is defined as the tim~integrated concentration of iodine outside over the time-integrated concentration within the emergency zone, of 20 to 100 for filters built,
. 11aintained, and.operated according to Regulatory Guide 1.52 (an IPF of 100 requires deep bed filters).
Such systems are likely to provide a sufficient reduction in iodine concentration only if the source is at some distance from the inlets.. Thus, in most cases only plants with high stacks <~ 100 m) would meet Criterion 19 with this system.
Normally the staff suggests that these systems be 1110dified to allow isolation and operation with recircu-lated air since only minor ducting changes are necessary.
Zone isolation, with filtered recirculated air. These systems have a greater potential for controlling iodine than those having once-through filters. IPFs ranging from 20 to over 150 can be achieved.
These are the usual designs for plants having vents located at containment roof level. A system having a* recirculation rate of 5000 cfm and a filter efficiency of 9SS would be rated as follows:
6.4-7 Rev. 1
Rev. 1
-~--*----*--**e----
- -----**-*--*-~-------------e-Infiltration (cfm)
IPF*
200 25 100 49 50 96 25 191
- Within the.range of interest, the iodine protection factor is directly proportional to recirculation flow rate times efficiency.
Infiltration should be determined conservatively. The calculated or measured gross leakage is used to determine the infiltration rate that will be applied in the evaluation of the radiological consequences of postulated accidents. This rate fs determined as follows:
(i) The leakage from the control room when pressurized to 1/8-inch water gauge is calculated on the basis of the gross leakage data. One-half of this value is used to represent the base infiltration rate *
. Component leak rates may be used to calculate gross leakage (see, for example, References 8 and 9).
(ii) The base infiltration rate is augmented by adding to it the estimated contribution of opening and closing of doors associated with such activ-ities as the required emergency procedures ex.ternal to the control room.
Normally, 10 cfm is used for th.is additional cont~ibution.
l i 1 fl An additional factor that is used to modify the base infiltration rate is the enhancement of the infiltration occurring at the dampers or valves upstream of recirculation fans.
When closed, these dampers typically are exposed to a several-inch water gauge pressure differential. This is accounted for by an additional infiltration contribution over the base infiltration at 1/8-incti water gauge.
The use of an infiltration rate that is based on calculation is acceptable except in the case where the applicant has assumed exceptionally low rates of infiltration. In these cases, more substantial verification or proof may be required. For instance, ff an applicant submits an analysis that shows a gross leakage rate.of less than 0.06 volume changes per hour,
- the reviewer would require that the gross leakage be verified by periodic tests as described. in Regulatory Position C.5 of Regulatory Guide l.95.
(3) Zone isolation, with filtered recirculated air, and with a positive pressure.
This system is essentially the same as the preceding one. However, an additional operational mode is possible. Makeup air for pressurization is amnitted. It is filtered before entering the emergency zone. Pressurization reduces the unfiltered inleakage that is assumed to occur-when the emergency 6.4-8
~
~
/
) -
~..
)
)
j
- j
'.. }
1*
(
Q
-r
~
J
- * (.
...... ***~-...
zone is not pressurized. Assuming a filter fan capacity of 5000 cfm and a filter efficiency.of 951, the following protection factors result (flows in cfm):
IPF (Assuming 1!F (Assuming Makeue Air Recirculated Air No Infiltrationl Infiltrationlltl 400 4600 238 159 750 4250 128 101 1000 4000 96 80 The lilakeup flow rate should have adequate margin to assure that the control woom will be maintained at a pressure of at least 1/8-inch water gauge.
The applicant should indicate that an acceptance test will be performed to verify adequate pressurization. If the makeup rate is less than 0.5 volume changes per hour, supporting calculations are required to verify adequate air flow.
If the *akeup rate is less than 0.25 volume changes per hour, periodic verification testing is required in addition to the calculations and the acceptance test.
A.question that often arises is whether pressurization" or "isolation and recirculation" of the control room is to be preferred. Which design gives the. lowest doses depends upon the assumptions as to unfiltered inleakage.
Isolation is generally preferred in that it wi.11 limit the entrance of noble gases (not filterable) and, in addition, it is a better approach when the accident involves a short-term. "puff release.
11 If infiltration is.*
25 cfm or less, "isolation" would be best in* any event.
A second question related to the first involves.the method of operation: The following possibilities have been considered:
(
(i) Automatic isolation with subsequent 111anual control of pressurization.
(ii) Automatic isolation with iimnediate automatic pressurization.
The first is advantageous in the case of external puff releases.
Si111Ple isolation would minimize the buildup of the unfilterable noble gases. It would also protect the filters fro11 excessive concentrations in the case of a chlorine release. However, the second method does guarantee that infiltration (unfiltered) is reduced to near zero. f11111ediately upon accident detection.
This would be beneficial inthe case where the contamination transport path No1"11ally 10 cflt infiltration is ass1111ed for conservatism. This flow could be reduced or eli-
- fnated if the applicant provides assurance that backflow (primarily as a result of ingress and egress) will not occur. This 11ay mean installing two-door vestibules or equivalent.
6.4-9 Rev. 1
-...--__,.-------~~--------:--**--.-,--,----- -* ::..,-*-.. -..
- < i Rev. l to the e11ergency zone is mainly inside the building. Method (f) should be used in the case of a toxic gas release and either method (i) or (ii) should*
be used in the case of a radiological release, provided Criterion 19 guidelines can be satisfied.
(A substantial time delay should be assumed where 111anual isolation is. assumed, e.g., 20 minutes for the purposes of dose calculations.)
(4) Dual air inlets for the emergency zone. Several plants have utilized this concept.
The viability of the dual inlet concept depends upon whether or not the placement of the inlets assures that one inlet will always be free fro*
contamination.
The assurance of a contamination-free inlet depends in part upon building wake effects, terrain*, and the possibility of wind stagnation or reversal. For ~xample, fn a situation where the inlets are located at the extreme edges of the plant structures (e.g., one on the north side and one on the south side), it is possible under certain low probability conditions for both inlets to be contaminated from the same point source.
Reference 7 presents the interim position for dealing with the evaluation of X/Q's for dual inlet systems.
- Witn dual inlets placed on plant structures are on opposite sides of potential radiation release points (e.g, containment building), and are capable of functioning with an assumed single active failure in the inlet isolation system,*the following considerations 111ay be ap~lied to the evaluation of* the control room X/Q's:
(f). Dual inlet designs without manual or automatic selection control -
Equation (6) of Reference 7 may be used with respect to the least favorable inlet location to estimate X/Q's.
The estimated values can be reduced by a factor of two (2) to account for dilution effects associated with a dual inlet configuration. This is based upon the dilution derived fro11 drawing fn equal amounts of clean and contaminated air through two open inlets.
(ii) Dual inlet designs limited to manual selection control - Equation (6) of Reference 7 may be used with respect to the more favorable inlet location to estimate the X/Q's.
The estimated values can be reduced by a factor of four (4) to account for dilution.effects associated with a dual inlet configuration and. the relative probability. that the operator will make the proper inlet selection. The reduction
.factor is contfngent.. upon having redundant radiation detectors within each air inlet.. The reduction factor is based on the judgment that trained control ro011.operators, in conjunction*with radiation alarm indication, will select and close the contaminated air inlet.
~ff) Dual inlet designs with aut0111atfc selection control features -
Equation (6) of Reference 7 may be used with respect to the 110re 6.4-10
_ _,,. )
)
. -~
(
r**
e*
favorable inlet location to estimate the X/Q's.
The estimated values can be reduced by about a factor of ten (10) to account for the ability to select 11 "clean" air inlet.
The actual factor may be somewhat higher if the inlet configuration begins to approach the remote air inlet concept such that the probability of having one clearrair i"nlet is relatively high.
Plant configuration and 11eteorological conditions should be used as the principal basis for reduction factors greater than ten (10).
The reduction factor of ten (10) or more is contingent upon having redundant radiation detectors in each inlet and the provisions of acceptable control logic which would be used in the automatic selection of a clean air inlet.
Because damage to the ducting might seriously affect the system capability to protect the operators, the ducting should be seismic Category I and should be protected against tornado missiles.
In addition, the number and placement of dampers aust be such as to assure both flow and isolation in each inlet assuming one single active component failure.
(See Appendix A for information on the damper repair alternative.) The location of the intakes with respect to the plant security fence should also be reviewed.
(5) Bottled ai~ supply for a limited ti11e.
In some plant designs the containment pressure is reduced below atllospheric within one hour after a OBA.
This generally assures that after one hour significant radioactive material will not be released from the containment.
Such a design makes it feasible to 11111intain the control room above atmospheric pressure by use of bottled air.
Periodic pressurization tests are required to determine that the rated flow (nol'l!lally about 300 to 600 cfm) is sufficient to pressurize the control room to at least 1/8-inch water gauge.
The system is also required to be composed of several separate circuits (one of which is assumed to be inoperative to account for a possible single failure).
At least one (nonredundant) once-through filter system for pressurization as a standby for accidents of long duration is also desirable.
Compressed air bottles should be protected fr011 tornado missiles or internally-generated missiles and should be placed so as not to cause damage to vital equipment or interference with operation if they fail.
- 4.
Emergency Standby Filters
- 5.
Refer to Standard Review Plan 6.5. l.
Relative Location of Source and Control Room This review area involves identification of all potential sources of toxic, radioactive, or othentise potentially hazardous gases and analysis of their transport to the control room.
There are three basic categories:
OBA radioactive sources, toxic gases such as 6.4-ll Rev. 1
*- ~-*-- --*----- -.**** *- --.. *:* ---.
i
.l Rev. 1 e -- ---~----*-*-*.
-~-----
chlorine, and gases with the potential for being released inside confined areas adjacent to the control room.
- a.
OBA Radioactive Sources
- b.
The LOCA source terms determined in Appendix A to Standard Review Plan 15.6.5 review are referred to and routinely used to evaluate radiation levels external to the control room.
The disper6al from the containment or the standby gas treatment vent is determined with a building wake diffusion model.
This model is discussed in Reference 7. Other DBAs are reviewed to determine whether they might constitute a more severe hazard than the LOCA.
If this is suspected, an additional analysis is performed for the suspect DBAs.
The HMB provides the meteorological input and reviews the AAB calculation of X/Q values.
Toxic Gases The applicant is asked to identify those toxic substances stored (or transported) on or in the vicinity of the site which may pose a threat to the reactor oper-.
ators by producing toxic gases upon accidental release. The method used to determine whether the quantity or location of the toxic material is such as to require closer study is described in Regulatory Guide 1.78 (Ref. 3). This guide also discusses the methods for analyzing the degree of risk and states, in general terms, the various protective measures that could be instituted if the hazard is found to be too great.
In the case of chlorine, specific acceptable protective provisions have been determined; these are described in detail in Reference 4.
In sumiiary, the following provisions or their equivalent are required *(pertaining to the emergency zone ventilation system):
(1) Quick-acting toxic gas detectors.
(2) Automatic emergency zone isolation.
(3) Emergency zone leaktightness.
(4) Limited fresh air makeup rates.
- (5) Breathing apparatus and associated bottled air supply.
(Note that the best solution for a particular case will depend on the toxic gas in question and on the specific ventilation syste11 design.)
- c.
Confined Area Releases The reviewer studies the control building layout in.relation to potential sources inside the control building or adjacent connected buildings.
The following con-cerns are checked:
6.4-12
\\
.. )
)
. ~
- ~
- 6.
(.
c~*
(1) Storage locations of co2 or other ffrefighting materials should be such as to eliminate the possibiHty of significant quantities of the gases entering the
- emergency zone.
(The ASB has the primary responsibility in this area.)
(2) The ventilation zones adjacent to the emergency zone should be~onfigured and balanced to preclude air flow toward the emergency zone.
(3) All pressurized equipment. and* piping (e.g., main steam lines and. turbines) that coul.d cause significant pressure gradient~ when failed inside buildings should be isolated from the emergency zone by multiple barriers such as multiple door vestibules or* their equ~valent.
Radiation Shielding Control roOlll operators as well as other plant personnel are protected from radiation sources associated with a nonnally operating plant by various cOlllbinations of shield-ing and d;stance.
The adequacy of this type of protection*for nol'lllc11 operating conditions is reviewed and evaluated by the RAB.
To a large extent the same' radia-tion shielding (and missile barriers) also provides protection from design basis accident radiation sources.
This is especially true with respect to the control room walls which usually consist of at least 18 inches of concrete. In lllOSt cases; the radiation. c0tning from external design basis accident radiation sources fs attenuated to negligible levels.
However, the following items. should be considered qualitatively in assessing the adequacy of control room radiation shielding:
- a.
Control room structure boundary.
Wall, ceiling, and floor materials and thH:k-
. ness should be reviewed. Eighteen inches to two feet of concrete or its equivalerit will be adequate in 110st cases.
- b.
Radiation streaming.
The control room structure'boundary should.be reviewed with respect to penetrations (e.g., doors, ducts, stairways, etc.). The potential for radiation streaming from accident sources should be identifJed, and if deemed necessary, quantitatively evaluated. Support from the RAB may be required for SOiie radiation streaming dose calculations.
- c.
Radiation shielding from internal sources. If sources internal to the control roOll C011plex are identified, radiation shielding aga~nst them should be reviewed.
Typical sources fn this category include contaminated filter trains, or airborne radioactivity in enclosures *adjacent to the control room.
Evaluations of radiation shielding effectiveness with respect to the above items should be perfor11ed using si11plified analytical 110dels for point, line, or volume sources such *as those presented in References 10 and 11.
If llOre! extended analysis is required, analytical support fro11 the RAB should be requested. The applicant*s
- coverage of the above items should also be reviewed in terms of c011pl,teness, method of analysis, and assumptfons.
Rev. 1
- -----**-**~--,.-~* -----*----,,*------*-*--*--*.,. -**---** --...
- .~.......
't *.~~-
- .f"**. *.
9*
- 7.
Independent Analyses
- a.
Control Room Doses Although the applicant is required to calculate doses to the control room operators, independent analyses are made by the AAB because of the diversH;y of control room habitability system designs and the engineering judgment involved in their evaluation.
Using* the approach indicated in Reference 7, the source terms and doses due to a OBA are calculated.
The source terms determined by the AAB's independent analysis of LPZ doses for a LOCA are used.
The methods and assumptions for this calculation are presented in Appendix A to Standard Review Plan 15.6.5.
The control room doses are determined by estimating the X/Q from the source points to the emergency zone using meteorological input supplied by the HMB, by deten11ining the credit for the emergency zone's protection features, and by calculating the dose.
Figure 6.4-1 shows a form which may be used to su11111arize the information that is needed for the control room dose calculation.
The effective X/Q's are used for calculating the doses.
The dose is then compared with the guidelines of General Design Criterion 19.
If the guidelines are exceeded, the applicant is asked to improve the system.
In the event that other DBAs are expected to result in doses comparable to or higher than the
- LOCA, additional analyses are performed.
The limiting accidents are compared with Criterion 19.
' b.
Other Analyses Special case analyses are performed when questions are raised about certain poten-tial sources of toxic or radioactive gases.
The methods used in these analyses*
confonu to current OBA methods concerning dispersion and dose calculations.
Regulatory Guide 1.78 should be consulted by the site analyst to see if nearby facilities could present a potential hazard that requires detailed analysis.
IV.
EVALUAT!ON FINDINGS The reviewer verifies that sufficient information has been provided and that the review and calculations support conclusions of the following type, to be included in the staff's safety evaluation report:
- 1.
If the plant meets Criterion 19, the following statement or its equivalent is made:
Rev. 1 "The applicant proposes to meet General Design Criterion 19 of Appendix A to 10 CFR Part 50 by use of concrete shielding and by installing redundant~~ cfm recirculating charcoal filters in the control roOll ventilation system.
These fil\\ers will be automatically activated upon an accident signal, high radiation signal, or high chlorine signal.
Independent calculations of the potential radiation doses to control roo~ personnel following a LOCA show the resultant doses to be within the guidelines of Criterion 19."
6.4-~4
__ )
)
/
'\\ j
- -*~
- "."-
- , -*,... *.;*....,_~~,-...;*:t-.":.-."";--
( '
- -. /
(
,1
~...
~
- -** ~.o/.:..... ------.
9*-
- 2.
If the design is not adequate, the fact is stated. Alternatives such as an increase in the charcoal filter flow rate may be indicated as is given fn the example below:
"The staff has calculated the potential radiation doses to control-room personnel following a LOCA.
The resultant whole body doses are within the g~idelines of Criterion 19.
The thyroid dose resulting from exposure to radioactive iodine exceeds the dose guidelines.
The applicant will be required to commit to increasing the filtration system size from 2000 cfm to 4000 cfm.
This increased filtration will be sufficient to keep the estimated thyroid doses within the guidelines."
- 3.
If special protection provisions for toxic gases are not required, the following state-ment or its equivalent is made:
"The habitability of the control room was evaluated using the procedures described in Regulatory Guide 1.78.
As indicated in Section 2.2, no offsite storage or transport of chemicals is close enough to the plant to be considered a hazard.
There are no onsite chemicals that can be considered hazardous under Regulatory Guide l. 78.
A sodium hypochlorite biocide system will be used, thus eliminating an onsite chlorine hazard.
Therefore, special provisions for protection against toxic gases will not be required. Self-contained breathing apparatus is provided for the.
emergency crew to provide assurance.of control room habitability iri the event of occurrences such as s11oke* hazards."
4.*
If special protection provisions are required, compliance or noncompliance, with the guidelines of Regulatory Guides 1.78 and l.95 should be stated.
V.
REFERENCES
- 1.
10 CFR Part 50, Appendix A, General Design Criterion 19, "Control Room."
- 2.
Regulatory Guide 1.52, "~esign, Testing, and Maintenance Criteria for Engineered-*
Safety-Feature Atmosphere Cleanup System Air Filtration and Adsorption Units of Light-Water-Cooled Nuclear Power Plants."
- 3.
Regulatory Guide 1.78, "Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release."
- 4.
Draft'Regulatory Guide 1.95, "Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release."
- 5.
Draft Regulatory.Guide 8.X, "Acceptable Programs for Respiratory Protection."
- 6.
"Manual of Respiratory Protection Against Airborne Radioactive Material,"
WASH-1287, U.S. Atomic Energy C011111ission (1974)~
6.4-15
... _ -* *-~*** ',!......,.
Rev. 1
]. :
l i -*
- i.
- 7.
- 8.
. ~** --,::,.;.,_~*------~-~-
.. e K.G. Murphy and K.M. Campe, "Nuclear Power Plant Control Room Vent nation System
- .Design for Meeting General Design Criterion 19," 13th AEC Air Cleaning Conference, August 1974.
"Leakage Characteristics of Openings for Reactor Housing Components,"
NAA-SR-MEM0~5137, Atomics International, Div. of North American Aviation, Inc.,
June 20, 1960.
- 9.
R. L. Koontz, et al., "Leakage Characteristks of Conventional Building Components for Reactor Housing Construction," Trans. Am. Nucl. Soc., November 1961.
- 10.
R.G. Jaeger, et al., eds., "Engineering Compendium on Radiation Shielding,"
Vol. 1, "Shielding Fundamentals and Methods," Springer-Verlag (1968).
- 11.
N.M. Schaeffer, "Reactor Shielding for Nuclear Engineers," TID-75951, U.S. Atomic.
Energy Commission.
Rev. 1 6.4-1~
)
)
-~.
/
~-..
... )
. ~;..
(
e**
SECTION 6.4 APPENDIX A ACCEPTANCE CRITERIA FOR VALVE OR DAMPER REPAIR ALTERNATIVE The control room ventilation system must meet the criterion that it work properly even with a single failure of an active component.
In certain cases, complex valve or damper configurations are required to meet the single failure criterion. For example, assurance of the isolation and operability of each leg of a dual inlet system at various times after a postulated accident coula requ1 re a fciur*va*1 ve-arrangement-in-which-two-pa irs-of-series-valves-are-connected-i n parallel. The 111echnical, power, and control COlllJ>onents of such arrangements combine to fonn a rather c011plex system. Credit will be allowed for an alternative system that allowed the failed valve to be aanually repositioned so that ft will not interfere with the operation of the system.
For example, in the case of a dual inlet system, if credit for repair is given, then two* valves in series in each leg of the dual inlet would be acceptable. Where a valve fails closed but meets the criteria given below, credit would be allowed for the valve to be repositioned and locked in.an open posit.ion.
The approval of the repair option is contingent upon the intrinsic reliability of *the internal COlllponents of the.valve* or damper and also upon the ease and ability to overcome the failure of the external actuating components (e*lectrical relays, 110tors, hydraulic pistons-, etc.).
The following cri.teria or their equivalent will be required:
- 1.
The valve or damper components must be listed as to which are* considered internal (nonrepairable) and which external (repairable). These must be designed to 11eet the following criteria.
- a.
Internal valve c011ponents (COllJ>Onents that are difficult to.repair*11anually without opening the ductwork) *ust be judged to have a very 1~ probability of failure.
The c0111ponent design details will be reviewed and characteristics such as simplicity, ruggedness, and suspectibility to postulated failure 11echanisms will be considered in
- arriving at an engineered judgment of the acceptability of the internal COllponent design with respect to reliability. For example, a butterfly valve welded or keyed onto a pivot shaft.would be considered a high reliability internal COllpOnent
- Conversely, multiple-blade dampers, actuated by multi-element linkages or pneumatically-operated components internal to the ducts, would be viewed as being subject to failure.
- b.
External valve COllponents (c011ponents including 110tors and power supplies that are to be assumed repairable or re11<>vable) *ust be designed to ensure that the failed valve component can be bypassed easily and safely and' that the valve can be aanipulated into an acceptable position. The electronic c011ponents.Ust be isolated fl'Oll other equfp1tent to assure that the repair oper*tions do not result in further equip!lent failure.
6.4-17 Rev. 1
.. '."'t
- 2.
The location and positioning of the valve or damper must permit easy access from the control room for convenient repair, especially under applicable OBA conditions.
- 3.
Appropriate control room instrumentation should be provided for a clear indication*and annunciation of valve or damper malfunction.
- 4.
Periodic manipulation of the valve or damper by control room operators should be required for training purposes and to verify proper manual operability of the valve or damper.
- 5.
The need for manual manipulations of the failed valve or damper should not be recurrent during the course of the accident. Manipulation should not occur more than once during
\\
__ _)
--- tJie act-iaent;- Adjustment-or-rea-lignliient-of -other-pa~ts of the-system should _be pQs~ibl~ _______ _
from the control room with the failed valve in a fixed position.
- 6.
The time for repair used in the computation of control room exposures should be taken as the time necessary to repair the valve plus a one-half hour margin.
No manual correction will be credited during the first two hours of the accident.
- 7.
Compliance with the above criteria should be documented in the SAR whenever the repair option is used.
Rev. 1 6.4-18
)
,J...
... f
-. '.* -l.
j
- 1
~
c;
.. _*... 3
- .. *. l
. :... f
~... !
MOORAHDUM TO:
--**e FIGURE 6.4-1 S1111111ary Sheet for Control Room Dose Analysis cc:
L. Hulman R.W. Houston (Habitability File)
(Site Analyst)
(Meteorologist)
CONCERNING CONTROL ROOM DOSE ANALYSIS FOR The fo 11 owing su!Mlari zes the X/Q' s used in determining the control room operator dose for the subject plant:
. VENTILATION SYSTEM DESCRIPTION SKETCH OF SYSTEM (and inlets/sources if applicable)
Sllf4ATION OF X/Q ANALYSIS Source/Receptor Type and Distance S/D Ratio Number of 22 1/2° Wind Direction Sectors that Result in Exposure Central Wind Sector SS Wind Speed (II/sec)
Projected Area of Wake (m2)
Wind Speed Factor Wind Direction Factor 0-8 hr 8-24 hr 1-4 day 4-30 day ACTION REQUESTED Site Analyst 1
K Factor (sector wind is blowing.f!:2!!!)
40% Wind Speed Cm/sec) 5% X/Q (sec/m3)
Occupancy Factor 1
1 0.6 0.4 Effective X/Q's For your infol"lllation only Please use the effective X/Q's in TACT run and provide control room doses.
In addi-tion, please SURlllarize safety system assumptions and indicate their status (interim or final).
Meteorologist These are interim X/Q's.
Please review to determine their reasonableness.
These are final X/Q's.
Please deteT'lline if they are accurate based on your analysis of site data.
Please Contact -----------
6.4-19 Rev. 1
~- -,-":,~--~--
-*... **.- :*-. '~..... ---::--*- ~--:.-:--:.. -=-*-:.--. ~*-:-:-* -- *: -~**-:-... -.....
.i
~
'.,. t
.. i
_: j
-':<"**-~"":'"?"-*"'I NUREG-75/087 U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION SECTIONS 2.2.1 - 2.2.2 REVIEW RESPONSIBILITIES IDENTIFICATION OF POTENTIAL HAZARDS IN SITE VICl.NITY Primary - Accident Analysis Branch. (AAB)
Secondary - None I.
AREAS OF REVIEW
~ocations and separation distances from the site of industrial_, military, and transportation I facilities and routes in the vicinity of the site. Such facilities and routes include air, grounl1-;-and-water-traffic1 pipel-t nes,-and-f.ixed_manufac.t_uri ng_,_p'.--'ro--:-ce~s-:s-'i_n,,_g ::_* _a_nd_~~--i-----
storage facilities. Potential external hazards or hazardous materials 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 infonnation concerning the.presence of potential external hazards which 1s to be used in further review in Sections 2.2.3. 3.5.1.5, and 3.5.1.6.
II. ACCEPTANCE CRITERIA
- 1.
-~ta in the SAR adequately describes the locations and distances of inciustrial, 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 trans-ported, are adequate to permit evaluations of possible hazards in Part 3 review sections dealing with speciftc 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
. I provided to establish a basis for evaluating the potential *hazard to the plant.
III. REVIEW PROCEDURES Selection and emphasis of vartous aspects of the areas covered by this review plan will be made by the reviewer on each case. The jud!J11ent 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 items of special safety significance are involved. The following procedures are followed:
USNRC STANDARD REVIEW PLAN tu*llOIMc*-ot*ee......-*1.....,,.*-*-~--
_.. _..of...........,.-._- pollcioL -
- *-for_....._ e..-.... c-... -*, -- Md 1o ___,,.. __
,.... __....,...,_2ot __,......,_c-er......,.._..,.._,,.
ew:
"4-.....
,.,...,. ______._ ___ u.a.-.........,.c-- '1'n._., __
...-.--.-.D.C:-
Rev.
.. ), -
- -*,__~--* *-- *-'-' '.*~. '*"'-*-'-
-~'.i.-..:.'f,o;.;;,._,,.,,,..* ~~.-
- 1.
The reviewer should be especially alert. in the construction pennit(CP) stage review, for any potentially hazardous activities in close proximity of the plant. si_nce the variety of activities having damage potential at ranges under about one kilorneter can be very extensive. All identified facilities.and activities within eight kilorneters (5 miles) of the plant should be reviewed. Facilities and activities a~-greater distances should be considered if they otherwise have the potential for-a'ffecting plant safety-related features. At the operating license (OL) stage. lllOSt hazards will already have been identified. Emphasis should be placed on any new infonnation.
At the operating license stage. any analyses pertaining to potential accidents involv-ing hazardous materials or activities in the vicinity of the plant will be reviewed to ensure that results are appropriate in-light of any new data or experience which*
is then available. Facilities which are likely to either produce or consume hazardous materials should be investigated as possible sources of.traffic of hazardous materials
)
-~--------~past-the-s-i-te.-----------------~----:------~--------------1
. ~
- 2.
Information should be obtained frorn sources other than the SAR wherever available, and should be used to check the accuracy and cornpleteness of the information *subnitted in the SAR.
This independent information may be obtained from sources such as U.S.
Geological Survey (USGS) maps and aerial photos, published documents. contacts with state and federal agencies, and frorn other nuclear plant applications (especially if they are located in the same general area or on the same waterway.) Infonnation shoul.d also be obtained during the site visit* and subsequent discussions with loc;:al officials. (See Standard Review Plan 2.1.l for further guidance with,.egard to site visi_ts.) An attempt should be made to investigate future potential hazards over the proposed life of the plant.
- 3.
- The specific fofonnation relating to types of potentially hazardous material. includ-ing distance. quantity. and frequency of shipment. is reviewed to eliminate as many
. of the potential accident situations as possible by inspection. based on past review experience. At* the operating license stage. nearby industrial. military and trans-portation facilities and transportation re1utes will be reviewed for any changes or*
additions which may affect the safe operation of the plant. If these changes alter the data or assumptions used in previous hazards evaluations or demonstrate the need for nE!W ones. appropriate evaluations will be performed.
For pipeline hazards. Reference 7 may be used as an example of an acceptable risk assessment. For cryogenic fuels, Reference 9 may be used. and for ta~k barge risks. Reference 8. For military aviation, Reference 10 111ay be used. Safe separation distances for explosives are identified in Reference 2, and for toxic chemicals, References 3 and 4 should be consulted.
The distance fran nearby railroad lines is checked to determine if the plant is within the range of a 0 rocketing0 tank car which. from Reference 5. is taken to be
. 350 meters with the range for smaller pieces extending to 500 meters.
Rev. l 2.2.1-2
- -------... :-*-****---* ---------..... -~-~-
.'I I
l
"4)
'*J
(
(*
- 4.
.-_* ~-~--
- L----~*-'*'*
Potential accidents which cannot be eliminated from consideration as design basis events because the consequences of the accidents, 1f they. should occur, could be serious enough to affect plant safety-related features. are identiffed. *Potential accidents so identified are assessed in detail, using criteria in Standard Review Plan Sections 2.2.3 1 3.5.1.5 1 or 3.5.1.6, as appropriate.
IV.
EVALUATION FINDINGS The-reviewer verifies that sufficient infonnation has been provided, and that his evalu-ation fs sufficiently complete and adequate to support conclusions of the following type, to be used in the staff's safety evaluation report:
"The nature and extent of activities involving potentially hazardous aaterials which are conducted at nearby industrial, military, and transportation facilities have been evaluated to identify any such activfttes which have the potential for adversely affecting plant safety-related structures. Based on evaluation of 1nfonnat1on con-tained fn the SAR, as well as information independently obtained by the staff, ft is concluded that all potentially hazardous activities in the*vfc1nity of the plant have been identified. The hazards associated with these activities have been reviewed and are discussed in Sections ___ and of this SER.
11 If the.activities are iclentified as being potentially hazardous, the evaluations described.
1n Standard Review Plans 2.2.3; 3.5.1.5.and 3.5.1.6 are pe~fonned with respect to the*
I.
inherent capability of the plant or special plant design measures to prev~nt radiological releases 1n excess of the 10 CFR Part 100 guidelines.
V.
REFERENCES..
- 1.
Department of the Army Technical Manual TM5-1300, 11Structures to Resist the Effects of Accidental Explosions, 11 June 1969.
- 2.
Regulatory Guide 1.91, 11Evaluation of Explosions Postulated to Occur on Transportation Routes Near Nuclear Power Plant Sites. 11
- 3.
- Regulatory Guide 1.78, *Assumptions for Evaluating the Hab~tability of a Nuclear Power Pfant Control Room During a Postulated Hazardous Chemical Release. 11
- 4.
Regulatory Guide 1.95, "Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release."
- 5.
National Transportation Safety Board Railroad Accident Report, *Southern Railway Company, Train 154, Derailment with Fire and Explosion, Laurel, Mississippi, January 25, 1969, 0 October 6, 1969.
- 6.
Regulatory Guide 1.70, *standard Fonnat and Content of Safety Analysis Reports for Nuclear Power Plants," Revision 2.
2.2.1-3 Rev. 1
*-*--* **- -~**. *-****-**~. :.
~.
- 7.
NUREG-0014 Safety Evaluation Report, Hartsville Nuclear Plants Al, A2, Bl, and B2, April 1976 ~ Docket STN 50-518.
- 8.
Safety Evaluation of the Beaver Valley Power Station, Unit No. 2 November 9, 1976 and supplements. Docket 50-412.
- 9.
Safety Evaluation Report, Hope Creek Generating Station, Units 1 and 2, Supplement No. 5, March 1976, Docket 50-354 and 50-355.
- 10. Project 485, Aircraft Considerations, Preapplication Site Review, Boardman Nuclear Plant. October 1973.
- *
- U. S. COVERNllENT !'RINTINC OFFICE :
1978~720-387/277 Rev. 1 2.2.1-4
. _;-***** --- ;..... ~--***
~ -...
)
l
(_
-, ~
.... -*. ;-,.c-.-...4.---. -.,,-
.*. -:,,-.,---=*:*.,_,;
NUREG-75/087 U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN*
OFFICE OF NUCLEAR REACTOR REGULATION SECTION 2.2.3 EVALUATION OF POTENTIAL ACCIDENTS REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAB)
Secondary - Applied Statistics Branch (ASB/MPA)*
I.
AREAS OF REVIEW The applicant's identification of potential accident situations in the vicinity of the plant~s reviewed to_ d~tennine the compl~teness of.and the bases.upon whi:h these potential I
'----a-cc~1*Clents were or were not-a*ccOll'lllodated1n-the-des-1gn-. -(-See-Standard-Rev-iew-~Jans-2.2.* J _________ _
(~
. j and 2.2.2.)
The applicant's probability analyses of potential accidents involving hclzardous materials or activities in the vicinity of the plant, if such analyses have been perfonned, are also reviewed by ASB/MPA on request by AAB to detennine that approp".'iate data and ana*lytical models have been utilized.
The analyses of the consequences of accidents involving nearby industrial~ military, and transportation facilities which have been identified as design basis events are reviewed.
. II.
ACCEPTANCE CRITERIA The identification of design* bas.is events resulting from the presence of hazardous materials or activities in the vicinity of *the plant is acceptable if the design basis events. include each postulated type of accident for which the expected rate of occurrence of potential exposures in excess of the 10 CFR Part 100 guidelines is estimated to exceed the NRC staff.
objective of approximately 10-7 per year. Because of the difficult; of assigning accurate numeri ca 1 values to 'the expected rate of unprecedented potenti a 1 hazards generally con-sidered in this review plan, judgment must be used as to the accepta~ility of the overall risk presented.
The probability of occurrence of the initiating events leading to potential consequences in excess of 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 low probabilities of the events under consideration, data are often not available to pennit accurate calculation of probabilities. Accordingly, the expected rate.of occur-rence of potential exposures.in excess of the 10 CFR Part 100 guidelines of approximately lo-6 per year is acceptable ff, when combined with reasonable qualitative arguments, the*
realistic probability can be shown to be lower.
UBNRC STANDARD REV!EW PLAN
___.....,._PNIMo9dfM-*--ot-Oltlceol--orllogulnlonnaff-l0<--ol..,.alc8llontto--d
~*
nudur power planU. TMM documenu an lftede baia.ble to die public
- PM of the Commtul°" ~Y to info"" the nuc::IHr industry *d the
_.. public ol,..u1n..,.,.-u- -
Poflclm. S,..dMd -
.....,,.,. not oubotilut* for,..ulnory gu-or - c:o.-**,..u_ Md
-..---*----The--lllM--*..,..,to-2ol ____
c:.n....1-.~11-...
.. _., ______,....... -p!M.
___,....._..__...........,.* __._.c..--*..... --to--*1--~*
____,_,..... *11-*---*-c.ti.U.L-......-.c-1 ' **----.......
-.--..-.D.C,-,
Rev.
I'
~.,
. I.,.
. --. ~
-. : 1
~
~ t
. 'I
- i
. ~*
The effects of design basis events have been adequately considered if analyses of the effects of those accidents on the safety-related features of the plant have been perfonned
- and measures. (e.g., hardening, ffre protection) to mftfgate the consequences of such events have been taken.
III. REVIEW PROCEDURES In sane cases ft may be necessary to consult w1th or obtain specific data fran other branches, such as the Structural Engineering Branch (SEB) or Auxiliary Systems Branch (ASB), regarding possible effects of external events on plant structures or components.
The applicant's probability ca*lculations are reviewed, and an independent probability analysis fs perfonned by the staff ff the potential hazard is cons.idered significant
)
enough to affect the licensability of the site or is important to the identification of aesTgn-basts-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, 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 performed.
The design parameters (e.g., overpressure) and physical phenomena (e.g., gas concentration) selected ~Y 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 been adequately accommodated 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 evalu~tion of the effects of
- these accidents on control room habitability should be made fn SAR Section 6.4.and on the operation of diesels and other safety-related e'quipment in SAR Chapter 9.
Special attention should be given to the review of standardized designs which propose criteria involving individual numerical probability criteri.a for individual classes of external 1111n-made "8zards. In such instances the reviewer should establish that the envelope also in~ludes an overall criterion that limi.ts the aggregate probability of exceed-ing design criteria associated wfth all of the identified external man-made: hazards
- Similarly, special attention should be given to the review of a site where several llliln-made
_hazards are identified, but none of which, individually, has a probability exceeding the acceptance cr~teria stated herein. The objective of this special review should be to assure that the aggregate probability of an outcome that may lead to unacceptable plant damage meets t.he 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
..... ~
I l
'4".*,...... '-
~
~'..;.
I
- .=-;
-~~~1
.. *I
... ~
i
=. !
.. f.
... t.
,., ~
. i
(
(
overpressure is about lo-7 per reactor year from accidents at a nearby industrial facility, and approximately equal probabilities of exceeding design pressure from railway accidents, highway accidents and from shipping accidents. Individually each may be judged acceptably lowi the aggregate probability may be judged sufficiently great that addi!ional features of design are warranted.)
IV.
EVALUATION FINDINGS If the reviewer verifies that sufficient infonnation 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:
_. __ "._T_~e __ appli~~nt__has td_~n~ifled __ J?~~ential a~~~dents ~h~_~h cou~~-~c~ur in the vicinity of the plant, and from these has selected those which should be considered as design 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 regard to potential accidents which may occur as the result of activities at nearby industrial, military, and transportation facilities.A V.
REFERENCES Regulatory Guide 1.70, *standard Format and Content of Safety Analysis Reports for Nuclear Power Plants," Revision 2.
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 21 March 28, 1977.
Docket Nos.
50-354, 355.
Section 2, Supplement 2 to the Floating Nuclear Plant Safety Evaluation Report, Docket No. STN 50-437 1 September 1976.
2.2.3-3 Rev. l
*-*-* -.*:-o;...... *
~.
l":.: ;'
~ *...
...