ML19322C807

Reg Guide 1.95,Revision 1, Protection of Nuclear Power Plant Control Room Operators Against Accidental Chlorine Release

ML19322C807
Person / Time
Site:	Crane
Issue date:	01/31/1977
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
Shared Package
ML19322C797	List: ML19322C796 ML19322C799 ML19322C803 ML19322C807 ML19322C809 ML19322C810
References
TASK-TF, TASK-TMR REGGD-01.095, REGGD-1.095, NUDOCS 8001240569
Download: ML19322C807 (6)

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U.S. NUCLEAR REGULATORY COMMISSION Januiry 1977 e

PUGULATORYGUIDE t

OFFICE OF STANDARDS DEVELOPMENT REGULATORY GUIDE 1.95 PROTECTION OF NUCLEAR POWER PLANT CONTROL ROOM OPERATORS AGAINST AN ACCIDENTAL CHLORINE RELEASE t

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A. INTRODUCTION Regulatory Guide 1.78, " Assumptions for

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Evaluating the Habitability of a Nuclear Power Plant i

Criterion 4, " Environmental and missile design Control Room During a Postulated Hazardous t

bases." of Appendix A. " General D: sign Criteria for Chemical Release," identifies chlorine as a hazardous j

N# car Power Plants," to 10 CFR Part 50,"Licens-chemical which, if present in the control room at-i in'g of Production and Utilization Facilities," re-mosphere in sufficient quantity, could result in the quires, in part, that structures, systems, and compo-control room becoming uninhabitable. It is the pur-nents important to safety be designed to accom-pose of this guide to describe specific design features i

medate th: =ffects of and to be compatible with the and procedures that are acceptable to mitigate i

environmental conditions asso:iated with op: ration, hazards to control room operators from an accid:n-maintenan :, testing, and postulated accidents.

tal chlorine release. Although this guide was Criterien 19, " Control room." requires that a control developed to provide protection from an onsite e

room be provided from which actions can be taken to chlorine release, the protection provisions described i

operate the nuclear power unit safely under normal here at: also expected to be sufficient for an offsite conditions and to maintain it in a safe condition un-chlorine release. The positions stated in this guide are der accident conditions.

based on the specific physical properties and es physiological effects of chlorine.

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The re! case of chlorine could potentially result in Two basic accident tvnes can be postulated: a long-

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SiI;5d$ [eNib$s d$shn fe'a'tNe$ an[pfoledt[res term, low-leakage-rate release and a short-term puff release. The ma.icnty of chlonne releas:s rxp:nenced thm at: a:::ptable to th: NRC staff for the prote:-

t dat: have been of tne first type, mvolvmg leakage tic. of nuclear plant control room op:.ators acainst

• . an at:id:ntal chlorine rei:ase. The Advisory 'Com-from valves or fittings and resultmg m a long term mitte: on Reactor Safecuards has been constmed releasa with a leakag rate from near zero to less than on* Pound of chlorine per s:cond. Given warning.

encernire this guide and has concurred in the nly breathing apparatus is necessary to protect the re:uisten position-.

4 control room operator from this kmd of releas:.

Be DISCUSS!ON However. b::ause such a release might continue un-abated for many hours, self-contained breathing ap.

Many cuelear power plants us: chlorine for water paratus, a tank source of air with manifold outlets, or treatment in th: circulating wate'r system and in dher

.cquivalent prote: tion capable of operation for an ex.

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aux!Uary systems. Chlorine is normally stored on the

, tended period of time should be available.

sit: es 1%ified gas in one-ton tanks or large railroad cars (t.s Neally 16 to 55 tons).

A 1-ss p obable but more severe accident would be

.s the failure of a manhole cover on the chlorine con.

tain:r er the outright failure of the container itself.

• Un s in na:e s.:estanme changes from rreucus issa.

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" Such failure e uld cccur during the transportati:n cf inlet (n 15 meter elevati:n ft:m gt:und level was a container as a result of a hrndling mishap or c:uld used). The maximum a!!owable chl:rine weights were m: pts suA as carthquakes, flooding, fire, expl:sive calculating the control room concentratitns (signifi.

p) be due to naturally or accidently produced envir:n-determined by using worst case conditi:ns fer t >

overpressure, or missiles. A failure of this type could cant parameters being wind speed, cloud dimensions, result in a puff release of about 25% of the chlorine.

normal air exchange rate, time to isolate, and isolated The balance of the chlorine would be vaporized and air exchange rate). For certain control room rwased over an extended period of time. As a result characteristics and high wind speed, the maximum

.of the cloud formed by the release from such an acci-operator exposure occurs before isolation. For other d:nt. the chlorine concentration inside the control cases with other control room characteristics and low roem mi;ht incr:as: rapidly. In the absence of special wind speed, the maximum operator exposure occurs design measures to limit the buildup within the con-two minutes after isolation and is primarily due to in.

trol retoti,' the operators might be incapacitated nitration. The six control room types listed in the before they are able to don breathing apparatus.

table span the expected range of protections required for n'ost plants. Other combinations of the signifi-Ad:quate protection of the control room operators cant parameters are possible, but those listed in the against the types of accidental chlorine release discus-table should provide sufficient guidance for most sed above will b: achieved if features are included in cases.

the plant design to (1) automatically isolate the con-trol room if there is a rel:ase. (2) make the controi This guide does not address the protection of in-l toom sufficiently leak tight, and (3) provide equip-dividuals either outsid: the control room or within j

ment and procedures for ensuring the use of the control room but not directly involved in reactor breathine apparatus by the control room operators.

operations. Breathing apparatus should be presided Protection provisions adequate for the large instan-and be readily accessible throughout the plant in ta. ecus release will also provid: protection against order to eliminate the need for personnel to seek th: !cw 1:akag: rate release. Staff analysis of control shelter in the control room during a chlorine release, room designs and the degree of protection afforded by each design has resulted in criteria for acceptance.

Th: features and procedur:s described in this guide as will be discussed in the next s:ction. Thes: criteria apply to plants having conventional ventilation at: bas:d on the limitation (given in Regulatory systems. Any different methods of protection Guid: 1.75) that the chlorine concentration within proposed will be evaluated on a case by-case basis.

th: control room should not exceed 15 ppm by C. REGULATORY POSITION volume (45 m;/m') within two minutes after the iperarcrr arc ~ m:dc av.are -cf-th: p: u:n 4 - Control room op:rators should be prctected

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chierine. This concentration, the toxicity limit,is the against the effects of an accidental chlorine release as maximum concentration that can be tolerated for two described below.

minutes without physical incapacitation of an aserat: human (i.e., severe coughing, eve: burn or

1. LiquifrJ chlorine should not be stored within

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severe' skin irritation).

100 meten 4 a control room: or its fresh air miets.

Table 1 gives the maximum allowable weight of a (Small qt r ies for laboratory use,20 lbs or less, are single container of chiorine as a function of distance lixempt.)

fron-the control room for various control room tvces. It is based on an instantaneous relere of 25ci

2. If a chlorine container having an inventory of o'f' the contents of the chlorine container and an al-150 lbs or less is stored more than 100 meters from lowable chlorin: concentration in the control room the control room or its fresh air inlets, the capability for manual isolation of the control room should be of 45 ma,/m, the toxicity limit, for two minutes. The 8

initial s aud dimensions assume expansion of the provided.

chlorine 2as into a spherical cloud having a Gaussian

3. For single container quantities exceeding 150 lb, concentr' tion gradient. Dispersion of the cloud was the maumum allowabl: c,nlorine inventory m a smgle calculat:d using the instantan:cus release diffusion Co.ntainer stored at spectised distances from th: con.

model app armt in Appendix B of Regulatory Guide trol room gr its fresh air inlet is given in Table 1 for 1.7b. For thosi cas:s where the control room was located a short distance from the release point and control room Types I through VI(described below).

For each control room type, the maximum allowable the amount of chlorin: release was small, the model chlorine inventory in a single container is given as a was adjusted to a!!ou for additional dispersion in the function of distance from the control room. If there vertical direction by assuming uniform mixing betwc:n the ground and the elevation of the fresh air are,several chlorine containers, only the failure of the large'st container is normally considered uni:ss the

' Two minutes is considered surncient time for a trarned operater to put a self centained breathing apparatus into cperation, if 2 Control room is denned to include a!! zones seruced by the

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~ failure of a single co$triner could cause a chlorine dampers. The detector trip signal should also ret o#

rel:ase from several containers.

an alarm and provide a readout in the control room.

An alternative to the installation of remote d:tectors

a. Type ! control rooms should include the follow-would be to provide an isolation system using local r

inc )rotective features:

detectors eut having an isolation time of effectively zero. This can be accomplished by ensuring that the (1) Quick-response chlorine detectors located in time required for chlorine to travel from the chlorine the fresh air inlets. Within 10 seconds' after arrival of detector to the isolation damper, within the inlet

,th: chlorine, d:tection shoulo initiate complete ductinc. is equal to or greater than the time required

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closure of isolation damp:rs to the control room.

to detect tF chlorine and close the isolation damper.

(2) A nor nal fresh air makeup rate of less than

f. Type VI control rooms should include the one air prange per hour. The fresh air inlet should be protective features in paragraph e except that the at least 15 meters above grade.

control room isolated air exchange rate should be reduced to 0.015 air change per hour or less. For (3) Low-leakage construction with an equivalent isolated exchance rates between 0.015 hr-' and 0.06 air exchang: rate of less than 0.06 hr" wh:n all ht", linear interpolation of the weights given for penetrations are exposed to a 1/8 inch water page control room Types V and VIin Table I can be rr de.

pt:ssure differential. Construction details should be Verification testing is required within this range of provid:d to show that this limit is met-exchange rates (s:: Regulatory Position 5).

(4) Low-leakage dampers or valves installed on

4. The following should be applied to all control the upstream side of recirculation fans or other loca-room types (I through VI):

tions where negative systems pressure exists and w her: inleakage from chlorine contaminated outsid:

a. Immediately after control room isolation, the att is possible.

emergency re:irculating charcoal filter or equivalent equipment desicned to remove or otherwise limit the

b. T p: !! control rooms should include the accumulation 5f chloriac within the control room 3

protectne features of paragraph a except that the should be started up and operated.

isolation time should be 4 seconds or less rather than 10 snonds or less.

b. Steps should be taken to ensure that the isolated exchance rate is not inadvertently in:reased by design

. Typ: !!! control rooms should include the or oper'ating error. For instance, the following should 2

p ro te:t". : featur:s of paragraph a except that the be consid:rei normal fresh air makeup rate should be limited to 0.3 air change per hour or less.

G) An administrative procedure should require that all doors leadinc to the control room be kept

d. Type IV control rooms should include the closed when not in u'sc.

prote:tive featurcs of paracraph a except that th:

isolatier tim: and the normal air exchance rate (2) Ventilation equipment for the control room should be equal to or less than 4 seconds and 0.3 air asd for the adjacent zones should be reviewed to en-chance per hour. :sp::tively. In addition, the :on-sure that enhane:d air achange htween theisolated troi room isolated air exchang: rate should be control room and the outside will not occur (c.c.. if l

reduced to 0.015 air chance p:r hour or less (se:

there is a chlorine release, exhaust fans should be description of required leak rate verification test in stopped and/or isolated from the :ontrol room ven-i R:;ulatory Position 5).

tilation zone by low-leakage damp: s or valves).

e. Typ: V controirooms shouldincludetheprotec-(3) A control room exit leading directly to the

-is : i:atures of paracraph a with the addition of outside of the building should have two low-leakage l remote chlorine detectors locat:d at the chlorine doors in series.

sterag: and unloading lo:ation. These additional dete: tors should be placed and the detector trip

c. The use of full fae: self-contained pressur -

points adjusted so as to ensure d:tection of either demand-typi breathinc apparatus (or the ecuivalent) 1:sk or a container rupture. A dete: tor trip signal and the use of protective clothing should be con-should accomp.ish automati: isolation of the control sidered in the dev:lopm:nt of a chlorine releas:

' h is the tim e inte vat bemer the time the chier ne emergency plan. B::ause calculations indicate that concentration es:ceds 5 ppm at 9. isolation dampers and the chlorine concentrations may in:: case rapidly, ce e: tors are upstream fror. the isolaten dampers cred:t wiH t'e

.. - plan provisions an'd rehearsal of these tre the dar pers are completely closed. Note that if the chlorine emercen:V aised for the trasel time between the detectors and the provistons at: n ::ssary to ensure donning of eampen breathing apparatus on detection of high chlorine 2

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concentrations. Storage provisi:ns for breathing ap-(0) Setsmic Quahjication. Inc ctwns exemon paratus and procedures for their use should be such system should be designated as Seismic Category I that operators can begin using the apparatus within and be qualified as such.

tw a ntnutes after an alarm. Adequate air capacity for S

the breathing apparatus (at least six hours) should be (5) Ensironmental Qualification. The detection readily available onsite to ensure that sufficient time system should be qualified for all expected environ-is availabi: to transport additional bottled air from ments and for severe environments that could clearly offsite ic:ations. This offsite supply should be lead to or be a result of a chlorine release. The instal-

' capr.ble of delivering s:veral hundred hours of bot-lation of the detectors should ensure that they are tied air to members of the emergency crew. A protected from adverse temperature effects, minimum emergency crew should consist of those p:rsonnel required to maintain the plant in a safe (6) Maintenance. Testing and Calibration. The cond'ition including orderly shutdown or scram of manufacturer's maintenance recommendations are th: reactor. As a guideline. a minimum of five units acceptable provided they follow sound engineering of br athing apparatus should be provided for the practice and are compatible with th: proposed ap-emerg:ncy crew.

plication. A routin: operational check should be con-ducted at one week intervals.

d. The air supply apparatus should meet the single failure criterion and be designated Seismic Category Verificauon testmg and calibration of the

!. (In the case of s:lf-contained breathing apparatus, chlorine detectors and verification testing of the the single failure criterion may be met by supplying system response time should be conducted at six-one extra unit for every three units required.)

nIonth intervals.

The isolation system components should be of a quality that ensures high reliability and availability.

5. The gross leakage characteristic of the control One m:thod to meet thes: goals is to provide a room should be determined by pressurizing the con-trol room to 1/ -inch water gage and determining the S

! ssstem that m::ts th: requirements of IEEE 279.

l " Criteria for Protection Systems for Nuclear Power pressurization Cow rate.(The use of a higher pressure Generating Stations." In all cases, the isolation differential is a:ceptable p ovided the Dow rate is ss stem. r::::culatine filt:r svstem. and air condition.

conservatnely adjusted to correspond to 1/8-inch me system snould ine:: IEEE-279 since they are re-w ater gag:.) For air exchang: rates of less than 0.06 l quire'd to mamtain a habitable environm:nt in the br. periodic seri6 cation testing should be per-contro roam durmg d: sign basis radiological events.

formed. An a ::ptable method for periodic testing m

would be th: use of a permanently installed y

Spe:;D: acceptance criteria for the chlorine dete:-

calibrated pressurization fan. The syst:m would have l

uen sy stem and allied a:tuattnc electronics are as fol-a known pressure versus now charact:risti: so that the leak rate could be determined by measurine the j

l low s:

control room pressur: differential. T:sring should be j

(1) Chlorine Concentration L et c!. D:tector5 conducted at least every six months and after any ma-should b: aole to detect and signal a chlorm: con-jor alteration that may affect the control room i

ntranon of 5 ppm.

leakage.

(:) Syncm Response Tm:c. The syst:m response

6. Emergency procedures to b: initiated in th:

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tim:. whi h in:orporates the dete: tor r:sponu ame.

event of a chlorme release should be provided.

l the vah: c!asure time, and associat:J instrum:nt Methods of det:: ting the event by station personnel,

. d:! ass, shculd be less than or equal to the required both during normal workday operation and during i iscla' tion time.

minimum staf0nc periods (late night and weekend shift staffing should be discussed. Instrumentation (3) Sing!c Fa:/ure Cr:teria. The chlorine detection that has bein),provided for th: d:tection cf chlorine

! system should be redundant and physically separate should be des:ribed including sensitivity; action in-to accomphsh de:oupling of th::ffe:ts cf unsafe en-

. itiated by dete: ting instrument and level at w hich this uronmental factors. c!::tr:: transients, physical a::i-action is initiat:d; te:hnical sp::incation hmitations dents. and component failure.

on instrument availability; and instructions for maintenance. calibration, and testing. Crit:ria should l Local det:: tors should consist of two physically be defined for the isolation of the control room, for separate channels for ca h fresh air inlet Each chan-th: use of protective breathing apparatus and other nel should consist of a separate power supply, detec-protective measures, and for maintenane: of the tor, actuating ci::tronics, and int:rconnecting ca-

. plant in a safe condition including the capability for bling. Remoie detectors should also consist of two ord:rly shutdown or scram of the reactor. Criteria i

separate channels havine detectors located at the and pro::dures for evacuating noness:ntial personn:1 chlorm: unloading facility.

from the station should also be defined.

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complying with specified portions of the Commis-The purpose of this section is to provide informa-sion's regulations, the method described herein is b:-

tion to applicants regarding the NRC staffs plans for ing and will continue to be used in the evaluation of

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ysing t'n' is regulatory guide, submittals for construction permit applications until this guide is revised as a result of suggestions from the This guide reflects current NRC staff practice.

public or additional staff review.

Therefore. except in those cases in which the appli-s Z.

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