ML20114E887

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AEC Div of Licensing & Regulation Rept to ACRS on Consolidated Edison Co of Ny,Inc Ravenswood Rept 1 Engineered Safeguards
ML20114E887
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Site: 05000204
Issue date: 09/25/1963
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EI 2 []Q;3 U. S. ATOMIC ENERGY COMMISSION DIVISION OF LICENSING AND REGULATION REPORT TO ADVISORY COMMITTEE ON REACTOR SAFEGUARDS f.

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CONSOLIDATED EDISON COMPANY OF NEW YORK. INC.

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RAVENSVOOD ENGINEERED SAFEGUARDS REPORT NO. 1 l

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Nate by the Director, Division of Licensine and Reculation l

The attached report has been prepared by R. S. Boyd and Y

reembers of the staff of the Division'of Licensing and Regulation for consideration by the Advisory Comittee on Reactor Saf eguards at its October 1963 meeting.

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l 9210120301 920520 PDR ORG NRCHIST PDR

s u.LSt'.21.2n Consolidated Edison Company has proposed that a 2030 Mw(t) pressurized vater reactor be located in New York City (the borough of Queens), on the bank of the East River, at its existing Ravenswood site.

An application for a construction permit "to own and construct" such a 6

Iacility was f11ed with the Comission in December 1962.

I-A check list on the Ravenswood plant was prepared by the staff and l

t f j transmitted to the Comittee in January 1963.

At a subcomitt.ee_

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in March, the staff outlined its approach to the evaluation.

' meeting if ]U Since that time there have been a number of meettn?,s with the applicant, including an. ACR5 subcomittee meeting on September 11, and a list of

\\&{3 questions have been sent to the applicant on various aspects of the engineered safeguards.

This report,'thich describes the discussion at these meetings and the extent of our evaluation to date, involves only the engineered safeguards of the proposed facility.

Su frerv Svstem, Description The Ravensvood plant is generally similar to, but slightly larger than, its three sister plantst those of Southern California Edison, Connecticut Yankee, and City of 1os Angeles.

The containment system l

is the same as that proposed for the City of i.os Angeles. As these i

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plants are being or have been subjected to various stages of con-i struction permit or site acceptability review, ~ both the staf f and the Committee are becoeing increasingly familar with the basic concepts of t

the eeneral design. However, all of these plants are in the early 1

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cesign stages, and therefore comprehensive and_detalled information on r

theirgsign LLngt yet available.

The engineered safeguards systems being evaluated at this time i

for tne Ravenswood plant are the fo!!ovingt t

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(1) Containment building and penetrations. The containment building consists of two 0.25 inch steel membranes separated by two feet of pervious concrete and supported externally by about 5.5 feet of

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reinforced concrete.

  • 4e understand that the design leakage rate for each barrier, defined by the steel membranes, will be 0.17./ day of the contained volume evaluated with a 15 psi pressure differential across each rembrane. It is intended that the pressure in the pervious concrete region between the two membranes be maintained et 10 inches of Hg below l

stmospheric (about 5 psi) so that all leakage, from both barriers, will Y

be into the " negative pressure zone."

l The application states that all containment penetrations for pipes, i.

electrical leads, ducts, and access are arranged as " double barrier i

devices" and con ein negative pressure ecnes. Some penetrations, notably the ventilation' ducts, when sealed are vented to the negative l

pressure zone. In other cases, the penetration sleeves are perforated in the negative pressure zone.

Additional, more detatted informatiott on i

penetrations has been requested to aid in our evaluation of the poten-t tiality of dire:t penetration leakage.

(2) Pumpback system - To maintain the negative pressure zone at design conditions,'a pumpback system of three compressors is provided.

Air is evacuated from the zone, as: required, and is' pumped into the I

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containment volu:te. The system is sized so that one compressor is i

capable of maintaining the design vacuum if,the leak tight integrity of the steel membranes is maintained. The maintenance of thi negative pressure zone by the pumpback system, under all conditions, D h j

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basis for the applicant's representation of a net zero leaEage system 4

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pressure zone).

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A leak detection system is provided to assure that net zero out-a leakage is maintained.

Air passing through the pumpback system is a

1 metered to determine leakage through-both barriers. Overpressure in J;

the containment in relieved through the stack and is also metered.

The overpressure represents the inleakage through the outside barrier.

i Sy subtracting this value from the total leakage, a measure of the 1

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inner barrier leakage is obtained, Tnere are not sufficient details on j

this system, or significant experience with similar continuous leak 4

race monitoring systems to judce the acceptability of the proposed system.

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(3) Safety injection system - This system is basically the same as that originally described for the Southern California Edison Plant.

l It has been sized to provide sufficient water to prevent core melting in the event the largest pipe cennected to the recirculation Icep is severed.- More information on this system has been requested. In our i

I evaluation we have assumed, consistent with the system performance described by Westinghouse for the Southern California Edison plant, that 1

under accident conditions postuisting a recirculation piping rupture i

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v. Icast en equivalent six per cent of the core fission product inventoty could be released to the eer.tainment.

(4) Containment spray system - This system serves.to reduce the

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butiding pressure in the event of a reactor pipe rupture accident.

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Water is provided f rom the containment building sump which collects water released from the primary system augmented by that supplied-j by the safety injection system. The performance of this system is T'

3 of particular importance in our evaluation since the building j

pressure provides the driving f orce for fission product release f rom i

the containment.

From oral information presented la recent meetingt ith the p cant, one might expect a 507. reduction in pressure in 1

i three-four hours and in ten-tvelve hours the containment pressure j

vould be essentially atmospheric if the spray system functions as

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required. More detailed information has been requested regarding the i

operation and performance of this system.

l (5) Ventilation recirculation system - A filter system is f

nrovided to clean up activity after a fission product release in the containment. The system consists of three banks of absolute filters i

i with three 4.000 cfm pumps providing recirculation. Rather large i

reduction f actors -are claimed and more information has been requested j

i to obtain a better understanding of the system before attempting-to l

quantitatively evaluate it.-

The site of this plant can be characterized'by stating that the V

-exclusion boundary is about 80 feet, and that the daytime and nightime l

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population within a one-half mile radius of - the site is esticated f

to be 28,000 and 18,800 people respectively.

Similar figures fer a l

five mile radius are 5,469,000 and_2,976,000.

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The Aveliention i

3 IT Consolidated Edison has indicated that its application is based

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i upon designs provided by Vestinghouse Electric Corporation and Stone

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and Webster Engineering Corporation. However, no construction contracts j

have been agreed upon, and there are no guarantees that Westinghouse

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and Stone and Webster vould be among the contractors if plant con-4 l

struction were authorized.

It may be _ for this reason that specific l

design inf ormation is generally lacking in the application, especially-l vith regard to the engineered safeguards.

Stone and Webster has i

indicated, orally, that its _vork is based upon preliminary design for the-4.

f City of Los Angeles..As the Los Angeles design becomes firm. more information can be expected that could be applied to the Ravenswood l-evaluation. We hope that the ansvers to our written questions vill-l eq provide an indication of_the.depthlf technical:information. Upon which the application is based.

Philosoehv of Evaluation Averench

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The scope of our review of this application has been directed into i

five different categories. These aret

_ Design and operational aspects of_.the proposed

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,. Vi engineered safeguards._

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(t (2). Environmental consequences.of accidents.-

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(3) Unusual plant fe.

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(4) Ceneral plant characteristics.

(5) Accident and safety considerations.

We are concentrating our review efforts in the first two areas only, l-with the view that until the site is hown to be acceptable, analysis of the general p an systems would be premature.-

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Remarks on the aspects of our review with respect to these first two items are presented in the folleving sections of this report.

Sinly stated, our approach is to determine _how effective _the..

l engineered saf eguards systems can be expected to be (1 tem No.1 above)

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and to then compare this determination with a judgement of how effective j

they need to be (Item No. 2).

To determine how ef f ective the engineered safeguarch need to be in i

this proposed location requires an analysis.of the conseguence.s to.

the public of release of radioactive material from t_he_ proposed i

reactor location. 11ovever, the usually applied site criteria outlined l

in 10 CFR 100 and in TID l'.844 are not strictly applicable in this case.

For example. the two hour dose at the site boundary criterion assumes j

that a reasonable upper limit of evacuation time at the site boundary is two hours. For this site, evacuation at the site boundary or j

beyond is not a credible possibility because of the dense population i'

distribution.

Additionally, consideration of a total potential dose of 25 rem whole body, 300 rem to the thyroid to a small number of people at n e

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i rales with a-population center of 25,000 people 1.3n miles from the nitecannotdirectlybeequatedtopotentialdosesofkh'remor hS rem t

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to 25,000m people residing less than 1.3n miles from the site. The f

j regulations indicate an awareness of the effect of total integrated

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population dose considerations, but specific criteria to evaluate this l

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effect, other than the city distance criterton, have not yet been l

l developad.

1 Because of these problems, and the lack of any established precedent, 4

i-it is our plan to determina a spectrum of potential consequences in terms of population-dose distributions.

The potential consequences, would r

take the following forms _b people would receive a dose greater than i rem,

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c people would receive a dose between j and k rem, and sa on.

4 Encineered Saf econrds Syst ems -

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All of the saf er rds systems proposed. serve an important part

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in the applicant's aim to obtain and maintain essentially zero escape j.

of fissien products in the event of an accident.

At the September'11 l

aubcommittee meeting the applicant stated that the engineered sale-

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guards systems essential _to maintain containment integrity,' excluding 1

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a rupture of either barrier, are the pumpback compressor system and I

at least one other engineered safeguard (such as an air cooling system),

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but nd:necessarily the safety injection system.

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8 In order to judge the cembined effectiveness of the proposed vstems we are directing our attentien to the followingt (1) A determination of the general adequacy of the containment scheme, based upon the arguments of

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(2)

Construction characteristics of the containment, including materials specifications and general i'

  • 7 performance requirements of the structure, and specifically loadings and missile protection.

(3) General investigation of the adequacy and effective-ness of the proposed penetrations including isolation and leak testing mechanisms.

(4)

Study of the reliability and effectiveness of the pumpback, leak detection, and ventilation and purge systems. Also included would be an evaluation of the ability of the pervious concrete environment to perform its intended function and an investigation tf interactions between the containment and the spent fuel building.

(5) Similar studies involving the functioning of the containment spray system, the safety injection system, the recirculation and filter system and the various heat removel systems.

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The meetings held with representatives of the applicant have been helpful in obtaining an understanding of their views on the t

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safeguards systems, but little definitive information upon which to t

j make engineering judgments has been obtained.

k'e expect that the extent j

of such definitive information available vill be indicated to us and J

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to the Comittee through the ansvers to our written questions, and j

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perhaps through pending meetings with the applicant.

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Evaluation of Harards 5

l Two extreme accident considerations have been postulated and h]

I These are called the maximum credible evaluated by the applicant.

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, -,7 The maximum credible j

a:cident and the'<0 erst conceivable accident.

f accident has been defined as the complete severance of the largest

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pipe connected to the primary coolant piping with the assumption N i

that core protection is provided by the safety injection"sy' stem. -

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The only radioactive materials released to the containment would be l

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those in the primary coolant at-the time of the accident. However,

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the negative pressure zone is maintained and the net escape of fission i

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products from the containment is sero.

The vorst conceivable i c 4,6 s

accident (incredible by the applicant's standards) assumes that the entire contents of the primary coolanc system are released I

l-instantaneously into the containment. This might be caused by a' i

i complete shear of the primary cooient piping.- Simultaneously, l

i complete core meltdown results and releases, fractions of the accumo-lated' fission products in the proportion described in.T!D 14E44 I

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Again, however, eecause of the design of the containment system.

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all the water, sir, steam, and fission products are retained within the containment and no leakage to the outside environment occurie_

i Secause of the seven feet of concrete shielding, the highest dose i

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k rate due to direct radiat.on is 2 mr per incur at the site boundary.

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q g- ~ ' We have not accepted the premise tha*: the net outleakage in the event of such accidents would be absolutely zero.

By a ecmprehensive study of the proposed engineered safe-guards arci possible mechanisms that could provide a breater than eero outleakage, we are attempting to define an accident or groups of accidents that would in our opinion represent upper limits of the radioactive haeard incident to reactor operations.

If a simple

.mafeguards scheme is previded for a plant with a remote site, it mght be possible to evaluate the resultant consequences with the simplified techniques and assumptions provided in TID 14844

However, I

this is not the case in this proposed location. Without distance to rely on, an evaluation of safeguards must include consideration of a variety of ways in which the safeguards might fail to perform satis _

factorily. The evaluation of the Ravensvood application involves many

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g cases which require investigation, some of which are complicated by time-dependent factors. We believe that it'vould also be useful to f

determine the accident potential at this facility with conservative and realistic postulates.

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t As more et;hasis is placed on reliance on a number of engineered _ safeguards, so must an evalu,ation of _ hazards become precomplex.

It is f or this reason that we have concluded that 1

a computer should be used to bandle the calculation of potential

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rad 1oactive hazard _to_th_e_public__in._the event of a fission product i

l release from the_Containmrent at Ravenswood.

The computer programs we are using calculate fission product 4c 2

inventory which can be-released to t,he containment as a function of j

l time vith any_particular_ distribution. We have used the TID l

fractions as a convenient standard. By analyzing the possible i

perfomance of the safeguards system a function of release fraction d

outside the cents'nment versus time is obtained and from this input 4

j dose s as a function of time and distance downwind and crossvind are con uted for various weather conditions (using Sutton's equations).

Isodose lines can then be drawn on a site map that shows population j

distribution. Dose distribution as a function of time and population is then easily shevn.

1 Based on a simplified study of the safeguards systems and some early remarks by representatives of the applicant on the perfomance i

l' of the systems several computer runs were made. The main purpose of this was, however, to " debug" the computer program and to check the 1

results by simplified band calculations.

Eight cases were initially run on the computer. Tnese were combinations of the folleving parameters 8 full power operation for 3

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21 months (n cbtain the fission product inventory), half-power opera-1 I

l tion for one year, lapse weather conditions, inversion venther i

conditions, fission product release fraction assuming no attenuation i

by the core spray system and 1007. tneltdown of the fuel, and fission u

product release fraction assuming that the containment spray system i

l uorks and 67. of the core melts (107. of the fission products are released i

i to the containment). For reference purposes, a leak rate of 0.17. of the

,j containment volume / day was assumed.

io rnore precisely evaluate the likelihood and consequences of

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i fission product releases, several additional problems are to be run on the computer which are intended to show the parametric effects of "n icus operational aspects of the engineered safeguards systems.

he runs vill consider various degrees of ef fectiveness of the systems

,a function of time.

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It is our intention to cornplete the evaluation of the proposed i

engineered safeguards systems, based upon further information from the applicant, and our further analysis of accident consequences and to gesent the results of this phase of the evaluation to the Comittee in l;

titee for the December meeting. Our conclusions as to the acceptability of the plant site and associated safeguards would be formulated as a re-i sult of this evaluation and analysis.

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Il ADVISORY COMMITTEE ON RCACTOR SAFEGUARDS UNITED STATES ATOMIC ENERGY COMMISSION W Af.HINGTON. D.C. 20545 November 18, 1964 p.

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/=,9 Bonorable Glenn T. Seaborg Chaiman U. S. Atomic Energy Ccmission Washington, D. C.

Subject:

REPORT ON EUG1EERED SAFEGUARDS

Dear Dr. Seaborg:

In response to the request of the Cc cr.ission, the Adviscry Cot =ittee on Reactor Safeguads has reviewed the question of "encineered safe-guad s" as they are used nov or are currently considered for use in nuclear reactor power plants. This letter s = wizes the results of the Comittee's reviews.

The number of sites economicany suitable for the location of large nuclost power reactors is limited.

Apart from safety considerations, the chief requirements are (a) a sufficient cooling vater supply must be available for the turbine condensers ani (b) the cost of electrical trnnamission from the reactor plant to the area of use must be kept lov. The first makes it necessary to select sites bordering on large rivers, large lakes or the scacoast; while the second mkes it desir-able to locate as close as feasible to civic or industrial centers.

Presently stated site Guides do not favor selection of ::any economic-any desirable locations.

The health and safety of the public an assured if fission products are retained within the reactor or its containment. Tb accomplish this aim, a strong program stressing nuclear reactor safety has been adopted in the United States. Strenuous effort is made to be sun that accidentsviu not occur.. This effort starts in the original design groups and is carried along through the construction and oper-I tion phases with reviews and approvals required at appropriate inter-vals.

It is the intent of this effort to eliminate reactor accidents.

Ikwever, since the field of nucint reat'or technology is new and since there may stin be some harstrds vbich have been overlooked, dependence I

must also be placed upon safeguants engineend specifically to limit the consequences in the unlikely event of a major accident, or to pre.

vent such an accident.

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Eonorable Glenn T. Seaborg m eber 18, 1964

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sted with respect j

in each case, the engi'2eered safeguard cu.

to the specific nuclear plant for which it t.oded.

It is equally inportant to assess the degree of confidence u. t the safeguard vill t

function properly in an emerCency. An engineered safeguard that must l

remain operable for the life of the plant but cannot be tested without ruinous effects would not usually be accorded the same i=portance as

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cne that can te tested periodically.

4 It is important to recognir.e that engineered safeguards are designed l

to allev the siting of reactors at locations where, without such safc-i Cuards, protection of the public would not be adequate._ The advantages j

cf a remote site cannot be exactly balanced by engineered safeguards.

j On the other hand, the advantages of a remote site'may be temporary,-

l if appreciable inenasm in populstion density occur near the reactor, i

7ev ritos presently-in use are such that some engineered safeEuards i

5 are not desirable. Tiras, the protection of the public ultimately de-l l

. ends on a co=bination of engineered safeguards and adequate distances.

j Engineered safeguards which canJustify decrease of the distances naast be extraordinarily reliable and consistent with the best engineering l

practices as used for applications where failures can te catastrophic.

To be vorthy of consideration, en6 neered safeguarde cust be carefully 1

l designed, constructed and installed, equipped with adequate suxiliary_

p ver, and continuously maintained.

Certain designs are based.on sound I

engineering principles supported by caterials acceptance tests; others l

require developmental and proof testing.

In any case, provisions for i

regular and careful testing are required vbere deterioration may be ex-i pected. The acceptance of engineered safectards to n.itigate unfavor-l able aspects of reactor sites should-continue to be' based on positive j

evidence that these design objectives can be attained.

In addition,

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there vill probably be a continuin6 need to develop new devices and i

design concepts as reactors are proposed for less and less remote sites.

1 The principal engineered safeguardt include:

(1) contairment and con-I firement, (2) containment pressure and temperature reducin s t

. 3) air cleaning systems to remove fission products, and (g) ys ems,

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and sefety injection systems.- Discussion of the important features of these is appended hereto, as are conclusions regarding their value.

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hi ?xtract of the conclusions ic as follows:

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When eccptently designed, constructed, maintained, and test--

ed, contairsent and certain confinement systems are considered to be effective safeguanis.

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i Honorable Glenn T. Seabors november 18, 1964 2.

With careful attention to the contairment vessel and to the external connections, such as the use of reliably actuated valves in series in pri::ary system lines and a means of preventing pressure buildup from afterheat, a pressure suppression method is an acceptable engineered safeguard against primary coolant line rupture.

3 A building spray system can be a valuable adjunct to con-taircent, if it is carefully designed and maintained, if it has ade-quate vater supply and backup emergency power, and if it is periodie.

ally tested for proper functioning of its cocponents.

Conservative estimates of the ability to reduce containment pressure are then con.

cidered acceptabic.

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With the orce reservations as are applied to building spray l

systems, heat exchange nethods of limiting containment pressure build.

up are censidered to be acceptabic engineered safeguards, i

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Iecause it has not been shevn that all accidents which could occur in a reactor are of a sequential nature involving first, a re-lease of stored energy, and later of fission fragments, and because the engineering design of pressure control systems is in the process of development, a confinement system based on sequential release is 3

not generally censidtred to be of sufficient reliability for use as an engineered safeguard in populated areas.

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The nature of fission product releases to be expected in the unlikely event of a major accident is not yet vell enough known to per-mit more than c:.nservative lover bounds on the efficiency to be deter-mined for air cleaning cystems. Reliable icver limits may, however, be assumed when individual cases are reviewed.

7 Core spray and safety injection systems cannot be relied upon as the sule ergineered safeguards in a nuclear power plant.

Neverthe-less, prevention of core melting after an unlikely loss of primary cool-ant would greatly reduce the cyposure of the public.

Thus, the inclu-sion of a reactor core fission product heat removal system as an en-gineered safeguard is usually essential.

It is the opinion of the Mvisory Cormittee on Reactor Safeguards that the including of properly engineered safeguards in reactor plants can l

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Honorable Glenn T. Seaborg 4-November 16, 1964 i

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pemit the reduction of distances required for protection of the pub-i lie, and that engineered safeguards of selected type should make fen-l cible the siting of power reactors at many locations not otherwise i

considered as suitabic.

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Sincerely yours, 1

h ic/EerbertY.outa Herbert Kouts Chaiman

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E Feport on Engineered Saf1 guards

/ddendum fal CO!'IAUDE!.'T /dID COhTESE!O Ccntainnent is desi6ned to prevent the escape of injurious a:: cunts of fission products resultir4 from any failure in a maclear system.

In the usual plant, fission products are held within sequential barriers:

first, in the fuel; second, incide the fuel cladding; third, within the primary cooling system; ana fourth, in the plant contain:ent or confinement system. This discussion is directed prinnrily to the last, implying that failure of the first three to hold fission products s:uct ustally be considered credible.

Ole ters containment or confinenent cs used here vill mean the contain-nent shell or structure, and itc accessories as described later.

Con-tainmente are intended to hold the fission products and primry cool-aut which may be released, except for inherent leahage.

Confinenents usually allev the raterials discharged by the accident includir4 noble gases to be relet. sed in a directed nnnrer during which time most of the radioactive halogens and particulates may be trapped and retained.

Various versions of these systems ar6 Eiven below, with the expected i

perfo2mnce in retaining fission products in the unlikely event of a

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r2jor accident:

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Double centainment, i.e., two envelopes, in which 7.cahaSe throuch the inner may be (a) purped back to the contained space, or (b) directed to a stock f

with or without air cleaaing.- Fission products i

released may be held belov a very srall fraction per day of the content of the containment gas.

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Sine,le containment of the nuclear system inc1tui-ing the entire pri m coolant system. Fission products released nicht vary from a fraction of a percent to several percent per day cf the con-tainr nt contents.

3 Ginnle contaireent of the nuelcar system except that, as in some boillng water reactors, the pri-rary ecolant may pass outside the containment to a turbine and condenser and be returued.

In these partial contain=ents, the isolation valves in the l

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Addendum fl (Cont'd) coolant lines are essential parts of the centain-rent. Ikpected fission product release ray be about as in (2) above.

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Confinement consists of a structure from which cases and vapors may be drawn by a blower through air cleaning systens ani vented.

Since air clean-ing systeni, ordinarily do not re:::ove noble gases, as cuch as half of the radioactive content cf the gases in the confinement n.icht be relcated.

Con-finement systems uay include designs for relesse of the large amount of energy in non-radioactive vapers and gases, such as pressuri::ed water, be-fcre reMsc of fission products fret fuel claiidra, e.E., in case of failure of a pipe in the primary cooling s; sten.

'esign maxim a pressu:t in the containment rsy vc.ry from inches of vater to several atmospheres. Tne contaircent or confinement structure may vary from an industrial-type building whic nominally gas t16ht, to

c. steel or reinforced concrete pressure cu.. ainer.

Concrete without lining is usually not i= pervious enough to act as a high pressure con-tainer.

Sere are various codes applicable to the design, construction and test of contair=cnt structures such as the Uniform Duilding Code, and those of the American Society of Mechanical Engineers and tM Acerican Con-crete Institute.

Codes give the c.ininus requirements fer design, fabri-cation and testing. Pere compliance with appropriate conce ray be in-adequate for this nuclear service.

Competent designere sill be aware of such additional needs.

Bere are rany accessories and auxiliaries that if incorporated must be considered as integral parts of the containment structure. A re-presentative list includes the following vith parenthetical notes of some of their important' features:

(a) access openings and closures including air locks, (seals; airlock door interlocks; certainty of door closare durira reactor operatior),

(b) vacuu: relief valves or systers (assuran:'e of closure when needed; safe disposal of effluent; protection in case of relief failure),

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Addendtn y1 (Cont'd) r (c) ventilating air inlet ani outlet isolation valves (double valving and last-ditch manual control),

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(d) penetration seals for pipes and electric and l

control leads (ace deterioration of sealing compounds),

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(e) valves for clcsing pipes penetrating the con-nechnr.ical failure at the penetration) prevent tainment (double valving; supports to (f) themal insu~ ation to enntle keeping the ten-perature of cteel contain::ent vessels within 4

i the ducti!e range, i

(g) protection against missiles, (h) special protection against esrthquakes, tsunamis, hi6h vinis, etc.,

(1) essential electric pcVer, vater and cocpressed air supplies and c=ergency back-up for them (alternate a tomatic operating power sources; controls for valving and auydliaries with last-ditch manual control; suitable operating con-trols for auxiliaries in cuergencies); and (j) chutes or cc.nal Sates for fuel hand 11n6

'Iesting of the containment and of its eccessories and auxiliaries is the only assurance of their capability and reliability. Initial tests for mechanical strenS h after construction are routine.

Ieak testing t

involves detection of the leaks and the determination of total leak-a6e rate.

Since many_ leaks, such as those through access seals and seals around electrical-leads, may increase as the sealant ages, peri-odic testing is necessary.

Icaks throu6h netal cracks or fissures do not generally show increased flow vith pressure other than that ex-pected from hydro-dy e ies. Sealed joints, however, may be tight at lov pressure and leak at higher pressure. Testing these below service or design pressure is not always definitive. - In many cases, double l

seals at penetrations enable testing of these seals without pressuri:-

ing the entire contairnene.. This is a desirable and effective test of such seals, but it tells nothin6 about the rest of the containment.

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Aidendum#1(Cont'd)

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Increased leakace rate of the ccuposite contaircent durirg service is an indication of deterioration.

Continuous cenitorirs of leak-l age where possible is desirable as a chech against r_isopere.., ion.

Careful design and testing of gas handl.ing equipment is required.

Contaircent effectiveness is greatly dependent on adtinistrative control. This includes assurance that operatiomsuch as the clos-ing of openings and valves and the maintenance of seals, valves, closure operating mechanisms, controls ard aux 11;cr/ services are perfectly carried out. Follev-up chechs of critical operations and independent re-checks aft (r all maintenance is necessary and should be made a matter of written record.

Periodic drspection of opel-ability of apparatus and contr:1 and sensirs mechcrdscs should be nado and recorded.

Tne type end desicn of each containment must be dependent on the needs of the nuclear p.e.nt of which it is a part.

Che amount of leakage remissible depends on the type, power, design and cpera-tion of the plant, as well as the nature of the site. Ice con-tainment is a machine e.nd must be designed, constructed, eperated, checked, serviced, repaired and naintained c.s one.

Since safety of many people may depend on its perfornirg as intended in an emer-cency, each of these operations should be better done than co= par-able non-nuclear operations.

When co petently designed, constructed, rr.intained, and' tested, con-tainnent and certain confinement systcOE are Considered tO be effec-tive safeguards, i

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i Report on Engineered Safecaards

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/diendu tG I

PEEESkEIC".AJgIOILSYREF l~

Containnent systems for vater reactors (boiling and pressurized) are required to raintain their integrity upon release of the ener6Y evolved in the unlikely event of nuclear excursions, metal-vater reactions, and cocplete prhry syste= depressurization as miCht occur following a j

rajor rupture. The principal contribution of energy, and hence contain-cent system pressures, would result from the flashing of pr h ry'systen vater. Several rathods ray be e= ployed to renove heat and thus to re.

duce containnent desiCn size and pressure.

1 a means of pressure reduction-known as the pressure suppression sys-ter., involves use of a lar6e reservoir of water through which all con-tainei vapors mst pass via c'.:ltiple subrerged vents.

Steam, the prin-c1 pal contributor to containnent pressure, is condensed in passage i

through the water, and non-ccadensible cases are cooled. This method has been specifically adapted to the direct cycle boiling water reactor in which only the reactor vessel and a few auxiliaries and connecting piping sre contained.

'~ne nethod is dependent on raintenz.nce of water level in the suppression pool, and on rellati'ity of valving in steem, l

feed vater and other piping pcnetrating the ccntainmen-The entire nethod has not been tested under accident conditions, but elenents have been satisfactorily tested under s$ralated accident ccnditions.

Since 1

reliability of the method does not depend on action of personnel or l-nechanical cacponents, pressure suppression perfornance tests do not i

eppear necessary. With careful attention to the containment vessel ana its external connections, such as the use of reliably actuated' valves in series in prirary system lines and a means of preventing pressure buildup from afterheat, the prescure suppression rathod pro-vides an adequate en6 neered safeguard agnir.nt pricary coolent line i

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rupture.

A second nee xi of pressu e reduction involves the use of a spray sys-tem vithin a containment structure. Tnis system is effective in con-densing vater vapor and removing sensible heat from contained gases.

l It cay be actuated either automatically or manually. The effective-ness of a spray system nrant be carefully evaluated for each application, using a conservatively calculated sequence of events. Testing under l

accident conditions'is usually not practical due to potential damage to electrical and control equipnent. A building spray system can be a valuable adjunct to containnent, if it is carefully designed and I

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Addendum #2 (Cont'd) 2-i rnintained, if it has adequate water supply and backup enercency power, I

and if it is periodically tested for proper functioning of its components.

Conservative estimates of the ability to reduce contain:aent pressure are g

then considered acceptable, i

A third cethod of pressure reduction involves the rencval of vapor space heat by heat exchangers (see discussion under Air Cleaning Systems).

3 Iient generated within the containment during normal operation as well as heat produced following an accident may_be controlled or removed by air recirculation. Such systems usim'1y consist of c:ultiple fans ani heat exchangers.

IIeat accu =ulated in the beat exchangers may be transferred l

to the nor=al coolant systens,.or to a-separate or alternate supply of 5

'oclant water.

'~ne use of such syste=s during norral operating times a

cives a hiSher assurance of availability-under accident conditions.

Each-up coclant supplies and alternate or parallel power supply are essential to rake certain such units vill runction adequately and for the necessary time after en accident. The. system is of greatest value in reintaining reasonabic pressures and tc peratures in containment structures for lorg pericacfollowing accidental releases. With the same reservations as are epplied to building spray systers, heat exchange nethods of 1%iting con-i tain=ent pressure buildup are considered to be acceptable er.gineered safeguards.

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A fourth nethod of pressure ecntrol involves release of water vapor to the environuent following a rystem rupture, and then establishing con-taira nt prior to core meltirs and fission product release. The acci-dent for which this systen is designed consists of a loss of coolant in which the stean release precedes the fuel zelting by 'a predictable period.

'his system requires the use of very le.rge da=pers which r:ust close tight, necessary reliable administrative control, and a proper-understanding of the accident conditions. Such a systen, at the present time, is not considered of sufficient reliability as an engineered safe-guard for use in populated creas.

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Report on Encincered Safeguards i

/ddendun #3 t

4 AIR CLEMING SYSTE'Is i

Sie function of an air cleaning system as an-;ercineered safesard is to remove and te retain fission products from an unlikely partial cr total fuel melt-aovn.

Fission prcducts that are thus retained should be fixed in a form that prevents redispersion.

Components of the air cleaning system should be so located that decontamination and essential handling can be accomplished readily and without hazard to the health and safety of the public.

For cleaning or decontn -ination purposes, the released fission products from a reactor fuel melt-devn may be divided into four groups. These are: the noble Eases (kry iodine); volatile solids (pton and xenon); the halocens (brnMm and i

such at tellurium, selenium, cesium and

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ruthenium); and other solids (primarily strontium, yttrium and barium).

Iecause of their chemical nature and short hnH-life,. radioactive noble cases can usually be treated only by containment or controlled release i

from elevated locations such as tall stacks. Therefore, with noble i

gases consideration must be given to meteorolocical dispersion and dilu-tion as influenced by characteristics of the~surroundin6 envirorment..

It is convenient to divide the rcr:aininc fission products into.tvo phy-nical groups - gases and particulates.

Cases'(essentially iodine and' i

bromine in elemental' form) are removed by adsorbents such as activated charcoal, by chemi-sorption on silver,'or by absorption in a reactant solution.

Particulates which rance in size from several microns down to less than 0.l' micron can be removed by impingement' scrubbers, elec-trostatic precipators, or filters.. The final device in a particulate cleaning train is usually one based on mechanical filtration princi-ples.- Containment spray or " dousing" systems for condensing steam may also serve as decontamination syrtems because of the gas contacting and impincement action of the spray droplets. Th:: n:ultiple contactirs which is possible vJthin a contained gas volume makes a containment vessel with sprays equivalent to a scrubbing chrmber.

Eslocen pses may.be adsorbed trpon the surfaces cf released particulates 1

and may react with them.

Eence, it is necessary to use a' combination of adsorption, absorption, and filtration devices to remove _ halogens.

Eecause it *'me ray occur in both inor6anic cnd orCanic states, the gas cleaning i im must be capable of removing both. Since the halogens

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1-Addendum (3 adsorbed on partiedates are not irreversibly bound, it is necessary to follow the filter with an adsorber. A liquid scrubber should be folloved by both when raxi um deconterination is necessary.

The air cleaning components of a reactor safety system include:

a ventilation system, a heat removal device, air cleaners, and an air mover with motor.- The system must be capable of working continuously in hot, saturated steam envircreents for a period of time long enough =

to remove the required pcrtion of the released fission products from the containment or cor.firemer.t system. To handle-the anticipated release, the air cleaning system must hcVe sufficient capacity in flow, in adso*. ben and chemically reactive raterials, and in filtration

- surface. Adscrption and filtration systems must be designed and in-stalled sc that the decay heat of collected fiss Mn products vill not cause combustion or destruction of their media or everheatir.g to the point where collected fission products vill be rH ispersed. The media must also be protected against shock vaves, miss__.s, moisture entrain-ment, liquid slugging, and radiation damage, as well as corrosion and cher ical attack.. The duct vcr': and filter housing should be 1.rotected against mechanical injuxy or : n sile damage to avoid typassing or lednge of untreated air. L e system should be' leak tested at the same pressure dif ferential as it vould have to cndure unier accident condi-tions.

I;ecauce electrical power is necessary for circulating and recirculating both air and water, it is essential that bachxp power be available for mMntaining minimal flow rates.

The decontamination efficiency required of an air cleaning system vill depend on whether the system is once-through or. recirculating. The decontemination Cactors needed vill be based on the dose to the environ-ment and the dilution to be assumed for stack dispersion. - In recirculat-ing systems, the deconteination factor. is related to the number of con-tairment volumes passed through the cleanup system. Decontarination factors of 10 to 1000 or more may be requirad in most applications.

Gas leaks which bypass filters or adsorbers in effect decrease air clenning efficiency. 'Jhen an iodine reno.d efficiency of 9?iis pro-jected, a bypass or leak around the beds of 1% leads to double the iodine release. Appropriate design and testing of associr_ted gas baniling equipment is required.

Er reliable perfomance of an air cleanint; system must be assured by frequent "in-place" testing which includes ronitoring with gases and

P Addendum #3 (cont'd) <

1 particulatec that sicalate the expected fission productc. Ease of test-ing for leaks, and access for inspection of senis, gaskets.and cla=ps are necessary. A continuous monitor of resistance or pressure drop through the cleaning system is desirable vbere the decontaination unit is always in use.

In the case of emergency or standby cleaning systems, at least quarterly operation and checking of both air mover and cleaner i

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is desirable.

Tne nature of fission product releases to be expected in the unlikely event of a I:njor accident is not yet vell enough known to permit more -

than conservative 1cuer bounds on the efficiency to be deten::ined for i

cir cleaning. Reliable IcVer bounds r.ay, hwever, be assumed when individual cases are reviewed.

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Tseport on Tngineered Safecuarde Addendum t%

COPI-SPRt Y AFD SAFETY-IL'EC'~'ICII SYSTTES s

The terms co) -spray and cafety-injection r re used to designate systems designed to supply coolant to the core cf a water reactor to pm vent meltdevn in the event of an unlikely lors of coolant accident or a major coolant leak.

Thece sycters are intended to remove the fission-product heat produced in the core after the reactor has been shut down.

Ilow-ever, they mi ht not function for sev' ~ ' ~ nsons in the event of an S

accident, such as, stvered lines to the reactor vessel and lov vater cupplies.

"herefore, reliance cc.nnot be placed on cystens such as these as the sole engineered safeguards in the plant. Severtheless, preven-tion of ccre celting after an unlikely loss of primary coolant would greatly reduce the exposure of the public.

Thus, the inclucion of a reactor core ficcion product heat removal systen as en engineered safe-guard is usuany essential.

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i The cere-spray and safety-injection syctcus consist of the piping, which connects the reactor-plant water storage facilities to the reactor cool-ant system, and also any nececsary pumps, valves, auxiliary piping, spray nozzles or rings in the vecsel, and instrumentation. The design details -

vill vary from one nuclear plant to another.

In the unlikely event of a:A major losc-of-coolant accident, these systens are designed to introduce /s.

large volumes of water into the reactor coolant system to replace vater i passing out of the rupture into the containment vessel. When this is pl done through separate spray rings located in the reactor vessel that distribute water over the core, the system 10 called a spray cystem; in other forms it is called a safety-injection cysten.

A second function $

nay be to circulate and cool, through heat exchangers, the water that bac accu =ulated in the containnent vessel.

If the reactor requires a soluble neutron poison for cold shutdown, the cystem should drav vater frcm a storage tank maintained with the nececsary concentration cf poisor and heated if necessary.

Chief among the factorc that rust be considered in the design of a core-spray or safety-injection systen are:

1.

Accurance that the systen vill start when needed and vill deliver the required amount of water.

Adequate e=crgency power sources cast be assured.

2.

Provisions to prevent a nge to cupply lines during normal operation and any accident

Addendun iA (Cont'd) conditions that night involve motion of the reactor vessel.

Slow distribution over the core, ihny reac-tor desir;ns involve corpenents in the struc-tu2twhich could interfere with the injection of caergency coolant.

It is often difficult to establirk the circunstances under which adequate d tribution can be achieved.

Care-ful anal; and tests are required to deter-rtne whc.sr the safety injection system as designed can prevent core meltdown and even octal-water reacticns (in certain cores) in the unlikely event of a loss-of-coolant uccident.

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hovision for cissile protection and accidental 9

injury to in.portant corr;>onents of the systens, lik Avoidance of t'. mal shoch problens.

Failure 5

r due to thermi,; hock could impeir the opera-bility of the $ stem.

5:f Protection of E ternal parts of the sefety o.

injectioncychanagainstfreezing.

7 Provision f$.-~briodiccheckonoperability of cor.:ponent,. p

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