ML19308B272

Min Containment Pressure Model for PWR ECCS Performance Evaluation

ML19308B272
Person / Time
Site:	Oconee
Issue date:	06/13/1975
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML19308B271	List: ML19308B270 ML19308B272
References
CSB-6-1, NUDOCS 7912180880
Download: ML19308B272 (9)

Text

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~s BitANCH 1[CHNICAL P051T10:1 CSB 6-1 9

HINIMLN C0!1TAlt.!4ETIT PRE $5URE MODEL FOR PWR ICCS PCRFORMA*;CE EVALUAT10:1 A.

BAC,rJ_ROU 0_

Paragraph I.D.? of Appendix K to 10 CFR Part 50 (Ref.1) ' requires that the containment j

pressure used to. evaluate the performance Croability of a pressurized water reactor (PWR) emergency core cooling system (ECCS) not exceed a pressure calculated conservatively for that purpose. It further requires that the calculation include the effects of operation of all installed pressure-reducing systems and processes. Therefore, the following br.anch technical position has been developed to provide guidance in the perforc.ance of minir'un containment pressure analysis. The approach described beloa applies only to the [CCS-related containr.cnt pressure evaluation and not to the containment functional capability evaluation for postulated design basis accidents.

B.

BRA'lCH TECH':ICAL POSIT 10!;

1.

Input Infor-ation for t'odel.

a.

Initial Contain-?nt Internal Conditions lhe minirmn containment gas tem;creture, ninimu. contain ent pressure, and raximum huaidity that say be encountered under limiting nort:31 operatinct conditions should be used.

b.

Initial Outside Contain ent t.-tien_tio-ditions A reascnably los arbient temperature external to the contain-ent shcald be used.

c.

Contain-ent Volu-e The maxic:an net f ree co'.tain :ent volu c should be used. This raxi.un frce voluce should be deterrined frc-. the gross contein ent volu c r:irus the volu es of interrial structures such as v. alls and floors, structural steel, rajor ecuip cnt.

and piping. The individus) volume calculations should reflect the uncertainty in the component volur..cs.

2.

Active Heat Sinks a.

Sprpay and Fan Coolina Systems

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l The operation cf all engineered safety feature containment heat removal systems I

operating at maximum heat removal capacity; i.e.. with all contair.:ent spray tfalns operating at maximum flow conditions and all caergency fan cooler units f

operating, should be assumed. in addition, the minimun temperature of the stored f<

water for the spray cooling system and the. cooling water supplied to the fan j

coolers, based on technical specification 11mits, should be assumed.

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Deviations from the foregoing will be accepted if it can be shown that the worst conditions regarding a single active failure, stored water temperature. and cooling water temperature have been selected from the standpoint of the overall ELCS model.

b.

Containment Stea, Mixing With Spilled FCCS Water The spillage of subcooled ECCS water into the containment provides an additional heat sink as the subcooled ECCS water mixes with the steam in the contain.ent.

The ef fect of the steam-water mixing should be considered in the contain. ment pressure calculations, g

c.

Containment Stee:S Mixing With Water from Ice Melt The water resulting from ice reiting in an ice condenser contaircent provides an additional heat sink as the sub, cooled water mixes with the steam while draining i

from the ice condenser into the lower containment volume. The effect of.the steam-water mixing should be considered in the containment pressure calculations.

3.

Ibssive Heat Sinks a.

Identification The passive heat sinks that should be included in the contain.cnt evaluation

^

model should be established by identifying those structures and components within the containecnt that could influence the pressure response. The kinds. of sthic-tures and components.that should be included are listed in Table 1.

N.

Data on passive heat sinks have becn compiled from previous reviews and have j

been used as a basis for the simplified nodci outlined belod. This rodel is acceptable for minimum contain cnt pressure analyses for construction pen 91t applications, and until such tine (i.e., at the operatir.g license review) that a f

complete identification of available heat sir.ks can be ecde. This si.plified approach has also been folle.;cd for o; crating plants b/ liccr. secs co Diying with Section 50.46 (a)(2) of 10 CFR Part 53. For such cases, and for conste.;ction permit reviews,v.here a detailed listing of heat sinks wit'hin the cor.tair ent often cannot be provided, the following procedure may be used to model tnc passive heat sinks within the containment:

1 (1) Use the surface arca and thickness of the primary containe.ent steel hell or steel liner and associated anchors and concrete. as appropriate.

(2). Estimate the exposed surface area of other steel heat sinks in accordance with Figure 1 and assu=c an average thickness of 3/8 inch.

i (3) Model the internal concrete structures as a slab with a thickness of I foot 2

and exposed surface of 160,000 ft,

The heat sink thermophysical properties that would be acceptable are shown in Table 2.

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At the operating license stage, applicants should provide a detailed If st of passive heat sinks, with appropriate dimensions and properties.

b.

Heat Transfer Coefficients The following conservative condensing heat transfer coefficients for heat transfer to the exposed passive heat sinks during the blowdown and post-blowdown phases of the loss-of-coolant accident should be used (See Figure 2):

(1) During the blowdown phase, assume a linear increase in the condensing heat 2

j transfer coefficient from hinitial=8 Btu /hr-ft

• F at t = 0, to a peak "value four times greater than the,maxinum calculated condensing hcat trans.

fer coefficient at.the end of blowdown, using the Tagami correlation (Ref. 2),

hm,= 72.5 [

0.62 where h,, = na (num heat transfer coefficient, Btu /hr-ft

'F

~

Q

= primary coolant energy Btu V

= net free containe.cnt volune, ft t

= time interval to end of blowdown, sec.

p (2) During the long-tern post-blowdown phase of the accident, characterized by low turbulence in the contaircent att'osphere, asstrr.e condensing heat transfe'r coefficients 1.2 times greater than those predicted by the Uchida data (Ref. 3) and given in Table 3.

(3) During the transition phase of the accident, tettleen the end of blowdown and the long-tem post-bloedown phase, a reasonably ccnservative exponential transition in the condensing heat transfer coefficient should be assu-cd (sce Figure 2).

The calculated condensing heat transfer coefficients based en the above rethad

• should be applied to all exposed passive heat sirks, both retal and cc screte, and for both. painted and unpainted surfaces.

Heat transfer between adjoining r.aterials in passive heat sinks should 'e based c

g on the assumption of no resistance to heat flow at the r:aterial interfaces. An j

example of this is the contaircent liner to concrete' interface.

C.

REFERENC.ES-1.

10 CFR 550.46, " Acceptance Criteria for Emergency Core Cooling Systems for Light k' ster j

Nuclear Power Reactors " and 10 CFR Part 50, Appendix K. "ECCS Evaluation Model's."

2.

T. Tagami.." Interim Report on Safety Assessments and Facilities Establish ent Project l

in Japan for Period Ending June 1965 (No.1)," prepared for the National React ~ Testing

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Station. Februtry 28,1966(unpublishedwork).

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1 3.

H. Uchida A. Oyama, and Y. Toga, " Evaluation of Post Incident Cooling Systems of Light-Water Power P.eactors," Proc. Third International Conference on the Peaceful Uses of 9

Atomic Energy, Volume 13, Sessfoi 3.9, United Nations Geneva (1964).

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TABLE 1 O

IDENTIFICATIO*10F CO*4TAl?NENT HEAT $1r4K5 Containmnt Building (e.g., ilner plate and external concrete walls, floor, and sump, and 1.

lineranchors).

Containment Internal Structures (e.g., internal separation walls and floors, refueling 2.

pool and fuel transfer pit walls, and shleiding walls).

3.

Supports (e.g., react 6r vessel. steem generator.' pumps, tanks., major components, pipe supports,andstorageracks).

Uninsulated Systems and Components (e.g.. cold water systems, heating, ventilation' and 4.

air conditionin; systems, pumps. motors, fan coolers, recombiners, and tanks).

5.

P.iscellaneous Equipnent (e.g.. ladders. gratings, electrical cable trays and cranes).

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HCAT SINK THER!40 PHYSICAL PROP [RTit$

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l Spec 1fIc 1hermal Denstjy Heat Conductivity

, Material Ib/ft Stu/lb *F 8tu/hrft,'1 L

Concrete 145 0.156 0.92 i

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Steel,,

490 0.12 21.0 i

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UCHIDA HfAT_TRAtl$rtR C0trricity Mass Heat Transfer Mass Heat Traxsfer Ratio Coefficignt Ratio Coefficigit

[1b air /lb steau)

[ Btu /hr.f t.'r)

(1b air /lb stead [Ctu/hr.f t.?r,),

50 2

3 29 20 8

2.3 37 18 9

1.8 46 4

10 1.3 63 14 10 14, 0.8 98 7

17 0.5 140

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5 21 0.1 280 4

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Figure 1

• Area of Steel liest Sinks Inside Containment 5-M cu

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3 Containment Free Volume, x 10 fg i.

Revised 12/74 I.

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I Figure 2 Condensing Itcat Transfer Coefficients for Static Heat Sinks

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w oo h

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