ML20091L570

Forwards Revised Draft Response to Request for Addl Info Re Demister in Standby Gas Treatment Sys,Per Effluent Treatment Branch 840413 Request.Calculation Summaries Also Encl. Revised Response Will Be Incorporated in FSAR

ML20091L570
Person / Time
Site:	Limerick
Issue date:	06/04/1984
From:	Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8406080112
Download: ML20091L570 (12)

Text

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PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 JOHN S. KEMPER June 4, 1984 vicents ornt ONGONEE RtNG AND RESE ARCH Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.

20555

Subject:

Limerick Generating Station, Units 1&2 Demister in the Standby Gas Treatment System

References:

1)

PECO and NRC Conference Call dated April 13, 1984.

2)

J.

S.

Kemper to A.

Schwencer letter dated April 13, 1984.

File:

GOVT 1-1 (NRC)

Dear Mr. Schwencer:

This letter responds to a request made by the Effluent Treatment Branch Reviewer in the reference 1) conference call.

The attached calculation summaries provide the technical justification for why water droplets will not reach the SGTS filters. They also provide information on the size of water droplets which would be evaporated by the SCTS heaters.

The response to RAI 460.23 transmitted in reference letter 2) has been revised to incorporate the technical conclusions reached and documented in the calculation summaries.

The attached revised draft response to RAI 460.23 will be incorporated into the FSAR, exactly as it appears on the attachment, in the revision scheduled for July 1984.

The calculation summaries will not be incorporated into the FSAR.

Sincerely, 8406000112 840604

% h l#e-M PDR ADOCK 05000352 O

O A

PDR RJS/gra/052984435 cc:

See Attached Service List l

i

r.

cc: Judge Lawrence Brenner (w/ enclosure)

Judge Richard F. Cole (w/ enclosure)

Troy B.' Conner, Jr., Esq.

(w/ enclosure)

Ann P. Hodgdon, Esq.

(w/ enclosure)

Mr. Frank R. Rm ano (w/ enclosure)

Mr. Robert L. Anthony (w/ enclosure)

Charles W. Elliot, Esq.

(w/ enclosure)

Zori G. Ferkin, Esq.

(w/ enclosure)

Mr. Thcznas Gerusky (w/ enclosure)

Director, Penna. Energency (w/ enclosure)

Management Agency Angus R. Inve, Esq.

(w/ enclosure)

David Wersan, Esq.

(w/ enclosure)

Robert J. Sugarman, Esq.

(w/ enclosure)

Spence W. Perry, Esq.

(w/ enclosure)

Jay M. Gutierrez, Esq.

(w/ enclosure)

Atcnic Safety & Licensing (u/ enclosure)

Appeal Board Atcnic Safety & Licensing (w/ enclosure)

Board Panel Docket & Service Section (w/ enclosure)

Martha W. Bush, Esq.

(w/ enclosure)

Mr. James Wiggins (w/ enclosure)

Mr. Timothy R. S. Campbell (w/ enclosure)

Ms. Phyllis Zitzer (w/ enclosure)

Judge Peter A. Morris (w/ enclosure) l l

i l

l t

L

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I e

r

(

i Respanse 460.23.

The absence required for the SGTS filters.

A demister is not of water droplets in the air stream entering the SGTS filters during post-LOCA isolation, refueling area isolation and

. primary containment purging is assured based on the-

.P following:

s so that The SGTS intake is downstream of the RERS filter' in the air stream entrained water droplets cannot exist entering the SGTS filters during post-LOCA reactor enclo-The absence of water drop-sure isolation and drawdown.

lets in the RERS air stream during reactor enclosure iso-lation was demonstrated in the response to NRC Ouestion 460.4.

There are no sources of water droplets in the refueling As area which could enter the duct connection to SGTS.

discussed below, water droplets from condensation will not reach the SGTS filters during refueling area isolation be-cause of the tortuous flow path and low velocities through The duct the ducts, and low point drains in the ducts.

from the refueling area to the SGTS filters passes through j

I reactor enclosure for approximately 260 feet the Unit If condensation l

and includes at least 20 bends and turns.

l does occur, the amount of condensation would be minor,

~

based upon the potential amount of water vapor in the air One inch diameter low point drains are provided stream.

for the portion of ductwork in the reactor enclosure to i

ensure that any condensation will be drained from the duct.

When refueling area drawdown begins, the flowrate could As water vapor reach 3000 cfm for a short period of time.

accumulates in the refueling area, the flowrate will be l

During the period when any significant con-decreasing.

densation could occur in the ducts, the flowrate in the duct will be no more than POO cfm.

The air velocity during this period varies from approximately 162 to 325 feet per minute (1.8-3.7 mph) for the majority of the ductwork.

The ductwork in the control enclosure that leads to the SGTS filters is completely insulated and rises immediately more than 15 feet through one vertical upward 90 degree I

The turn, one additional 90 degree turn and three bends.

refueling area exhaust air velocity is 162 fpm (1.8 mph) in this portion of the duct.

This velocity is not i

i sufficient to overcome the force of gravity to impart Con-a vertical upward velocity to any water droplets.

densation of water vapor in the insulated ductwork will be negligible.

i The safety-related SGTS heaters are capable of reducing (3000 cfm maximum for

.the relative humidity (RH) of the air, this mode), from 100 percent RH to less than 70' percent RH.

P-56(a)/5 '

-.=..=..:.

a I

z...

4 l

Water droplets will not reach the SGTS filters primary containment purging because of the reasons discussed below.

is highly unlikely that water droplets will enter the As dis-It purge lines during primary containment purging.

cussed in the response to question 460.5, the P' o pre-l 1 plant ventative maintenance program will maintain nor Any reakage i

t leaks to low flow dripping type leakages.(such as those due to failed y

with spraying water droplets,will be identified and cor-seals in pumps and valves),

As discussed rected as part of the maintenance program.it can be shown that in the response to question 460.5, There are any droplets formed travel less than 20 feet.

no potential sources of water droplets within 20 feet of There are the suppression chamber purge exhaust opening.

no pumps, and only a few valves, within 20 feet of the dry-The closest valve is 8 feet 4

well purge exhaust opening.Because the purge system is used away from the opening.

only a limited period of power operation (typically less than 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year), it is highly unlikely that a valve seal would fail and spray water into the drywell j

purge exhaust opening during purge system operation.

If water droplets are hypothetically assumed to enter the purge exhaust ducts, or if condensation within the duct-work occurs, the water droplets would not reach the SGTS filters because of the tortuous flow path, the insulated 3

i ductwork in the control structure, and the SGTS heaters, Purge air exhausted from the drywell flows approximately in the reactor enclosure through three valves, j

215 feet two vertical upward turns and four additional bends and turns with a flow rate of 11,000 cfm at a velocity of 2240 j

The fpm (25.5 mph) in the duct, and 3731 fpm in the pipe.

1 purge air from the suppressien chamber flows more than 160 feet in the reactor enclosure through valves and six bends and turns with a flow rate of 9750 cfm and a velocity of 1986 fpm (22.6 mph) in the duct, and 6008 fpm in the pipe.

At these velocities, if condensation occurs within the ductwork, it is possible for some water droplets to be Condensation within the l

entrained in the air stream.

reactor enclosure ductwork could occur while purging.the suppression chamber, but no significant condenaation would i

occur while purging the drywell because the drywell is i

maintained at a low relative' humidity by the'drywell i

coolers.. No significant condensation would occur in the control enclosure ductwork for either purge mode because it is insulated.

b

! P-56(a)/5 1

-.___..__,__..-.._,._--._.__m._.__.,._.,.

i I~'

The environmental conditions within the reactor 6 1

ductwork will be such that only surface type condensation Droplets will coalesce on the inside surface could occur.

i of the duct creating larger doplets, forming condensate flow on the bottom of the duct.

Much of this flow yill l

drain to low points in the ductwork and be removed via J

j drains, and therefore never enters the air stream.* Much s

{ofthecondensatewhichdoesbecomeentrainedintheair-i stream is subsequently removed from the airstream due to i

Water droplets the many bends and turns in the duct.

greater than 20 microns in size are removed by the bends j

i including a square elbow with turning vanes, i

and turns, (See page 64 which act like course moisture separators.

I Water of the " Nuclear Air Cleaning Handbook," ERDA 76-21).

droplets less then 20 microns in size may reach the SGTS f

ed which demon-itowever, analyses have been per orm heaters.

strate that the SGTS heaters can evaporate all water droplets less than 25 microns in size.

Thus, no water droplets will i'

reach the SGTS filters.

4 The effects of water droplets on the SGTS HEPA filters were evaluated, even though there is no credible way for water l

(Effects on the char-droplets to reach the HEPA filters.

coal filters were not evaluated because the HEPA filters are j

upstream of the charcoal filters, and would collect any water j

When HEPA droplets postulated to be in the airstream).

filters are exposed to high concentrations of liquid, plugging 4

i could occur which would decrease airflow through them.

l Decreased efficiency in collecting particulate matter would not occur unless plugging is severe enough to rupture the l

NEPA filter.

Based on page 65 of the " Nuclear Air Cleaning 4

Handbook" by ERDA, (ERDA 76-21), if the maximum water delivery j

rate is kept below 0.18 gpm per 1000 cfm of airflow, plugging Analyses have been performed which demonstrate will not occur.

that even if all of the condensation that forms in the duct l

during the worst case condition of suppression pool purging is hypothetically assumed to reach the HEPA filters in the i

l l

form'of water droplets, the condensate loading is only 8.33x10-3 gpm/1000 cim, which is well below 0.18 gpm/1000 cfm.

j Thus, plugging of the filters would not' occur.

1 Analyses were performed to demonstrate that the SGTS heaters are capable of reducing the relative humidity of the air from l

during suppression pool purning (9750 CFM for this mode) 100 percent RN, with entrained droplets, to less than 70 The SGTS heaters are percent RH,.with no entrained droplets.

also capable of' reducing the' relative humidity of the air i

)

from'100 during drywell purging (11,000 CFM for this mode),

i l

percent RH to less than '70 percent RM.

i i

J P-56(a)/5 t I

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-,_,,,_e

-...._-m.v.,

,,,_m,__._,_,.,__.._,____m_,_,,__m-

,. *.g CONDITIONS OF AIR ENTERING SGT5 FILTERS

- CALCULATION

SUMMARY

P i

p

Purpose:

The purpose of this calculation is to determine air conditions r

entering the SGTS filters during suppression-pool purge, and the effect on SGTS filter performance from any entrained water droplets.

Method of Calculation:

The calculation consists of the following two parts.

Determination of the relative humidity of the air 1.

entering the SGTS filters.

Determination of the quantity of condensation in the form of water droplets that could reach the filters.

2.

Part 1 - Relative Humidity This part of the calculation is based on the host balance for"the heat tr i.e. that the moist air stream, is equal to the heat-loss of moist air".

the duct Heat transferred through duct = A Up

't<+to _ ta D

2 Heat loss of air = M (hi-ho) also h =.24t + w (1061+.444t)

where, 2

ft Ap = Surf ace Area of Duct, 2

D = Overall heat transmission coefficient, Stu/h,

'F, ft U

ti = Temperature of entering air, *F (saturated)

'F (also saturated) to = Temperature of air leaving the duct,

'F t, = Ambient air temperature,

= Weight of sat.urated air in duct, 1bs/hr M

h

= Enthalpy of entering air, stu/lb i

i ho = Enthalpy of leaving air, Stu/lb

-l-T-36/28(4/20/04)

/

= Enthalpy of air at dry bulb temperature't h

and humidity ratio W The heat balance equation is solved by trial and error.Ney$, humidity a leaving air temperature t is assumed.

d.

ratio W at this temperature and 100% saturation is, calculate

First, d

Then enthalpy h is calculated and values of temperature t an i

d enthalpy h are substituted in the heat balance equat on an This process is repeated until a reasonableWith th evaluated.

l balance is obtained. conditions of air leaving the heater and entering l

l are calculated.

Part 2 - Ouantity of Condensation The total quantity of condensation formed in the SGTS duct is calculated by the difference of the humidity ratios of entering and leaving conditions times the flow rate.

ion In order to determine how much of the total condensat TS could be entrained in the airstream and travel to the SG filters, the type of condensation is evaluated.

i ely Moist air exhausted from the suppression pool is conservat v 00%.

assumed to be 100'F DB and have a relative humidity of 1 is The inside surface temperature of the uninsulate To form fog type con-servatively assumed to be at 65'F.

This con-densation, a supersaturated condition must exist.

dition is determined by computing the ratio of the vapor pressure of moist air to the vapor pressure at the ductIf this rati than 3.5 a supersaturated condition will exist and fog type surface temperature.

Otherwise, only surface con-condensation will be formed. Refer to the " Theory of Fog densation will take place.

Condensation" by A.G. AMIELIN, translated to En LEM 1967.

There-The conditions stated above produce a ratio of 3.1. Droplets fore, only surface type condensation is expected.

will coalesce on the inside surface of the duct creating larger droplets, forming condensate flow on the bottomMuch l

About 50 percent of of the duct.

the ductwork and be removed via drains.the c ducts in Much this manner, and therefore never enters the air stream.

of the condensate which does become entrained in the

~

.T-36/28(4/20/E4)

.' i '*

airstream is subsequently removed f rom the g2ps,trgagoue-Water droplets-to the many bends and turns in the duct, d

greater than 20 microns in size are removed by the ben s and turns, including a square elbow with turning va.nes,(See pge 64 which act like coarse moisture separators.of the " Nuclear I Water droplets less than 20 microns in size may reach the I SGTS heaters.

h A separate calculation was performed to determine w at s

size of droplets would be evaporated by the SGTS heater.

ra-See the " Calculation Summary of Water Droplet Size EvapoIt wa l

which ted by the SGTS Heaters".that the SGTS heaters would evaporate are less than 25 microns in size.

will reach the SGTS filters.

The effects of water droplets on the SGTS HEPA filters for were evaluated, even though there is no credible way (Effects water droplets to reach the HEPA filters.

h on the charcoal filters were not evaluated because in would collect any water droplets postulated to be the airstream).

f When HEPA filters are exposed to high concentrations o liquid, plugging could occur which would decrease airflow Decreased ef ficiency in collecting parti-culate matter would not occur unless plugging is severeBased on page 65 through them.

enough to rupture the HEPA filter.

(ERDA 76-21),

the " Nuclear Air Cleaning Handbook" by ERDA,if the per 1000 cfm of airflow, plugging will not occur.

Results/

Conclusion:

100% saturated air and a 55 KW Starting with 100*F, electric heater, the relative humidity of air ente i

1.

the SGTS filters has been calculated to be 65%.

Because of the bends.nd turns in the SGTS duct, and the SGTS heaters, no tater droplets will reach the 2.

However, even if all of the condensa-d tion that forms in the duct is hypothetically assum SGTS filters.

l The basis plugging of the filters would not occur.

for this conclusion is that the condensate loadin which is well below 0.18 gpm/1000 cfm.

-3~

T-36/28(5/1/84)

..~n

--,_ J

y WATER DROPLET SIZE EVAPORATED BY THE SGTS

- CALCULATION

Purpose:

i what size of

.fThepurposeofthiscalculationistodetermnewater droplets i rated by the SGTS heaters.

Method of Calculation:

f The method of calculation is based on the heat balance ois, the That it.

a water droplet. water droplet is equal to the heat transferred to is Radiative, convective, and conductive heat transferHeat transfer occurs in accounted for in the calculation.in the upstream duct where droplets id three sections; first, can see the heating elements second, the heaters th r,At three fe heater, the duct size starts increasing up to a size equal in the down-stream duct.

The velocity of the air to the SGTS HEPA filter size.

which is decreases in this expansion section of duct, accounted for in the calculation.

The following equations are used in the calculation:

Heat Balance on Droplet _

b

" brad + bec - Mhg D

Ep = McCy (To - 32)

C

+ 32 To = Ep/Mo y

= Mo g (TD(0))

U Ep(0) 2

= N'D (t)

AD " A (t)

D Mo = (g (To(0)) f D'o/6 Ep = Eo + b At radiative heat transfer

-T4

)

brad " f A (t)er(T D

sD Habs abs T-36/28(4/20/84)

's.

1

/I4(X -X)2+pH

),

0$X<X1 f, = DH I

.X 1XiX2 Shape Factor 1

=1 X>X2

= D /(4(X-X2) +D

)

H

.g

.c' Dg =)f4Agfg AD (TA(x) - Toft))

convective & conductive hcc"hcc heat transfer 2

Ap= 77 D ( t)

I 6

=g((Mn(t)

D(t)

Y f(Tp)TT hec = Nu k/D Nu = 2.0 + 0.6 Pr 1/3 Gr 1/4 (Ranz and Marshall Correlation)

Pr = C eVk Prandtl No. (Pr = 0.89) p ConSt.

2 Grashof No.

Gr = variable 3 (t) p2 8ATf4 Gr = D 9

Mass Transfer E = (bec + brad)/hgg(To(t))

Velocity in Expansion Section VA = Const. =VA1H for X>X3

= V A /A(X)

V(X)

IH H)(X-X )/(Xmax-X )

3 3

A(X) =AH + (A -A 2

(X-X )/(Xmax-X )I

= V /[(1+(A /A -1) 3 3

V(X) 1 2

H l

T-36/28(4/20/84) _

't" The symbols used in the equations are defined as follows:

}

Energy Rate of Droplet l

=

D Radiative Heat Transfer f

=

rad Convective and Conductive Heat Transfer f

=

ec Evaporated Mass of Droplet

=

Mass of Droplet l p

=

Enthalpy of gas hg

=

Specific Heat at Constant Vblume Cy

=

Temperature of Droplet To

=

Internal Energy Uf

=

Area of Droplet Ap

=

Time t

=

Droplet Diameter D

=

Specific Weight of Water ff

=

Shape Factor is-

=

Stef an - Boltzmann Constant er

=

Heater Element Temperature TH

=

Distance of Droplet at time t X

=

Distance to Heater Inlet XI

=

Distance to Heater Outlet X2-

=

Distance to Start of Transition X3

=

Distance to HEPA Filter Xmax

=

Equivalent Heater Diameter Convective and Conductive Heat Transfer Coefficient DH

=

hec

=

Air Temperature TA

=

Conductivity K

=

Specific Heat at Constant Pressure C

=

p viscosity AA

=

Density of Air P

=

Acceleration of Gravity

=

g Coefficient of Expansion S

=

Enthalpy of f3uid and gas hfg

=

Air velocity V

=

Cross Sectional Area of Heater AH

=

REPA Filter Face Area A2

=

Air Flowrate MA

=

Change in Air Temperature Through Heater ATA

=

The following input data was used.

_100'F To(0)

=

.100*F T (0)

=

A 1004 H(0 )

=

9750 cfm

=

A 15'F

&TA

=

550*F TH

=

g 4.88.ft2

=

2 i

78.08 ft

=

A2 8 ft XI

=

9 ft-X2

=

12 ft '

X3

-=

20 ft Xmax

=

T-36/28(5/0 3/84 )

_3-

..=.:

~*'

==

Conclusion:==

With the above input data, a water droplet size dte2E micrgns Thus, all in diameter has been conservatively calculated.

water droplets equal to or less than 25 microns in gize

~

will be evaporated by the SGTS heater.

-t The " Calculation Summary of Conditions of Air Entering I SGTS Filters" concludes that no water droplets greater than 20 microns in size will reach the SCTS heaters.

Therefore, no water droplets will reach the SGTS filters.

I T-36/28(4/20/84),

-