ML20091L570
| 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 vicents ornt June 4, 1984 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 PDR ADOCK 05000352
% h l#e-O M 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
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e r i Respanse 460.23. (
A demister is not required for the SGTS filters. The absence 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' entrained water droplets cannot exist in the air stream entering the SGTS filters during Thepost-LOCA absence of reactor water enclo- 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 discussed below, water droplets from condensation will not duct connection to SGTS.
reach the SGTS filters during refueling area isolation be-cause of the tortuous flow path and low velocities through the ducts, and low point drains in the ducts. The duct from the refueling area to the SGTS filters passes through the Unit I reactor enclosure for approximately 260 feet j
l If condensation 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 stream. One inch diameter low point drains are provided 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 As water vapor could reach 3000 cfm for a short period of time.
accumulates in the refueling area, the flowrate will be l
decreasing. During the period when any significant con-
- densation could occur in the ducts, The the air flowrate velocity in the duct will be no more than POO cfm.
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 I
more than 15 feet through one vertical upward 90 degreeThe turn, one additional 90 degree turn and three bends.
refueling area exhaust air velocity This is 162 fpm velocity is (1.8 not mph) i in this portion of the duct.
i sufficient to overcome the force of gravity to impart a vertical upward velocity to any water droplets. Con-densation of water vapor in the insulated ductwork will be i
negligible.
The safety-related SGTS heaters are capable of reducing
.the relative humidity (RH) of the air, (3000 cfm maximum for this mode), from 100 percent RH to less than 70' percent RH.
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- Water droplets will not reach the SGTS filters
' primary containment purging because of the reasons discussed below.
It is highly unlikely that water droplets will enter As dis- the purge lines during primary containment purging. o pre-l cussed in the response to question 460.5, the P' 1 plant i
ventative maintenance program will maintainAny nor reakage
- ty leaks to low flow dripping type leakages.(such as those due to failed with sealsspraying in pumpswater and valves), droplets,will be identified and cor-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 20There feet of are
' the suppression chamber purge exhaust opening.
no pumps, and only a few valves, within 20 feet of the dry-4 The closest valve is 8 feet 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 j
valve seal would fail and spray water into the drywell 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 3
i filters because of the tortuous flow path, the insulated ductwork in the control structure, and the SGTS heaters, Purge air exhausted from the drywell flows approximately 215 feet in the reactor enclosure through three valves, j
two vertical upward turns and four additional bends and j
turns with a flow rate of 11,000 cfm at a velocity of 2240 The 1
fpm (25.5 mph) in the duct, and 3731 fpm in the pipe.
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 l
entrained in the air stream. Condensation within the reactor enclosure ductwork could occur while purging.the i
', suppression chamber, but no significant condenaation would occur while purging the drywell because the drywell is l 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.
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1 The ductwork environmental will be such conditions that onlywithin surface thetype reactor 6 condensation could occur. Droplets will coalesce on the inside surface i of the duct creating larger doplets, forming condensate yill flow on the bottom of the duct. Much of this flow via l
s drain to low points in the ductwork and be removed J
j drains, and therefore never enters the air stream.* Much i
{ofthecondensatewhichdoesbecomeentrainedintheair-stream is subsequently removed from theWater airstream due to i droplets j the many bends and turns in the duct.
greater than 20 microns in size are removed by the bends i
i and turns, including a square elbow with turning (See vanes, page 64 which act like course moisture separators.
of the " Nuclear Air Cleaning Handbook," ERDA 76-21). Water I ,
droplets less then 20 microns in size may reach edthe SGTS which demon- ;
heaters. itowever, analyses have been per orm f
strate that the SGTS heaters can Thus, evaporate no all droplets water water droplets will i
less than 25 microns in size.
4 reach the SGTS filters.
The effects of water droplets on the SGTS HEPA filters were evaluated, even though there is no credible way for water l
j droplets to reach the HEPA filters. (Effects on the char-coal filters were not evaluated because the HEPA filters are upstream of the charcoal filters, and would collect any water j
droplets postulated to be in the airstream). When HEPA ,
4 filters are exposed to high concentrations of liquid, plugging '
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 NEPA filter. Based on page 65 of the " Nuclear Air Cleaning 4
l 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 will not occur. Analyses have been performed which demonstrate that even if all of the condensation that forms in the duct l
i during the worst case condition of suppression pool purging !
is hypothetically assumed to reach the HEPA filters in the l l form'of water droplets, the condensate loading is only j
8.33x10-3 gpm/1000 cim, which is well below 0.18 gpm/1000 cfm.
1 Thus, plugging of the filters would not' occur.
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 percent RH,.with no entrained droplets. The SGTS heaters are i
also capable of' reducing the' relative humidity of the air from'100 )
during drywell purging (11,000 CFM for this mode), i percent RH to less than '70 percent RM. i l
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,. *.g CONDITIONS OF AIR ENTERING SGT5 FILTERS
- CALCULATION
SUMMARY
i P
p
Purpose:
r The purpose of this calculation is to determine air conditions 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. ,
- 1. Determination of the relative humidity of the air -
entering the SGTS filters.
- 2. Determination of the quantity of condensation in the form of water droplets that could reach the filters.
Part 1 - Relative Humidity This part of the calculation i.e. that is based on the host balance for"the heat tr the moist air stream, the duct is equal to the heat-loss of moist air".
Heat transferred through duct = A DUp 't<+to _ ta 2 ,
Heat loss of air = M (hi-ho)
- where, also h = .24t + w (1061+ .444t) ft 2 Ap = Surf ace Area of Duct,
'F, ft 2 UD = Overall heat transmission coefficient, Stu/h, ti = Temperature of entering air, *F (saturated)
'F (also saturated) to = Temperature of air leaving the duct, t, = Ambient air temperature, 'F M = Weight of sat.urated air in duct, 1bs/hr hi = Enthalpy of entering air, stu/lb i
ho = Enthalpy of leaving air, Stu/lb
-l-T-36/28(4/20/04)
/
l h
= Enthalpy of air at dry bulb temperature't l and humidity ratio W The heat balance equation is solved by trial and error.Ney$, humidity First, a leaving air temperature t is assumed.
d.
ratio W at this temperature and 100% saturation is, calculate 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 evaluated. This process is repeated until a reasonableWith th l l
balance is obtained. conditions of air leaving the heater and entering 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 TS In order to determine how much of the total condensat could be type filters, the entrained in the airstream of condensation is evaluated. and travel to the SG i ely Moist air exhausted from the suppression pool is conservat v 00%.
assumed to be 100'F DB and have a relative humidity is of 1 The inside surface temperature To form fogof typethe con-uninsulate 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 surface temperature.
than 3.5 a supersaturated condition Otherwise, will exist and fogcon-only surface type condensation will be formed. Refer to the " Theory of Fog densation will take place.
LEM Condensation" by A.G. AMIELIN, translated to En 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 l l
larger droplets, forming condensateAbout flow 50 onpercent the bottomMuch of of the duct. ducts in the ductwork this manner, and be and therefore never removed enters the airvia drains.the stream.
Much co of the condensate which does become entrained in the
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airstream is subsequently removed f rom Water droplets-the g2ps,trgagoue-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 s at size of droplets would be evaporated by the SGTS heater ra- .
See the " Calculation Summary of Water Dropletwhich Size EvapoIt wa l
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 in because would collect any water droplets postulated to be the airstream). f When HEPA filters are exposed to high concentrations o liquid, plugging could occur Decreased ef which would ficiency in decrease collecting parti- airflow through them.
culate matter would not occur unless plugging is severeBased on page 65 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 i 1.
Starting with 100*F, electric heater, the relative humidity of air ente the SGTS filters has been calculated to be 65%.
Because of the bends .nd turns in the SGTS duct, and 2.
the SGTS heaters, no tater However, evendroplets if all ofwill thereach condensa-the d
SGTS filters. l tion that forms in the duct is hypothetically The basis assum plugging of the filters would not occur.
for this conclusion is that the condensate loadin l which is well below 0.18 gpm/1000 cfm.
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T-36/28(5/1/84)
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- WATER DROPLET SIZE EVAPORATED BY THE SGTS
- CALCULATION
SUMMARY
Purpose:
i what size of
.fThepurposeofthiscalculationistodetermnewater droplets i rated by the SGTS heaters.
Method of Calculation: f The method of calculation That is based on the heat it.
balance ois, the a water droplet. water droplet is equal to the heat transferred to is Radiative, convective, and conductive heat transferHeat transfer in occurs accounted for in the calculation.in the upstream duct where droplets three sections; first, id can see the heating elements second, the heaters th r ,At three fe in the down-stream heater, the duct size duct.starts increasing up to The velocity of athesize airequal to the SGTSinHEPA decreases filter size.section of duct, which is this expansion accounted for in the calculation.
The following equations are used in the calculation:
Heat Balance on Droplet _
bD " brad + bec - Mh g Ep = McCy (To - 32)
To = Ep/MoCy + 32 Ep(0) = MoU g (TD(0))
= N'D2 (t)
Mo = (g (To(0)) f D'o/6 Ep = Eo + b At
-T4D ) radiative heat transfer b rad " f sD A (t)er(T H abs abs T-36/28(4/20/84)
. 's.
1 I
f, = DH /I4(X -X)2+pH I
),
0$X<X1 I Shape Factor l
=1 , .X11XiX2
.g = DH /(4(X-X2) +D ) , X>X2
.c
' Dg =)f4Agfg convective & conductive hcc"hcc AD (TA(x) - Toft)) heat transfer Ap= 77 D2 ( t)
D(t) I 6
=g((Mn(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 peVk Prandtl No. (Pr = 0.89)
ConSt.
Gr = D 3 (t) p29 8ATf4 2 Grashof No. Gr = variable Mass Transfer E = (bec + brad)/hgg(To(t))
Velocity in Expansion Section VA = Const. =VA1H for X>X3 V(X) = VIH A /A(X)
A(X) =AH + (A2-A H)(X-X3 )/(Xmax-X3 )
V(X) = V1 /[(1+(A2 /AH-1) (X-X3 )/(Xmax-X3 )I l
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The symbols used in the equations are defined as follows:
D
= Energy Rate of Droplet l rad = Radiative Heat Transfer f ec = Convective and Conductive Heat Transfer f l
= Evaporated Mass of Droplet ;
l p = Mass of Droplet hg = Enthalpy of gas Cy = Specific Heat at Constant Vblume To = Temperature of Droplet
= Internal Energy Uf = Area of Droplet Ap t = Time D = Droplet Diameter ff
= Specific Weight of Water is- = Shape Factor er = Stef an - Boltzmann Constant TH
= Heater Element Temperature X = Distance of Droplet at time t XI = Distance to Heater Inlet X2-
= Distance to Heater Outlet X3
= Distance to Start of Transition Xmax
= Distance to HEPA Filter DH
= Equivalent Heater Diameter hec = Convective and Conductive Heat Transfer Coefficient TA
= Air Temperature K = Conductivity Cp = Specific Heat at Constant Pressure AA = viscosity
= Density of Air P = Acceleration of Gravity g
S = Coefficient of Expansion hfg = Enthalpy of f3uid and gas V = Air velocity AH
= Cross Sectional Area of Heater A2
= REPA Filter Face Area MA = Air Flowrate ATA = Change in Air Temperature Through Heater The following input data was used.
To(0) = _100'F T A(0) = .100*F H(0 ) = 1004 A
= 9750 cfm
&TA
= 15'F TH
= 550*F i g .
= 4.88.ft2 2
78.08 ft A2 = 8 ft XI
X2 9 ft-X3
-= 12 ft '
= 20 ft Xmax
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Conclusion:
With the above input data, a water droplet size dte2E Thus, micrgns 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 I The " Calculation Summary of Conditions of Air Entering SGTS Filters" concludes that no water droplets greater than 20 microns Therefore, in size no water will reach droplets will the SCTS reach the heaters.
SGTS filters.
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