ML19261E537
| ML19261E537 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/21/1979 |
| From: | SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | |
| Shared Package | |
| ML19261E535 | List: |
| References | |
| NUDOCS 7908280642 | |
| Download: ML19261E537 (7) | |
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V. C. SUMMER NUCLEAR STATION UlllT 1 FUEL HAtlDl_ING BUILDING EXFILTRATION AllALYSIS FOR A POSTULATED FUEL HANDLING ACCIDENT An exfiltration analysis was performed to demonstrate the capability of the Fuel Handling Building (FHB) ventilation system to mitigate the consequences of a fuel handling accident.
Assumptions and design data, equations, and calculations used for the, nalysis are listed in Table A.
The FHB venti'ation system consists of supply and exhaust components which are balanced to obtain negative pressures in the FHB to prevent outflow of air.
Supply fans deliver filtered and heated (i f requi red) outside ai r.
Air is supplied to one side of the fuel pool and sweeps across to exhaus t registers on the other side.
Radioactiv: ty escaping f rom the fuel pool is picked up by the exhaust.
Exhaust air is drawn through HEPA and charcoal filters by one of two 100 percent sys tem capaci ty f ans, each rated at 30,000 cubic feet per minute (cfm) at a total pressure of 9.3 inches water gage (in. wg).
Assumptions used to calculate activity in the FHB for the postulated fuel handling accident are identical to those presented in Section 15.4.5 of the FSAR for the Regulatory 1.25 case and are summarized in Table B.
For the evaluation of offsite doses, it is assumed that air which infiltrated into the bul.lding is mixed uniformly wi th the supplied ai r as i t passes over the fuel pool.
Thus, for wind conditions which cause unfiltered air to exfiltrate through the sides of the building, the division of activity released to the envi ronmen t is assumed proportional to the flow rates of the filtered and unfiltered exhaust s treams.
In addi tion, no credi t is taken for the decay of activity due to holdup in the FHB.
Fuel handling accident doses are presented in Table C.
The doses listed are well within the guidelines of 10CFR100.
o^0 353 7 908 2 806 u,
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TABLE A VENTILATI0il EXFILTRAT10!1 AllALYSIS FOR A POSTULATED FUEL llAllDr.ING ACCIDEilT Assumptions and Detign Data Wind direction southwest flote - Prevailing wind is southwest.
This wind direction is used in the calculations and should be worst case since exfiltration is estimated to be maximum primarily due to building arrangement.
Wind velocities 1, 5, 10 M/s External pressure coefficients, Cp windward wall 0.8 Iceward wall
-0.5 side wall
-0 7
Reference:
ANSI Standard A58.1-1972, page 19 Overall air leakage rate per unit area of exterior wall, C:
2 wind velocity (H/s)
C (cfh/ft )
1 2
5 30 10 120 Notes - The following conservative factors were included in the C selections:
1.
Worst case C published in ASHRAE 1977 Fundamentals Handbook (page 21.6) was multiplied by 2, 2.
Wors t case wall was porous.
V. C. Summer FHB walls and personnel doors are taped and scaled.
3 Full velocity pressure i s' assumed for wall differential pressures.
Leakage, through roof 0
Area of walls exposed to wind:
2 west 4382 ft north 9485 cast 5790 south 2063 southeast 1200 o^0 354
-A2-Description of FilB exterior walls:
Hetal siding with tra,slucent panels.
Panels scaled at facto ry.
Siding / panel joints and attachments sealed at site with tape.
Description of FilB exterior doors:
wes t and north walls - no doors cast wall - 3 perscnnel doors 3'x7' which are gasketed I roll-up door 16'x22' south and southeast wall - 1 roll-up door 7'x10' No other openings in exterior walls.
Air leakage from adjacent buildings assumed = 0.
Auxiliary Building internal pressure 1.s controlled to be negative.
Reactor Building is sealed.
Mixing of supply and infil trated ai r 100 percent Fraction of release filtered 30,000/(30,000 + exfil tration flow)
Equations 1.
Q = C (o P)"A Where:
Q = volume flow rate of air filtrating through a wall C = flow coef ficient, volume flow rate per unit area d P = pressure differential across wall n = flow exponent, between 0.5 and 1, usually near 0.65 for leakage openings A = wall area Refe rence : ASHRAE 1977 Fundamentals Handbook, page 21.4 2.
Pw-Pi = Pw-P1 1+(Aw/Al)i/n Where:
P = wind pressure A = leakage area n = flav exponent = 0.65 w - windward 1 - inside 1 = Iceward
Reference:
ASHRAE 1977 Fundamentals Handbook, page 21.4 2
3 P =.00241 Cp Va Where:
P = wind pressure on walls, inches water gage (in wg)
Cp = external pressure coef ficient for walls Va = wind velocity, meters per second (fi/s)
Refe rence : ASilRAE 1977 Fundamentals llandbook, page 21.1 g,
-A3-Calculations 1.
Wall pressure di f ferenti al. Wind velocity = 10 ll/s Pw-Pi = Pw-P1 Equation 2 1+ (Aw/Al) I/0 Pw =.00241 x 0.8 x (10)2 =.193 in wg Equation 3 P1.=.00241 x (-0 5)(10)2 =.121 in Og Aw = 4382 + 2063 =.422 Ali 9485 + 5790 314 _ =.248 Pw-P i =.193 +.121
=
1+(.422)1.54 1+.265 Pi =.193
.248 =
.055 in wg
. Ps =.00241 x (-0 7)(10)2 =
.169 in wg 6 P1 =
.055-(.121) =.066 d Ps =
.055-(.169) =.114 2.
Leakage flow rate with FHB supply and exhaust fans off. Wind velocity = 10 M/s
- Q = C (dP) A Equation 1 a.
Infiltration Q = 120 (.248).65 x 6445 = 5208 cfm 60 b.
Exfi l t ra t ion QI = 2 (.066).65 x 15275 = 5222 cfm Qs = 2 (.114).65 x 1200 = 586 cfm c.
Net volume flow rate Exfiltration = 5222. + 586 - 5208 = 600 cfm For conservatism, assume an exfiltration flow rate of 1200 cfm to be used in the analysis of radiological consequences of a fucI handling acci den t. An analysis assuming both supply and exhaust fans off is also considered to be conservative.
Normally the supply and exhaust components of the ventilation system would be balanced to prevent exfiltration at the worst case condi tion.
In this case, the ventilation exhaust would be set at least 1200 cfm more than the supply.
"^0 356
_A4-3 Wall pressure differential. Wind velocity = 5 M/s Pw =.00241 x 0.8 (5)2 =.048 P1 =.00241 (-0.5)(5)2 =
.030 f=.422 Pw-Pi =.048 +.030 =.062 1.265 Pi =.048
.062 =
.014 Ps =.00241 (-0. 7) (5) 2 =
.042 d Pl =.014 - (.030) =.016
~
A Ps =.014 - (.042) =.028 4.
Leakage flow rate with FHB supply and exhaust f ans off. Wind veloci ty = 5 M/s Infi l t ra, tion a.
4 = 30 (.062).65 x 6445 = 529 cfm To~
b.
Exfiltration Q1 =.5(.016).65 x 15275 = 519 cfm Qs =.5(.028).65 x 1200 = 59 cfm c.
liet volume flow rate Exfil tration = 519 + 59 - 529 = 49 cfm (Assume a rate of 2 x 50 = 100 cfm for conservatism) 5.
Exfiltration is considered to be negligible below wind velocity = 5 H/s O
^^0 357
TABLE B RADIOLOGICAL ASSUMPTI0nS FOR A POSTULATED FUEL HFlDLil1G ACCIDENT - EXFILTRATl0fl AllALYSIS_
Power Level 2900 Hegawatts-thermal Power Peaking Factor 1.65 Number of Rods Failed 1 Fuel Assembly Fraction of Inventory in Gap:
Noble Gases 10 percent Kr-85 30 percent lodines 10 percent Effective lodine Decontamination Factor in Pool 100 Filter Efficiencies:
Elemental lodine 90 percent Organic lodine 70 percent iodine Fractions Leaving Pool:
Elemental 75 percent O rgani c 25 percent Shutdown Time 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> Accident Atmospheric Dilution Factors:
3 0-1 hour at I mile 4.08 x 10_-0 sec/m 0
3 0-1 hour at 3 miles 1.01 x 10 sec/m Atnospheric Dispersion Model No change in stability with increased wind speed.
Dose inversely proportional to wind speed for a given release quantity.
^^0 358
TABLE C FUEL llAf1DLl!1G ACCIDEllT DOSES - EXFILTRATI0ff AllALYSIS Integrated Thyroid Doses For 10 M/S Wind Speed Location Distance Exposure Time Dos e Exclusion Boundary 1 mile 2 hr.
1.14 rem Low Population Zone 3 miles Course of Accident 0.28 rem Integrated Wholt: Body Dose For 10 M/S Wind Speed Location Distance Exposure Time Dose Exclusion Boundary 1 mile 2 hr.
. 0 90 rem Low Population Zone 3 miles Course of Accident 0.003 rem Integrated Thyroio "oses for 5 M/S Wind Speed Location Distance Exposure Time Dose Exclusion Boundary 1 mile 2 hr.
1.9 rem Low Population Zone 3 miles Course of Accident 0.47 rem Integrated Whole Body Dose for 5 M/S Wind Speed Location Distance Exposure Time Dose Exclusion Boundary 1 mile 2 hr.
0.11 rem Low Population Zone 3 miles Course of Accident 0.006 rem At Negligible Exfiltration Rate Equal to 1 M/S Wind Speed Thyroid Dose Whole Body Dose Exclusion Boundary 16.3 rem 0.95 rem Low Population Zone 0.95 rem 0.055 rem
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