ML20150A736
| ML20150A736 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/09/1988 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8803160022 | |
| Download: ML20150A736 (11) | |
Text
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'N Commonwealth Edison c
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/ One Fir,.t N:lional Plaza. Chicago, Illinois g
Address Reply to: Post Offc2 Box 767 Chicago, Illinois 60690 0767 March 9, 1988 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555
Subject:
LaSalle County Station Units 1 and 2 Proposed Technical Specificd ion Change for Facility Operating Licenses NPF-ll and NPF-18 A:nmonia Detection System NRC Docket Nos. 50-373 and 50-374 References (a): Letter dated March 6, 1987 transmitting Proposed Technical Specification Change to Allow Removal of Ammonia Detectors (b): Letter dated January 6, 1988 transmitting Revision 5 of the Report "Habitability of the LaSalle County Station Control Room Following Postulated Accident Involving Shipments of Anhydrous Ammonia in the Vicinity of LaSalle County Station."
Dear Sir:
Commonwealth Edison transmitted a proposed technical specification amendment (Reference (a)) which would allow removal of the requirement for the Ammonia Detection System at LaSalle County Station.
Subsequent, additional information became available which enhanced the basis for that request.
That information was transmitted in Reference (b).
Members of the NRC Staff requested clarification of the material presented in References (a) and (b) and that a detailed description be provided of the conservatisms involved in the calculations.
Those descriptions, a cross reference between this supplement and Reference (b) are included in the attachment to this let.ter.
If you have any questions, please contact this office.
Very truly yours, C. M. Allen Nuclear Licensing Administrator CMA/Im t
8803160022 080309 PDR ADOCK 05000373 4327K P
Supplement 1 TABLE OF COMTENTS Page 1.0 SUKMARY I
2.0 CALCULATION OF REALISTIC PROBA8ILITY 1
4 3.0 CONCLUL'10NS
4.0 REFERENCES
4 CROSS-REFERE,lCE OF EXHIBITS 5
EXHIBITS (S-1 through ISS) 6-9 ERRATA SHEET FOR REVISION 5; OATED OECEMBER 1987 10 i
11
4 Supplement 1 1.0
SUMMARY
Section 9.0 of Revision 5, "Discussion of Results", described the magni-tudes of conservative and realistic probabilities of causing uninhabit-able conditions in the LaSalle Control Room due to accidental release of anhydrous ammonia in the vicinity of the LaSalle County Station. The conservatisms involved in calculating the aggregate probability of 2.85 x 10~0 per year were also described and presented in Exhibit 13 ~of Revision 5.
The purpose of this supplement is to present a detailed description of the conservatisms involved in the calculations, and to show that these probabilities are indeed lower, when combined with realistic assumptions.
Methods of calculating realistic probability are also described in this Supplement. The realistic aggregate probability has been calculated to be 2.0 x 10-7/ year (Exhibit 15S).
Exhibits 14 and 15 presented in Revision 5 have been revised and two new exhibits have been included to support the realistic aggregate probability presented in this Supple-ment. Finally, a <.coss-reference, of exhibits between Revision 5 and this Supplemerit, and an errata sheet for Revision 5 are also included for clarification of information presented.
2.0 CALCULATION OF REALISTIC AGGREGATE PROBABILITY The calculated individual conservative probability of offsite and onsite sources of anhydrous ammonia that could result in uninhabitable condi-tions in the control room was shown in Exhibit 13 of Revision 5.
The maximum ingividual probability of such an event was shown to be 8.44 x 10~ per year in Exhibit 10 of Revision 5.
Simi probability of these sources was shown to be 2.85 x 10~garly, aggregate per year in Exhibit 13 of Revision 5.
To calculate the realistic aggregate probability, preserted in this Sup-t contributing to this conservative aggregate probabil-plement, each eveg/ year was analyzed in terms of conservatisms involved ity of 2.85 x 10~
s in the Revision 5 assessment. Based on realistic accident conditions, a probability assessment was made of individual events in the following manner:
2.1 Barge Traffic The probability of causing uninhabitable conditions due to release s ammonia from 121 ammonia barges was shown to be of anhydroy/ year in Exhibit 9 of Revision 5.
This probability is 3.15 x 10~
based on accidents involving complete rupture of an 1800-ton pressurized anhydrous ammonia carrying barge which instantly releases its contents. -..
Supplemen8 1 Anhydrous ammonia, when spilled on water, produces a buoyant plume of ammonia vapor (Reference 27).
On the basis of spill studies of liquid ammonia on water and corresponding numerical models developed (Reference 27), the concentration at the control room intake and the height of rise of the ammonia plume can be predicted.
The concen-trations of ammonia at the control room intake due to an 1800-ton spill at a distance from the Illinois River to _the plant have been calculated. These concentrations range between negligible and 6.6 ppm depending _ upon atmosheric stability conditions (Exhibit S-1).
The concentration of 6.6 ppm is well below the toxicity _ limit of 100 ppm. The heights of rise of the ammonia plume due to this 1800-ton spill are estimated to range approximately between 900 and 5000 feet (Exhibit S-1).
These concentrations and heights of rise are based on the wind velocity which results in maximum control room concen-tration of ammonia under neutral and stable atmospheric condi-tions.
As shown in Exhibit S-1, an ammonia plume released due to barge accidents would not cause uninhibitable conditions in the control room under the stable dispersion conditions (stability Class F) which represent the worst five percent meteorlogy at the LaSalle County Station site.
Therefore, the conservative probability of causing uninhabitable can be reduced from 3.15x10~gm due to 121 barge shipments per year conditions in the control ro
/ year (Exhibit 9 of Revision 5) to Zero.
2.2 Off-site Storage Tanks (Xaiser Agricultural and Seneca Port Authority)
The conservative probability of causing uninhubitable conditions due to release of anhydrous ammonia from the refrigerated storage tanks was shown in Exhibit 12 of Revision 5.
This is based on accidents involving complete rupture and subsequent release of.the entire tank contents. This calculation also assumed that all stability classes would be sufficient to cause the control room to become uninhabit-able (See Section 7.0 of Revision 5).
The realistic probability of causing uninhabitable conditions due to release of anhydrous ammonia from these refrigerated storage tanks is shown in Exhibit 14 of Revision 5.
A reevaluation of the assumptions has determined that the probabil-and it remains at 2.0 x 10 -9r Agricultural tanks would not change ity attributable to the Kais per year (Exhibit 14 of Revision 5).
However.further investigations of the Seneca' Port Authority Tank (30,000 tons) indicated that there is an earthen dike of sufficient height to contain the entire contents of the tank (Reference S-1).
l Therefore, the realistic probability attributable to the Seneca Port tank was revised. Assuming a complete ruptura of the tank and using WRC NUREG-0570 (Reference S-2), it is shown in Exhibit S-2 that i
under stability Class F, the concentration in the control room is j
J t
~
Supplement 1 79.4 ppm. This concentration is lower than the toxicity limit of 100 ppn. Therefore, the conservative probability of causing unin-hibitable conditions in the control room due to releases from the Seneca Port tank can be reduced from 4.87 x 10-7 (Exhibit 12 of Revision 5) to zero (Exhibit 14S).
2.3 Tank Trucks on County Road 6-The conservative probability of causing uninhibitable conditions County Road due to release of anhydrous ammonia from tank trucks og/ year.
6 was shown in Exhibit 10 of Revision 5 to be 8.44x10-This calculation assumed 50 tank truck shipments on County Road 6.
This assumption is conservative because according to the owner of Walter -
Seed and Fertilizer Inc., located at Grand Ridge, Illinois, most of the annual shipments to his distribution center are supplied by W.
R. Grace Company, located in Henry, Illinois on Illinois Highway 18, approximately 35 miles southwest of the LaSalle County Station (Reference 15).
Even if some anhydrous ammonia is supplied by Kaiser Agricultural located in Marseilles, Illinois on U.S. Highway 6 approximately 5 miles northwest of the LaSalle County Station, the tank trucks would haul anhydrous ammonia to Walter Seed and Fertilizer Inc. via U.S. Highway 6 and Illinois Highway 23 (Reference 15).
Illinois Highway 23 is more than 5 mines. west of the station.
Therefore, based on the location of distribution centers and whole-sale and retail suppliers, it can be concluded that County Road 6 would not be used to transport anhydrous ammonia in tank trucks and the conservative probability of causing uninhabitable conditions in reduced from 8.44 x 10 -yank truck shipments on County Road 6 can be the control room due to
/ year to zero.
2.4 Fertilizer Tanks on Station Service Road and on Leased Land As discussed in Sections 3.2.1 and 6.0 of Revision 5, approximately 300 acres of land within the exterior fenced area of the station are leased to farmers.
Currently, these farmers use 28% granular nitro-gen to fertilize the leased lands. However, to account for the 4
potential use of anhydrous ammonia, a conservative probability to cause uninhabitable conditions in the control room due to accidental releases from farm fertilizer containers on the LaSalle Station serviceroadandtheleasedlandswer9 calculated. This was shown to be 2.70 x 10-7/ year and 2.74 x 10 / year in Exhibit 11 of Revision 5. for the respective events.
The assumption that anhydrous amonia is used as a fertilizer on the leased lands is conservative because Comonwealth Edison Company has the option to stipulate a condition in the lease agreement with the farmers which would prohibit the use of anhydrous ammonia. The text of this condition would be similar to one listed below:.
Supplement 1 Tenant agrees not to use or transport across the leased premises, anhydrous ammonia fertilizer NH, or any trailers, tanks and 3
storage facilities containing tfits fertilizer.
Based on this 10-7/ year and 2.74 x 10~ytipulation, the probabilities of 2.70 x
/ year due to accidental releases from farm fer_tilizer containers on LaSalle Station service road and the leased lands,-
respectively, can be reduced to zero for both events.
In summary, based on a realistic probability assessment of individual events described above, the conservatige aggregate probability shown in of Revision 5 of 2.85 x 10~ / year can be reduced to Exhibit 1)/ year (Exhibit 15S).
2.0 x 10~
3.0 CONCLUSION
S An evaluation of transportation of anhydrous ammonia and the impact of accidents on the LaSalle County Station per Regulatory Guide 1.78 and NUREG-0800, using realistic assumptions, has been performed.
The conser-vative aggregate probability of causing uninhabitable conditions at the LaSalle Cognty Station control room has been calculated to be 2.85 x 10~ / year as shown in Exhibit 13 of Revision 5.
This probability is of the same order of magnitude as the probability criteria specified by NUREG-0800. However, as discussed in this Supplement, when the con-servatism in the calculated probability is removed by reasonable assump-tions, the exposure risk becomes 2.0 x 10-7/ year (Exhibit 15S).
This probability is shown to be an order of magnitude less than the conserva-tive probability criteria specified by NUREG-0800. Therefore, the toxic hazard posed by the accidental release of anhydrous annonia in the vicinity of the LaSalle County Station is not considered a significant risk to the safe operation of the station.
4.0 REFERENCES
S-1.
Glen Mcdonald, Plant Operations Manager, Seneca Port Authority, in Telephone Conversation with Sargent & Lundy Engineers, January 18, 1988.
S-2.
NUREG-0570, Toxic Vapor Concentrations in the Control Room Following a Postulated Accidental Release, prepared by J. Wing, June 1979.
i i l
Supplement 1 CROSS-REFERENCE OF EXHIBITS Some of the exhibits in Ravision 5 have been revised.
The following cross-reference table lists the new exhibit numbers, included in Supplement 1, and the corresponding exhibits, if any, in Revision 5.
Revision 5 Supplement 1 Exhibit S-1 (new)
Exhibit S-2 (new)
Exhibit 14 Exhibit 14S*-
Exhibit 15 Exhibit 155*
- A revision is indicated on Exhi. bits by a bar on the right-hand margin.
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Supplement 1 EXHIBIT S-1 HEIGHT OF RISE OF PLUME FROM ANHYDROUS A* 0NIA BARGE SPILL
- Mass of ammnia spilled, tons 1800 Maximum radius of spill, ft 374 Time for complete vaporization, te, sec 109 Fraction vaporized %
40 0
3 Density of vapor (-28.1 F),1b/ft, Py 0.05556 3
7 Volume of vapor, V, ft 2.59 x 10 y
Fractional density of vapor relative to air (1 - Pv/Pa) = 6v 0.259 5
4 3
6.33 x 10 Buoyancy flux, FP = Yv g a v/Ti te, ft /sec Atm spheric stability Neutral Stable Wind speed, U, ft/sec 16.4 5
3 Buoyancy length, lp = F /0,ft 144 5066 p
Pltne rise coefficient C = (1.51p)1/3 5.99 19.7 Distance to control room, L, ft 22700 22700 Height of rise Z = CL2/3,ft 4805 NA Concentration of amonia at intake under neutral conditions negligible NA Brunt Vaisalla frequency, u 0.01304 Stratification parameter, So = V/1p w 0.0757 Maximum height of rise, Z< = 1p (So)2/3,ft 906 Horizontal travel distance to reach maximum plume height, X.c = (Z.c /C)1.5,f t 313 Atm spheric stability Stable Height of control room intake above Illinois River, ft 372 Plume dispersion coefficient (vertical) dir., ft 131 Distance of intake from pitme center, Zd, ft 534 Concentration of antonia at plume center Co, ppm 26960 Concentration of armonia at intake under stable
- dh2 r conditions C=C e z, ppm 6.6 g
l
- Analysis based on Reference 27, Page 227 NA = Not Applicable i,
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Supplement 1 EXHIBIT S-2 REALISTIC PROBABILITY OF UNINHABITABLE CONDITIONS IN CONTROL ROOM 00E TO ACCIDENTAL RELEASE OF AP ONIA AT SENECA PORT AUTHORITY STORAGE TANX*
Chemical Anhydrous Annonia (refrigerated)
Quantity, tons 30,000 Diameter of area enclosed by dike, ft.
500 2
Area of,urface within dike, ft 196350 Temperature of soil, OF 70 Temperature of annonia, OF
-28.1 Heat transfer from soil to NH, cal /m sec 197x54.5/6 3
Heat transfer by convection, cal /m sec 87 Heat Transfer by soil Radiation, cal /m sec 97 Heat transfer by atmospheric radiation, cal /m see 115 2271105 Heat transferred to annonia 1st 2 minutes of spill, cal /m Quantity of annonia evaporated during ist 2 minutes, Ib 32800 Rate of neat transfer to annonia at 2 minutes, cal /m sec 1279 Rate of annonia boil off at 2 minutes, lb/sec 155 Distance from control room, miles 6
Stability class F
Horizontal dispersion coefficient, ft.
904 Vertical dispersion coefficient, ft.
130 Wind speed, ft/sec.
3.28 Concentration at control room intake, Co, ppm 3017 Control room air exchange rate, R, hr~1 0.8 Concentration in grol room after 2 (t) minutes, C = Co (1-e -R
), ppm 79.4 1
- Analysis based on NUREG-0570, Reference S-2
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Supplement 1 EXHIBIT 14S REALISTIC PROBABILITY OF UNINHABITABLE CONDITIONS IN LASALLE COUNTY STATION CONTROL ROOM DUE TO ACCIDENTAL RELEASE OF ANHYDROUS #HONIA FROM OFFSITE STORAGE TANKS Seneca Kaiser Agricultural Port Source Chemical Authority.
Quantity 1 - 20,000 ton tank 30,000 tons 1 - 25,000 ton tank Distance from !.aSalle Station 5 miles Wind Sector N
Probability of wind blowing 0.01
~
from sector (stability classes E, F, & G & all wind speeds)
Estimated accident frequency 10-5 per year (Reference 33)
PROBABILITY OF CONTROL ROOM 2.0 X 10~7/ year BECOMING UNINHABITABLE 4
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Supplement 1 EXHIBIT ISS REALISTIC AGGREGATE PROBABILITY OF UNINdABITABLE CONDITIONS IN LASALLE COUNTY STATION CONTROL ROOM Event Probability / Year Barge Traffic (Exhibit S-1)
Kaiser Agricultural Chemical Tanks 2.0 x 10-2 (Exhibit 14S)
Seneca Port Authority Tank (Exhibit 14S)
Tank Trucks on County Road 6 (Section 2.3)
Fertilizer Tanks on Station Service Road (Section 2.4)
Fertilizer Tanks on Leased Land (Section 2.4) 2.0 x 10-7/ year