ML18005A751
| ML18005A751 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 01/04/1989 |
| From: | CAROLINA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML18005A750 | List: |
| References | |
| NUDOCS 8901120076 | |
| Download: ML18005A751 (15) | |
Text
ENCLOSURE 4 SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT CHLORINE DETECTION SYSTEM TECHNICAL SPECIFICATION PAGES
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INOEX LIMITING CONDITIONS FOR OPERATION AND SURVEILLANCE REOUIREMcHTS
'ECTION TABLE 3-3-6 RADIATIOH MONITORING IHSTRUMENTATIOH FOR PLANT OPERATIONS...........................
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TABLE 4.3"3 RADIATIOH MONITORING IHSTRUMEHTATION fOR PLANT OPERATIONS 'SURVEILLANCE REQUIREMEHTS...... -. -... -.
Movable Incore Detectors................--
Selsmlc Instrumentatson..................
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TABLE 3. 3-7 SEISMIC MONITORING IHSTRUMEHTATION.............. -..
TABL
- 4. 3-4 SEISMIC MONITORING INSTRUMENTATION SURVEILLANCE REQUIREMENTS...................................-..-
Meteorological Ins rumentation...........................
TABLE 3. 3-8 METEOROLOGICAL MONITOR!HG IHSTRUMEHTATIOH.............
TABLc 4.3-5 METEOROI OGICAL MOHITORIHG INSTRUMENTATION SURVEILLANCE R EQ UIREMEHTS o
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Remote Shutdown System........................---...
TABLE 3.3-9 REMOTE SHUTDOWN SYSTEM..............--...-.--
TABLE 4. 3-6 REMOTE SHUTDOWN MONITQRIHG INSTRUMENTATION SURVEILLANCE REQUIREMEHTS...........-...-..---..--
Accident MonHoring Instrumentation.................-----
TABLE 3.3-10 ACCIDENT MOHITQRING IHSTRUMEHTATIOH....----.-----.-.-
TABLE 4.3-7 ACCIDENT MONITORING IHSTRUMEHTATIOH SURVEILLANCE EQUIREMENTS.............................................
R PAGE 3/4 3-51 3/4 3"54 3/4 3-56 3/4 3-57 3/4 3-68 3/4 3-59 3/4 3-60 3/4 3-61 3/4 3"62 3/4 3-63 3/4 3"64 3/4 3-65 3/4 3-66 3/4 3-68 3/4 '3"70 Metal Impact Monitoring System.................-.........
Radioactive Liquid Effluent Monitoring Ins rumentation...
TABLE 3.3-12 RADIOACTIVE LIQUID EFFLUENT MONITORING IHSTRUMEHTATION.................................-.....-..
TABLE 4. 3-8 RADIOACTIVE LIQUID EFFLUcHT MONITORING IHSTRUMEHTATIOH SURVEILLANCE REQUIREM~cS Radioac.ive Gaseous Effluent Monitoring Ins rumentati TABLE 3.3-13 RADIOACTIVE GAScOUS EFFLUEHT MONITORING ZHSiRUMEHTAiION....
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TABLE 4.3-9 RADIOACTIVE GASEOUS ErFLUEHT MOHITORING INSTRUMENTATION SURVEILLANCE REQUIREcMEHTS............
3/4.3. 4 TURBINE OVERSPEED PROTECTION........ -.... -.. -.....
SHEAROH HARRIS - UNIT 1 vi on..
TABLE 3.3-11 (DELcTED).....................-......-
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3/4 3"73 3/4 3"74 3/4 3-75 3/4 3"76 3/4 3-79 3/4 3"82 3/4 3-83 3/4 3-86 3/4 3-89
INSTRUMENTATION CHLORINE DETECTION SYSTEMS5pecr A'rca+:~n 3/4 g. y.g Q/cE'Mi 3 ~
3 '
Two i'ndependent Chlorine Detector, Trains, with their Trip Setpoints adju ed to actuate at a chlorine concentra'tion of less than or equal to fiv
- ppm, s
11 bc OPERABLE.
Each train shall consist of:
a detector at each Control om Ventilation System intake (both normal and emergency);
and detector a
the chlorine storage area whenever liquid chlorine is prese t at the storage rea in quantities greater than 20 lbs.
APPLICABILITY:
11 MODES ACTION:
b With one Chl ine Detector Train inoperable, rest@re the inoperable system to OP LE status within 7 days or wit+a the nezt 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> initiate and mai ain operation of the Contr/o Room Area Ventilatioa System in the reer culatioa mode of operati n
Vith both Chlorine De ctor Trains inoperable, within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> initiate and maintain operation thc Control oom Area Veatilatioa System in the recirculation mode o
operation.
Ce The provisions of Spccificatx a 0.4 are not applicable.
SURVEILLANCE RE UIRRfENTS 4 3.3.7 Each Chlorine Detector Train shall be d
onstrated OPERABLE by performance of a CHANNEL CHECK t least once per 1
- hours, aa AHALOC CHANNEL OPERATIONAL TEST at least onc per 31 days and a
C EL CALIBRATION at least once per 1B months.
SHEARON HARRIS - UNIT 3/4 3-72
g
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PLANT SYSTEMS CONTROL ROOM EMERGENCY FILTRATION SYSTEM SURVEILLANCE REOUIREMENTS Continued C.
Revisions 2, March 1978, and the system flow rate is 4000 c m
10K during system operation when tested in accordance with ANSI N510"1980; and 2.
Verifying, within 31 days ofter removal, that a laboratory analysis of a representative carbon sample obtained in accor dance with Regulatory Position C.6.b of Regulatory Guide 1.52, Revision 2, March 1978, meets the laboratory testing criteria
~ of Regulatory Position C.6.a of Regulatory Guide 1.52, Revi-sion 2, March 1978, by showing a methyl iodide penetration of
'ess than 0.175 when tested at a temperature of 30~C and at a
relative humidity of 70" in accordance with ASTM 03803.
After every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of charcoal adsorber operation, by verifying, within 31 days after removal, that a laboratory analysis of a repre-sentative carbon sample obtained in accordance with Regulatory Posi-tion C.6.b of Regulatory Guide 1.52, Revision 2, March 1978, meets the laboratory testing criteria of Regulatory Position C.6.a of Regulatory Guide 1.52, Revision 2, March 1978, by showing a methyl iodide penetration of less than 0. 175 when tested at a tempera ure of 30 C and at a relative humidity of 70 in accordance with ASTM 03803.
d.
At l.east once per 18 months b~:
1.
Verifying that the pressure drop across the combined HEPA fil-ters and charcoal adsorber banks is less than 5.3. inches water gauge while operating the system at a flow rate of 4000 cfm 10K; 2.
Verifying that, on either a Safety Injection or a High Radiation test signal, the system automatically switches into an isolation with recirculation mode of operation wi h flow through the HEPA filters 'and charcoal adsorber banks; 3.
Verifying that the system maintains the control room at a positive pressure of greater than or equal to 1/8 inch Water Gauge at less than ot equal to a pressurization flow of 315 cfm relative to adjacent areas during system operation; 4.
Verifying that the heaters dissipate 14
- 1. 4 kW when tes ed in accordance wi h ANSI N510-1980; and Mete Fe'cf
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5-seconds-arA e-HEPAf-i-l-t';ers-and SHEARON HARRIS - UNIT 1 3/4 7-15
IHSTRUMEHTATION.
)
BASES REMOTE SHUTDOWN SYSTEM Continued This capability is consistent with General Design Criterion 3 and Appendix R
to 10 CFR Part 50.
3/4. 3.3. 6 ACCIDENT MONITORING INSTRUMENTATION The OPERABILITY of the accident monitoring instrumentation ensures that suffi-cient information is available on selected plant parameters to monitor and assess these variables following an accident.
This capability is consistent with the recommendations of Regulatory Guide 1.97, Revision 3, "Instrumentation for Light-Water Cooled Nuclear Power Plants to Assess Plant Conditions During and Following an Accident," May 1983 and HUREG-0737, "Clarification of TMI Action Plan Requirements,"
November 1980.
3/4. 3.3. 7 e
LITY of the Chlorine Detection Systems ensures u ficient capa-bility is avas romptly detect and ini 'otective action in the event of an accidental ch o
1 1s capability is required to pro-tect control room personn s con 'ith the recommendations of Regu-latory Guide 1.
>sion 1, "Protection of Huc er Plant Control Room
~
Oper gainst an Accidental Chlorine Release,"
January 3/4. 3.3. 8 DELETED 3/4.3. 3. 9 METAL IMPACT MONITORING SYSTEM The OPERABILITY of the Metal Impact Monitoring System ensures that sufficien capability is available. to detect loose metallic parts in the Reactor System and avoid or mitigate damage to Reactor System components.
The allowable out-.
of-service times and surveillance requirements are consistent with the recom-mendations of Regulatory Guide 1.133, "Loose-Part Detec.ion Program for the Primary System of Light-Water Cooled Reactors,"
May 1981.
3/4.3.3. 10 RADIOACTIVE LIOUID EFFLUEHT MONITORING INSTRUMEHTATIOH The radioactive liquid effluent instrumentation is provided to monitor and con-
'trol, as applicable, the releases of radioactive ma erials in liquid effluents during actual or potential releases of liquid effluents.
The Alarm/Trip Set-points for these instruments shall be calculated and adjusted in accordance wiD the me hodology and parameters in the OOCM to ensure that the alarm/trip will occur priar to exceeding he limits of 10 CFR Part 20.
The OPERABIL~i and use of this instrumentation is consis ent with the requirements of General Design Cri eria. 60, 63, and 64 of Appendix A to 10 CFR Part 50.
SHEARON HARRIS - UNiT 1 B 3/4 3-5
ENCLOSURE 5
SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 REQUEST FOR LICENSE AMENDMENT CHLORINE DETECTION SYSTEM PROBABILISTIC RISK ANALYSIS OF ACCIDENTS RELATED TO THE TRANSPORTATION OF CHLORINE IN THE VICINITYOF THE SHEARON HARRIS NUCLEAR PLANT
PROBABILISTIC RISK ANALYSIS OF ACCIDENTS RELATED TO THE TRANSPORTATION OF CHLORINE IN THE VICINITYOF THE SHEARON HARRIS NUCLEAR POWER PLANT 1.
INTRODUCTION CP&L has previously performed studies to assess the habitability of the Shearon Harris control room in case of postulated accidental ruptures of stationary or transient sources of chlorine in the vicinity of the Shearon Harris Nuclear Power Plant.
The analyses included the postulated rupture of the on-site chlorine storage tank as well as accidents involving a chlorine tank truck on U.S. Highway 1 or a tank car on the Seaboard Cost Line ( part of the Seaboard System Railroad, now a part of CSX Transportation),
both occurring at the points on these routes nearest to SHNPP.
Those analyses took credit for the chlorine detectors, located both in the control room fresh air intake duct and in the vicinity of the on-site chlorine storage tank, which would isolate the control room ventilation system and warn the control room operators in case of a chlorine release accident.
Following guidance of Regulatory Guides 1.78 and 1.95, the analyses showed that the control room operators were adequately protected against credible chlorine release accidents.
CP&L has since removed the railway tank car used as the on-site storage tank from the SHNPP site.
An amendment to Technical Specification 3.3.3.7 which eliminated the requirement for chlorine detectors in the chlorine storage area when no more than 20 pounds of chlorine are stored there was issued on August 23, 1988 '
new study has now been preformed to determine if, in light of the absence of significant quantities of chlorine on site, the requirement for chlorine detectors in the control room ventilation system should be eliminated as well.
These new analyses, which took credit for the ability of the control room operators to detect chlorine by odor and to protect themselves by donning breathing apparatus, calculated the probability that accidents involving the transportation of chlorine on U.S.
1 and on the Seaboard Cost Line could pose a hazard to the SHNPP control room.
2.
METHODOLOGY The first part of the study was estimating the frequency of clorine tank trucks on U.S.
1 and railroad tank cars on the Seaboard Cost Line in the SHNPP vicinity.
Next, analyses were performed to determine the probability that a
shipment along either route could pose a hazard.
These analyses utilized Ebasco's TOXCHM computer program, which incorporates the methodology described in Regulatory Guide 1.95.
2.1 Shipment Frequencies 2.1.1 Highway As far as could be determined, no specific information on the shipment of chlorine over U.S 1 (nor over any other highway in North Carolina) has ever been published.
According to the Director of Zone Operations, State Highway
- Patrol, the State of North Carolina does not maintain records of shipments of hazardous materials (other than spent nuclear fuel)
A study performed by the Office of Technology Assessment of the U.S. Congress
[1] showed that no such data on either the state or national level was available.
(136CRS)
In the absence of site-specific statistical data, a variety of sources were
. consulted to enable an estimate of the frequency of chlorine tank trucks on U.S.
1.
Studies had been performed on the transportation of hazardous materials in Virginia in 1977-78 [2].
These studies reported the percentage of trucks which carry hazardous materials on various highways in that state, as well as a breakdown of the types of materials carried.
Because of the close proximity of the two states, these data can be used to estimate shipments in North Carolina.
The North Carolina Division of Highways, furnished the daily vehicular traffic on U.ST 1 in 1986, as well as an estimate of the frequency of truck traffic [8] ~
The Chlorine Institute [3] reported that there is only one commercial chlorine producer in North Carolina, namely the LCP Co. in Acme, NC.
In a telephone conversation, the plant manager of that facility stated that no chlorine was shipped by highway [4].
The 1977 Commodity Transportation
- Survey, conducted by the U.S.
Census Bureau, reported the total tonnage of chlorine shipped from manufacturers to customers in the state, and also furnished a nation-wide split of chlorine transportation by truck, railroad and other means.
An inquiry to one other chlorine producer in the area
[5] showed that they also did not ship chlorine by truck.
Finally, the Chlorine Institute reported that there are only 100 chlorine tank trucks operating in all of North America, 13 of which are used for short hauls within California.
2.1.2 Railroad CSX Transportation, the current operator of the Seaboard Coast Line, reported that the line from Raleigh to Hamlet, NC (gust south of Sanford) is no longer a main line, due to the closing of the tracks north of Raleigh.
The traffic on that section consists entirely of switch trains, involving the local transfer of cars, and does not include long distance trains, such as those that might be expected to carry chlorine cars for out-of-state shippers.
A representative of the CSX Hazmat Section estimated that not more than one or two chlorine shipments per year could be expected on this track.
A computer log of the traffic on that line during the last ten days of August 1988 showed no chlorine being shi.pped [7].
The LCP plant in Acme reported that most of their production was sent to a near-by paper mill and that only one to two tank cars per month were shipped elsewhere, one consumer being the CPRL Brunswick plant.
In the absence of more specific data, the 1977 Commodity Transportation Study can be used to form a conservative estimate of rail shipment frequencies of chlorine.
2.2 The TOXCHM Computer Program The hazards posed by postulated chlorine release accidents in the SHNPP vicinity to the control room operators were evaluated using a version of the TOXCHM computer program adapted to this purpose.
This program, which is based on a model described in NUREG-0570 [6], was originally written by the NRC staff to evaluate the impact of a chemical release accident on a nuclear power plant.
The model predicts toxic gas concentrations at the control room fresh air intake duct as well as inside the control room following an accident.
(136CRS)
2.2.1 Joint Frequency Table A file containing the average joint frequencies for 39 combinations of wind speed and stability class was constructed, using data collected by the SHNPP on site meteorological monitoring program during the years 1976-87.
To obtain greater precision than that furnished in the report of these data, the frequencies were recalculated, using the number of hours for each occurrence and the total number of observations.
2.2.2 Meteorological Parameters A file of meteorological data, including all 39 combinations of stability class and wind speed discussed in Section 2.2.1 (excluding those with a zero frequency) was constructed for use by TOXCHM.
Since the consequences of a chlorine release accident for a given wind speed and stability class worsen with increasing temperatures, the highest plausible temperatures were used for each combination of wind speed and stability class.
Classes E G are likely to occur only at night. It was therefore assumed that both the ground and the air temperatures were 86 F, the highest likely nighttime temperature at the SHNPP site.
Classes A D could occur in the daytime.
For these
- cases, the air temperature was assumed to be 104 F, while the ground was 122 F.
These temperatures represent extreme conditions and are therefore highly conservative.
Each windspeed range was assigned the average speed in that range.
Calms were assumed to represent a range of 0 to.75 mph, while the value 25 mph was assigned to the highest range
(> 25).
The values of 90 and 275 cal/sec/m were assigned to the nighttime (Classes E G) and daytime (Classes A D)
- cases, respectively, as in the original TOXCHM program.
The meteorological data used by the program is listed in Table 1.
(136CRS)
Table 1
METEOROLOGICAL CASES CASE No+
1 2
3 4
5 6
7 8
9 10ll 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 STABILITY CLASS G
F E
D A
G F
E B
A G
F E
D C
B A
G F
E D
C A
F E
D C
B A
E D
C B
A D
WIND SPEED (mph)
~ 4
.4
~ 4
.4
~ 4 2.1 2.1 2,1 2
1 F 1 2.1 2
1 5 5 5'
5' 5 5 5 5 5 5 5 5 10 0 10.0 10 '
10 0 10 0 10 0 10' 15' 15 '
15 '
15 '
15 5 15 5
21o7 21.7 21 7
21 ~ 7 21 '
25 0 25' TEMPERATURE AIR 86.
86.
86.
104.
104.
86.
86.
86.
104
'04
'04.
104.
86 ~
86 ~
86.
104
'04
'04
'04.
86.
86.
86.
104
'04
'04
'04.
86.
86 104.
104
'04
'04
'6
~
104 104.
104.
104 ~
104.
104.
(deg F)
GROUND 86 ~
86.
86.
122.
122
'6.
86.
86.
122
'22
'122.
122.
86 86 ~
86 ~
122 122
'22.
122
'6.
86 ~
86.
122
'22 122 122.
86 ~
86.
122 122.
122 122.
86 ~
122
'22.
122
'22
'22
'22 THERMAL FLUX
( cal/sec/m~*2) 90.
90.
90.
275.
275 90.
90.
90
'75.
275.
275 ~
275 90
'0
'0.
275.
275.
275.
275.
90.
90.
90.
275.
275.
275.
275 90.
90.
275 ~
275 ~
275.
275 90.
275.
275.
275.
275.
275.
275.
(136CRS)
2.3 Method of Analysis 2.3.1 Estimation of Shipment Frequencies
~Hi hwa Large highway shipments of chlorine occur primarily in tow forms:
tank trucks, which carry 18 tons in a single tank, or trucks which carry one ton containers of the liquified gas.
The 1977-78 Virginia surveys
[2] showed one truck carrying chlorine out of 9,314 trucks sampled (the amount of chlorine was not specified).
The North Carolina Division of Highways reports 7,000 vehicles per day on U.S.
1 with the percentage of trucks is estimated to be between 10 and 15 [8].
Combining these statistics (using the higher figure of 15X for the U.S 1 truck traffic), we find that 41 chlorine trucks per year can be expected to pass the vicinity of SHNPP.
This value may be compared to the total number of truck shipments of chlorine destined for North Carolina in 1977.
The 1977 Commodity Transportation Survey
[11] reported that 66,000 tons of chlorine were shipped into the state during that year.
Using the nationwide statistics from the same survey, 16X of these shipments are estimated to have been by truck. If the average truck-load was 18 tons (the capacity of the chlorine tanker truck), then approximately 58 7 chlorine trucks entered the state that year (not including possible shipments that transited the state)
~
Since U ST 1 is not part of the interstate
- system, which is the primary route for long-distance travel by heavy trucks, and is but one of many major highways in the state, the assumption that 41, or approximately 7X of these 587 trucks used this route is conservative.
(It is unlikely that chlorine being shipped through North Carolina would travel by tank truck; furthermore, any such trucks would probably not use U.S.
- 1) ~
Railroad Although no shipments of chlorine are currently reported on the Seaboard Coast Line tracks near
- SHNPP, a conservative estimate can be made by again noting that 66,000 tons of chlorine were shipped into North Carolina in 1977
'ccording to nation~de statistics, 74X of these shipments would have been by rail. If the average car-load was 90 tons (the capacity of the largest chlorine tank cars),
then approximately 543 chlorine tank cars entered the state that year (not including possible shipments that transited the state).
The track in question is no longer a main line and chlorine shipments over this line are not likely [7].
However, in order to perform a conservative analysis, it was assumed that 10X, or approximately 54, of the estimated 543 cars pass over this track annually.
2' '
Accident Scenarios
~Hf hwa Tanks trucks traveling on U.S.
1 were assumed to carry 18 tons of chlorine in a single tank.
The closest point on the road is 6,965 feet from the control room, at a bearing of 330 degrees.
The road is assumed to follow a straight line within a five-mile radius of the plant.
(136CRS)
Railroad
.Railroad tank cars being transported on the Seaboard Coast Line were assumed to carry 90 tons of chlorine in a single tank.
The closest point on the track is 10,740 feet from the control room, at a bearing of 326 degrees.
The track is assumed to follow a straight line within a five-mile radius of the plant ~
2.3.3 Analytical Procedure The portion of the given transportation route within a five~le radius of the control room was divided into 100 segments.
An accident involving the total loss of lading of a single chlorine container was postulated to occur at the center of each segment.
The probability that such an accident could cause the concentration in the control room to exceed the toxicity level of 15 ppm (in accord with Regulatory Guide 1.78) was calculated, using the meteorological data in Table 1 and the joint frequencies of occurrence of stability classy wind speed and direction, as discussed above.
The overall annual probability that chlorine shipments could pose a hazard to SHNPP was calculated, using data on the frequency of shipment of chlorine in the SHNPP vicinity and national ace)dent statistics from NUREG/CR-2650 [10], which utilized a value of 1.3 x 10 accidents per vehicle~le to predict truck accidents causing large releases of hazardous materials, and a corresponding value of 8 x 10 for railroad tank cars'his methodology is similar to the model described in NUREG/CR-3685 [9] while retaining the superior thermodynamic release model embodied in TOXCHM.
3.
RESULTS The results of the analysis showed that the total probability of an accident on the railroad which results in toxic chlorine concentrations in the control room being exceeded before the operators can don breathing apparatu~ is 2.2 x 10 per year
~
The correspond)ng value for trucks is 3 x 10 per year, for a total'robability of 2 '
x 10 per year.
4 ~
CONCLUSIONS Regulatory Guide 1.70 and the Standard Review Plan do not require the consideration of accidents with an annual probability of less than 10 per year.
Accordingly, an accident involving the transportation of chlorine in the SHNPP vicinity need not be considered in the safety evaluation of the'lant, provided that control room personnel have access to breathing apparatus and are trained to recognize chlorine by its odor.
These results thus justify a petition for relief from the present technical specification, which would require operating chlorine detectors in the control room HVAC system event if there were no chlorine on site and the requirements for chlorine detectors in the chlorine storage area were eliminated.
(136CRS)
5.
DISCUSSION 5.1 Consequence of Shipment Frequency Estimates The primary contribution to the calculated probability of a hazard is from the railroad, which accounts for roughly 90% of the total.
The actual number of chlorine cars shipped on this track is probably far less than that assumed for this analysis.
Were it to be as much as four times higher,
- however, the probab)lity of a chlorine hazard would still be less than the threshold value of 10 per year.
Similarly, a twenty-five-fold increase in the estimated truck traffic would not cause the threshold to be exceeded, notwithstanding the fact that few, if any, of the estimated number of trucks are chlorine
- tankers, instead of the more common general purpose vehicles carrying chlorine in one ton or smaller containers.
An accident involving the latter type vehicle would have a negligible impact on the SHNPP control room.
5.2 Applicability of Model Assumptions One aspect of the model which requires justification is the assumption that the route segment within five miles of SHNPP follows a straight line.
UPS.
1 does in fact follow a straight line to the northeast of the plant.
Northwest of the plant,
- however, the road bends away from the plant, then bends again to resume its original direction.
At all points on this route segment,
- however, the road either follows the line assumed in the model or is at a greater distance.
Since the impact of the postulated accident decreases with
- distance, the assumption that the road follows a straight line is conservative.
The Seaboard Cost Line generally follows a straight line to the northeast of the plant.
A slight curvature first carries the track beyond the hypothetical straight line, then brings it closer to the plant than assumed, at a distance of about 24,500 feet'his has no effect on the results,
- however, since the analysis shows that an accident at that distance would have no impact on SHNPP.
In the northwestern direction, beginning at a point 19,700 feet from the plant, the track begins to curve in a direction that brings it closer to the plant than assumed by the model.
The results of the analysis include impacts of accidents upto 23,910 feet away.
The straight-line model assumes a length of track of 4,847 feet between these two distances, when in fact measurement of the track on the 1:24,000 U.S. Geological Survey maps of the area show the actual track segment between these two distances from the plant to be less than 7,750 feet, or approximately 2,900 feet more than predicted.
To estimate the contribution that this additional 2,900-foot segment could make to the results of the analysis, it is assumed, for the sake of conservatism, that this entire segment lies at a distance of 19,700 feet from the plant.
The analysis shows that an accident at this would have an impact only under meteorological conditions described by case 13 and only if the wind were within a.96 fan.
The histori,cal meteorological data, discussed in Section 2.2.1, shows that the wind is from the west under the case 13 conditions
.014% of the time.
Combining these factors with the assumed accident and chlorine tayk car frequencies results in an additional annual probability of 1.4 x 10
, an increase of less than 0.1%.
- Thus, the assumption that the route follows a straight line has a negligible effect on the calculated results.
(136CRS)
REFERENCES 1.
U.S. Congress, Office of Technology Assessment, 1986:
Trans rtation of Hazardous Materials.
OTA-SET-304, U.S. Government Printing Office.
2.
- Price, D. L., J.
W. Schmidt and R. W. Kates, 1981:
Multi Modal Hazardous Materials Transportation in Virginia.
VDOTS/SPO-16 (unpublished)
~
3.
Lyden, M., 1988:
Personal communication.
4.
- Sears, H., 1988:
Personal communication.
5.
- Coursey, M., 1988:
Personal communication.
6 ~
Wing, James, 1979:
Toxic Va or Concentrations in the Control Room Followin a Postulated Accidental Release.
NUREG-0570, U,ST Nuclear Regulatory Commission.
7.
Cook, E.,
1988:
Personal communication.
8 ~
Gold, T.,
1988:
Personal communication.
9.
- Chanin, D. I., A. W. Shiver and D, ED Bennet, 1984:
Toxic Gas Accident Anal sis Code User 's Manual.
NUREG/CR-3685, U.ST Nuclear Regulatory Commission.
10.
- Bennett, D. E.,
and DE C. Heath, 1982:
Allowable Shi nt Fre uencies for the Trans rt of Toxic Gases near Nuclear Power Plants.
NUREG/CR-2650, U.S. Nuclear Regulatory Commission.
ll Britt, L., 1988:
Personal communication.
(136CRS)
0 1