ML20077S163

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Analysis to Support Removal of FCS Toxic Gas Monitoring Sys
ML20077S163
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Site: Fort Calhoun Omaha Public Power District icon.png
Issue date: 08/31/1994
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OMAHA PUBLIC POWER DISTRICT
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ML20077S152 List:
References
NUDOCS 9501230319
Download: ML20077S163 (40)
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Text

.. . . ~. - -. ._ . - - - . - ._.

n Attachment 2 r

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e Analysis to Support Removal of the '

Fort Calhoun Station Toxic Gas Monitoring System l

August, 1994 Omaha Public Power District 1

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l 9501230319 950109 PDR ADOCK 05000285 P

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1 TABLE OF CONTENTS i

l L I ST O F TAB LES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i i

1.0 INTRODUCTION

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2.0 BACKGROUND

........................................... 1 3.0 APPLICABLE REGULATORY CRITERIA ....................... 2 I

I 4.0 ANALYSIS METHODOLOGY ................................. 5 '

5.0 HIGHWAY ANALYSIS RESULTS ............................. 11 1

6.0 RAILR0AD ANALYSIS RESULTS ............................ 13 7.0 PIPELINE ANALYSIS RESULTS ............................ 26 8.0 0FF-SITE FACILITIES RESULTS . . . . . . ............. 27 i

9.0 BARGE TRAFFIC ANALYSIS RESULTS ....................... 31 l J

10. 0 ON-S I T E R ESU LT S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2

11.0 CONCLUSION

S ......................................... 34 12.C REFERENCES .......................................... 36 j l

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1 LIST OF TABLES Number Title- Paae 5.1 Control Room Concentrations of Hazardous 13 Chemicals from Highway Accidents 6.1 Hazardous Materials Shipped by Rail 17

- 6.2 Estimated Shipments to be Made on Cargill l Rail Spur 18  !

6.3 Control Room Concentrations of Hazardous Chemicals from Rail Accidents 18 6.4 Rail Shipment Cumulative Frequency of Control Room Habitability Loss 19 6.5 FCS Meteorological Site Data 19  :

8.1 Off-Site Facilities that Store or Manufacture Airborne Toxic Materials 30 8.2 Control Room Concentrations of Hazardous ,

Chemicals from Tank Failure Accidents 31 8.3 Off-Site Tank Failure Cumulative Frequency of Cont' col Room Habitability Loss 31 11.1 Cumulative Toxic Hazard Frequency of Off-Site Sources 35 i

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1.0 INTRODUCTION

This submittal documents an analysis which justifies the removal of the Toxic Gas Monitoring System (TGMS) at the Fort Calhoun Station (FCS). The applicable regulatory requirements and the basis for the current TGMS were reviewed. The analysis results indicate that the regulatory requirements as defined in NUREG-0737, Item III.D.3.4, Standard Review Plan Section 2.2.3 and Regulatory Guide 1.78 can be met for FCS without the need for a TGMS.

2.0 BACKGROUND

l 2.1 Existing Toxic Gas Monitoring System The FCS Toxic Gas Monitoring System is described in USAR Sections 9.10 and 14.23. The Technical Specification Requirements for this system appear in Sections 2.22 and 3.1. The TGMS currently s.amples the control room Heating Ventilation Air Conditioning (HVAC) fresh air intake for six toxic gases. A TGMS actuation occurs when the currently monitored gas concentrations reach predetermined setpoints. TGMS actuation includes annunciation with the following sequence of events: the fresh air dampers shut automatically, and the control room ventilation shuts down simultaneously to stop infiltration of toxic gases through the closed dampers. These automatic events provide the control room operators time to don breathing apparatus (ref. 9).  !

The FCS TGMS was installed to meet- NUREG-0737 Item III.D.3.4 requirements for control room habitability following a postulated on-site or off-site chemical release (ref.1). The original evaluation (ref. 2) showed that:

1. The following off-site chemicals shipped by rail or stored at facilities were identified as potential hazards to the control room personnel.

Anunonia Hydrochloric Acid i 1

2. The following on-site chemicals were identified as potential j hazards to the control room personnel. l Hydrofluoric Acid l Sulfuric Acid 1 Hydrazine l Chlorine Thus, the basis for the current TGMS at FCS are the on-site and off-site chemical releases.

With the installation of the TGMS it was determined that the requirements of NUREG-0737 had been met, and that the operators would be protected against the worst postulated toxic chemical release accident (ref. 2). )

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2.2 Impact of the TGMS on FCS Since its installation, the FCS TGMS has been an operational burden. Three sets of monitors (two channels per monitor) were initially installed to detect the six potentially toxic chemicals identified above. As an indication of the maintenance intensity a total of 259 maintenance work orders have been generated since January,1985 to correct problems with these monitors. There have been many instances of spurious trouble alarms and resulting actuation, yet no actual off-site events have occurred involving the release of toxic gases. These monitors are required to detect minute quantities of toxic chemicals. Spurious alarms require operator response, and therefore, distract control room operators. Also, the spurious alarms decrease the effectiveness of alarms in a real emergency due to decreased operater sensitivity. There have been a few small on-site releases which have not impacted the control room. There also was a Licensee Event Report written for an event which was related to the operation of the TGMS which occured last year. The cost to maintain this system annually is on the order of $100,000.

3.0 APPLICABLE REGULATORY CRITERIA The basis for the existing FCS TGMS is NUREG-0737, Item III.D.3, " Control Room Habitability Requirements". As noted in Section 2.0, the TGMS was installed for off-site and on-site release requirements. There have been significant changes recently which require the original submittal to be updated with respect to off-site and on-site sources. Thus, justification for removal of the TGMS requires that on-site and off-site chemical hazards be reevaluated.

Given that the scope of analysis involves off-site and on-site chemical releases, the below identified Standard Review Plan (SRP) sections and Regulatory Guides (RG) were determined to be appropriate. These are as follows:

SRP 2.2.1-2.2.2 " Identification of Potential Hazards in Site Vicinity" SRP 2.2.3 " Evaluation of Potential Accidents" SRP 6.4 " Habitability Systems" RG 1.78 " Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release" RG 1.95 " Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release" 2

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The guidance provided in these documents is summarized below in the context  ;

of the proposed changes.

SRP 2.2.1 and 2.2.2. " Identification of Potential Hazards in Site Vicinity" This document provides guidance to identify potential external hazards. It is' pointed out that hazards which are identified as a result of transportation or storage require further review under SRP 2.2.3. The hazard applicable to this proposed change is the transportation and storage of toxic chemicals on-site and off-site (ref. 4).

SRP 2.2.3 " Evaluation of Potential Accident" Given a potential hazard identified under SRP Sections 2.2.1 and 2.2.2, SRP  ;

Section 2.2.3 is used to determine which events must be considered further as design basis events. The SRP Section 2.2.3 acceptance criteria states (ref.

4):

"Accordingly, the expected rate of occurrence of potential exposures in excess of the 10CFR Part 100 guidelines of approximately 10-6 per year is acceptable if, when combined with reasonable qualitative arguments, the realistic probability can be shown to be lower."  ;

SRP Section 2.2.3 goes on to say that if accidents involving the release of chemicals do not meet the above acceptance criteria, an evaluation of the effects of these analyses on control room habitability should be made using SRP 6.4, " Habitability Systems."

A deterministic design basis accident analysis was performed for the original licensing submittal consistent with NUREG-0737 requirements. The original analysis employed site specific meteorology for on-site and off-site accidents, along with previously recorded transportation frequencies and estimates of the probability of occurrence for a given off-site accident. This approach was taken to eliminate those accidents for which the probability of ,

exceeding airborne toxicity limits is less than .1E-07 events per year.

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SRP 6.4 " Habitability Systems" The toxic gas portion of SRP 6.4 references Regulatory Guide 1.78 as the j method to be used to determine whether the quantity or location of toxic material is such that additional analysis is necessary. The referenced methods to be used in any additional analyses are Regulatory Guides 1.78 and 1.95. I l

Reaulatory Guide 1.78 " Assumptions for Evaluatina the Habitability of a Nuclear Power Plant Control Room Durina a Postulated Hazardous Chemical Release" l

The purpose of Regulatory Guide 1.78 is to identify chemicals which could render the control room uninhabitable. Screening criteria are provided in terms of proximity (within a five mile radius) and frequency (10 per year for truck and 30 per year for rail) of shipments. A list of some hazardous chemicals and their toxicity limits was also provided (ref. 5).  !

For those chemicals which could not be eliminated by the proximity / frequency / weight screening criteria, Regulatory Guide 1.78 provides  !

methodology for calculation of control room toxic concentration versus time l after an accidental release. The acceptance criterion for Regulatory Guide i 1.78 is that the time from detection to the time when the toxicity limit is reached must be greater than two minutes to allow operators to don self-contained breathing apparatus.

The origiral analysis (ref. 6) performed showed that this criterion was 1 satisfied with the exception of six chemicals (Ammonia, Chlorine, Hydrochloric Acid, Gasoline and Sulfuric Acid). The TGMS was designed to provide automatic ,

detection and control room isolation such that this two-minute criterion could )

be met for these six chemicals.

Reaulatory Guide 1.95 " Protection of Nuclear Power Plant Control Room Operators Aaainst an Accidental Chlorine Release" Regulatory Guide 1.95 was developed to provide control room operator protection from an accidental on-site Chlorine release. It uses the methodology of Regulatory Guide 1.78 to calculate the allowable weight of a single Chlorine container as a function of distance from the control room. The I original submittal identified that Chlorine cylinders used in the water  ;

treatment plant were stored on-site and thus the Regulatory Guide 1.95 analysis was applicable.

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L A.thALYSIS METHODOLOGY This report addresses potential chemical releases from on-site and off-site accidents. All transportation routes were considered for potential off-site releases. A new survey was conducted for off-site storage of potential hazard chemicals. Changes in FCS operations has necessitated a new on-site analysis (ref. 6). The general apprcach applied for on-site and off-site considerations consisted of the following steps. Note that steps 1 and 2 involve deterministic analyses, and steps 3 and 4 involve probabilistic analyses. The probabilistic analyses are only performed for those chemicals that exceeded the deterministic screening criteria of steps 1 and 2.

Sten 1 - Hazardous Chemical Identification For the purposes of this analysis, a chemical is identified as hazardous if it meets all of the following criteria:

a. Transportation and/or storage of a chemical occurs within a l five-mile radius of the plant,
b. Shipment frequency is greater than 10 per year for truck or 30 per year for rail.
c. Chemic61 appears on either the Regulatory Guide 1.78 list of potentially hazardous chemicals or the Environmental Protection Agency's (EPA's) list of Extremely Hazardous Substances (ref. 7).

Sten 2 - Control Room Concentrations For each chemical identified as being hazardous in Step 1, a calcuiation of control room concentration versus time is performed. The accident is assumed to occur at the transportation and/or storage location closest to the control room intake. No credit was taken for operation of the TGMS. The calculations were performed using the T0XIC 5.2 computer code (ref. 6), following the guidance of Regulatory Guide 1.78. The T0XIC 5.2 code accounts for such parameters as chemical volatility, atmospheric dispersion and control room intake / exhaust flow. The ~ T0XIC 5.2 code is a dispersion modelling code utilizing the Pasquill-Gifford equations. This code is used to predict the movement of toxic clouds from accident sites and calculates buildup of toxic concentration within the control room.

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Sten 2 - Control Room Concentrations (Continued)

In accordance with Regulatory Guide 1.78 chemicals are judged not to require an automatic detection system if either:

a, control room concentrations never reach toxic limits, or

b. there is at least two minutes between the time that the toxic gas is detectable by smell by the operating crew and the time that the toxic limit is reached.

The toxicity limits used in these calcuiations are based on the "Immediately Dangerous to Life and Health" (IDLH) concentrations published by the National Institute of Occupational Safety and Health (NIOSH) (ref. 8). The chemical toxicity limits are those prorosed by NIOSH since these limits are based upon acute short-term toxic releases. The NIOSH toxicity lidts were established based upon serious irreversible health effects or u o as a result of a single exposure for a relatively short period of time. This approach is consistent with methods described in Regulatory Guide 1.78. For conservatism the toxicity limit for Carbon Dioxide stated in Regulatory Guide 1.78 was used in this analysis.

The IDLH values, by definition, were developed for a maximum 30 minute exposure at the maximum IDLH concentration. The Regulatory Guide 1.78 toxic limits assume only a two minute exposure to a concentration that begins low (at detection) and increases to the limit at the end of the two minutes. There have been previous utility suomittals (e.g., Vermont Yankee, Safety Evaluation Report for Vermont Yankee's Technical Specification Amendment, Docket No.

50-271, supporting Amendment No. 132 to Facility Operating License No. DPR-28, dated October 24,1991) which stir late usage of IDLH toxic limits. Subsequent work in toxicity limits since irception of Regulatory Guide 1.78 has provided justification for use of the IDLH values. NRC workshops conducted with toxicity experts revealed that for Chlorine, Ammonia, and Sulfur Dioxide, use of the ICLH values versus Regulatory Guide 1.78 values was warranted. The use of IDLH values is conservative compared to Regulatory Guide 1.78. Therefore, based on these arguments, for all chemicals of interest to this evaluation except for Carbon Dioxide, the IDLH toxic limits were used.

Due to the lack of raadily retrievable information for the chemical properties of Gasoline, the conservative chemical properties of Pentane were used for an initial screening.

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Sten 3 - Probability of Control Room Uninhabitability If it was. found, through a deterministic analysis, in Steps 1 and 2 above (employing conservative assumptions), that the control room could become uninhabitable, then a probabilistic risk assessment was performed. The i acceptance criterion for the toxic material being analyzed is a demonstration ,

that the core damage frequency due to off-site and on-site toxic releases is less than 1E-06/yr. Sections 2.2.3 of the SRP and 5.2.4 of NUREG-1407 state i that if the original design basis does not meet RG 1.78 requirements, the licensee may choose an alternate approach of demonstrating that the probability of occurrence of the-original design basis event is sufficiently ,

low (i.e, less than 1E-05/yr) and the conditional core damage probability is judged to be less than 1E-01. For this analysis, the core damage frequency is  ;

equal to the probability of loss of control room habitability (from all on-site and off-site sources) times the conditional core damage probability.  :

For chemicals which required probabilistic analysis the annual probability of control room uninhabitability is calculated using the following information ,

(ref. 10):  :

Potential off-site Releases .

For Rail. Truck. and Barae Shioments:

n=s 12 j=7 F= I Nship xPrel xIPscen xI(Pstab xD rack t xP mp) i n=1 11 j=1 ,

where:

F= frequency of loss of control room (event frequency / year) l 1

Nship= shipment frequency for each shipment route and toxic chemical per year (shipments / year) -

Pre 1= probabilityofaspillpermiletraveled(spills / shipment-mile)

Pscen= probability of a release scenario (e.g., maximum concentration or I maximum duration-concentration)

Pstab= probability of a specific atmospheric stability class (A-G)

Dt rack = critical length of transportation route where a spill could result in loss of control room habitability for a given scenario (miles)  :

Pi mp= probability of plant impact; the normalized probability that the wind is directed from the hazardous length of track to the control room.

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l For Pinelines:

n2 j7 F = Pfail x IPscen xDpipe x I(Pstab xPwind xPimp)  ;

M re-F= frequency of control room uninhabitability (event frequency /yr)

Pf ai1= vessel failure rate (failures /yr)

Pscen= probability of release scenario (e.g., maximum concentration or maximum duration-concentration)

Pi mp= probability of plant impact (0 or 1)

Pstab= probability of specific atmospheric stability class (A-G)

Pwind= probability cf winds blowing from a specific wind sector to the i Fort Calhoun site.

Off-site Storaae Facilities:

n=2 j7 F = Pfail x IPscen x I(Pstab xP nd wi xP mp) i n=1 j=1 where:

F= frequency of control room uninhabitability (event frequency /yr)

Pf a11= vessel failure rate (failures /yr) ,

Pscen= probability of release scenario (e.g., maximum concentration or maximum duration-concentration)

Pi mp= probability of plant impact (0 or 1)

Pstab= probability of specific atmospheric stability class (A-G)

Pwind= probability of winds blowing from a specific wind sector to'the Fort Calhoun site ,

Steo 4 - Conditional Core Damaae Freaufacy NUREG-1407 further states if the original design basis hazard combined with the conditional core damage probability is not less than IE-06/yr, additional J analysis may be needed. For this analysis, the core damage frequency is equal '

to the probability of loss of control room habitability (from all on-site and I off-site sources) times the conditional core damage probability (ref. 10). ,

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e For Rail. Truck. and Barae Shinments: 1 n=s i=2 j=7 F = 0.001 x I Nship xPrel xIPscen xI(Pstab xD rick t xP mp) i n=1 i=1 j=1  !

l where:  !

F= frequencyofcoremelt(eventfrequency/ year) l

.001= frequency of core melt given a loss of control room habitability.

The frequency of core melt has been previoJsly shown to be actually on the order less than 0.0001 per the IPEEE model developed by 0 PPD for NRC submittal in response to Generic Letter 88-20.

Nship= shipment frequency for each shipment route and toxic chemical per year (shipments / year)

Pre 1= probability of a spill per mile traveled (spills / shipment-mile)

Pscen= probability of a release scenario (e.g., maximum concentration or maximum duration-concentration)

Pstab= probability of a specific atmospheric stability class (A-G)

Ot rack = critical length of transportation route where a spill could result in loss of control room habitability for a given scenario (miles)

Pi mp" probability of plant impact; the normalized probability that the wind is directed from the hazardous length of track to the control room.

For Pioelines:

n=2 j=7 F = 0.001 x P fall x IPscen xDpipe x I(Pstab xP ndwi xP mp) i n=1 j=1 where:

F= frequency of core melt (event frequency /yr)

.001= frequency of core melt given a loss of contrcl room habitability Prat 1= pipeline failure rate (failures /yr)

Pscen= probability of release scenario (a.g., maximum concentration or maximum duration-concentration) 9

For Pinelines: (Continued)

Dpipe= critical length of pipe (mi)

Pimp = probability of plant impact (0 or 1)

Pstab= probability of specific atmospheric stability class (A-G)

Pwind" Probability of winds blowing from a specific wind sector to the Fort Calhoun site.

4 For Off-Site Storace Facilitiest i n=2 j=7 F = 0.001 x Prail x IPscen x I(Pstab xPwind xP mp) i n=1 j=1 where:

F= frequency of core melt (event frequency /yr)

.001= frequency of core melt given a loss of control room habitability Pf ai1= vessel failure rate (failures /yr)

Ps cen" Probability of release scenario (e.g., maximum concentration or maximum duration-concentration) ,

Pi mp* Probability of plant impact (0 or 1)

Pstab= probability of specific atmospheric stability class (A-G)

Pwind" Probability of winds blowing from a specific wind sector to the :

Fort Calhoun site ,

l Step 4 calculates the frequency of conditional core damage resulting from off-site chemical releases. In order to cause such a release, the control room uninhabitability must lead to a plant trip as stated in the equations above with operating crew and equipment failure. This in turn would have to lead to a failure of a critical safety function such as core cooling ar decay heat removal. The SRP Section 2.2.3 guideline of IE-07/ year actually refers to the frequency of a 10CFR100 fission product release involving significant core damage.

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5.0 HIGHWAY ANALYSIS RESULIS The highway analysis involved a survey of chemicals which are shipped within a five mile radius of the power plant. The highway analysis involves Steps 1 and 2 for all identified hazardous material with the exception of Ammonia. Transportation of Ammonia required additional analysis per steps 3 and 4.

5.1 HAZARDOUS CHEMICAL IDENTIFICATION Contacts were made of local chemical distributors and facilities which could store or use potentially hazardous chemicals (ref. 6). There are four highways within five miles from the control room (U. S. 30, U. S. 75, State 91 and State 133). The Cargill Corporation was contacted for future truck / highway

- shipments since their corn milling and processing plant, located 1.3 miles north of FCS, will be going into production in early 1995 and significant quantities of Ethanol and Carbon Dioxide will be shipped from their facility.

The chemicals identified during the survey were compared to Regulatory Guide 1.78 and EPA's list of Extremely Hazardous Substances. The chemicals which are shipped within the frequency of the screening requirements above and within five miles of FCS which were considered toxic were as follows:

Ammonia Ethanol Carbon Dioxide Hydrochloric Acid Propane Diesel Fuel Sulfuric Acid Gasoline Propane is classified by the American Conference of Governmental Hygienists as an asphyxiant. Asphyxiants pose a hazard mainly by dislodging oxygen. When  :

the oxygen concentration drops below 18% asphyxiation occurs. This can only i occur if the Propane concentration reaches 14%. Concentrations of this magnitude are possible only in the immediate vicinity of the accident source.

Diesel Fuel poses an environmental hazard due to the particulates emitted after combustion. In addition, Diesel Fuel has a very low volatility and it is unlikely for a plume of the vapor products of diesel to travel from an accident on a highway to the plant.

Therefore, no further review or analysis of Propane or Diesel Fuel is  ;

required. ,

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T, 5.2 CONTROL ROOM CONCENTRATIONS t

Loss of control room habitability occurs when the control room concentration of a identified hazardous chemical exceeds its " toxic limits" in less than two minutes after detection. The toxic limits for all chemicals with exception to Carbon Dioxide were the NIOSH "Insnediately Dangerous to Life and Health (IDLH) concentrations.

To calculate control room concentrations as a result of a truck release, the computer program T0XIC 5.2 was used. Control room habitability is maintained if control room concentrations remain less than the IDLH value, or if there is at least two minutes between the time the toxic gas is detected by smell by the operators and the time that the IDLH value is reached. The limit of two minutes is stipulated in Regulatory Guide 1.78 (ref. 5). ,

The results indicated that of the hazardous chemicals shipped over the highways within five miles of the control room, only an Ammonia release would exceed the deterministic analysis. Table 5.1 provides a summary of highway .

shipments along with the IDLH value.

As shown in Table 5.1 the maximum control room concentration for each '

chemical except for Aninonia is less than its corresponding IDLH value.

Therefore, the " toxic limit" is not reached and control room habitability is maintained in the event of a postulated highway accident (Ethanol, Carbon Dioxide, Hydrochloric Acid, Gasoline, and Sulfuric Acid).

For the Ammonia truck accident a probabilistic assessment was performed. '

From the analysis performed it was determined that the control room uninhabitable risk factor was 9.51E-07/ year, with an estimated core damage frequencyof9.51E-10/ year.

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Table 5.1 Control Room Concentrations of Hazardous Chemicals from Highway Accidents  ;

Chemical Quantity Maximum Control IDLH Room Concentration (oom) (oom)

Amonia 40,000 lbs. exceeded IDLH 300 Hydrochloric Acid 5,000 gal. 15 100 (4 trucks per week)

Carbon Dioxide 20 tons 1,633 10,000 (24 trucks pe,- day) '

Ethanol *9,600 gal. 109.0 1,000 (20 trucks per day)

Sulfuric Acid 4,000 gal. na na (1 truck per month)

Gasoline 8,300 gal. 232 300 (7 trucks per week)

  • an actual release of 29,000 gallons (standard rail car capacity) was assumed since the frequency of shipments is significant na -

designates "not applicable" since Sulfuric Acid is a non-volatile ,

chemical and was determined not to be a hazard to the control room.

6.0 RAILROAD ANALYSIS RESULTS The railroad analysis involves Steps I through 4 from Section_ 4.0,

" Analysis Methodol ogy. " The sections below show that, of the hazardous chemicals identified, only Sulfur Dioxide, Ammonia, and Chlorine exceed the Regulatory Guide 1.78 criteria. Therefore, probabilistic analyses (Sections 6.3 and 6.4) were performed for Sulfur Dioxide, Chlorine, and Ammonia. Table 6.1 provides a list of all rail shipments on the main line. Table 6.2 provides a list of all shipments moved c- the rail spur (ref. 6).

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4 6.1 HAZARD 0US CHEMICAL IDENTIFICATION One railroad operates within the five mile radius from the control room.

Chicago and Northwestern Railway has a main rail line 2.2 miles north of the plant. Reestablishment of a rail spur is currently underway by Chicago and Northwestern Railway 0.4 miles west of the control room intake. This rail spur will be rerouted through the Cargill corn milling and processing plant which is currently under construction. Representatives from Chicago and Northwestern  ;

provided a list of all chemicals transported on the main line. Representatives of Cargill provided a list of all chemicals which would be transported on the rail spur.

As indicated in Section 5.1, the chemicals listed were compared to Regulatory Guide 1.78 and EPA's list of Extremely Hazardous Substances.

Chemicals which appeared on either list were considered for further evaluation. The chemicals which were considered toxic and were or will be  ;

shipped frequently are as follows:

Gasoline Ethanol Carbon Dioxide Sulfur Dioxide Amonia Chlorine 6.2 CONTROL ROOM CONCENTRATIONS As in Section 5.2, the computer code T0XIC 5.2 was used to calculate the control room concentrations. For chemicals that act as asphyxiants (e.g.  ;

Carbon Dioxide), control room habitability was assumed to be lost if the concentration exceeded the Regulatory Guide 1.78 toxic limit. For Carbon Dioxide it was assumed that the gas would not be detected prior to reaching asphyxiation level, thus the two-minute warning criterion is not used.

1 The T0XIC 5.2 analysis results are listed in Table 6.1. The IDLH value, volume shipped and maximum control room concentration are listed. From the deterministic analyses performed it was determined that in the event of a Sulfur Dioxide, Amonia or Chlorine spill from a catastrophic rail car failure <

the IDLH values would be exceeded. The other hazardous chemicals including Gasoline, Ethanol, and Carbon Dioxide were screened out and no further analysis was required. The requirements of Regulatory Guide 1.78 were met for Gasoline, Ethanol, Carbon Dioxide releases. Therefore, further analysis is required for Sulfur Dioxide, Amonia and Chlorine to determine the probability of control room uninhabitability.

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6.3 PROBABILITY OF CONTROL ROOM UNINHABITABILITY A hazard model was developed to calculate the annual probability (F) of control room uninhabitability as ducribed in section 4.0. The probability of loss of control room habitability given a release, varies as a function of distance from the control room fresh air intake, wind direction, speed, and atmospheric stability.

For Rail car accidents the frequency of loss of control room is established as:

n=s i=2 j=7 F= I Nship xPre1xIPscenxI(PstabxD rackxP t mp) i n=1 i=1 j=1 where: I F= frequency of loss of control room (event frequency / year)

Nship= shipment frequency for each shipment route and toxic chemical per year (shipments / year). From surveys provided by Chicago and Northwestern Railway, and information provided by Cargill, Table l 6.1 for rail shipments has been established. The appropriate number of cars / year was used in the probability analysis for each specific hazardous material which could not meet deterministic requirements. As an example, for Chlorine 190 cars are shipped per ,

year on the main rail line. I Nship = 190 Prel" Probability of a spill per mile traveled (spills / shipment-mile).

From studies of accident data in the Handbook of Chemical Hazards Analysis Procedures, USEPA, 1989, it was shown that the mainline accidentrateisapproximately6E-07/ car-milewith70%ofreleases l from railcars involving a partial loss of cargo through 2" holes  ;

and 30% involving a total loss of cargo. It was conservatively 1 assumed that a total loss of cargo occurs. Since the cars travel at a much slower speed on a rail spur (5 mph) the probability of total loss of cargo is reduced.

Pre 1= 6E-07/ car-milemainline Pre 1= 3E-07 car-mile rail spur D rack = critical length of transportation route where a spill could result i

in loss of control room habitability for a given scenario (miles).

These values are calculated for a particular shipment of a hazardous material. For example for Chlorine the critical track length was found to be; Dt rack = 5.921 miles.

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1 Pstab= probability of a specific atmospheric stability class (A-G).

The probability of a specific atmospheric stability class is dependent upon site specific data (ref. 6). The following information is provided for classes A-G; Stability Class Probability of Wind Stability A 0.027 B 0.055 C 0.069 0 0.407 E 0.299 F 0.115 G 0.028 Pscen= probability of a release scenario (e.g., maximum concentration or maximum duration-conc <:ntration). As stated above 70% of releases are partial losses (maximum duration releases) and 30% of tSe releases are complete losses (maximum concentration). Both situations were analyzed to determine the greatest impact.

Therefore, depending upon a maximum duration or maximum concentration release, .

Pscen= 0.70 or 0.30 P imp= probability of plant impact; the normalized probability that the wind is directed from the hazardous length of track to the control room. The probability of plant impact was calculated. This probability is a function of probability of location in a specific wind sector, probability of a specific atmospheric class, and length of track in a particular sector. For Chlorine rail shipments 2.2 miles from the plant it was found that the probability of plant impact was; Pi np= 4.50E-02 (for atmospheric classes A-G)

Table 6.4 provides a summary of the rail probabilities for loss of control room habitability for those chemicals which where determined hazardous and could not meet the deterministic criteria.

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f Table 6.1 -

Hazardous Materials Shipped o' y Rail Comodi ty Units Tons Toxic Discosition Waste Flansnable If q.N05, 83(i) 12 Solid, will settle before reaching plant.

nickel powder Not in acute hazard.

Fireworks 236(1) 16 Not an acute hazard.

Aerosols 38(1) 17 Not an acute hazard.

Cigarette Lighters 58(i) 12 Ifbutane,butanetivis1900mg/m3 which Translates to an allowable shipment of 247 tons. This is in excess of the shipment capacity. Not an acute toxic hazard, t Flammable liquid, NOS 252(1) 11 Classified as a flammable liq.

Not an acute toxic hazard.

Paint 244(f) 23 Not an acute toxic hazard.

Adhesives 117(1) 16 Not an acute toxic hazard.

Resin solution 242(1) 17 Not an acute toxic hazard.

Combustible liquid plastics 33(f) 16 Classified as a combustible liquid.

resins or gum, NOS Not an acute toxic hazard.

Nitrostarch, wet 39(1) 19 Not an acute toxic hazard.

Trichlorisocyanuric acid 56(i) 17 Not an acute toxic hazard.

Calcium hypochlorite 41(1) 18 Not an acute toxf; hazard.

Organophosphorous 39(i) 22 Not an acute toxic hazard.

pesticide

! Corrosive, NOS 204(i) 16 Classified as a corrosive liquid. Not an acute toxic hazard.

Dodecybenzesulfonic acid 58(i) 19 Not an acute toxic hazard.

Cleaning compound 10(1) 20 Not an acute toxic hazard.

Corrosive solid N05 90(i) 20 Classified as a corrosive Sulphamic acid Solid, not an acute toxic hazard.

Alkaline liquid NOS 41(1) 16 Classified as an alkaline. Not an acute toxic hazard.

Battery wet, filled 308(i) 17 Sulfuric Acid, not an acute toxic hazard Environmentally hazardous 132(1) 20 Not an acute toxic hazard.

substance NOS Mixed loads, no single 34847(i) 11 Not an acute toxic hazard. >

hazard class Chlorine 190 90 Must analyze, requires PRA j Anhydecus Anmonta 32 78 Must analyze, requires PRA 0xygen 95 79 Not an acute toxic hazard.

White phosphorous 190 98 Not an acute toxic hazard.

Phosphoric acid 49 97 Not an acute toxic hazard.

Sodium hydroxide 91 99 Not an acute toxic hazard. l E0llit .

NOS refers to 'not otherwise specified". A shipping term for classes of substances to '

which a restriction applies, individual members of which are not listed in the regulations.

(i) refers to intermodal shipments. Intennodal shipments involve mixed shipments of hazardous material with potentially non-hazardous materials. The reported shipment weights for intennodal shipments are for the entire carload. The toxic disposition is made by reviewing toxicological and volatility data for each chemical.

17 l

1 l

- . . -- ., , . . . . , , .. .n.r. - --

4 Table 6.2 Estimated Shipments To be Made on Cargill Rail Spur Hazardous Chemical Quantity Number of Shipments ner Year Gasoline 28,000 gal. 104 Ethar.01 29,000 gal. 2,372.5 Carbon Dioxide 60 tons 2,920 Sulfur Dioxide 90 tons 26 Table 6.3

?

Control Room Concentrations of Hazardous Chemicals from Rail Accidents Chemical Quantity Maximum Control IDLH Room Concentration (nom) (nom)

Gasoline 28,000 gal. 238

  • 300 Ethanol 29,000 gal. 207.2 1,000 Carbon Dioxide 60 ton 5,576.3 10,000 Sulfur Dioxide 90 ton exceeded IDLH 100 Ammonia 90 ton exceeded IDLH 300 Chlorine 78 ton exceeded IDLH 30 Since Gasoline is a mixture of hydrocarbon compounds of varying compositions, it is not possible to determine pure chemical properties for Gasoline. The conservative chemical properties of Pentane were used for an initial screening. The volatile property of Pentane maximizes the source term of the spill. The results from the T0XIC code analysis indicate that 2.4 minutes would be available between the time Gasoline is sensed in the control room and when the IDLH limit (control room becomes uninhabitable) is reached.

Therefore, no further analysis was deemed necessary since Gasoline meets the deterministic screening requirements of Section 4.0, Step 2.

18

Table 6.4 Rail Shipment Cumulative Frequency of Control Room Habitability Loss Hazardous Chemical Freauencv/vear Ammonia 1.45E-08 Chlorine 2.04E-07 Sulfur Dioxide 5.50E-08 Cumulative Frequency 2.73E-07/ year Table 6.5 (ref. 2)

Fort Calhoun Station Meteorological Site Data  :

Stability Stability Frequency of Wind Direction Frequency of Class Class Average Stability Wind Direction Windspeed (m/ Class (%) Within Stabil-sec) ity Class (%)

l A 3.5 2.7 NNE 5.4 l A 3.5 2.7 ;4E 3.4 A 3.5 2.7 ENE 2.4

~~

A 3.5 2.7 E 1.6 A 3.5 2.7 ESE 2.1 A 3.5 2.7 SE 3.0 A 3.5 2.7 SSE 6.6 A 3.5 2.7 5 7.3 A 3.5 2.7 SSW 5.6 A 3.5 2.7 SW 3.2 A 3.5 2.7 WSW 2.4 A 3.5 2.7 W 5.3 A 3.5 2.7 WNW 8.4 A 3.5 2.7 NW 15.4 A 3.5 2.7 NNW 17.9 A 3.5 2.7 N 10.0 1

19 l

Table 6.5 (cont'd)

Fort Calhoun Station Meteorological Site Data Stability Stability Frequency of Wind Direction Frequency of r Class Class Average Stability Wind Direction Windspeed(m/ Class (%) Within Stabil-sec) ity Class (%)

B 3.6 5.5 NNE 3.9 B 3.6 5.5 NE 3.7 8 3.6 5.5 ENE 2.6 B 3.6 5.5 E 2.6 8 3.6 5.5 ESE 3.9 8 3.6 5.5 SE 5.3 B 3.6 5.5 SSE 9.7 8 3.6 5.5 S 11.5 B 3.6 5.5 SSW 6.7 B 3.6 5.5 SW 4.6 B 3.6 5.5 WSW 3.0 B 3.6 5.5 W 3.1 B 3.6 5.5 WNW 5.4 8 3.6 5.5 NW 10.5 B 3.6 5.5 NNW 13.9  !

B 3.6 5.5 N 9.6 l C 3.6 6.9 NNE 3.9 C 3.6 6.9 NE 2.6 C 3.6 6.9 ENE 2.7 C 3.6 6.9 E 3.1 C 3.6 6.9 ESE 4.5 C 3.6 6.9 SE 7.0 C 3.6 6.9 SSE 10.6 C 3.6 6.9 S 10.7 C 3.6 6.9 SSW 6.9 I C 3.6 6.9 SW 4.2 ,

C 3.6 6.9 WSW 2.4 C 3.6 6.9 W 3.3 1

20

1 I

Table 6.5 (cont 'd)

Fort Calhoun Station Meteorological Site Data I

l Stability Stability Frequency of Wind Direction Frequency of  !

Class Class Average Stability Wind Direction Windspeed (m/ Class (%) Within Stabil-sec) ity Class (%) j C 3.6 6.9 WNW 4.7 C 3.6 6.9 NW 11.6 C 3.6 6.9 NNW 13.4  ;

C 3.6 6.9 N 8.5 i D 3.6 40.7 NNE 3.9 l D 3.6 40.7 NE 2.9 0 3.6 40.7 ENE 3.0 D 3.6 40.7 E 4.0 D 3.6 40.7 ESE 5.1 )

D 3.6 40.7 SE 8.7 D 3.6 40.7 SSE 12.0 j D 3.6 40.7 S 10.1  !

D 3.6 40.7 SSW 5.5 ,

D 3.6 40.7 SW 2.7 0 3.6 40.7 WSW 2.2 D 3.6 40.7 W 2.6 D 3.6 40.7 WNW 4.9 l D 3.6 40.7 NW 11.6

- i D 3.6 40.7 NNW 13.7 0 3.6 40.7 N 7.1 l E 2.7 29.9 NNE 1.8 l

)

E 2,7 29.9 NE 1.6 l E 2.7 29.9 ENE 1.7 E 2.7 29.9 E 2.9 E 2.7 29.9 ESE 6.2 l E 2.7 29.9 SE 13.1 E 2.7 29.9 SSE 12.0 E 2.7 29.9 S 10.8 E 2.7 29.9 SSW 6.2 21

I Table 6.5 (cont'd)

Fort Calhoun Station Meteorological Site Data l Stability Stability Frequency of Wind Direction Frequency of Class Class Average Stability Wind Direction Windspeed(m/ Class (%) Within Stabil-sec) ity Class E 2.7 29.9 SW 3.6 E 2.7 29.9 WSW 3.3 E 2.7 29.9 W 5.7 E 2.7 29.9 WNW 10.1 E 2.7 29.9 NW 11.2 E 2.7 29.9 NNW 6.6 E 2.7 29.9 N 3.4 F 1.8 11.5 NNE 1.3 F 1.8 11.5 NE 1.5 F 1.8 11.5 ENE 1.5 F 1.8 11.5 E 2.6 l F 1.8 11.5 ESE 8.2 F 1.8 11.5 SE 12.2 F 1.8 11.5 SSE 7.7 F 1.8 11.5 S 10.1 F 1.8 11.5 SSW 8.9 F 1.8 11.5 SW 6.1 F 1.8 11.5 WSW 6.0 F 1.8 11.5 W 9.0 F 1.8 11.5 WNW 13.0 F 1.8 11.5 NW 7.4 F 1.8 11.5 NNW 2.4 F 1.8 11.5 N 2.3 i

I 22

Table 6.5 (cont'd)

Fort Calhoun Station Meteorological Site Data Frequency of Wind Direction Frequency of Stability Stability Class Class Average Stability Wind Direction Windspeed(m/ Class (%) Within Stabil-sec) ity Class (%)

G 1.7 2.8 NNE 2.4 G 1.7 2.8 NE 2.8 G 1.7 2.8 ENE 2.4 G 1.7 2.8 E 4.6 G 1.7 2.8 ESE 12.2 G 1.7 2.8 SE 11.0 G 1.7 2.8 SSE 8.6 G 1.7 2.8 S 8.0 l

G 1.7 2.8 SSW 9.5 G 1.7 2.8 SW 7.4 G 1.7 2.8 WSW 5.2 G 1.7 2.8 W 7.2 G 1.7 2.8 WNW 6.3 G 1.7 2.8 NW 4.7 G 1.7 2.8 NNW 3.2 G 1.7 2.8 N 4.1 6.4 Frequency of Conditional Core Damage as a Function of Rail Shipments I Sections 6.1 and 6.2 show that rail shipments of Ammonia, Chlorine and Sulfur Dioxide are the only events which do not satisfy the deterministic ,

criteria of Regulatory Guide 1.78. SRP Section 2.2.3 requires that such an I accident be considered as a design basis event only if the frequency exceeds  !

1E-06/ year. To calculate the probability of conditional core damage as a result of shipping Ammonia, Chlorine and Sulfur Dioxide by rail, the frequency of loss of control room must be analyzed.

23 l

l l

4 6.4.1 Initiating Event  !

The initiating event considered in this section is a Chlorine, Ammonia or Sulfur Dioxide shipment accident either on the main line or the rail spur. As calculated in section 6,3, the frequency of this initiating event is  !

2.74E-07/ year. This initiating event does not lead directly to core damage.

For core damage to occur, a severe plant transient and trip must occur, and there must be failure of a critical safety function.

6.4.2 Frequency of Core Damage The core damage frequency from this initiating event is calculated as follows:

P = F x Peore F= 2.74E-07/ year Peore= 0.001 (in actuality a value of 7.4E-05 was calculated, as described below, however, to be conservative a value of 0.001 was used in this analysis. Use of 0.001 accounts for any uncertainties or biases which were not explicitly accounted.

Thus,P=2.74E-10/ year The value for Pcore was developed from OPPD's Individual Plant Examination (IPE) for FCS (ref.10). _The IPE was developed to evaluate the frequency of core damage events at FCS. The IPE developed a model that estimates the probability of core damage following an initiating event that challenges continued plant operation or is a design basis accident. Several initiating event types were evaluated in the IPE. The following event types were included in the IPE which would require consideration for applicability to the toxic gas release event:

1) Transients
2) LOCA (Loss of Coolant Accident)
3) SGTR (Steam Generator Tube Rupture) l

' 4) ISLOCA (Interfacing System LOCA)

5) LOOP /SB0 (Loss of off-site Power / Station Blackout)
6) Special Initiators (i.e., support system failures) l l

24

From a review of the event types and the automatic response without operator intervention for most events it was determined that only transient initiators required further evaluation, with respect to applicability to a toxic gas release. The calculation of the conditional core damage probability for an unmitigated plant trip is based upon incapacitation of the FCS operators in the event of a toxic hazard. It was assumed that the transient, concurrent with toxic release would occur four hours into the operators eight-hour shift.  ;

The quantification of the conditional core damage probability was based on the dominant cutsets from the FCS IPE. The cutsets represented in this  !

Calculation include all Cutsets involving operator actions which could be impacted by a toxic gas condition. The calculation involved the following steps: 1) identify all cutsets involving manual reactor trip and 2) set a human error rate for human actions in the first four hours.

The FCS has a number of automated functions which preclude the need for operator actions following a manual reactor trip.

Motor-driven main feedwater and condensate pumps continue to operate to remove decay heat following a plant trip.

Feedwater regulating valves automatically ramp down to control steam generator level following a plant trip.

Steam generator water level control exists which prevents steam generator overfill.

In the event of low steam generator level, two 100% capacity auxiliary feedwater pumps automatically start.

Adequate inventory exists in the condenser hotwell and emergency feedwater storage tank to assure coolant makeup to the steam generators for more than four hours. 4 I

25 l

The resulting core damage probability was calculated to be 7.4E-05. The dominant contributors to this probability were cutsets involving unavailability of the off-site power supply with subsequent independent failures causing failure of the Auxiliary Feedwater System. Given the uncertainties involved in this analysis, this result was conservatively rounded to 1E-03.

Utilizing the conservative conditional core damage probability of IE-03 with the frequency for loss of control room habitability yields a conditional core damage frequency of 2.74E-10/ year. This result shows that the estimated conditional core damage frequency due to a rail accident, causing a loss of off-site power, is well below the SRP Section 2.2.3 and NUREG-1407 guidelines of 1E-06. Thus, this event does not require consideration as a design basis event, and the Regulatory Guide 1.78 provisions for an automatic detection system are not required.

7.0 PIPELINE ANALYSIS RESULTS The pipeline analysis involved a survey of chemicals which are transported via pipeline within a five mile radius of the FCS control room. The pipeline analysis was resolved by a Step 1 and 2 evaluation for Ammonia.

7.1 HAZARD 0US CHEMICAL IDENTIFICATION The only potentially toxic material identified in the latest survey that is l

transported by pipeline is Ammonia (ref. 6). These pipelines are operated by l

Gulf Central Pipeline Company and Mid-American Pipeline Company. Although LPG and natural gas are also shipped by pipeline, they are considered simple asphyxiants and do not pose a toxic hazard. The Mid-American Pipeline Company stated that the maximum flowrate within their 4" Annonia line is 600 barrels per hour. This corresponds to a flow rate of 18 kg/sec. Information from the Gulf Central Pipeline Company was not available. However, the Gulf Central pipeline is 6" in diameter and since flowrate varies with the square of the pipe radius, a size correction factor of 2.25 was applied to adjust the Mid-American data for use with the Gulf Central pipeline. In addition, the Gul f Central pipeline operates at a maximum of 1440 psig whereas the Mid-American pipeline operates at a maximum of 1125 psig. The combined effect of the pressure difference and the pipe size difference is estimated to make the Gulf Central pipeline flowrate approximately three times larger than the Mid-American pipeline florrate.

26

7.2 CONTROL ROOM CONCENTRATIONS As in Section 5.2, the computer code T0XIC 5.2 was used to calculate the control room concentrations. The releases were assumed to last a duration of 1 hr. The controlling factor in the dispersion results is the first two minutes of the release which r.egates the overly conservative estimate of release duration. This is consistent with the release methodology of catastrophic pipe failures also. The modelling results indicate that the maximum control room concentration under stability class G conditions for the Mid-American Pipeline is 43 ppm and 106 ppm for the Gulf Central Pipeline. The limits for Ammonia (300 ppm) chosen for this analysis are based on NUREG/CR-5669 which was based on evaluation of exposure data to determine a suitable short term toxic limit.

Therefore, it is concluded that the hazard from Amonia transported by pipeline does not require further analysis.

8.0 0FF-SITE FACILITIES RESULTS A mail survey followed by on-site visits and phone calls to manufacturers, within the five mile radius area of FCS control room was performed to determine the amount of toxic material stored in off-site storage facilities.

In addition to the chemicals noted in Table 8.1, Propane, Kerosene, and Diesel fuel were also identified. However, these are screened out on the basis that they are either asphyxiants or low volatility materials which would preclude an acute toxic hazard at the plant.

8.1 HAZARD 0US CHEMICAL IDENTIFICATION The chemicals which must be considered for further evaluation are Ethanol, Gasoline, Carbon Dioxide, Hydrochloric Acid, Sulfur Dioxide, and Ammonia. The Gasoline stored at the Cargill facility was determined to be the most bounding since all other sources of Gasoline were further away in distance (greater than 2 miles and the volume of Gasoline stored was less than what will be stored at the Cargill facility. Gasoline will be stored at the Cargill facility in a 60,000 gallon tank. The Gasoline storage tank at Cargill is located 1.3 miles from the plant.

8.2 CONTROL ROOM CONCENTRATION As performed in Section 5.2, the computer code T0XIC 5.2 was used to calculate the control room concentrations. For chemicals that act as asphyxiants (e.g. Carbon Dioxide), control room habitability was lost if the concentration exceeded the Regulatory Guide 1.78 toxic limit. For Carbon Dioxide it was assumed that the gas would not be detected prior to reaching asphyxiation level, thus the two-minute warning criterion is not used.

27

The results are listed in Table 8.2. The IDLH value, volume stored and maximum control room concentration are listed. From the analyses pe- ormed it was determined that in the event of a Sulfur Dioxide or Mr ia tank catastrophic spill that the IDLH values would be exceeded. It is also determined that if a maximum duration leak occured in a Carbon Di: le tank that the IDLH values would be exceeded. The other hazardous . iical s; Ga:oline, Ethanol, Hydrochloric Acid and Sulfuric Acid were screenec at and no further analysis was required. The requirements of Regulatory Gui: 1.78 were met for Gasoline, Ethanol, and Hydrochloric Acid releases. Sulfurn Acid was screened out based on its non-volatile characteristics (98% conc.).

Therefore, further analysis was required _ for Sulfur Dioxide, Anunonia and Carbon Dioxide to determine the probability of control room uninhabitability.

8.3 PROBABILITY OF CONTROL ROOM UNINHABITABILITY A hazard model was developed to calculate the annual probability (F) of control room uninhabitability as described in Section 4.0. The probability of loss of control room habitability given a release, varies as a function of distance from the control room fresh air intake, wind direction, speed, and atmospheric stability.

For off-site tank accidents the frequency of loss of control room was provided in Section 4.0. The assigned probabilities to these events is as follows:

Off-Site Storaae Facilities:

n=2 ja7 F = P fati x IPscen x Z(Pstab xP,ing xP mp) i n1 j-1 where: t F = frequency of control room uninhabitability (event frequency /yr)

Prati = vessel failure rate (failures /yr)

Prat 1 = 1E-04/yr. (ref.10)

Pscen = probability of release scenario (e.g., maximum concentration or-maximum duration-concentration) (ref. 10)

Pscen = 90% of releases involving a partial loss of cargo (maximum-concentration),10% of releases involve a release through a 2" orifice (maximum-duration)

Pt mp = probability of plant impact (0 or 1) 28

,p_6 a s-Pstab = probability of syific atmospheric stability class (A-G) which is the same as reported ir section 6.3.

P,ing = probability of winds blowing from a specific wind sector to the Fort Calhoun site, Table 6.5 provides the meteorological probability of winds blowing from a specific sector for the Fort Calhoun Station site.

The frequency of control room loss of habitability can be found in Table 8.3 for each hazardous chemical release. The total frequency from release of off-sitehazardouschemicalswasdeterminedtobe1.61E-06/ year.

8.4 Frequency of Conditional Core Damage as a Function of Off-Site Releases ,

Sections 8.1 and 8.2 show that off-site releases of Ammonia, Carbon Dioxide and Sulfur Dioxide are the only events which do not satisfy the deterministic criteria of Regulatory Guide 1.78. SRP Section 2.2.3 requires that such an accident be censidered as a design basis event only if the frequency exceeds 1E-06/ year. To calculate the probability of conditional core damage as a result of off-site storage of Ammonia, Sulfur Dioxide and Carbon Dioxide the frequency of loss of control room habitability must be analyzed.  ;

8.4.1 Initiating Event .

The initiating event considered in this section is an Ammonia, Sulfur Dioxide or Carbon Dioxide tank failure. As calculated in Section 8.3, the frequency of this initiating event is 1.61E-06/ year. This initiating event does not lead directly to core damage. For core damage to occur, a severe plant transient and trip must occur, and there must be failure of a critical safety function.

8.4.2 Frequency of Core Qamage The core damage frequency from this initiating event is estimated as follows: '

P = F x Peore F= 1.61E-06/ year Peore = 0.001 (in actuality a value less than 7.4E-05 was calculated per Section 6.4.2), however, to be conservative a value of 0.001 was used in this analysis.

Therefore,P=1.61E-09/ year This result shows that the estimated conditional core damage frequency due to a rail or storage accident is well below the SRP Section 2.2.3 and NUREG-1407 guidelines. Thus, this event does not require consideration as a design basis event, and the Regulatory Guide 1.78 provisions for an automatic detection system are not required.

29

l 1

~

l Table 8.1 1

Off-Site Facilities that Store or Manufacture j Airborne Toxic Materials i

Facility Dist.from Control Chemical Amount of Toxic Materiai Room Intake Miles / Direction i Fairway 011 and 3.7/295*,from Gasoline (2)7,500 gal. Gasoline tanks ,

Propane North '

Neilson Service 3.1/293 ,"" Gasoline 8,000 gallon Gasoline tank Station (location 1) i Neilson Service 3.6/291","" Gasoline 8,000 gallon Gasoline tank Station (location 2)  ;

Cargill- 1.3/0',"" ""

Ethanol 1.4 million gallon tank ,

Carbon Dioxide (3)600 ton tanks Sulfuric Acid 7,000 gallon tank Gasoline 60,000 gallon tank Ammonia 15,000lbs. tank Hydrochloric acid (aq.) 25,000 gallon tank Sulfur Dioxide 28,000 gallon tank Terra 1.5/320',"" Amonia 30,000 gallon Anmonia tank 0250 psi 60 ton (aq.) Ammonia tank Agricultural 1.8/320',"" Ammonia (2)25,000 ton Ammonia l Minerals tanks 0-28 F, '

Corporation (2)30,000 gallon Amonia tanks 0250 psi, two smaller tanks of (aq.) Ammonia 1

i 30

Table 8.2 Control Room Concentrations of Hazardous Chemicals from Tank Fallure Accidents Chemical Quantity Maximum Control IDLH Room Concentration (oom) (com)

Amonia 25,000 ton exceeded IDLH 300 30,000 gal. exceeded IDLH 300 Sulfur Dioxide 28,000 gal, exceeded IDLH 100 Hydrochloric Acid 25,000 gal . 12.82 100 4

Carbon Dioxide 600 tons exceeded IDLH 10,000 Gasoline 60,000 gal. 211.7 300 Ethanol 1.4 million gal 216.4 1,000 T ble 8.3 Off-Site Tank Failure Cumulative Frequency of Control Room Habitability Loss Hazardous Chemical Freauencv/vear Amonia 1.16E-06 Carbon Dioxide 3.09E-07 Sulfur Dioxide 1.4E-07 Cumulative Frequency 1.61E-06/ year

, 1.0 BARGE TRAFFIC RESULTS There were no toxic materials identified in the latest survey as well as the previous survey in 1981 that were shipped by barge within 5 miles of the plant. As such, a calculation to determine the toxic hazard posed by barge shipments is not required.

31

1 l

10.0 ON-SITE RESULTS The previous toxic gas analysis which is documented in the Fort Calhoun Station USAR (Section 14.23) indicated that monitors for Chlorine, Hydrazine, Hydrogen Fluoride, and Sulfuric Acid were required because of on-site storage of these chemicals. USAR Table 14.23-1 indicated that the rupture of tanks containing Sulfuric Acid, Hydrazine, Chlorine, Hydrogen Fluoride-HF (HF from

UF6 cylinders) would cause the control room atmosphere to exceed the criteria of Regulatory Guide 1.78. As of 1993 the Chlorine and UF6 cylinders are no longer on-site. The Sulfuric Acid tank is anticipated to be removed through a ,

modification process in the future. Thus, the only remaining chemical of the I original analysis which requires evaluation is Hydrazint. Since the Sulfuric Acid tank has not been removed as of this date it will also be addressed in this analysis.

A new chemical, Ethanolamine, has been added to this analysis. Ethanolamine ]

in high concentrations poses a toxic hazard (NIOSH limits, ref. 8) . All chemicals other than Hydrazine, Ethanolamine, and Sulfuric Acid did not require further analysis due to the fact that there was not a sufficient volume of the chemical or that it was not a toxic hazard. In order to determine the potential impacts to control room habitability by postulated i releases of toxic materials it was necessary to determine the release rates from the storage vessels. l The toxic gas release rate at the location of the spill must be determined.

For 35% aqueous Hydrazine at the storage area, the release is based on evaporation. No initial flashing or puff release occurs for this liquid due to ,

its low vapor pressures and high boiling point. The Hydrazine tank is assumed l to fail and spill its entire volume instantaneously. This type of event is characterized as the maximum concentration accident per Regulatory Guide.1.78.

For aqueous Hydrazine at ambient temperatures the vapor pressure is 10.0 mmHg per the Material Safety Data Sheets (MSDS).

10.1 On-Site Hydrazine Concentration The Hydrazine is assumed to evaporate at a rate dependent on the surface 1 temperature over each time increment until all the chemical has evaporated.

This analysis is considered very conservative since: (1) the Hydrazine containers are stored indoors, (2) the Hydrazine plume would have to exit the building to get to the Control Room air intake on the opposite side of the plant, (3)^ the Control Room personnel -would not be subjected to an internal plume since the Control Room ventilation is at a positive pressure compared to the turbine building, (4) no building wake effects were taken into consideration, and (5) several different release paths were considered, the path assumed for this analysis was determined to 4 conservative.

I 32 u __.

4 It was calculated that the control- room concentration as a result of a Hydrazine spill would result in a control room concentration of; crc = (2.6E-07)(1.40E-51) = 3.654E-58 g/cm3 The toxic limit of Hydrazine is 80 ppm or roughly 1.1E-07 g/cm3. Therefore, it is shown that a Hydrazine spill at ground level cannot impact the air intake in any appreciable concentrations.

10.2 On-Site Sulfuric Acid Storage Analysis Regulatory Guide 1.78 and NUREG-0570 list Sulfuric Acid as a compound which should be considered in the toxic gas analysis. Since it is not credible that there would be any vapor for release should a catastrophic failure of the 225,000 gallon tank occur, application of toxic gas monitoring is not warranted. Previous analysis assumed that a pool of 35,000 sq. ft, would occur upon tank rupture, and all the contents would vaporize at 100 *F. This is not a credible scenario for several reasons, (1) a cement berm is under the

! Sulfuric Acid tue to drain the tank contents to the chemical ponds, (2) the Sulfuric Acid would not vaporize until a temperature greater than at least 250 s "F (vapor pressure does not reach 1 mmHg until a temperature of greater than 300 "F), (3) normal prevalent atmospheric temperatures average 50-55 *F, the maximum air temperatures for this region are near 105 *F which is '

significantly lower than what is required to vaporize the liquid (Sulfuric

(

Acid tank is outside), and (4) the Sulfuric Acid tank is anticipated to be {

removed in the future through a modification. Therefore, it can be concluded  !

that Sulfuric Acid does not pose an acute airborne toxic hazard to the plant. I

( Based upon this evaluation, there is no need for toxic gas monitors to monitor Sulfuric Acid releases.

10.3 On-Site Ethanolamine Storage Analysis Although Regulatory Guide 1.78 and NUREG-0570 do not explicitly state that Ethanolamine is a toxic material, it should be noted that according to the ,

Department of Health and Human Services, that this chemical can pose toxic l concerns. Ethanolamine will be in3ected into the Secondary Systems in lieu of J Morpholine in 1994. This chemical nas an IDLH limit of 1000 ppm, 30 minute exposure. Ethanolamine has a 3 ppm limit for Threshold Limit Value (TLV) (8

! hour per day, 40 hour4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per week) limit. Therefore, this chemical is considered in this analysis because of its bulk storage quantity. Ethanolamine will be stored in the Turbine Building and Warehouse.

f l

33

In this analysis, the entire contents of a container of Ethanolamine is assumed to spill and form a pool. This analysis is considered very conservative since: (1) the Ethanolamine containers are stored internal to the plant, (2) the Ethanolamine plume would have to exit the' building to get to the Control Room air intake on the opposite side of the plant, (3) this could happen if the turbine building truck bay doors were open and non prevailing winds would have to blow the plume over the intake, (4) the Control Room personnel would not be subjected to an internal plume since the Control Room .

ventilation is at a positive pressure compared to the turbine building and (5) !

no building wake effects were taken into consideration.

It was calculated that the concentration of Ethanolamine in the control room would be; crc = (1.13E-6)(2.486E-92) = 2.81E-98 g/cm3 r

The toxic limit of Ethanolamine is 1,000 ppm or roughly 2.5E-6 g/cm3 Therefore, it is shown that even if the air intake were located at ground ,

level, the toxic concentrat' 1 would not be exceeded, and based upon the  !

analysis presented here the toxic limits will not be exceeded as a result of a catastrophic rupture of the Ethanolamine tank. Thus, a probabilistic analysis l 1s not required.

11.0 CONCLUSION

S .

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The analysis considered in this report evaluates control room habitability in order to address NUREG-0737, Item III.D.3.4, requirements for on-site and off-site toxic chemical releases. The evaluation includes both deterministic and pre .hilistic analyses, and takes no credit for tne existing TGMS The determ'.amic analyses show that the Regulatory Guide 1.78 guidelines are met for all chemicals except Ammonia, Chlorine, Sulfur Dioxide and Carbon Dioxide.

The combined probabilistic analyses, sumarized in Table 11.1, show that the probability of conditional core damage due to an on-site or off-site chemical ,

release is well below the SRP Section 2.2.3 guideline for consideration as a i design basis event. .

Together these analyses show that the TGMS is not required to meet the egulatory criteria specified in NUREG-0737, Item III.D.3.4. Since NUREG-0737 is the basis for the TGMS, this analysis justifies removal of the TGMS at the Fort Calhoun Station.

34

Table 11.1 Cumulative Toxic Hazard Frequency of On-Site and Off-Site Sources Source Chenical Frequency of Control Estimated Core Room Habitability Damage Frcquency (oer year) (oer year)

Rail Ammonia 1.45E-8 1.45E-11 Rail Chlorine 2.04E-7 2.04E-10 Trucks Ammonia 9.51E-7 9.51E-10 ,

Tanks Ammonia 1.16E-6 1.16E-09 l Rail spur Sulfur Dioxide 5.50E-8 5.50E-11 Cargill Sulfur Dioxide 1.40E-7 1.40E-10 Cargill Carbon Dioxide 3.09E-7 3.09E-10 Summing the Estimated Core Damage Frequency Yields Total Fort Calhoun Toxic Hazard Frequency 2.83E-09/ year 35

12.0 REFERENCES

1. NUREG-0737, "TMI Action Plan," Item III.D
2. Fort Calhoun Station Updated Safety Analysis Report (USAR)

Sections 2 and 14,

3. Fort Calhoun Station Technical Specifications
4. NUREG-0800, Standard Review Plan for the Review of Safety Anclysis Reports for Nuclear Power Plants- LWR Edition, Sections 2.2.1, 2.2.2, 2.2.3, June 1987
5. Regulatory Guide 1.78, " Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release," June,1974
6. OPPD Engineering Analysis, EA-FC-94-012, Rev. 0, " Toxic Hazards Analysis"
7. " Technical Guidance for Hazard Analysis, Emergency Planning for Extremely Hazardous Substanc" U.S. Environmental Protection Agency, Federal Emergency Management Agency, U. S. Department of Transportation, December, 1987
8. " Pocket Guide to Chemical Hazards," National Institute of Occupational Safety and Health, September, 1985 ,
9. NUREG/CR-5669(PNL-7522), " Evaluation of Exposure Limits to Toxic Gases for Nuclear Reactor Control Room Operators" , July 1991
10. Omaha Public Power District, Fort Calhoun Station, Individual Plant Examination Submittal, December 1993 (LIC-93-0278) 36

{

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LIC-94-0258 ,

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