ML20090D398

Toxic Chemical Study

ML20090D398
Person / Time
Site:	Prairie Island
Issue date:	06/20/1984
From:	BECHTEL GROUP, INC.
To:
Shared Package
ML20090D366	List: ML20090D365 ML20090D376 ML20090D398
References
TAC-53458, TAC-53459, TAC-55476, TAC-55477, NUDOCS 8407180219
Download: ML20090D398 (9)

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F PRAIRIE ISLAND GENERATING STATION T0XIC CHEMICAL STUDY

-Incapacitation Levels-r i

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Prepared for the Northern States Power Company By the Bechtel Power. Corporation June 20 1984 I-t I

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PRAIRIE ISLAND GENERATING STATION i

T0XIC CHEMICAL STUDY

-Incapacitation Levels-Table of Contents Page 1.

Introduction 1

2.

NUREG/CR-1741 Models 2

3.

Chemical Description 2

4.

Analysis Performed 4

5.

Results and Conclusions 5

6.

References 7

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PRAIRIE ISLAND GENERATING STAT 80N T0XIC CHEMICAL STUDY I

-Incapacitation Levels-f 1.

INTRODUCTION l

i In May of 1981 a Main Control Room Habitability study was l

performed for the Prairie Island power plant (Reference 1).

That study concluded that four toxic chemicals would exceed the Threshold Limit Value (TLV) levels in the control room if an accidental spill occurred. Consequently it was recommended i

that monitors be installed to detect these chemicals. The possible sources of these chemicals are: on-site storage, the f

Burlington Northern Railroad, the Chicago, Milwaukee and Saint Paul Railroad, ard barge traffic on the Mississippi river.

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The Main Control Room Habitability Study also determined setpoints for the monitors and required response times to l

comply with Regulatory Guide 1.78.

To insure compliance with Regulatory Guide 1.78 which specifies that operators have at least two minutes. to-put on self contained breathing apparatus, conitors were. set either equal to or below TLV levels.

With the TLY used as a monitor setpoint, operators will have adequate time before the Short-Term Exposure Limit (STEL) is reached..Both the TLV and the STEL are set for long-term occupational exposure, not a one-time exposure situation.

i In early 1981, NUREG/CR-1741 entitled "Models for the Estimation of Incapacitation Times Following Exposures to Toxic Gases or Yapors" was published. The report presents another methodology to predict operator incapacitation for one-time exposure to toxic chemicals..It consisted of using 5 models

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(A-E) covering significant physiological and toxicological effects to humans.

This Toxic Chemical-Incapacitation Level Study has been undertaken to determine the possibility of eliminating some of the 4 chemicals currently being monitored by applying the i

techniques of NUREG/CR-1741 to Prairie Island.

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2.

NUREG/CR-1741 MODELS Human exposure to airborne toxic materials produces a wide range of physiological and toxicological effects.

For incapacitation effects there is a threshold concentration below which the body can eliminate, transform or otherwise act on tile y

chemical to negate its effects. Above this threshold, there i

are two principal physiological modes which dominate:

concentration dependence and dose dependence.

For concentration dependent chemicals, the total dose received is not as important as the concentration of the chemical during i

exposure.

Dose dependent chemicals produce an effect that is directly related to the total exposure regardless of the concentration at any given time.

NUREG/CR-1741 presents 5 models to describe incapacitation.

t However all the chemicals at Prairie Island fall into the range i

of the first or "A" model which is described below.

Model A.

Concentration Dependent - Immediate Sensory Irritants: This model describes a procedure for predicting the time to incapacitation for immediate sensory irritants (e.g.

Ammonia, Chlorine, Hydrogen i

Chloride, and Formaldehyde). The effects are

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concentration and not dose dependent.

l i-Chemicals classified as immediate sensory irritants are l

corrosive or desiccant in their action.

They inflame skin or mucous membrane especially when moist.

They stimulate nerve endings in the eyes, nose, and oral cavity and inhibit respiration.

They have essentially the same effect on animals as on humans and the exposure t

concentration is of greater significance than the duration l-of the exposure.

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3.. CHEMICAL DESCRIPTION Presented below is a summary of each of the four toxic i

chemicals that are in question at Prairie Island. The i

information is taken from literature on the subject.

The summaries focus on the effects these chemicals have on human beings.

When such data was not available results on animals were presented.

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Ammonia, NH3

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r Ammonia is a colorless gas with a sharp, intensely irritating odor.

It has an odor threshold of 46.8 ppm for humans (Reference 4). Complaint levels of 20-25 ppm were first observed.

Human effects such as eye irritation sometimes with lacrimation, nose, throat, and chest i

irritation (coughing, edema of lungs) were found at concentrations up to 700 ppm, depending on exposure time (Reference 2,3,5).

The chemical then becomes lethal

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I starting at 2000 ppm concentration even for exposures of a very short duration (Reference 2).

i glorine,CL2 Chlorine in its gaseous form is greenish-yellow in color.

It has a disagreeable, suffocating and irritating odor which is readily detectable at 3-5 ppm.

Irritant effects to eyes, nose, throat and/or face were noted at low concentrations. Effects on the upper and lower respiratory tracts and pulmonary edema were reported at high concentrations.

Chlorine becomes highly dangerous for exposures of 30 minutes at 40-60 ppm; it becomes fatal for exposures of 30-60 minutes at 833 ppm and fatal in a few breaths at 1000 ppm (Reference 2). There were reports 1

on effects of concentrations around 5 ppm covering respiratory complaints, corrosion of teeth, inflammation of mucous membranes of nose and increased tuberculosis susceptibility (Reference 5).

Hydrogen Chloride, HCL Hydrogen Chloride or hydrochloric acid in gaseous form is colorless with a suffocating odor (Reference 5).

It causes irritating effects to the human nose and throat if inhaled at concentrations as low as 5 ppm and becomes barely tolerable at 50-100 ppm for a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> exposure (Reference 3,5).

Breathing HCL gas was found to be dangerous from concentrations of 1000 ppm and is fatal to humans for even a few minute exposure at 1300 ppm (Reference 2).,

Formaldehyde, HCHO l

Formaldehyde, a suspected carcinogen, is dstectable by most people at levels below 1 ppm (Reference 3,4,5).

Humans have experienced irritant effects on the eyes, noses, throat and upper respiratory tract at concentrations of 1 to 12 ppm. At high concentrations, severe respiratory tract irritations which lead to deatn were reported in humans.

Inhalation studies on rats anc mice indicated that formaldehyde has a carcinogenic effect l

on rats.

Rats developed nasal cavity squamous cell I

carcinomas after 12-24 months's exposure to 15 ppm with deaths during this period.

Fatalities were also observed for rats exposed up to 81 ppm (Reference 5).

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ANALYSIS PREFORMED The Bechtel standard computer code T0XGAS (NE314) described in appendix A of the Main Control Room Habitability Study and modified to include the models of NUREG/CR-1741 was used to perform the analysis.

Using the results of the analysis a determination was made as to which toxic chemicals still required monitoring. The assumptions made in the analysis were essentially the same as the those used in the Main Control Rocm l

Habitability Study except that the evaporation rate for r

formaldehyde was modeled using a turbulent rather than a laminar flow across the spill. This results in conservative concentrations at the control room air intake. As in the Main Control Room Habitability Study it is assumed that the contrei l

room HVAC system is in normal operation during the postulateo accident (i.e.

that there is no control room isolation), and that chemical monitoring is achieved just by the operators ability to detect the chemical. Using these assumptions the times to first detection of the chemical and the times to incapacitation were calculated. Chemicals that have at least 2 I

minutes between detection and incapacitation will not need to be monitored for operator protection.

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• The mass transfer coefficient for turbulent flow that shoulc be added to Appendix A of the Main Control Room Habitability Study (Reference 1) is:

hd = 0.037(D/L)(Re)0.8 (Sc)l/3 See References 1 and 6 for more information.

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RESULTS AND CONCLUSIONS l

Of the four chemicals analyzed, two chemicals, Ammonia and Hydrogen Chloride allowed ' ample time from detection levels to r

I incapacitation levels; Formaldehyde resulted in marginal time,

.and Chlorine did not provide adequate time to take protective measures. The results for each chemical are described below:

i Ammonia Detection levels for Ammonia released from a barge accident are reached 2 minutes and 19 seconds before i

incapacitation levels are reached.

Thus, operators will have enough time to put on breathing apparatus once the i

odor is detected. Ammonia released from an accident involving the Burlington Northern Railroad will be detected 8 minutes and 7 seconds before incapacitation levels are reached. Since these times are greater than 2 minutes, no monitor is required for ammonia.

Hydrogen Chloride Detection levels for Hydrogen Chloride are reached 7 i

minutes and 11 seconds before incapacitation levels are reached. Thus, operators will have ample time to take corrective measures, and therefore, no monitoring is required.

Formaldehyde I

Detection levels for Formaldehyde are reached 1 minute and 59 seconds before incapacitation levels are reached. This time is just short of the 2 minutes quideline of 4

Regulatory Guide 1.78 to give the operators time to put on breathing apparatus.

Since the calculation of Formaldehyde has several convervatisms built in, it is recommended that the detector be deleted. Modeling more realistically any one i

of the following conservatisms would result in times from detection to incapacitation greater than 2 minutes, thus allowing the operators time to take protective measures.

- Formaldehyde concentration conservative assumptions:

1. The accident is assumed to occur at the closest approach to the control room.

2. The entire content of the tank car is assumed to i

spill.

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3. No credit :f s' takin for ground absorption.

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5. No crid{t is taken'for dispersjon by intervening ~

structures or topography,;.

yT Chlorine: Detection levels fo'rhhlorir[safipilled on the site occur only 33 secon,ds before 4 capycitation levels n

are reached;'thus mcnitors willicentirse to be needed for chlorine.

Chlorinedpilled from the Chicago, Milwaukee and Saint Paul Railroad Wili be; datected 'l minute and 8 s.

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' 4aconds before incaoacitation, which,is also too short a 1

time)to take pro,tectiva ection.

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Conclusion:==

As discussed above, ef, the fcur chemicels

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identified by the. Main Control Room Habitability Study as being potentially hazardous to control room operetors, Chlorine will

• i reach -incapacitation levels before operators can take protectTVe actions. Therefore, to insure that the operators are protected, it is recommended that the monitor for this chemical be retained, and automatic isolation of the control

- room be required.to insure'that control room operators nave sufficient time to take protective measures. For the other chemicals:JAmmonia, Hydrogen Chloride and Formaldehyde,'no I

s monitoring will be required. s For these chemicals a training program should beiinstituted, fcr operators to recognize the e characteristic odors and to take appropriate protective

'deasures.

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REFERENCES l

1.

" Prairie. Island Main Control Room Habitability Study" l

Prepared by the Bechtel Power Corporation on May 1981 2.

Effects of Exposure to Toxic Gases - First Aid and Medical l

Treatment by Braker, Mossman and Siegel, Secona Edition l

3.

Patty's Industria'l Hygiene and Toxicology by George D. ind i

Florence E. Clayton, Volumes 2A & 2B, Third Edition, f

i 4.

Dept. of Transportation, " Coast Guard CHRIS Hazardous Chemical Data", Oct. 1978.

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" Documentation of the Threshold Limit Value", Fourth Edition,1980, American Conference of Government Industrial Hygienists Inc.

6.

" User Manual for Bechtel S.C.P. T0XGAS NE314 Release 2",

Bechtel Power Corporation, May 1982.

(Bechtel Proprietary)

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7. NUREG/CR-1741 "Models for the Estimation of Incapacitation Times Following Exposure to Toxic Gases and Vapors", Gordon J.

Smith, David E. Bennet, Sandia National Laboratories, Dec -

1980. L

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