IAEA0886 INTERTRAN-I & II.

INTERTRAN-I and INTERTRAN-II.

INTERTRAN calculates the radiological impact from incident-free shipments and from vehicular accidents involving radioactive materials. It also addresses accidents which may occur during handling. The output in the incident-free case is given as annual integrated population dose to various population subgroups from the specified primary and secondary transport mode (road, rail, air, or water). In the accident case, both early and latent health effects are analyzed in the form of early fatalities and mortalities, latent cancer fatalities, and genetic effects.

INTERTRAN is divided into a number of submodels including a standard shipment model, transportation model, accident categorization model, material dispersibility model, atmospheric dispersion model, population density model, and health effects model In the standard shipment model user-specified individual shipments of up to 80 standard materials by any of 10 different transport situations are combined so that a standard shipment consists of an average shipment of a material transported by a specified transport mode or a combination of two transport modes. The model is used to meet the code's limitation of no more than 200 different shipments per run.

The transportation model consists of a traffic pattern section, a shipment section, and an accident rate section. In the traffic pattern section the fraction of travel in each of three population zones (rural, suburban, and urban) is specified. These fractions are used in calculating the dose in the incident-free case and in calculating the probability of an accident occurring in the different zones. This section also contains the parameters used to determine the dose during shipment stops and the dose to persons in the vicinity of the transport link. The shipment data section deals with the parameters used to evaluate the dose to crew, handlers, passengers, and flight attendants as well as the dose received while the cargo is stored. The accident rate section calculates the accident rate depending on the severity of the accident and the population zone where it is assumed to occur. An overall accident rate and a fractional occurrence of the accident severities are specified for each transport mode. These are combined with the accident risk factors which give the fractional accident rate in a population zone to the overall accident rate for each mode, severity category, and population zone.

The accident categorization model contains frequencies of occurrence fordifferent accident severities in different environments. For every severity category and each of the package types a package failure fraction is determined. This fraction describes the relative degree of damage to the packages of a shipment from an accident. The probability of a certain accident is given by the overall accident rate for the actual mode, the fractional occurrence of the actual accident severity category for that mode, and the accident rate factor for the population density zone, the accident severity category, and the transport mode.

The material dispersibility model takes into consideration the dispersibility difference due to the chemical and physical properties of the materials shipped. Each of the eleven dispersibility categories is assigned an aerosolization factor for each accident severity category. The aerosolization factor describes the fraction of the available material which is aerosolized and readily dispersed. When combined with the package failure fraction, the aerosolization factor gives the amount of material dispersed in an accident.

The atmospheric dispersion model calculates the time-integrated concentration at a specific distance from the release. Isodose curves can be generated, and the amount of material deposited during the passage of the cloud and the resulting depletion of the cloud are also calculated.

The population density model uses three separate population zones with evenly-distributed population. They are urban or high-population density, suburban or medium-population density, and rural or low-population density. For incident-free transport by road a factor which is the ratio of pedestrian density to population density in the area is inserted. In the accident dose calculations in the urban zone the population is divided into two parts - one representing people inside buildings, the other representing people on the streets. The pedestrian density factor is applied to the population density of those on the street.

The health effects model analyzes early fatalities and morbidities, latent cancer fatalities, and genetic effects. In the case of dispersible materials the one-year lung and marrow doses are used to calculate the probability of an early fatality for an individual. The expected number of early mortalities is calculated by comparing the individual organ dose with a threshold value. If the dose exceeds the threshold value, the expected number of early fatalities and morbidities is the number of exposed persons. The probability of cancer developing later in life for an exposed person is assumed to be porportional to the dose. Thus, the expected number of latent cancer effects in the exposed population is calculated as the product of the population dose and the chronic effect risk factor. In the case of non-dispersible materials the whole body risk factor is used. In the case of dispersible materials the total risk is calculated as the sum of the risk to the individual organs most sensitive to radiation (lung, marrow, bone, thyroid, and gastrointestinal tract). Exposures of the gonads can induce gene mutations and chromosomal changes leading to hereditary defects. When assessing the total population detriment, a risk factor of 80*10**(-6) per person-rem for genetic effects in all subsequent generations is used.

Maxima of

• 3 population density zones

• 200 different shipments per run

• 10 different package types

• 80 material types

• 10 transport modes

• 11 accident severity categories

• 30 iso-dose areas

• 30 rem levels

• 8 organs for dose calculation

• 5 early fatality organs

• 11 material dispersivity categories

• 10 material categories

• INTERTRAN, NESC No. I886.3081, INTERTRAN Tape Description and Implementation Information, National Energy Software Center Note 85-63, April 25, 1985.