Exposure Due to Transportation of Nuclear Fuel Waste
Increased level of radiation exposure due to the transportation of nuclear fuel waste can be generally grouped into three categories: routine transportation operations; accidents including severe accidents during transportation or transfer; and terrorist attack during transportation, with possible catastrophic results.
Routine Transportation
Operations
During routine transportation
operations, radiation is continuously emitted through cask walls. In the
U.S., the Nuclear Regulatory Commission has set an exposure limit of 10
mrem per hour at 2 metres from the cask surface, or the equivalent of one
chest x-ray per hour of exposure. Three different scenarios must be considered
for routine operations: members of the public residing or working at locations
near shipping routes; vehicle occupants trapped in traffic gridlocks; and
worker exposure during transport (ie. drivers) or inspection.
According to studies cited by the State of Nevada (concerned about exposure during transportation of waste to the proposed site at Yucca Mountain) individuals who reside, work, or are institutionally confined at locations within 6 to 40 meters of a nuclear waste highway route, or within 6 to 50 meters of a nuclear waste rail route, could potentially receive yearly radiation doses equal to, or even in excess of, average annual background doses.
The Sandquist report, prepared for the U.S. Department of Energy, calculated maximum individual exposures (in millirems) per event to estimate maximum potential annual doses to individuals near truck cask shipping routes. Depending upon the number of truck shipments and distance from the route, maximally exposed individuals near highway routes could potentially receive annual doses ranging from 6 mrem to 960 mrem, equivalent to 2% to 266% of the average annual background radiation dose.
Estimation of exposures from rail transportation is more difficult, primarily because of uncertainties about service options (dedicated trains versus general freight service), number of casks per shipment, and continuous rail shipment or intermodal transfer. Maximally exposed individuals located within 20 meters of rail interchange/transfer points could potentially receive annual doses in the range of 150 mrem, assuming 500 rail cask/shipments per year and an average exposure time of 10 minutes per rail cask received.
Drivers and passengers of vehicles in traffic gridlock incidents could receive potentially significant radiation doses as a result of being trapped next to or near an undamaged truck cask for an extended period of time. Occupants of stopped vehicles in lanes adjacent to the cask vehicle could receive a maximum dose of 3 mrem, assuming a distance of 5 meters from the cask center and an exposure time of 30 minutes. The maximum dose from a gridlock incident could be as high as 40 mrem. It should be noted that one individual could be exposed in this way on more than one occasion, particularly if they are regular commuters along waste transport routes.
Workers responsible for safety inspections could receive yearly occupational doses significantly in excess of annual background doses. With each truck cask inspection estimated to take about 12 minutes , at a distance of 3 meters from the cask center (near the personnel barrier), and result in a dose of 2 mrem per event. An inspector could receive an annual dose of up to 2,500 mrem.
Accidents During Transportation
In severe transportation
accidents the cask radiation shielding could be damaged, resulting in elevated
gamma and neutron radiation levels around the damaged cask and possibly
in the release of some portion of cask contents which would result in the
contamination of a relatively large down-wind area with alpha-, beta- and
gamma-emitting isotopes (There are three types of radiation from nuclear
materials: alpha, beta and gamma).
Studies relied upon by the
State of Nevada examined three types of severe accidents. While design
details are not available for the proposed shipments to a Canadian repository,
the cask design and net source term assumptions have been deemed reasonably
close to what is currently expected for shipments to a repository or interim
storage facility by the State of Nevada, ie to the proposed Yucca Mountain
repository.
The most severe accident
scenario analysed in the Sandquist study involves a high-speed impact followed
by a long duration, high temperature fire fed by some external source of
petroleum fuel with a total release of about 6,159 curies. The most exposed
individuals would receives an estimated dose of about 10.2 rem, primarily
from inhalation of radionuclides (eg. an emergency responder located 70
meters directly downwind from the point of release for a period of "a few
hours". The radionuclides released by the accident are carried downwind
( in the plume of smoke from a petroleum fire) and contaminate an area
of about 110 square kilometers (42.5 square miles). The release from the
worst case rail accident in a typical urban area results in "22 latent
health effects"[ about half cancers, and half genetic disorders]. Cleanup
of the contaminated area, assuming that the accident occurs in a rural
area, could cost as much as $620 million (1985$) and require 460 days.
In an urban area, the cleanup cost is estimated to exceed $2 billion.
A review by the State of
the Nevada indicates that the Sandquist report, first published in 1985,
is still the best available reference for estimating exposures from severe
spent nuclear fuel transportation accidents. However, it notes that
there are some deficiencies in Sandquist's report including:
| Source: "Radiation Exposures
From Spent Nuclear Fuel and High-Level Nuclear Waste Transportation to
a Geologic Repository or Interim Storage Facility in Nevada", by Robert
J. Halstead. Provided by the State of Nevada Nuclear Waste Project Office.
Available at http://www.state.nv.us/nucwaste/trans/radexp.htm
Prepared by: Brennain Lloyd, Northwatch, June 2005 |
Briefing Note on Exposure Due to Transportation of Nuclear Fuel Waste (pdf)
Summary of Nuclear Waste Management Organization's Papers on Transportation
Sample Muncipal Resolution Opposing the Transportation of Nuclear Waste
State of Nevada Transportation Information
News stories on nuclear waste related transportation accidents
Nuclear
Waste Makes Haste - The Hazardous Roads to Yucca Mountain
July
31 - August 6, 2002, Village Voice
In
Nuclear Waste Site Debate, Visions of Transport Disaster
Washington
Post Staff Writers, Monday, July 8, 2002
Choosing
routes, testing safety
Christian
Science Monitor, June 27, 2002 edition
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