The assessment of ionizing radiation dose to the general
public resulting from a nuclear accident is a central
part of level 3 probabilistic risk analysis. This report
reviews dose assessment methods used recently either in
major studies (the SOARCA study by the Nuclear Regulatory
Council, and the Fukushima accident study by the United
Scientific Committee on the Effects of Atomic Radiation),
or in modern level 3 PRA analysis codes (VALMA, SILAM,
After a brief introduction to dose assessment, the
methods are introduced by study/code. The methods of the
Finnish VALMA code relies on work done at VTT previously,
and on international standards and guidelines. It takes
into account cloudshine, groundshine, inhalation and
ingestion. The dose assessment of SILAM handles the same
VALMA, and also rests on guidelines of IAEA and others.
The dose assessment of RODOS relies on simple methods,
but is quite versatile. The dose assessment used in the
SOARCA study is the one implemented in MACCS2, and
reflects the American way of dose assessment analysis.
The dose assessment used in the UNSCEAR study originates
Russia, considers cloudshine, grounshine and inhalation,
and contains submodels for finding radiation intensity in
free air, the effects of the locations of exposed people,
the whereabouts of people as a function of time, and
conversion of radiation intensity to absorbed doses.
It turns out that there has been relatively little
progress in dose assessment methods in the last 20 years.
Some suggestions on future research on improving the
accuracy and plausibility of dose assessments are made.
These rely on utilizing developments in modelling,
simulation and computation in the last decades.
|VTT Research Report
- dose assessment
- consequence analysis
- PRA methods