Indoor gamma radiation in Norwegian dwellings during the first three months after the Chernobyl accident

During the first month after the Chernobyl accident measurements of external radiation in about 900 randomly selected houses in Norway were carried out. The survey was originally planned to be a nationwide survey of natural radiation in Norwegian dwellings, and the first series of measurements were, by coincidence, started a few days before the accident. Follow-up measurements in selected houses in the third month after the accident, together with preliminary results of measurements on earth samples, were used to assess population doses, effective dose equivalents on the municipality level and the overall collective dose equivalent to the Norwegian population, from fall-out gamma radiation during the first three months after the accident. Follow-up measurements in the 900 houses are planned in order to assess shielding factors for houses and to improve the calculations of the indoor doses and dose equivalents for the first period after the accident. (author)