Economic evaluation of external safety measures in the ALARA regime

摘要

The current risk policy in the Netherlands under the Seveso-directive requires quantitative risk assessments for major hazards installations for which the risks are presented both as individual risk contours as well as group risks (fN-curves). The individual risk has a limit value below which the ALARA-regime (ALARA = As Low As Reasonably Achievable) exists. The group risk has an orientation value below which ALARA is applied. Important criteria for the choice of additional mitigating measures are the costs and benefits of the expected effects of the measures. A study has been done to identify whether economic evaluation instruments can be applied to further decision making on additional safety measures. The paper describes the findings of the study, which concluded that a restrictive cost-benefit analysis can be a useful instrument. Restrictive in this context means that current risk standards are not at stake. This entails that an evaluation regards various measures with a safety mitigating effect (either source-oriented measures or effect-oriented measures), which are part of the ALARA-regime (and should bring the risk contours closer to the facility). The more strict the restrictions (i.e. lower limit values) are, the lower the balance of costs and benefits of safety measures will be. It could even become negative. Then a cost-benefit-analysis might better be replaced by a cost-effectiveness-analysis. The findings will be illustrated with one case of an external safety situation related to major hazards.