EMERGENCY AT A LIGHT WATER REACTOR OR ITS SPENT FUEL POOL
4. RADIOLOGICAL HEALTH HAZARD CHARTS
4. RADIOLOGICAL HEALTH HAZARD CHARTS
Experience from past nuclear and radiological emergencies shows that placing the radiological health hazard into perspective is required, to help answer the public’s principal concern during an emergency (“Am I safe?”) and help explain what protective actions and other response actions are warranted to prevent members of the public, those responsible for protecting the public (i.e. decision makers), and others (e.g. medical staff) from taking inappropriate and damaging actions that are not justified based on the radiological health hazard [3, 5, 14, 15, 16]. These actions were often taken by the individuals concerned in the belief that they are protecting themselves, their family members or the public, and were often the result of failure to answer “Am I safe?” To answer this question, what is considered to be
‘safe’ in an emergency must be defined and tools developed (i.e. charts) that relate quantities measured/ reported (e.g. dose rate) during an emergency to the radiological health hazard (i.e.
is it safe or not). The definition of ‘safe’ has been developed and is available in Ref. [5].
For potential radioactive releases from a LWR core or its spent fuel pool, all the factors determining the possible radiological health hazard are understood and can be reasonably bounded. Consequently, calculations have been performed for severe releases resulting from emergencies at a LWR and its spent fuel pool that relate measured quantities to the possible radiological health hazard and the results presented in a set of charts, and provided in Ref. [5].
The charts have been developed to assess the radiological health hazard resulting from:
• Living in the affected area, based on the gamma dose rate at 1m above ground level.
• Having fission products on the skin, based on the gamma dose rate at 10 cm from skin.
• Consuming food, milk and water, based on the concentration of the marker radionuclides 131I and 137Cs in samples.
These charts can be used to directly relate a measured quantity to a radiological health hazard and will:
• Facilitate answering the public’s principal concern during an emergency (“Am I safe?”).
• Help the public, decision makers and others understand what protective actions and other response actions are appropriate/ inappropriate for ensuring the safety of everyone during the emergency.
• Help to identify those members of the public who might need a medical screening, examination or further assessment, in order to determine possible radiation induced health effects.
141 These tools were developed for the severe emergencies at NPPs and spent fuel pools of current designs. New reactor designs may warrant a significant revision of the overall emergency preparedness and response arrangements.
5. CONCLUSIONS
This paper provided information on the tools and criteria developed by the IAEA’s Incident and Emergency Centre, which include an emergency classification system, EALs, OILs and radiological health hazard charts that can be used as a last defence barrier to ensure effective protection of the public in the event of a severe emergency at a LWR or its spent fuel pool. Application of these tools and criteria will support the defence in depth strategy to limit the potential consequences of an emergency.
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143 CROSS-CUTTING ISSUES IN THE IMPLEMENTATION OF DEFENCE IN DEPTH
(TOPICAL SESSION 4)
144
INVITED PRESENTATION
DEFENCE IN DEPTH: ASSESSMENT OF COMPREHENSIVENESS AND