Anthony Waker Faculty of Energy Systems and Nuclear Science

 External Exposure  The source is external to the body CT Scanner: A few to 10s of mSv per examination

 Internal Exposure  The source is inside the body Approximately 1 mSv per year

 Total Exposure is the sum of all external and all internal doses Approximately 3 mSv per year

 Members of the public 1 mSv per year  Nuclear Energy Workers 20 mSv per year (100 mSv in 5 years, 50 mSv in any one year)  Fukushima workers – legal limit has been raised to 250 mSv Medical Radiation not counted

 External doses  Calibrated Instruments and dosimeters Calibrated instruments and dosimeters give a direct reading of the radiation dose to the individual

 Internal Doses  Whole body counters and Bioassay Whole body counters and bioassay are used to determine the intake of radioisotopes; what follows is a complicated calculation to convert an intake into a dose.

 Principal Concerns at moderate to low dose (mSv to a few Sv)  Cancer  Hereditary Disease  Radiation Effects on the Fetus The risk increases with dose

 Principal Concerns at high dose (1 Sv and up)  Radiation Sickness  Bone marrow damage  Gastrointestinal damage The severity increases with dose

 Risk to humans derived from  Atomic Bomb Survivors (Hiroshima and Nagasaki Life Span Study)  Medically exposed groups (ankylosing spondylitis; repeated fluoroscopic examination of tuberculosis patients in Massachusetts and Nova Scotia)  Occupationally exposed groups (radium dial- painters, uranium miners, former Soviet Union plutonium workers)

 Current Assessment of Risk  Cancer (4 to 10% per Sv)  Hereditary Disease (1/10 th of fatal cancer risk)  Radiation Effects on the Fetus (life-time cancer risk 20% per Sv)

 Cancer risk estimates apply to populations not to individuals

Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know PNAS November 25, 2003 vol. 100 no –13766 What is the lowest dose of X-ray or gamma ray radiation for which good evidence exists of increased cancer risk in humans………

Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know PNAS November 25, 2003 vol. 100 no –13766 ………the epidemiological data suggests that it is approximately mSv for an acute exposure and 50–100 mSv for a chronic exposure

 Effects at high dose result from the killing of stem cells that are used to supply replacement cells in the blood and for the lining of the intestines

 External exposures  Limit the time of exposure  Rotation of workers (shifts)  Increase the distance from the source  Shielding (put something between you and the source) Fukushima workers will be using all these measures of reducing dose

 Internal exposures  Protective clothing and breathing apparatus  Prevent spreading contamination by not moving out of contaminated area without changing protective clothing and boots; showers

 Very High Total Exposures  Nursing  Anti-biotics  Blood transfusions  Bone marrow transfusions

 External Exposure  Distance (exclusion zones and evacuation plans)  Internal Exposure  Staying out of the plume (exclusion)  Staying indoors  Preventing spread of contamination  Using Potassium Iodide