Occupational Exposure Management at Nuclear Power Plants - Third ISOE European Workshop, Portoroz, Slovenia 17-19 April 2002

The radiation environment in low earth orbital flights is complex. The paper summarises the component of the space radiation, describes the dosimetric methods usually applied for space radiation dosimetry, and gives the typical figures of the measured results. The last part deals with dose limitation system of astronauts. Introduction Although partly protected from galactic and solar cosmic radiation by the Earth’s magnetosphere in Low Earth Orbit (LEO) astronauts exposure levels during long-term missions (90 days to 180 days) by far exceed with exposures of up to more than 100 mSv the annual exposure limits set for workers in the nuclear industry, but are still below the yearly exposure limits of 500 mSv for NASA astronauts. During solar particle events the short term limits (300 mSv) may be approached or even exceeded, which certainly would not be life threatening, but raise the probability for developing cancer later in life considerably. In the interplanetary space, outside the Earth’s magnetic field even relatively benign Solar Particle Events (SPEs) can produce 1 Sv skin-absorbed doses while the huge SPE observed in August 1972 for example would have resulted in a skin-absorbed dose of 26 Sv behind a shielding of 0.5 g/cm and would have proved lethal had there been any Extravehicular Activity (EVA) during this event. Although new rocket technologies could reduce astronauts’ total exposure to space radiation during a human Mars mission, the time required for the mission which is now in the order of years remains still about half of this time. Therefore mission planners will need to consider a variety of countermeasures for the crew members including physical protection (e.g. shelters), active protection (e.g. magnetic protection), pharmacological protection, local protection (extra protection for critical areas of the body) etc. With full knowledge of these facts, accurate personal dose measurement will become increasingly important during human missions to Mars.