Sources of Radiation in the Environment Ground Zero (New Mexico)

ICRP Guidelines: the effective dose equivalent from all sources, excluding background radiation and medical procedures, to representative members of a critical group, should not exceed 1 mSv in any one year; effective dose equivalents of up to 5 mSv are permissible in some years provided that the total does not exceed 70 mSv over a lifetime. Working Framework ICRP Website:

Natural Sources: (a) Cosmic radiation (high energy protons and particles from the sun and other stars) Direct interaction - dose received depends on altitude and latitude Interaction with stable molecules production of radionuclides e.g. 14 N + 1 n 15 N 14 C + 1 p 14 N + 1 n 12 C + 3 H 3H2O3H2O global hydro-geological cycle 14 C 14 CO 2 global geochemical cycle National Radiological Protection Board (NRPB) estimate effective dose from cosmic radiation at about 300 Sv.y -1

Natural Sources: (b) Terrestrial radiation Earth originated from stellar material crust contains radioisotopes 40 K 3 mg.kg Th10-15 mg.kg U U U 3-4 mg.kg -1 NRBP estimates annual effective dose equivalents from these sources and their daughters to be around 400 Sv.y -1. Local variations due to locations and building materials. (c) Radon and its Daughters 220 Rn and 222 Rn arise from natural decay of 238 U and 232 Th Gaseous radioisotopes percolate through soil and are trapped in modern buildings adsorption on dust particles lung tissue potential for short-range and irradiation NRPB estimates around 800 Sv.y -1 from this source

Natural Sources: (d) Radioactivity in Food and Water mainly 226 Ra (and daughters 222 Rn and 218 Po) and 40 K. Examples: fish - Ra absorbed in partial replacement of Ca (Pacific salmon) plants - both 210 Po and 210 Pb enter food from soil and by wet and dry deposition from the atmosphere [tobacco leaves can absorb Ra decay products cigarettes activity 6-7 mSv.y -1 from this source] uptake of 40 K activity in plants and animals (0.2% body tissue) (NRPB 170 Sv.y -1 from this source) NRPB estimate total effective dose to individuals at 200 Sv.y -1

Medical Applications X-rays20 Sv per chest X-ray 99m Tcbone and brain scans Need to balance potential benefits from potential hazards e.g. anti-cancer treatments can involve high dose rates of X and radiation in addition to internally administered radio-nuclides, e.g. 131 I

Nuclear testing since 1945 but predominantly and >1000 documented tests Atmospheric testing:tests in Australia, Pacific, etc high atmospheric dispersal of subsequent fallout globally Hiroshima bomb: 14 ktonne 8 x Bq of activity including: 106 Ru, 137 Cs, 140 Ba, 144 Ce, 85 Kr, 89 Sr, 90 Sr, 99 Tc, and biologically significant 89,90 Sr, 131 I, 137 Cs Thermonuclear devices (hydrogen bombs) 3 H + fission products Activity from tests > Bq: 2x10 -5 Gy (northern hemisphere) 2x10 -6 Gy (southern hemisphere) Atmospheric and (latterly) underground testing. Moratorium but testing still continues Activation of surrounding materials other nuclides, e.g. 14 C Natural background 1 x Bq.y -1 From testing5 x Bq.y -1

Transuranics 238 U + 1 n 239 U 239 Np Pu + Most significant: 239 Pu (t ½ = 24,360y) Estimated 239 Pu activity of 1.5x10 16 Bq: NRPB estimate average effective dose today in the UK from weapons testing to be around 10 Sv.y -1. This was around 8 times higher in the 1960s.

Nuclear Reactor Operations mining (exposure to miners and contamination of water courses) purification, enrichment and fabrication of fuel elements NRPB estimates equivalent doses of 100 Sv.y -1 to populations close to reactors PWR with 100 tonnes of 3.5% enriched 235 U fuel contains 0.25 TBq of 235 Uand 1.1 TBq of 238 U unless an accident occurs, no fuel release expected gaseous products, 85 Kr (t ½ 10.8y) leakage to atmosphere activation products, 3 H fuel storage (cooling) water contamination (<350 Sv.y -1 ) Production of Fuel Reactor processes Fuel Reprocessing Separation of neutron absorbing fission products from unburnt fuel highly radioactive wastes