Nuclear Technologies and the Environment

What is radiation? Energy in transit Classified as non-ionizing or ionizing Can be a wave (photon) or a particle Can be charged or neutral

Types of Radiation  particles –+2 charge (2 protons, 2 neutrons, no electrons) –easily shielded -- rubber gloves or paper  particles –can be an electron or a positron –can be shielded with low z material -- aluminum, glass  -rays, x-rays –photons, have no charge –variable energies –shielded by concrete, steel, or lead neutrons –particles with neutral charge –interact strongly with boron and hydrogen

Sources of Radiation Natural Sources Cosmic Rays Sunlight Radon Living Things Soil, rocks Man-Made Sources Weapons Fallout Medical/Dental X-rays Nuclear/Coal Power Smoke Detectors Industrial Research (Universities, Laboratories)

Ionizing Radiation Has sufficient energy to electrically charge an atom by stripping electrons Chemical composition can be changed

Average Personal Annual Dose 40 mrem from your own body 50 mrem from medical exposures 70 mrem from natural sources 200 mrem from radon exposure 1 mrem from weapons testing fallout ~360 mrem total annual dose

Health Effects of Radiation Radiation changes living cells –body repairs low dose rate damage –body cannot repair large acute doses Degree of effect depends on dose intensity, length of exposure, and type of cell exposed

Biological Dose Limits Begin to detect blood changes at 25 rem Radiation sickness appears above 100 rem –nausea, vomiting – hair loss –exhaustion – increase cancer risk Doses above 500 rem are usually fatal without heroic medical treatment

Most people receive lifetimes doses of about 25 rem from background radiation. Since background radiation cannot be avoided, everyone is exposed on average to rem/year. The U.S. government limits doses above background to no more than 5 rem/year for occupational exposure and no more than 0.1 rem/year for the general public.

Mechanisms of Biological Damage Direct Effects –radiation itself interacts with cellular protein or DNA altering the chemical properties of the molecule Indirect Effects –radiation interacts with water in the body to create free radicals which then attack other cell molecules

Acute Effects of Radiation Exposure Hemopoietic Syndrome –occurs at doses between 25 and 50 rad –affects blood forming tissues & immune system –danger of bleeding and infection –usually recover Gastrointestinal Syndrome –occurs at doses greater than 1000 rad –affects intestinal tract and colon –body cannot absorb water or nutrients –death can occur within weeks without medical treatment Central Nervous System Syndrome –occurs at doses greater than 2000 rad –unconsciousness within minutes of exposure –death within 48 hours

Delayed Effects of Radiation Exposure Cancer development Genetic effects (have not been observed in humans) Cataracts

Engineers Protecting the Environment Radiological Engineering –containment buildings, shielding, glove boxes –dosimetry, protective clothing Storage and Transport Containers –spent fuel storage -- in pool, above ground –high-level waste canisters Disposal Engineering –packaging and containment barriers –repository design

What is Radioactive Waste? By-products of any activity involving the use of a radioactive material. Common sources are hospitals, industrial & research labs, power plants, and reprocessing & enrichment facilities.

Types of Radioactive Waste Low-Level Waste (LLW) –consists of paper, glass, gloves, clothing, tools –low contamination levels of isotopes with half-lives less than 30 years High-Level Waste (HLW) –consists of spent fuel, liquid reprocessing wastes, weapons wastes –highly radioactive with long lived isotopes Transuranic Waste (TRU) –consists of fuel and weapons processing wastes –contaminated with elements heavier than uranium

Environmental Effects of Weapons Testing Over 200 atmospheric weapons tests occurred between Environmental radiation contamination has been decreasing since 1963, but some effects remain –fission products --  and  emitters -- Sr-90, Cs-137 –neutron activation products C-14 from activated atmospheric nitrogen Co-60 from activated steel weapons parts & towers –unused weapons parts -- uranium, plutonium, tritium

Additional Environmental Effects of Weapons Testing Contamination of islands in the South Pacific were testing was conducted. Some islanders had to be removed from their homes in the seventies. Most have since returned. Destruction of indigenous plant and animal life due to heat and blast wave shock effects in addition to radiation damage.

Environmental Effects of the Chernobyl Accident Increased incidence of thyroid cancer in children No significant increase in leukemia Many stress-related illnesses appearing 600 million person-rem global dose –40% on former U.S.S.R., 50% in Europe, 10% elsewhere Unsure of food production and ecological changes Only 1% of original radiation remains today HUGE benefit from the tragedy -- new, vital data concerning human health effects of ionizing radiation

Environmental Effects of the Three Mile Island Accident VERY little radiation actually released outside of the reactor building No known increases in radiation related health effects - some stress-related increases Ongoing reactor clean-up Community fear is largest long-term effect No known effects on the surrounding ecology

Radioactive Waste Disposal Options LLW dispose in steel barrels inside concrete lined trenches. Clay soil cover retards water movement. SNL stored in reactor pool or in above ground casks until Yucca Mountain or other repository opens. HLW vitrified and placed in steel drums. Stored in warehouse until Yucca Mountain or other repository opens. TRU vitrified and put in steel canisters. Solid wastes are placed in storage boxes. Will be placed in New Mexico salt bed at the WIPP site.

Beneficial Uses of Radioisotopes Medical Sterilization Cancer Treatment Food Irradiation to kill parasites and microorganisms Tracers to learn about groundwater flow or biological processes Travel security measures

How Safe is Disposal? We CAN design packages to withstand the environment for up to 500 year. We CAN engineer barriers to retard the migration of possible releases. We attempt to predict how long that it would take for the radiation to reach the “accessible environment.” With proper monitoring, we could anticipate and react to foreseeable problems.

Storage Versus Disposal Disposal at central location - storage at several different sites Storage seen daily and actively monitored - some people believe disposal will be out of sight, out of mind (still actively monitored) Package integrity similar in both cases, but you can actually see containers stored above ground