Environmental Impacts ofNuclear Technologies - 2

Bill Menke, October 25, 2005

Part 1: Health Consequence ofNuclear Hazards

Isotopes thatcontribute tothe activityof nuclear

waste

• Ten years after removal from a reactor, the surface dose rate for a typical spent fuel assembly exceeds 100 Sv/hour

• Fatal dose is about 10 Sv, so exposure for a few minutes would be fatal

• Fuel rod activity would decay to roughly 0.1 Sv/hour after 10,000 years, so a few days of exposure would be fatal.

Biologically-active nuclides

Especially dangerous because they can be incorporated into body tissues and therefore expose the body to radiation over many years

Iodine

• I129 (half life of 15.7 million years)

• I131 (half life of 8 days)

– Iodine is soluable in water– Iodine used by thyroid gland– can cause Thyroid cancer– Iodine pills taken to dilute radioactive uptake

Strontium

• Sr90 (half life of 28 years)

– Strontium is concentrated in bones, because it is chemically similar to calcium

– Concentrated in food chain (e.g. cows eat grass contaminated with Sr90, and then people drink the cow’s milk

Cesium

• Cs134 (half life of 2.1 years)

• Cs137 (half life of 30 years)

– Rapidly absorbed and distributed throughout body

– Rapidly excreted from body

– Some tendency to be concentrated in muscles

Chernobyl Accident, April 25, 1986

Power reactor fire/meltdown caused by scandalously improper testing, although the design wasn’t the greatest, either.

Graphic moderator caught fire, and reactor core melted down.

No containment vessel, so atmospheric release occurred

Concretecontainmentheroicallybuilt aroundreactor afteraccident

Chernobyl release

• The main radionuclides in the cloud were:

• 131I (half-life = 8.1 days)

• 134Cs (half-life = 2.1 years)

• 137Cs (half-life = 30.2 years).

Deaths through 2005:

50 acute radiation poisoning deaths

9 thyroid cancer deaths, out of a total of about 4000 cases (high cure rate).

4000 possible cancer deaths in long term

among the 600,000 emergency workers and local residents exposed to high radiation. This amounts to a 3% increase in cancer death rate.

Military Usage

Hiroshima and Nagasaki Bombs• Hiroshima

– U235 bomb, 15 kT yield– 64,000 deaths in population of 250,000

• Nagasaki, 21 kT yield– Pu239 bomb– 39,000 deaths in population of 174,000

• Deaths– Most initial deaths due to blast, heat radiation– Radiation deaths mostly within 1 km of blast– Subsequently 400 cancer deaths over next 30 years– Some detectable Ce137 contamination of soil

Typical yield 250 kT

Is “fallout” (radioactive particulates) an unintended consequence of nuclear explosions?

Radionuclides in Fallout

• Pu239 (24,000 yrs)

• I131 (8 days)

• Ce137 (30 years)

• C14 (5,730 years)

• Sr90 (29 years)

Part 2: Nuclear Waste Disposal

Disposal

Whatare these ?

Disposal

SegmentsOfSubmarinesContainingReactorsAtHanford

Yucca Mountain

ControversialAndUnopenedWasteStorageFacility inNevada

Design goal

To continually isolate nuclear waste and protect people and the environment for at least 10,000 years

Design of tunnel

Note: invert = platform

Natural Hazards

Water table rise, especially if climate becomes wetter

Volcanic eruptions

Earthquakes

Anthropogenic Hazards

Terrorism

Warfare, intentionally bombing the site

Incidental human intrusion, e.g. drilling for ground water, mining

Purposeful human intrusion, to recover nuclear materials

Some of these hazardsare more amenable to

probabilistic analysis than others

Earthquakes

TSPA-SR Modelwith 1 Chance in10,000 of beingExceededEach Year

Used as a basisFor designingShaking-resistantcontainment

Climate Change• Wetter climate increase the chance of transport

of radionuclides by ground water.

• Current rainfall now 190 mm/yr, but was as high as 430 mm/yr during the glacial period.

• What is chance of major climate change in next 10,000 years? Can appeal to Pleistocene history, but what is the certainty.

Human Intervention• What will humans be doing 500 years from

now?

• Can compute the probability that someone unaware of the repository and drilling for water might accidentally breach a cannister, but the chances of humans drilling is less certain.

• What about mining of radionuclides for heat or weapons? Consider the following …

Lia, Georgia, Accident, 2001

• Three shepherds found a several canisters in the mountains that appeared to have melted nearby snow. They carried them back to their camp, to use them for warmth. They all developed severe radiation poisoning, e.g. lesion on their backs.

• The canisters contained Sr90 from an old Soviet thermoelectric generator dating from the cold war. The men received does of about 4 Sv. They survived, being treated 3 months in the hospital.