May 1, 2013 Positive Attitude

Virtuoso: someone who excels in the technique of an art, especially a musical performer

Do Now: What does this symbol mean to you?

Radioactive Waste

What is the primary concern associated with solid or liquid radioactive waste?

Remember – there are different types of nuclear radiation with different penetration energies (see slide)

Penetration energies of different types of nuclear radiation

Radioactive Waste

Important consideration: the radioactive material’s half-life

Half-life – the time required for half of the radioactive atoms present to decompose; half-lives of radioactive elements vary from fractions of a second to billions of years! (see slide)

Radioactive Waste

The more energetic the nuclear radiation and the longer a radioactive substance’s half life the greater the disposal problem

E.G., Plutonium has a half-life of ~ 24,000 years and emits highly energetic nuclear radiation; plutonium waste would require at least 10 half-lives isolated storage for even modest amounts to have the radioactivity reduced to “safe” exposure levels

Radioactive Waste

Radioactive waste possesses another significant environmental and economic problem to the U.S. (see slide)

Radioactive Waste

Radioactive waste classification is imprecise; two broad categories recognized: Low-level radioactive waste: low-energy radioactivity emission; nearly 90% of all radioactive waste (e.g., certain medical waste, smoke alarms, protective clothing and filters from nuclear power plants) High-level radioactive waste: high-energy radioactivity emission (e.g., depleted U-fuel rods, most nuclear plant waste)

Although nearly 90%of radioactive wasteis “low-level”, the highest energyradiation is associated with “high-level” waste,especially depleted (spent) nuclear fuel

Radioactive Waste Disposal

No permanent repository exists anywhere in the world for high-level radioactive waste; very few sites have been constructed to accept low-level radioactive waste

The U.S. government created the Waste Isolation Pilot Plant (WIPP) to store transuranic waste (a type of nuclear waste with low-energy radioactivity emission but very long half-lives) produced during more than 50 years of nuclear weapons research and production

Radioactive Waste Disposal

The waste will be deposited about 2,150 feet underground in tunnels and chambers dug into 225 million-year-old thick salt deposits

By law, no other low- or high-level radioactive waste can be deposited at the WIPP

The WIPP facility started receiving waste late in 2000 and should be able to store 6 million cubic feet of transuranic waste during its 35 year life expectancy (see slides)

Waste Isolation Pilot (WIPP) Plant Schematic Design

WIPP “multibarrier”containmentvessel

WIPP waste vessels are mechanically emplacedinto holes bored into salt walls

Radioactive Waste Disposal

Suggestions for high-level radioactive disposal:

1) Space disposal 2) Ice sheet disposal (Antarctica) 3) Deep seabed disposal 4) Subduction zones 5) Bedrock caverns (e.g., like WIPP) or bedrock disposal

(Yucca Mountain, Nevada?) See slide illustrating multibarrier approach of bedrock

disposal (most likely to be employed in the U.S. for commercial high-level radioactive waste)

Example of bedrockdisposal for high-level radioactivenuclear waste

Radioactive Waste Disposal

The Nuclear Waste Policy Act (NWPA) of 1982 mandated the establishment of two high-level radioactive waste disposal sites for commercial waste

In 1987 this Act was amended: only Yucca Mtn., Nevada was authorized to be investigated as a possible repository

The Yucca Mountain site has been beset by delays in the mandated Environmental Assessment and by legal challenges by state and local governments and individuals (see slide of Yucca Mtn. region seismicity)

Yucca Mountain, Nevada

Location of major faults Significant earthquakes

Radioactive Waste Disposal

The NWPA of 1982 mandated the government open a permanent storage facility for high-level radioactive waste by 1998 – if the Yucca Mountain site is completed it will likely not open to 2015 or beyond! The 2010 budget eliminated all funding for Yucca Mountain!

The average nuclear power plant in the U.S. produces about 500 pounds of plutonium per year and 30 metric tons of high-level radioactive waste each year!

Where is this high-level radioactive waste stored now? (see slide for example)

12/27/05

The Russian government (2006)proposed storing, for payment, high-level radioactive waste like spentfuel rods. A good idea?

Radioactive Waste Disposal

Technical and legal problems have also plagued construction of a new generation of low-level radioactive waste dumps – federal law is being violated

Discuss Michigan’s withdrawal from the Great Lakes compact on low-level radioactive waste disposal

Radioactive Waste Disposal

We need to also worry about radioactive material contamination of the environment from other sources (e.g., a Russian nuclear-powered submarine with nuclear missiles sank in the northern Atlantic Ocean in 1986 with about 200 pounds of plutonium - an unknown amount leaked into the ocean)

Summary

Two broad waste disposal philosophies exist:1) Dilute-and-Disperse (i.e., “The solution to

pollution is dilution”.); example – ocean dumping

2) Concentrate-and-Contain (i.e., concentrate waste and isolate it from the environment); example – secure landfills, bedrock disposal of nuclear waste

Remember – neither of these approaches is risk free