Transcript GSC 1620 Chapter 15 - Madison Central High / Overview

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 halflives 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 waste
is “low-level”,
the highest energy
radiation 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”
containment
vessel
WIPP waste vessels are mechanically emplaced
into 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 bedrock
disposal for
high-level radioactive
nuclear 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 spent
fuel 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

1)
2)
Two broad waste disposal philosophies exist:
Dilute-and-Disperse (i.e., “The solution to
pollution is dilution”.); example – ocean
dumping
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