Chapter 13.3Hazards and Costs of Nuclear Power Facilities
when uranium undergoes fission, direct products are unstable isotopes become stable by spontaneously ejecting subatomic
particles (alpha and beta particles), high-energy radiation (gamma and X-rays), or both
indirect products form as materials around the reactor are converted to unstable isotopes when the absorb neutrons from fission
radioactivity is measured in curies collectively, particles and radiation are referred to as
radioactive emissions
biological effects
radioactive emissions can penetrate biological tissue, resulting in radiation exposure
exposure measured as absorbed dose (J / kg) joules = energy unit kilogram = mass of body tissue
unit referred to as sieverts (Sv) in cases of high level radiation exposure
as radiation penetrates tissue, it displaces tissue, leaving behind ions
biological effects of radiation
high dose: radiation may cause enough damage to prevent cell division used in cancer treatment to destroy tumors whole body exposure results in radiation sickness
low dose: may damage DNA, leading to tumors or leukemia damage to egg or sperm cells (mutations) may lead to
birth defects effects may go unseen for 10 – 40 years after the event exposures of 100-500 millisieverts or more results in an
increased risk of developing cancer
sources of radiation
normal background radiation from uranium and radon underground, as well as from cosmic radiation
deliberate exposures come from medical and dental tests (primarily X-rays)
average person in U.S. receives a dose of about 3.6 mSv per year
radiation detectors pick up more radiation from most basement floors than from measurements in and around nuclear power plants
radioactive wastes
radioactive decay: process in which an unstable isotope becomes stable by releasing particles and radiation
half-life: time for half of the amount of a radioactive isotope to decay
each radioactive isotope has a characteristic half-life
disposal of radioactive waste
low-level low amount of radioactivity remains dangerous for a short period has short half-life (a few hundred years or less)
high-level high amount of radioactivity remains dangerous for a relatively long period has long half-life (tens of thousands of years)
disposal of radioactive waste
storage of low-level waste on-site until it has decayed enough to go into
regular trash or until amounts are large enough to go into hazardous waste landfill
necessary for relatively short period usually stored in barrels or drums
disposal of radioactive waste
Storage of high-level waste on-site until it can be shipped to an isolated
area necessary for relatively long period (tens of
thousands of years) must be stored in specially shielded
containers or in water pools; must be cooled before long-term storage
disposal of radioactive wastes current problem of nuclear waste disposal is two-
fold: short-term containment: allows radioactive decay of
short-lived isotopes; in 10 years, fission wastes lose 97% of their radioactivity
spent fuel is first stored in deep pool-like tanks on the sites of nuclear power plants
water in tanks helps to dissipate heat and prevent escape of radiation
current U.S. pools will be full by 2015 after a few years of decays, spent fuel may be paced in air-
cooled dry casks until long-term storage is available (able to resist flood, tornadoes, etc.)
disposal of radioactive wastes current problem of nuclear waste disposal
is two-fold: long-term containment: EPA recommended a
10,000 year minimum to provide protection from long-lived isotopes; government standards require isolation for 20 half-lives
military radioactive wastes
some of the worst failures in handling wastes have occurred at military facilities
wastes associated with the manufacture of nuclear weapons
U.S. activities have been top-secret Ex. releases of uranium dust, xenon-133, iodine-131, and
tritium into environment clean-up is now responsibility of Department of Energy DOE has spent $50 billion and full clean-up may require
$250 billion
military radioactive wastes
former U.S.S.R. worst case is complex called Chelyabinsk-65, near
the Ural Mts. nuclear wastes were discharged into the Techa River
and then into Lake Karachay for at least 20 years at least 1000 cases of leukemia have been traced to
radioactive contamination from site even today, standing on the shore of Lake Karachay
for an hour can result in enough radioactive contamination to cause radiation poisoning
military radioactive wastes
Megatons to Megawatts program private U.S. company oversees the dilution of
weapons-grade uranium to lower-grade power plant uranium
processed uranium sold to U.S. power plants at market price, with payments then sent to Russian government
high-level nuclear waste disposal
most countries (including U.S.) have decided that geologic burial is best ultimate fate for nuclear waste, but no nation has carried out the plan
basic problem is that no rock formation can be guaranteed to remain stable and dry for tens of thousands of years no spot without evidence of volcanic activity,
earthquake, or groundwater leaching in the past 10,000 years
Yucca Mt. nuclear waste disposal
Nuclear Waste Policy Act of 1982 required the U.S. government to begin receiving nuclear waste from commercial power plants by 1998
Yucca Mountain, NV site selected in 1987 studies have indicated that storerooms
1000 feet above current groundwater levels will be safe for at least 10,000 years
Yucca Mt. nuclear waste disposal
2004 court ruling said that time period was inadequate and caused EPA to extend the protection standard to 1 million years (and raised allowable dose maximum past 10,000 years to 3.5 mSv/year)
in 2002, President Bush signed a resolution (passed by Congress) voiding a veto by Nevada’s governor that had attempted to block further development at the site
Yucca Mt. could begin receiving waste from storage facilities around the country by 2018
nuclear power accidents
Three Mile Island (PA, 1979) partial meltdown due to series of human and
equipment failures resulting from flawed design
operators of the plant have paid $30 million to settle claims from the accident, although the company has never admitted that radiation-caused illnesses occurred
nuclear power accidents
Chernobyl (U.S.S.R., 1986) disabling plant safety systems for test of
standby diesel generators eventually led to: a steam explosion that blew the top off the reactor core meltdown release of 50 tons of dust and debris bearing 100-
200 million curies of radioactivity plume rained radioactive particles over thousands of
square miles 400x the radiation fallout associated with bombs dropped
on Hiroshima and Nagasaki
consequences of Chernobyl
135,000 people were evacuated and relocated reactor eventually was sealed with concrete and steel barbed-wire fence now surrounds a 1000 square mile exclusion
zone around the reactor site 2 engineers were directly killed by the explosion, along with 28
people brought in to contain the reactor after the explosion U.N. report offers assessment of impact: long-term confinement, and $800 million project undertaken by
28 governments, is set to conclude in 2010 over 4000 cases of thyroid cancer, mainly from children drinking
milk containing radioactive iodine several thousand additional deaths due to cancer are expected
(difficult to track)
new generations of reactors
Generation I: earliest, developed in 1950s and 1960s, few still in operation
Generation II: majority of today’s reactors, utilize many different designs
Generation III: newer designs with passive safety features, usually simpler and smaller power plants advanced boiling-water reactors (ABWR) two separate passive safety features cause water to
drain by gravity into the reactor design of choice in east Asia
new generations of reactors
Generation IV: now being designed, will likely be built in the next 20 years pebble-bed modular reactor (PBMR) will feed spherical carbon-coated uranium fuel
pebbles gradually through the reactor new designs are cheap to build, inherently
safe, and inexpensive to operate
worries about terrorism 3 main threats:
jetliner could fly into control building, triggering a LOCA strike force could overcome plant defenses and bring on a
core meltdown by manipulating the controls Both of the above scenarios would result in few, if any, immediate
civilian casualties, but effects of radiation (cancer, etc.) would be emerge over the course of many years
“dirty bombs” containing spent fuel rods could spread radioactivity over a large area
response: security around plants increased pools of spent fuels are most vulnerable locations
economics economic reasons slowed the development of
nuclear power plants beginning in the 1970s projected future energy demands were overly
ambitious increased safety standards caused cost to increase 5x public protests delayed construction
the lifespan of plants has been much shorter than expected embrittlement and corrosion
potential for Climate change has given nuclear power new hope, despite expense
advanced reactors
breeder (fast-neutron) reactors U-238 absorbs extra neutrons from fission reaction at
high speed U-238 is converted to plutonium (Pu-239), which can be
purified and used as fuel advantages:
extract more energy from recycled nuclear fuel; produce much less high-level waste than conventional nuclear power plants
disadvantages: Meltdown would be far more serious due to long half-life of Pu;
fuel can be purified into nuclear weapons far more easily; more expensive to build and operate
advanced reactors fusion reactors
solar energy is the result of the fusion of hydrogen nuclei to form larger atoms, such as helium
process is duplicated in hydrogen bombs in ideal world, hydrogen (for which there’s an inexhaustible
supply in water) is converted to nonpolluting inert gas, helium however, isotopes of hydrogen, deuterium (H-2) and tritium
(H-3) are used in d-t reaction currently, conducting fusion requires more energy than it
produces main problems are producing enough heat to cause H atoms
to fuse, then extracting heat for useful energy