PHYS 1110

Lecture 24

Professor Stephen Thornton

November 29, 2012

Reading QuizWhich of the following has the lowest death rate per unit of electrical energy generated?

A) gasB) coalC) nuclearD) hydro

Reading QuizWhich of the following has the lowest death rate per unit of electrical energy generated?

A) gasB) coalC) nuclearD) hydro

Remaining schedule:

Tuesday, Dec. 4: HW 7 on Ch. 10 due Quiz on Chs. 9 and 10

Thursday, Dec. 6: HW 8 on Ch. 11 due

Divide up into groups and discuss the following, then make reports.

•Mining•Conversion & Enrichment•Fuel•Reprocessing•Waste

Schematic of CANDU power reactor.

The first new power reactor beginning construction in the United States since 1977 is near Waynesboro, Georgia at Plant Vogtle. The two AP1000 units are being constructed by Southern Nuclear and are expected to be completed in 2016 and 2017. The Watts Bar 2 nuclear reactor in Tennessee was about 80% complete when construction was stopped on it in 1988. Construction resumed in 2007, and it is expected to be the first new nuclear reactor to be completed in more than a decade in the US. But it has gone over budget and behind schedule. It is now hoped that it will be finished by the end of 2015. As of October 2012 there were 64 nuclear reactors under construction in 13 countries, most of them in Asia, 26 in China, 10 in Russia, 7 in India. There are currently 434 operable nuclear reactors, capable of producing 373 GWe. The 64 under construction will add another 64 GWe, and many of the new ones will be Gen III.

Gen IV Reactors

•Nuclear waste that is radioactive for a few hundred, rather than thousands, of years.

•More energy yield (by 100-300) than existing nuclear fuel.

•Ability to consume current nuclear waste to produce electricity.

•Enhanced operational safety.

•Reduced capital costs.

Look over goals: 2 sustainability, 2 economic, 3 safety and reliability, 1 proliferation resistance

System NeutronSpectrum

Coolant Temp 0C FuelCycle

Size (MWe)

VHTR(Very high temperaturegas reactor)

thermal helium 900 to1000

open 250-300

SFR (Sodium-cooled fastreactor)

fast sodium 550 closed 30-150,300-1500,1000-2000

SCWR (Supercritical water- cooled reactor)

thermal/fast

water 510-625 open/closed

300-7001000-1500

GFR (Gas-cooled fastreactor)

fast helium 850 closed 1200

LFR (Lead-cooled fastreactor)

fast lead 480-800 closed 20-180,300-1200,600-1000

MSR (Molten salt reactor)

epithermal fluoridesalts

700-800 closed 1000

Generation IV Proposed Reactor Systems

QuizWhich of the following countries (or unions, areas) has the most nuclear reactors under construction?

A) ChinaB) European UnionC) United StatesD) South AmericaE) India and Pakistan

QuizWhich of the following countries (or unions, areas) has the most nuclear reactors under construction?

A) ChinaB) European UnionC) United StatesD) South AmericaE) India and Pakistan

QuizHow many nuclear reactors are currently operating throughout the world?

A) less than 100B) 100 to 200C) 200 to 300D) 300 to 400E) over 400

QuizHow many nuclear reactors are currently operating throughout the world?

A) less than 100B) 100 to 200C) 200 to 300D) 300 to 400E) over 400

QuizWhat is an example of a supercritical reaction?

A) a reaction that produces B) a fusion bombC) a fission bombD) a reaction caused by a slow neutronE) a reaction caused by a fast neutron

239 Pu

QuizWhat is an example of a supercritical reaction?

A) a reaction the produces B) a fusion bombC) a fission bombD) a reaction caused by a slow neutronE) a reaction caused by a fast neutron

239 Pu

QuizWhich of the following is not a cause of the nuclear renaissance of the 2000s?

A) economics B) security of fuel supplyC) low cost of natural gasD) increasing energy demandE) climate change

QuizWhich of the following is not a cause of the nuclear renaissance of the 2000s?

A) economics B) security of fuel supplyC) low cost of natural gasD) increasing energy demandE) climate change

Small nuclear reactors

• cheaper to construct and run than larger reactors.

• placed in remote areas not having sufficient electrical grids. 100,000 people.

• used in places like third-world or remote island countries.

• can be used for specialized purposes like desalination or hydrogen production.

• do not have to be custom designed.

• can be factory built and delivered as needed.

• have short construction times and can even be “shelf” ready.

• can be returned to specialized facilities for decommissioning.

• do not necessarily need to be cooled by water and, therefore, placed near large bodies of water. They can be cooled by air, gas, low-melting point metals.

The Westinghouse SMR design is a 225 MWe integral PWR with all its primary components located inside the reactor vessel. It utilizes passive safety systems and many other components that Westinghouse has gleaned from its many years of producing nuclear reactors including its recent AP1000, on which the SMR is based.

Left: schematic of Babcock & Wilcox mPower reactor. Right: underground containment structure for two mPower reactors.

The NuScale Reactor is a 45 MWe advanced light water reactor. Its passive cooling systems use natural circulation to maximize safety. The reactor vessel sits within a containment vessel inside a water filled pool that is built below grade. It uses a convection process (no pumps) to circulate water through the containment vessel. The reactor system can be operated solely for heat generation (160 MWt) for industrial applications, district heating, or for use in the production of synthetic fuels.

The Chinese HTR-PM is a 210 MWe high temperature, gas-cooled reactor. Helium gas is used to cool the reactor core, and graphite is the moderator. The fuel is ceramic coated kernels (called pebble bed module) and uranium, thorium, and platinum call all be used. The fuel kernels are small, 200-600 in diameter. A previous prototype reactor, HTR-10, was a smaller 10 MWe, and it was extensively tested at Tsinghua University in Beijing after it reached full power in 2003. It continues to operate today as a research reactor. Such a reactor has several safety features that make it attractive. For example, the HTR-10 underwent several tests to test its safety features: loss of offsite power, main helium coolant shutdown, loss of main heat sink, and withdrawal of all control rods. The current HTR-PM was designed by Tsinghua University and is under construction at Rongcheng, Shandong Province. The plan is to use two modules to reach 210 MWe, and customers may purchase multiple modules.

mm

238 239 239 23992 92 93 94n U U Np Pub b- -+ ® ® + ® +

The TerraPower Travelling Wave Reactor (TWR) The concept is that the reactor can breed its own fuel inside the reactor from natural or depleted 238U. It only needs a small amount of enriched 235U to begin the process. Thereafter neutrons produced by fission are in turn absorbed by 238U and in turn decay, eventually producing the fissile material 239Pu.

The TWR nuclear core does not move. We show a schematic of the “breed and burn” concept below. The reaction started on the far left with enriched 235U and the breeding and fission areas are moving slowly to the right, thus the traveling wave.

Fast breeder reactors and fusion reactors.

A fast breeder reactor (FBR) is a nuclear reactor that utilizes fast neutrons to produce more fissile material than it consumes. Remember nuclear fission normally produces fast neutrons that have to be slowed down or thermalized by a moderator. Reactions like the previous produce 239Pu from fast neutrons interacting with the highly abundant uranium isotope 238U. The extra 239Pu produced could be used to start another nuclear reactor. There was considerable interest in fast breeder reactors about 50 years ago, because of the fuel economy, and there was concern about lack of uranium reserves. There currently seems to be enough uranium reserves to last for decades, and there does not seem to be difficulty in finding new reserves when needed. Uranium enrichment using centrifuges and eventually lasers is much more economical than the older gaseous diffusion process.

Deaths from energy related accidents per unit of electricity generated.

The primary concern about nuclear reactors is if a large amount of radioactive fission products were dispersed over a wide area, where the radiation material could contaminate the soil and vegetation and be ingested by humans and animals. It is impossible, however, for a commercial nuclear reactor to detonate like a nuclear bomb, because the fuel is not highly enriched enough and it cannot be forced to a high enough density.

Except for the Chernobyl disaster, no nuclear workers or members of the public have ever died due to radiation received due to a commercial nuclear reactor event. There have been at least ten accidents in military and experimental reactors. Only one resulted in significant radiation release. There is also a significant difference in safety between well-developed countries in the OECD and non-OECD countries. Hydropower has caused many more fatalities/TWy, followed by coal and then natural gas. Nuclear is a factor of more than 200 safer than hydropower.

Attacks on Nuclear Facilities Year Event______________________________  1980 Iran bombed a nuclear complex in Iraq1981 Israel destroyed a nuclear research facility in Iraq1984-87 Iraq bombed a nuclear plant in Iran six times1991 USA bombed three nuclear reactors and an enrichment facility in Iraq2007 Iraq launched Scud missiles at an Israeli nuclear

power plant2008 Israel bombed a Syrian nuclear reactor under

construction.2013-14 Israel/United States will bomb Iranian nuclear facilities

There are a number of ways in which a nuclear reactor can fail. The primary concern is a loss of coolant, which may cause the fuel to melt or cause the containment vessel to overheat and melt. This event is called a nuclear meltdown. The Generation IV reactors presently being considered and designed hope to completely alleviate this concern.

The three primary objectives of nuclear safety systems in an accident or unexpected event are

•to shut down the reactor•to maintain it in a safe, shutdown stable condition, and •to prevent the release of radioactive waste during accidents or unexpected events.

Nuclear power plants, according to extensive studies, should be able to sustain a terrorist attack against them like the one that occurred in September 2001 against New York City’s World Trade Center and the Pentagon in Washington, DC.

There is general agreement that human error is perhaps the greatest concern. Safety culture in the workplace is extremely important, but there is evidence that operational practices are not easy to change. Many experts warn that the Fukushima nuclear disaster is a wakeup call that should force a reevaluation of nuclear safety, and there is evidence that is happening. Humans are prone to error, and operators must guard against complacency and avoid overconfidence. Experts argue that the single biggest internal factor in nuclear plant safety is the culture of security among regulators, operators and the workforce.

Divide up into groups, discuss, and make a report:

1)Economics of nuclear reactors2)Proliferation 3)Nuclear waste, environmental issues, pros and cons4)Future – start after cons

Projections of Global Nuclear Generation Capacity through 2030 by the International Atomic Energy Agency (2008). One low and one high projection.

Installed nuclear generating capacity in 2011 and estimated for 2020 and 2035.

Source: OECD Nuclear Energy Agency and the International Atomic Energy Agency.

QuizWhich of the following commercial nuclear reactors are most numerous?

A) Gen I B) Gen II C) Gen III D) Gen III+ E) Gen IV

QuizWhich of the following commercial nuclear reactors are most numerous?

A) Gen I B) Gen II C) Gen III D) Gen III+ E) Gen IV

QuizWhich of the following commercial nuclear reactors are now in operation?

A) Only Gen I B) Only Gen II C) Only Gen III D) Mostly Gen I and II E) Mostly Gen II and III

QuizWhich of the following commercial nuclear reactors are now in operation?

A) Only Gen I B) Only Gen II C) Only Gen III D) Mostly Gen I and II E) Mostly Gen II and III

QuizHow many nuclear reactors are currently under construction in the United States?

A) None B) 1 C) 2 D) 3 E) 5 or more

QuizHow many nuclear reactors are currently under construction in the United States?

A) None B) 1 C) 2 D) 3 E) 5 or more

QuizWhich of the following is not characteristic of a Small Nuclear Reactor?

A) Can be factory built and delivered as needed B) Can be left in place after decommissioning C) Can be used in specialized places like islands or for Disney World. D) Standard, not custom, designed E) Do not necessarily need water for cooling

QuizWhich of the following is not characteristic of a Small Nuclear Reactor?

A) Can be factory built and delivered as needed B) Can be left in place after decommissioning C) Can be used in specialized places like islands or for Disney World. D) Standard, not custom, designed E) Do not necessarily need water for cooling

Chapter 11 Energy Transmission and Storage

Electricity Generation Electricity is normally generated at values of 1000s of volts, but that is not ideal to transmit, so we first have to use transformers to increase the voltage.

Electric Power Transmission We will explain in this chapter why it is best to transmit electricity at values of 500,000 volts or higher. After being transformed at the power plant, the electricity is carefully connected to transmission lines which carry it sometimes long distances, even across international borders like from Canada to the United States or from France to Italy. The high voltage lines send the electricity to an electrical substation.

Electric Power Distribution Once the electricity reaches a substation normally owned by the local utility, the voltage is reduced substantially before being delivered to a local transformer when the voltage is reduced again before being delivered to the customer.

2 22

loss 2 2

P P RP I R R

V V= = =

For a given transmitted power P and resistance R of the transmission line, we minimize the power loss by using the highest possible voltage V. That is why overhead transmission lines have voltages above 100 kV. Values include 230, 345, 500 and 765 kV.

Transmission lines – electrical grid

Electrical energy must be generated as needed; a complex control system is required to match the electrical generation with the demand. The normal supply is provided by the base load, which consists of power plants like nuclear, coal, wind, and solar that cannot be turned on and off quickly. When the demand exceeds the supply, generating plants must be brought online for more supply. When the demand far exceeds the supply, then serious problems can occur, and generating plants and transmission shut down. This causes blackouts which have occurred in the US Northeast in 1965, 1977, 1996, 2003, and 2011. Sometimes rolling blackouts are engineered to prevent more widespread blackouts.