Nuclear power is for creating electrical energy, the use that is being looked at for the Tarsands is to produce steam for injection into the oilsands to release the bitumin, which is neither efficient nor cheap. Nuclear power to just produce steam is like hunting flies with a shotgun.
Delegate Bill Dearborn of Medicine Hat said the oilsands need a nuclear option as a bulwark against any future federal raids on Alberta's resource-based economy.
"We're familiar with these Liberal governments in Ottawa that have imposed unfair taxes on the oil and gas industry in the past,'' he said.
But delegate Don Dabbs said he has participated in a past provincial study on nuclear power and that it's not the way to go to generate steam power for the oilsands.
"A reactor to generate steam is not the principal purpose of a nuclear reactor. It's for electrical energy.
"It's a very expensive source of steam.''Thomas Savery (1650-1715)
Thomas Savery was an English military engineer and inventor who in 1698, patented the first crude steam engine, based on Denis Papin's Digester or pressure cooker of 1679.
Thomas Savery had been working on solving the problem of pumping water out of coal mines, his machine consisted of a closed vessel filled with water into which steam under pressure was introduced. This forced the water upwards and out of the mine shaft. Then a cold water sprinkler was used to condense the steam. This created a vacuum which sucked more water out of the mine shaft through a bottom valve.
BoilersThe high-pressure steam for a steam engine comes from a boiler. The boiler's job is to apply heat to water to create steam. There are two approaches: fire tube and water tube.
A fire-tube boiler was more common in the 1800s. It consists of a tank of water perforated with pipes. The hot gases from a coal or wood fire run through the pipes to heat the water in the tank, as shown here:
In a fire-tube boiler, the entire tank is under pressure, so if the tank bursts it creates a major explosion.
More common today are water-tube boilers, in which water runs through a rack of tubes that are positioned in the hot gases from the fire. The following simplified diagram shows you a typical layout for a water-tube boiler:
In a real boiler, things would be much more complicated because the goal of the boiler is to extract every possible bit of heat from the burning fuel to improve efficiency.
The CANDU reactor design has been developed since the 1950s in Canada. It uses natural uranium (0.7% U-235) oxide as fuel, hence needs a more efficient moderator, in this case heavy water (D2O).**
** with the CANDU system, the moderator is enriched (ie water) rather than the fuel, - a cost trade-off.
The moderator is in a large tank called a calandria, penetrated by several hundred horizontal pressure tubes which form channels for the fuel, cooled by a flow of heavy water under high pressure in the primary cooling circuit, reaching 290ƒC. As in the PWR, the primary coolant generates steam in a secondary circuit to drive the turbines. The pressure tube design means that the reactor can be refuelled progressively without shutting down, by isolating individual pressure tubes from the cooling circuit.
A CANDU fuel assembly consists of a bundle of 37 half metre long fuel rods (ceramic fuel pellets in zircaloy tubes) plus a support structure, with 12 bundles lying end to end in a fuel channel. Control rods penetrate the calandria vertically, and a secondary shutdown system involves adding gadolinium to the moderator. The heavy water moderator circulating through the body of the calandria vessel also yields some heat (though this circuit is not shown on the diagram above).
Steam generator (nuclear power)
From Wikipedia, the free encyclopedia
- This is an article about nuclear power plant equipment. For other uses, see steam generator.
Steam generators are heat exchanger used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops.
In commercial power plants steam generators can measure up to 70 feet in height and weigh as much as 800 tons. Each steam generator can contain anywhere from 3,000 to 16,000 tubes, each about three-quarters of an inch in diameter. The coolant is pumped, at high pressure to prevent boiling, from the reactor coolant pump, through the nuclear reactor core, and through the tube side of the steam generators before returning to the pump. This is referred to as the primary loop. That water flowing through the steam generator boils water on the shell side to produce steam in the secondary loop that is delivered to the turbines to make electricity. The steam is subsequently condensed via cooled water from the tertiary loop and returned to the steam generator to be heated once again. The tertiary cooling water may be recirculated to cooling towers where it sheds waste heat before returning to condense more steam. Once through tertiary cooling may otherwise be provided by a river, lake, ocean. This primary, secondary, tertiary cooling scheme is the most common way to extract usable energy from a controlled nuclear reaction.
These loops also have an important safety role because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the plant as the primary coolant becomes radioactive from its exposure to the core. For this reason, the integrity of the tubing is essential in minimizing the leakage of water between the two sides of the plant. There is the potential that if a tube bursts while a plant is operating; contaminated steam could escape directly to the secondary cooling loop. Thus during scheduled maintenance outages or shutdowns, some or all of the steam generator tubes are inspected by eddy-current testing.
In other types of reactors, such as the pressurised heavy water reactors of the CANDU design, the primary fluid is heavy water. Liquid metal cooled reactors such as the in Russian BN-600 reactor also use heat exchangers between primary metal coolant and at the secondary water coolant.
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