9. Inherently Safe Reactor Designs

3 the integral fast reactor ifr design the integral

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: IGN The Integral Fast Reactor (IFR) concept builds on the experience acquired from the successful operation of the experimental Breeder Reactor (EBR II), a 40 MW research reactor operated over 25 years by Argonne National Laboratory (ANL). It was sited at the Idaho National Engineering Laboratory (INEL) near Idaho Falls, Idaho in the USA. The experience of EBR II is the basis of other international effort in fast reactors including The Phenix and the Super Phenix in France. The concept also builds on the experience gained in the Fast Flux Test Facility (FFTF) at Hanford in the state of Washington, where the mixed oxide fuel (MOX) as a mixture of UO2 and PuO2 was tested. The IFR offers the advantage of fast reactors in their ability of breeding new fissile fuel, as the old fissile fuel is being consumed. This extends the available supplies of nuclear fissile fuels practically indefinitely. It offers a large degree of inherent safety from two perspectives: 1. The core of the reactor is immersed in a large pool of sodium liquid metal possessing a large thermal inertia, and capable of absorbing the heat generated by the fuel under any credible accident condition. 2. The coolant is operated at atmospheric pressure and is not pressurized like in the gas or water cooled designs. In the case of sudden depressurization of a pressurized coolant it is lost to the system. In the case of water as a coolant, it flashes into steam and is lost. This cannot happen in the case of the IFR since the coolant is operated at atmospheric pressure. If the coolant pumps fail, the reactor naturally shuts itself off, without the need for human intervention. If the secondary steam system shuts off, the reactor shuts itself off even without any control rod movements or actions on the part of the reactor operators. Fig 14: Flow Diagram of the Integral Fast Reactor Concept. One technical difficulty remains in that the liquid metal is chemically reactive with air and water. Thus, the coolant must be covered with an inert gas atmosphere, and double walled heat exchangers tubing must be used to avoid contact between the liquid metal and water. The IFR program devised an ingenious way of using metallic fuels effectively. The use of metallic fuels has been replaced by the use of ceramics as metal oxides to avoid a swelling problem and consequent rupturing of the cladding in earlier metallic fuels. The IFR uses a method for electrorefining the fuel onsite solving two problems at once. It is quicker and cheaper than in traditional fuel reprocessing, and the produced new fuel could be immediately loaded into the reactor core. The reprocessed metallic uranium, plutonium and zirconium fuel is spiked with a small percentage of fission products, making it useless for weapons manufacture and cannot be diverted to non-civilian activities. Thus the fuel is thought to offer nonproliferation characteristics and would be suitable for global deployment. Letting the fuel pellets float freely within the cladding has solved the swelling problem in metallic fuels. This allows them to swell freely. The noble gas fission gases such as Xenon and Krypton are evacuated from the fuel and migrate to a containment area in the head of the reactor. This also solves any problem of cladding rupture that would otherwise result from the pressure buildup caused by these gases. For enhanced heat transfer a little sodium is added to the fuel pellets. The ventilated fuel offers good burnup, compared with the previous metallic fuel designs. It is designed to have its center point temperature below the boiling point of the sodium coolant, due to its good thermal conductivity. As a result, if an accident occurs, the coolant would not boil like in the case of a light reactor system. The IFR seems is the best of any possible breeder design with the lowest doubling time and the highest breeding ratio. The product of fuel reprocessing does not contain any actinides such as uranium or plutonium, which are all recycled back to be burned in the core and produce energy. Accordingly, the fission products will be after about 200 years at the same level of radiological activity as the ores the uranium was initially mined from. The design, shown in Fig. 14, in this way solves the problem of disposing of the long-lived actinides in the waste from light water reactors. The fuel electrorefining process uses high temperature with the uranium and plutonium moved from an anode to a cathode leaving the waste product behind. These impurities collect in the anode compartment or remain dissolved in the electrolytic bath of molten salts. Dissolving the metallic fuel pins in a liquid cadmium bath at 900 degrees F, starts the process. The IFR has been the USA's contribution to programs on fast reactors in the industrialized nations with limited fossil fuel supplies such as Japan, France and the UK. 5. BRAYTON CYCLE CONCEPTS INTRODUCTION Gas cooled reactors using graphite as a moderator material offer a high degree of safety due to the large thermal inertia of the graphite. In addition, the fuel particles are enclos...
View Full Document

Ask a homework question - tutors are online