Answer the following questions by typing your answers into a text file and posti

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Answer the following questions by typing your answers into a text file and posting it back here as a .doc (word document file). For Help, use the Help & Resources menu link. 1. What is the number of neutrons in the U-235 nucleus? 2. When a neutron in absorbed by a U-235 nucleus, what is the resulting element, nucleon number and neutron number? 3. Carbon-14 decays emitting an electron (beta decay). What is the resulting element, nucleon number and neutron number? 4. Iodine-131 is radioactive with a half-life of 8.05 days. How long does it take for a sample to decay to one-eighth of its original number of nuclei? 5. U-236 is unstable and undergoes fission into Ba-141 and Kr-92. Determine the number of neutrons which are emitted in the process. 6. What is the function of the moderator in a nuclear reactor? 7. In a few sentences, explain the operation of a breeder reactor. 8. Do a search for information about the Pebble Bed reactor. What are the features that distinguish it from the typical water-cooled reactor?

Explanation / Answer

8.

The Pebble Bed Modular Reactor (PBMR) is a particular design of pebble bed reactor under development by South African company PBMR (Pty) Ltd since 1994. The project entails the construction of a demonstration power plant at Koeberg near Cape Town (now postponed indefinitely[1]) and a fuel plant at Pelindaba near Pretoria. The PBMR is characterised by inherently safe features, which mean that no human error or equipment failure can cause an accident that would harm the public.[2]

Heat from the PBMR can be used for a variety of industrial process applications, including process steam for cogeneration applications, in-situ oil sands recovery, ethanol applications, refinery and petrochemical applications.[3] The high temperature heat can also be used to reform methane to produce syngas (where the syngas can be used as feedstock to produce hydrogen, ammonia and methanol); and to produce hydrogen and oxygen by decomposing water thermochemically.

The PBMR is modular in that only small to mid-sized units will be designed. Larger power stations will be built by combining many of these modules. As of 2008, 400MWt was emerging as an optimum module size, considerably larger than the original concept size.[citation needed] The PBMR is fuelled and moderated by graphite fuel spheres each containing TRISO coated low enriched uranium oxide fuel particles. There are 15000 fuel particles per fuel sphere the size of a billiard ball. "Each fuel pebble contains 9 g of uranium, and this holds enough generation capacity to sustain a family of four, for a year. Five tons of coal and up to 23 000 m3 of water will be required to generate one pebble's energy.

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