NUCLEAR REACTOR CHEMISTRY

In nuclear chemistry, a fission reaction (see atomic energy) may be initiated by a neutron and may also result in the production of one or more neutrons, which if they reacted in like manner could start a chain reaction. Normally, moderators such as cadmium rods which absorb neutrons are placed In the reactor to control the rate of fission. 

All over the world, 432 nuclear power reactors are under operation and more than 36 GW of electricity could be produced as of December 31, 2001. There are several types of reactors such as boiling water reactor (BWR), pressurized water reactor (PWR), Canada deuterium uranium (CANDU), and others. In these reactors, light water is normally used not only as a coolant, but also as a moderator. On the contrary, in CANDU reactors, heavy water is taken. It is widely known that the quality control of coolant water, the so-called water chemistry, is inevitably important for keeping the integrity of the plant. 

A frequently asked question is What are the differences between nuclear physics and nuclear chemistry Clearly, the two endeavors overlap to a large extent, and in recognition of this overlap, they are collectively referred to by the catchall phrase nuclear science. But we believe that there are fundamental, important distinctions between these two fields. Besides the continuing close ties to traditional chemistry cited above, nuclear chemists tend to study nuclear problems in different ways than nuclear physicists. Much of nuclear physics is focused on detailed studies of the fundamental interactions operating between subatomic particles and the basic symmetries governing their behavior. Nuclear chemists, by contrast, have tended to focus on studies of more complex phenomena where statistical behavior is important. Nuclear chemists are more likely to be involved in applications of nuclear phenomena than nuclear physicists, although there is clearly a considerable overlap in their efforts. Some problems, such as the study of the nuclear fuel cycle in reactors or the migration of nuclides in the environment, are so inherently chemical that they involve chemists almost exclusively. 

Using nuclear chemistry, scientists today can change one element into another and even produce elements artificially. How are elements made artificially Some are produced as by-products in nuclear reactors. However, most are made by bombarding nuclei with small particles that have been accelerated to high speeds. This is done mainly in three instruments, shown in Figure 21.19. 

Many branches of chemistry are involved in nuclear medicine. Nuclear chemistry has developed accelerators and reactors for radionucUde production. Inorganic chemistry has provided the expertise for the development of metal-based radiopharmaceuticals, in particular, Tc radiopharmaceuticals, whereas organic chemistry has provided the knowledge base for the development of PET radiopharmaceuticals labeled with F, "C, and 0. Biochemistry... 

With the development of nuclear reactors and charged particle accelerators (commonly referred to as atom smashers ) over the second half of the twentieth century, the transmutation of one element into another has become commonplace. In fact some two dozen synthetic elements with atomic numbers higher than naturally occurring uranium have been produced by nuclear transmutation reactions. Thus, in principle, it is possible to achieve the alchemist s dream of transmuting lead into gold, but the cost of production via nuclear transmutation reactions would far exceed the value of the gold. SEE ALSO Alchemy Nuclear Chemistry Nuclear Fission Radioactivity Transactinides. 

The discovery of radioactivity a century ago opened up a new field in science, that of the atomic nucleus, which culminated 40 years later in the discovery of fission, and its practical consequences in the form of nuclear weapons and nuclear power reactors. That remains still die focus of news media as it influences international politics and national energy policies. However, nuclear science has contributed much more to our daily life as it has penetrated into practically every important area, sometimes in a pioneering way sometimes by providing conqiletely new solutions to old problems from the history of the universe and our civilisation to methods of food production and to our health from youth to old age. It is a fascinating field continuously developing. Nuclear chemistry is an important part of this. 

Otto Hahn (Germany) for his discovery of the fission of heavy nuclei. Hahn s and his colleague s work discovered nuclear fission, and in particular that uremium could be split in a chain reaction by nuclear fission. This discovery was perhaps recognized as much for its importance as it was for its potential cbnger to society if not properly used and controlled, and Hahn himself was keenly aware of the potential for danger. Nonetheless, this discovery paved the way for much future research into nuclear chemistry, as well as for the development of modern nuclear reactors. 

Although you may immediately think about nuclear reactors for energy, or nuclear bombs and their incredible devastation, concepts in nuclear chemistry are applied for many other, less dramatic purposes, one such example is carbon dating of ancient materials (see Chapter 4). 

The majority of chemistry focuses on an atom s electrons and how they interact with one another (bonding, orbitals, and so on). All these interactions, however, don t hold a candle to the powerful interactions that occur within the atom s nucleus. If you need proof, go stand outside in the sunlight for a few minutes. The heat that you feel is the result of our solar system s massive nuclear reactor, a.k.a. the Sun Thankfully, that reaction is situated millions of miles away otherwise we wouldn t exist. In fact, nuclear reactions are so powerful they can even transform elements into different elements — an Alchemist s dream (too bad it costs more to synthesize gold in using nuclear chemistry than the gold is worth ). 

There is an enormous number of radioanalytical procedures based on solvent extraction and here it is only possible to give a few examples. The examples chosen have been taken from the analysis of samples from the European PHEBUS project performed at the Nuclear Chemistry, Chalmers University of Technology. Very briefly, the Phebus reactor was used to study the products formed in severe reactor accidents. The released gases and aerosols were collected in filters and in water at different positions in the experimental setup. 

Another branch of physical chemistry is nuclear chemistry. Nuclear chemists work with radioactive materials, which may occur naturally or be produced artificially in nuclear reactors. Nuclear chemists study the properties of these substances and investigate ways in which radioactive materials may be useful in a wide range of appUcations, including medicine and agriculture among other fields. 

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