The Dawn Of Nuclear Energy

Ever since Einstein discovered the famous mass-energy relation and Lise Meitner decoded it as the reason behind energy production by fission, nuclear energy has been cited as the ultimate source for producing loads of energy. The fossil fuel crisis and the rising carbon footprints have put more importance into the development of nuclear energy. Nuclear reactors were first developed in the 1950s and since then work has rarely stopped in the realm of nuclear reactors.

About Nuclear Reactors
The first nuclear reactors were developed with the sole aim of gaining maximum possible energy conversion efficiency. Durability, cost and safety were scarcely part of the primary objectives. But with growing public knowledge of nuclear science and the invisible dangers of radiation coupled with nuclear disasters like the Three Mile Island and Chernobyl, the nuclear power plant engineers have been forced to focus on safety and durability of the reactors in addition to efficient energy production. The economic crisis has also sprung up a new demand of making power plants economically feasible in addition to being energy efficient.

Nuclear reactors are of two types mainly, Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR). New reactor technologies like fast neutron reactors, heavy water reactors and High-temperature gas cooled reactors are replacing these old reactors. Old and new reactors are characterized by generations. The Generation-1 reactors were the primitive ones that were developed in the 1950s and 1960s. The Generation-2 reactors constitute most of the reactors that currently produce commercial power. The Generation-3 reactors are the advanced reactors that were first developed in Japan. These are superior to the second generation reactors in many ways which are outlined below.

New vs. Old reactor technologies
The first key difference between the old and the new reactors is the passive safety procedures incorporated in the latest reactors. This means that the new reactors do not require active human or electro-mechanical device intervention to shut down the reactors when the conditions exceed the allowable limits. For instance,most reactors use cooling water flowing via natural convection for stability. Now humans or devices can fail or make mistakes but gravity always works which makes these reactors passively stable. The new reactors are cheaper in their construction. This reduction of costs has come from the realization that parts can be quickly and much more efficiently manufactured in factories rather than on site. These factory made parts are then shipped to the site. As a result construction has quickened and the new reactors are actually cheaper than the older ones.

Another new philosophy in the development of the new reactors is the favoring of durability rather than efficiency. The reactors are not operated at the highest temperature which leads to a loss in efficiency but prolongs the life of the reactors. This prolonged life of the reactor enables greater returns than the old reactors at the end even though the old ones were more energy efficient. The lower operating conditions also enhance safety. New reactors have simpler designs. Complex old designs were more energy efficient but were prone to failures and accidents owing to the complexity. The new reactors are simple and robust which makes them safe. New reactors also include safety procedures against catastrophes like aircraft impacts, earthquakes and tsunamis. Also the new reactors have more burnable absorbents to extend fuel life which leads to greater energy production.

Spent Nuclear Fuel Storage
The spent nuclear fuel is highly radioactive and it is important to store it safely so that it doesn't have any harmful effects. The two most popular storage methods are:

Spent Fuel Pool: In this, the spent fuel is stored in underwater pools that are about 40-50 feet deep in the ground. At this depth, there are sturdy metal racks that store the fuel along with water. The water cools the fuel and shields the radiation coming out. The metal racks are sometimes given more protective outside covering to further reduce the risk of radiation.

Dry Cask Storage: The spent nuclear fuel that has already been cooled is stored in casks that are steel cylinders which are typically bolted or welded close. The fuel inside is surrounded by inert gas. Each cylinder is further surrounded by a hard concrete structure to further provide radiation shielding. These casks are stored horizontally or vertically.

Safety Issues
Most people and organizations have paranoia of nuclear reactors due to its dangers of releasing harmful radioactive material that emits diseases or death which is invisible to the naked eye. The fears are not all baseless since there are various safety issues that come with nuclear power plants. The main issue is the waste disposal. The waste is radioactive and remains radioactive for several years. The storage methods currently used are safe on the outset but are heavily prone to disasters. Earthquakes can wreck underground fuel pools. Also the water in such pools can boil carrying with it radioactive waste that could be released in the atmosphere. The casks are also vulnerable to impacts and strikes. The new reactors are made pretty safe in operation with passive stability that effectively eliminates the danger of any unfortunate occurrences. However, these reactors are not fool proof to outside interventions. The Fukushima disaster showed how natural calamities can be extremely dangerous. Safety against militants and anti-social elements is also of paramount importance since nuclear fuel/reactor in wrong hands can cause widespread destruction within minutes.

Clearly reactor technology has evolved to a point where energy production by nuclear is considered safe. But we have to keep reminding ourselves of the potential dangers and consistently work towards safety considerations. As the saying goes, an ounce of prevention is worth a pound of cure.