The energy produced by the nuclear reaction is too great. The US atomic bomb attacks on Japan’s Hiroshima and Nagasaki during World War II and the explosion of the Chernobyl nuclear power plant in the former Soviet Union have left people with a deep psychological shadow over the potential damage of nuclear weapons or nuclear facilities. Many people Talk about “nuclear” discoloration.
But there is one thing that may surprise you-the undergraduates of Reed College in the United States actually operate a nuclear reactor! And the major of the undergraduates running this reactor has nothing to do with the nuclear major! We all know that nuclear reactors are very radioactive-nuclear reactors can produce alpha, beta, gamma radiation and neutron radiation. These radiations can cause cell damage and even DNA mutations that can make people sick or even cancer. Therefore, nuclear reactors are the best Managed by professionals. If a nuclear leak occurs accidentally, it will cause very serious damage to the ecosystem around the reactor.
nuclear power plant
Many universities in the world have nuclear reactors for scientific research, but almost all nuclear reactors in universities are managed by nuclear experts, doctors or masters in nuclear majors, and Reed College’s nuclear research reactor is the only one completely operated by undergraduates Nuclear reactors, and Reed College does not have a nuclear engineering department, or even any other engineering majors related to nuclear reactors. The nuclear research reactors of the school are mainly operated by students majoring in physics and chemistry.
These students who have just entered higher education are really bold! Of course, not all undergraduates can participate in the management of this nuclear reactor-students who intend to participate in the management must participate in a one-year nuclear safety seminar, and then the examination by the Nuclear Regulatory Commission, students who pass all the assessments can obtain management qualifications . The assessment is strict and the pass rate is not high. As of November 2018, only about 40 school students have obtained the qualification to manage nuclear reactors.
This nuclear reactor is very safe
Will operating this nuclear research reactor pose a danger to students? Reed College said: The school’s nuclear research reactor is a “zero risk facility”.
Why do you say that?
Nuclear reactors can be divided into three types according to their purposes: nuclear research reactors, nuclear production reactors, and nuclear power reactors. Nuclear research reactors use nuclear radiation generated by reactors for scientific research. They are generally built in universities and research institutes; nuclear production reactors are used to produce and collect elements produced by nuclear fission; nuclear power reactors are used to generate electricity or provide power and are built in nuclear power generation. Stations or various nuclear-powered ships.
Reed College’s Nuclear Reactor
Due to its small scale, nuclear research reactors are mainly characterized by less nuclear fuel and low power, which are much safer than other nuclear reactors. In fact, in the past 50 years, the nuclear reactor at Reed College only consumed 2.5 kilograms of concentrated uranium (20% concentration), and the maximum power of the nuclear reactor was only 250 kW. The enriched uranium (concentration of 2% to 5%) used by large nuclear power plants in a single year can reach several tons, and its power is hundreds of thousands of times that of Reed College’s nuclear reactor.
In addition to its small scale, the design of the Reed College nuclear reactor makes it nearly “zero risk”.
For the core of a nuclear reactor, on the one hand, attention should be paid to timely cooling to prevent the temperature from being too high to cause an explosion. On the other hand, it is also necessary to avoid the temperature of the core material (including fuel, moderator, and coolant) from being too low to ensure the reactor Operating efficiency. In other words, the temperature of the reactor cannot be too high or too low.
For safety reasons, the core fuel of commonly used nuclear reactors has the characteristics of automatically adjusting temperature, but the adjustment of many nuclear reactors has a certain hysteresis, that is, the temperature has increased or decreased, and the power has not immediately increased or Reduce, this will bring certain safety risks.
This problem is particularly prominent in traditional nuclear reactors that use a mixture of enriched uranium and phosphorus as fuel. But Reed College’s nuclear reactor is a uranium-hydrogen zirconium reactor, which uses a mixture of enriched uranium and zirconium hydride as fuel. This mixture is very sensitive to temperature changes—almost as soon as the temperature rises or falls, the adjustment starts immediately. , The safety factor is very high. This is because the hydrogen in the zirconium hydride will be released as the temperature rises, and can be absorbed back when the temperature drops, and these two processes can instantly reverse the temperature change trend of the fuel.
This reactor is dedicated to producing neutrons
Although the nuclear reactor is powerful, its principle is relatively simple: when a uranium 235 atom is bombarded by a neutron, the uranium 235 atom will absorb the neutron, and then split into a xenon atom and a strontium atom, and release two at the same time. Neutrons, or split into a barium atom and a krypton atom, releasing 3 neutrons at the same time. The neutrons produced by the fission bombard other uranium-235 atoms, causing new fission, and finally causing a continuous fission chain reaction. Uranium-235 fission can generate a lot of heat, which can make water boil and turn into water vapor, which drives gas turbines to generate electricity. This is the principle of nuclear power generation.
But the nuclear reactor at Reed College is not used to generate electricity. What do teachers and students use this reactor for? -The answer is neutron radiation. The chain reaction of uranium can produce a large number of neutrons, and neutron radiation can be used to detect elements. Different from other forms of radiation (α, β, γ, x-ray radiation), neutron radiation can activate the element to be measured. The reaction between neutrons and the element to be measured will produce a radionuclide, which will Decay, measuring the relevant data of the radionuclide production and decay of the element to be measured, can accurately identify different elements without separation, purification and other means, greatly improving the detection efficiency of the elements in the sample.
In addition to neutron radiation, nuclear research reactors can also conduct gamma radiation for research projects in biology and other disciplines, such as how radiation causes seed mutation. Since its establishment in 1968, Reed College’s reactor facilities have been used for research and education projects in the Portland area where the school is located, and have played a significant role in advancing the scientific development of the area.