Missouri S&T Nuclear Reactor

On your way to a degree, you will have a number of opportunities for hands-on experience with the Missouri S&T Nuclear Reactor, the first on-campus reactor in the state. The reactor, a 200-kilowatt swimming pool-type nuclear reactor, has been in operation since 1961.

The reactor pool contains 32,000 gallons of high-purity water, and is 9 feet wide, 19 feet long and 27-to-30 feet deep. The reactor core sits under 19 feet of water on a grid plate suspended from a movable bridge above the pool. The core consists of approximately 19 fuel elements and four control rods. Fuel elements each contain between nine and 18 fuel plates and have dimensions of three inches by three inches by three feet. Each fuel plate contains 12.5 grams of low-enriched Uranium-235. Fuel plates run the length of the fuel element and are 0.06 inch thick.

Control of nuclear reactions in the core are achieved using four control rods. Three of the control rods are safety rods, made of stainless steel containing natural boron, which is a strong neutron absorber. These rods are used for a coarse reactor control and safety shutdowns, or "scrams". The reg rod is made of just stainless steel and provides fine power control.

The Missouri S&T Reactor is equipped with several experimental facilities designed for research and laboratory activities. The graphite thermal column consists of a large (3.5 foot by 3.5 foot by five foo) graphite block, which provides an excellent source of slow neutrons. The beam port facility is a six inch diameter aluminum tube, which can be positioned between the reactor core and the ground floor experimental area, thus providing a convenient "beam" of high-energy neutrons for experiments. Several irradiation facilities are available, including two pneumatically controlled facilities. These facilities (called rabbits) allow samples to be remotely inserted into and removed from the reactor core for a preset irradiation time. One of the rabbit facilities is lined with cadmium, which effectively "screens-out" low-energy neutrons while letting high-energy neutrons through to bombard the sample. Several other irradiation facilities exist by which samples can be manually inserted into the core region or at the edge of the core.

The reactor facility is available for use by students, faculty and outside researchers. Use of the reactor by both college and high school students outside of the university is strongly encouraged. Anyone interested in participating in reactor-related laboratories; science projects and/or research projects should contact the Missouri S&T Nuclear Reactor director.

"The Blue Glow"(Cherenkov Radiation)

A brilliant blue glow engulfs the Missouri S&T reactor core when it is operating at a high power. This effect is known as Cherenkov radiation, named after the Russian scientist who developed the theory explaining the phenomena.

At full power (200 kW), the reactor core produces approximately 6.4E+15 fissions per second. Each fission event liberates a tremendous amount of energy. Part of this energy is carried away by fission products, which decay, producing high- energy beta particles. Often, beta particles are emitted with such high kinetic energies that their velocities exceed the speed of light in water. When this occurs, blue light is emitted and the reactor core "glows blue".

While no particle can exceed the speed of light in a vacuum (3.0E+8 m/sec), it is possible for a particle to travel faster than light in certain mediums, such as water. The speed of light in a particular medium is related to the speed of light in a vacuum and by the index of refraction. Water has an index of refraction of 1.3; thus the speed of light in water is 2.3E+8 m/s. Beta particles with kinetic energies in excess of 0.26 MeV travel at speeds in excess of 2.3E+8 m/s.

When the charged beta particle moves through water it tends to "polarize" (or orient) the water molecules in a direction adjacent to its path, thus "distorting" the local electric charge distribution. After the beta particle has passed, the molecules realign themselves in their original, random charge distribution. A pulse of electromagnetic radiation in the form of blue light is emitted as a result of this "reorientation." When the speed of the beta particle is less than the speed of the light, the pulses tend to "cancel" themselves by destructive interference; however, when the speed of the beta particle is greater than the speed of light then the light pulses are "amplified" through constructive interference. The phenomenon is analogous to the acoustic "sonic boom" observed when an object exceeds the speed of sound in air.

The intensity of the blue glow is directly proportional to the number of fissions occurring and the reactor power level. This property is utilized in Cherenkov detectors that measure the magnitude of Cherenkov radiation produced in a detector made of Lucite.

Cherenkov radiation becomes visible in the Missouri S&T Reactor core at a power of about 6 kW. At 200 kW the core glows brilliantly with a soft blue glow. The blue glow continues for some time after the reactor has been shut down due to the decay of fission products.