What is Neutron Radiation?

Neutron radiation is a rare process that occurs when the nucleus stabilizes by reducing one mass unit and only occurs in the range of fission products (relative atomic mass 70-160). Neutron radiation is usually released from the nucleus by artificial means.

The type of neutron-matter interaction depends mainly on the energy of the neutron. In radiation protection, neutrons can be divided into slow neutrons with an energy of less than 5 keV, neutrons with an energy range of 5 to 100 keV, and fast neutrons with an energy of 0.1 to 500 MeV according to the level of the neutron energy. A large category, in which the energy of slow neutrons is less than 1eV (usually 0.025eV) is also called thermal neutron.

Neutron radiation consists of free neutrons, which can be generated by spontaneous or induced nuclear fission,

When neutrons interact with matter, they mainly interact with the nuclear force in the nucleus, and do not interact with the electrons in the shell. Neutrons have a strong penetrating power when passing through substances, and the danger to the human body is more serious than the same dose of X-rays and gamma rays. After the human body is irradiated with neutrons, the gastrointestinal and male gonads will be severely damaged, the biological effect of inducing tumors is high, and it is easy to cause early death. At the same time, the injured body is susceptible to infection and the degree is heavy. The relative biological effect of the opacity of the eye lens is Or 2 to 14 times of X-rays. Causes hematopoietic organ failure, digestive system damage, and central nervous system damage. Can also cause malignant tumors, leukemias, cataracts and so on. Neutron radiation also has a genetic effect that affects the development of the offspring of the recipient. ^[2]

Neutron bullets can kill personnel in armor protection and buildings within an effective range. The injured person did not die immediately, but died slowly and very painfully. Without the medical treatment of the injured person, it could take up to 7 days.

The neutron flow acts for a short time. For battlefields that have been attacked by tactical nuclear weapons such as neutron bombs, they can quickly enter the target area to fight without fear of radioactive pollution.

Neutron radiation shielding process

Radiation protection is very important. In most cases in actual work, fast neutrons are encountered. When fast neutrons interact with matter, the fast neutrons scatter and decelerate first, and then the slow neutrons are absorbed to emit common particles or gamma rays. Therefore, neutron shielding can be divided into the following two processes:

(1) Slow down fast neutrons. Heavy elements or elements with large absorption cross sections and their compounds can be used to slow down neutrons and absorb secondary gamma rays. Among them, heavy elements can block fast neutrons, and elements with large cross sections can simultaneously block fast neutrons and absorb slow neutrons without releasing particles. Commonly used heavy elements are lead, tungsten, iron, barium, etc. Large-section elements that can absorb neutrons are commonly used lithium-6, boron-10, cadmium and their compounds or alloys, such as boron carbide, boron nitride, and lithiated There are also some rare earth elements such as boron. Generally, after fast neutrons are blocked with heavy elements, lighter materials (such as materials containing more hydrogen) need to be used to further slow down the slower neutrons. These materials have good radiation resistance, such as water, paraffin, polyethylene, polypropylene, polystyrene, polyester and other polymers. At the same time, they have a high content of hydrogen atoms that can block neutral neutrons and do not produce -ray secondary effect.
(2) Absorb slow neutrons. The neutron hazard can only be completely eliminated after slow neutron absorption. Common materials containing lithium or boron, such as lithium fluoride, lithium bromide, lithium hydroxide, boron oxide, boric acid, and boron carbide, etc. absorb slow neutrons and reduce the generation of secondary gamma rays. Obviously, the neutron radiation protection suit must have the function of slowing down fast neutrons and absorbing them. After mixing the fast neutron moderating material and the fine powder of the slow neutron absorbing substance, the spun neutron radiation-proof fiber or non-woven fabric is added during the spinning process or coated on the fabric in the way of finishing to obtain an excellent performance. Low and medium energy neutron shielding materials can achieve good neutron protection effect through reasonable clothing structure design. ^[3]

Neutron radiation protection equipment

At present, most of the equipment that generates neutron radiation is manually operated, so neutron radiation protective clothing is particularly important to ensure the safety of this type of staff. Neutron radiation protective clothing has been widely used in nuclear material refineries, petroleum logging instrument calibration rooms, nuclear reactor buildings, nuclear protection of new tanks, neutron protection for chariot crews and chemical defense commanders, road neutron measurement sites, Protection of medical staff and patients in the spatula treatment room and protection of defense ship building staff.