A substance that absorbs the absorption cross section of a large neutron.
Boric acid is a substance with large neutron absorption cross section。 It is mainly used in reactor to regulate reactivity。 Adding appropriate amount of boric acid can reduce reactivity。
The natural boron has two stable isotopes, that is, ~ (10) B and ~ (11) B, the abundance is 19.78% and 80.22% respectively. ~ (10) B has a unique characteristic of high absorption of neutron, the absorption cross section of ~ (10) B for thermal neutron is 3837 BA (1b=10, Pa). The absorption cross section of natural abundance boron is close to 750 Ba, and ~ (11) B is only 0.005 Ba, so ~ (10) B absorption cross section of thermal neutron is more than 5 times of natural abundance boron, is more than 20 times of graphite, is tradition The protective material is more than 500 times the concrete.
That is to say, boron -10 isotope is an efficient thermal neutron absorber. Therefore, in nuclear power plants, it is indispensable for safety and control systems. Special grade (SQ) boric acid is used in nuclear industry, and has a high proportion of boron -10. Therefore, boric acid can be used to terminate the nuclear reaction, absorb neutrons, and then rapidly solidified cement to block up the area.
It is precisely because of this characteristic of ~ (10) B isotopes that the related products of ~ (10) B isotopes have been widely used in military fields such as military protection, nuclear weapons and nuclear industry.
The addition of boric acid also has a function of vitrification at high temperatures, which allows for the diffusion of radioactive elements. (like glass factory burning glass)
In addition, boron -10 isotopes can also be used in neutron counting tubes, used as protective screens in nuclear reactors, adjusting rods, and also for cancer treatment.
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