Neutron absorbers properties

Moderators. Neutrons are most effectively slowed by collisions with nuclei of about the same mass. Thus the best moderators are those light atoms which do not capture neutrons. These are H, " He, Be and C. Of these He, being a gas, is insufficiently dense and Be is expensive and toxic, so the common moderators are highly purified graphite or the more expensive heavy water. In spite of its neutron-absorbing properties, which as mentioned above must be offset by using enriched fuel, ordinary water is also used because of its cheapness and excellent neutronmoderating ability. 

German pharmacist Friedrich Strohmeyer Soft metal chemically similar to zinc used in electroplating and for rechargeable batteries neutron-absorbing properties make it useful in nuclear power plants. 

Owing to their neutron-absorbing properties, some benzo fused 1,2-dihydro-1,2-azaborines have been suggested for use as neutron sensitive material in neutron detectors (67MI12100). 

Shipping casks, storage facilities, and process vessels involved in handling fissile materials contain neutronabsorbing materials—either for their neutron-absorbing properties or for structural reasons. These types of systems can be fiilly utilized, safely, only if the neutron absorbers are pnmcrly accounted for in the criticality analyses. The results from measurements on two such materials, copper and cqpper containing 1 wt% cadmium, were. .reported on previously. Since that time, the reactivity worths of several other materials, commonly considered for use as fixed neutron poisons, have been... 

A soluble zinc compound may be added to the coolant as a means of reducing radiation fields within the primary system and to reduce the potential for crud-induced power shift (CIPS). CIPS is caused by the precipitation of a boron-containing species in fuel cmd under certain conditions, and results in an abnormal power shift due to the neutron absorbing properties of the crud. 

HECTOR (heated experimental carbon thermal oscillator reactor) was used to measure the neutron absorbing properties of materials by moving them in and out of the reactor and the measuring the change in activity ... 

Heated experimental carbon thermal oscillator reactor. This was built at Winfirith and became operational in March 1963. Like the oscillator in GLEEP, this was intended to study the neutron absorbing properties of materials. ... 

The effect of the lanthanide contraction on the metal and ionic radii of hafnium has already been mentioned. That these radii are virtually identical for zirconium and hafnium has the result that the ratio of their densities, like that of their atomic weights, is very close to Zr Hf = 1 2.0. Indeed, the densities, the transition temperatures and the neutron-absorbing abilities are the only common properties of these two elements which differ... 

But numerous papers published during rece t decades showed that hydrogen can be a very useful alloying element for production of new materials (such as hydrogen accumulators, neutron absorbers, etc.) or new technologies for alloy processing with improved treatment parameters as well as with the improved final properties of the alloys. ... 

The nuclear reactor also must be shielded against the emission of radioactive material to the external environment. Suitable radiation controls include both thermal and biological shielding systems. Radiation from alpha particles (a rays) and beta particles ((3 rays) has little penetrating power, but gamma rays have deep penetration properties. Neutron radiation is, however, the primary area of risk. Typically, extremely thick concrete walls are used as a neutron absorber, but lead-lined concrete and special concretes are also used. 

Nerve growth factor snake venoms zinc, 6, 613 Neurospora crassa calcium transport, 6, 571 cation transport, 6, 559 Neurosporin, 6, 676 Neurotransmitters secretion calcium, 6, 595 Neutral complexes electrical properties, 6, 143 Neutron absorbers... 

While each of the above technologies offers certain unique advantages, those common to ceramic immobilization include a relative ease in fabrication, a high capacity for actinides or heavy metals compared to other technologies, the capacity for flexibility of feedstock, the ability to add neutron absorber materials for nuclear waste applications, and the ability to control the properties of the final waste form. 

Boron carbide is a relatively inexpensive hard material, which is used for its mechanical properties of strength and extreme hardness in armor-plates for body protection, in sandblast nozzles, and as an abrasive for grinding and cutoff wheels. In nuclear plants, boron carbide is used as the neutron absorbing material of the control rods. 

Boron has two stable isotopes, (80.4% abundance) and °B (19.6%). B has a very high neutron absorption cross section (it is a good absorber of neutrons). This property has been developed for use in the treatment of cancerous tumors in a process called boron neutron capture therapy (BNCT). Boron-containing compounds having a... 

Two naturally occurring isotopes of boron exist boron-10 and boron-11. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. Boron-10 is the isotope with high neutron-absorbing tendencies described earlier under Physical Properties. ... 

Titanium diboride is an advanced ceramic material with properties similar to those of metals such as high thermal and electrical conductivity. The other distinguishing features of this material are its excellent oxidation resistance and chemical corrosion resistance at elevated temperatures. It can be used as an abrasive and oxidation protection coating as well as the electrode material in aluminium refining. In addition, like other borides it can also be used as a neutron absorber. 

Samarium is used to dope calcium fluoride crystals for use in optical masers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors. The metal is priced at about 3.50/g (99.9%). Little is known of the toxicity of samarium therefore, it should be handled carefully. 

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