Nuclear reactors gadolinium

Gadolinium Oxide, Gd203, mw 362.52 wh to cream-colored powder, sp gr 7.407 at 15/4°, mp 2330° hygroscopic and absorbing C02 from the air in sol in w sol in acids except HF. Used in nuclear reactor control sods, neutron shields, catalysts, dielectric ceramics, filament coatings, special glasses and as P... 

Gadolinium s extremely high cross section for thermal neutrons, 4.6 x 10 24 m2 (46,000 bams) per atom, is the reason for its extensive use in the nuclear eneigy (see Nuclear reactors). It is used as a component of the fuel or control rods, where it acts as a consumable poison, a trap for neutrons in the reactor (39). 

Because europium, gadolinium (Gd), and dysprosium (Dy) are good absorbers of neutrons, they are used in control rods in nuclear reactors. Promethium (Pm) is the only synthetic element in the lanthanide series. 

It is obtained in small quantities from nuclear reactors and is used in specialized miniature batteries. Samarium (Sm) and gadolinium are used in electronics. Terbium (Tb) is used in solid-state devices and lasers. 

Gadolinium is a silvery white metal, malleable and ductile, with a white oxide and colorless salts. It is relatively stable in dry air but tarnishes in moist air and reacts slowly with water. Gadolinium has the highest thermal neutron capture cross-section of any element and is used as a component of control rods in nuclear reactors. It is ferromagnetic and used in equipment for magnetic cooling. 

Boron consists of two isotopes, B and B. The former, which accounts for 20% of natural boron, is a very strong neutron absorber and for that reason is used for the control rods in nuclear reactors and as a shield for nuclear radiation. A1 cm thick layer of boron enriched in the isotope B gives the same shielding action against neutrons as 20 cm of lead or 5 m of concrete (an alternative to boron is gadolinium). The pure boron isotope is however very expensive. In many applications natural boron is... 

In addition to their intrinsic theoretical interest and as models for other systems, the oxides of the rare earths have many practical uses. They are receiving attention in industry because of their potential use as control rods for nuclear reactors where samarium, gadolinium and europium oxides are incorporated into cermets or are used in fuel elements as burnable poisons. Radioactive europium and thulium oxides are used as heat sources and promethium oxide as a jS source. Lanthanide oxide catalysts may be... 

Gadohnium is the 40th most abundant element on Earth and the sixth most abundant of the rare-earths found in the Earths crust (6.4 ppm). Like many other rare-earths, gadolinium is found in monazite river sand in India and Brazil and the beach sand of Florida as well as in bastnasite ores in southern California. Similar to other rare-earths, gadolinium is recovered from its minerals by the ion-exchange process. It is also produced by nuclear fission in atomic reactors designed to produce electricity. 

Gadolinium oxide is used in control rods for neutron shielding in nuclear power reactors. It also is used in filament coatings, ceramics, special glasses and TV phosphor activator. The compound also is used as a catalyst. 

By contrast, the metals have so far found only limited application save for one important use in the field of nondestructive testing. With the proliferation of research reactors over the past decade, neutron radiography has become a practical tool in the aerospace, nuclear and engineering industries, yet without the availability of gadolinium and dysprosium in the form of thin foils, the technique would be severely restricted. 

Advanced fuel assembly (AFA) has been developed both for replacement of standard fuel at the operating reactors, and for new nuclear power plants with advanced WWER. The main difference of AFA, being the most effective as to economy, from standard fuel is application of only zirconium stmctural materials in the assembly active part. This allowed (in combination with specially developed refuelling patterns) to reduce the specific consumption of uranium approximately by 13%. Application of gadolinium burnable absorber instead of boron absorber allows to reduce this index by approximately 5% more. Application of AFA allows also to reduce enrichment of makeup fuel. Using of uranium-gadolinium fuel allows to reduce neutron fluence to the reactor vessel, to improve flexibility of fuel cycle, to exclude expenses for operation and storage of burnable absorber rods. 

Two of the Gd isotopes, namely, d and Gd, have excellent neutron-capture characteristics but are present in nature in only low concentrations. As a result, Gd has a very fast burnout rate and has limited use as nuclear control rod material in reactors and power plants [2]. Compounds of gadolinium are used in making phosphors for color TV tubes. The metal has superconductive properties. As little as 1% of the element has been found to improve the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation. The ethyl sulfate compound has extremely low noise characteristics. Hence, it may find use in multiplying the performance of high-frequency amplifiers. 

For finite reactor analysis, much of the contributors behaviors are lumped into few-group nuclear constants that are numerically fitted to values of various core parameters such as exposure, uranium and 11th1 urn concentrations, fuel temperature, coolant and moderator temperatures and densities and gadolinium concentrations in the moderator. The finite reactor analysis provides an examination of the reactivity effects of the power distributions since it models the radial and axial assembly distributions in the core. 

The Supplementary Safety System (SSS) is a backup shutdown system for the SRS reactors. The SSS can be actuated either manually or by the Automatic Backup Shutdown-Gang Temperature Monitor (ABS-GTM) or the ABS-Safety Compiuter. When actuated, the SSS injects a solution of gadolinium nitrate dissolved in heavy water into the reactor moderator through six spargers near the center of the reactor. Moderator circulation and diffusion distribute the nuclear poison through the reactor core. 

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