Process zirconium alloys

Above 40 wt % hydrogen content at room temperature, zirconium hydride is brittle, ie, has no tensile ductiHty, and it becomes more friable with increasing hydrogen content. This behavior and the reversibiHty of the hydride reaction are utilized ki preparing zirconium alloy powders for powder metallurgy purposes by the hydride—dehydride process. The mechanical and physical properties of zirconium hydride, and thek variation with hydrogen content of the hydride, are reviewed in Reference 127. 

Elektron A family of processes, operated by Magnesium Elektron, UK, for making magnesium, magnesium-zirconium alloys, and zirconium chemicals. In the 1920s and 30s, the names elektron and elektronmetall were used colloquially in Germany for magnesium metal. 

Even sub-ppm levels of some elements can affect properties and processing of steel and other alloys. The analysis of low- and high-alloy steels for environmentally important elements (Cd, Hg) as well as elements that affect the steel (Sb and Bi, for example) has been discussed [343]. ICP-MS has been used for semiquantitative and quantitative measurement of Gd, Sm, and Th in zirconium alloys [344]. 

Nuclear fuel rods consist of uranium oxide pellets contained in zirconium alloy or steel tubes. As the fission process proceeds, uranium is used up and fission products accumulate. A lot of these fission products are good neutron absorbers and reduce the efficiency of the fission process (by absorbing neutrons before they reach uranium atoms) so that the rods are removed for reprocessing before all the content has undergone fission. Fission of a atom produces two lighter atoms of approximate relative atomic masses around 90-100 and 130-140, with the main fission products being the intensely radioactive and short lived I (fi 8 d), °La, Pr, Zr, Ru, and Nb, and longer-lived... 

The Idaho Chemical Processing Plant is a versatile, multipurpose facility used for recovering highly enriched uranium from a variety of fuels in naval propulsion, research, and test reactors. Materials processed [Al] include aluminum-alloyed, zirconium-alloyed, stainless steel-based, and graphite-based fuels. The West Valley plant, although designed primarily for low-enriched uranium fuel from power reactors, also processed plutonium-enriched and thorium-based fuels. It is the only U.S. plant to have reprocessed fuel from commercial nuclear power plants. 

Uranium Dioxide Production. The majority of the world s nuclear reactors are fueled with slightly enriched UOg prepared in the form of dense sintered pellets that are encapsulated in small bore tubes of zirconium alloy or stainless steel. Hex at the required enrichment(s) is produced specifically for a given reactor charge and the first process step with the UFg is to convert it to UOg having the desired ceramic-grade quality. This means an oxide which after granulation and pelleting can be sintered quickly and uniformly to pellets of near stoichiometric density. 

Uranium dioxide has a number of properties that make it suitable for a fuel. The crystal structure is the fluorite (CaF2) type, similar to that of calcia-stabilised zirconia, and is stable to temperatures in excess of 2000 °C. Because it is a ceramic oxide, the material is refractory, chemically inert and resistant to corrosion Enrichment does not change these features. The oxide powder is pressed into pellets and sintered to a density of about 95 % maximum by traditional ceramic processing technology but is carried out in conditions that minimise risks from radiation effects. The pellets are contained in zirconium alloy (zircaloy) containers, which are then introduced into the reactor. The moderator, which... 

Raynor, W. M. Some Aspects of the lo de or Hot Wire Process for Manufacture of Zirconium. A.S.M. Symposium on Zirconium and Zirconium Alloys, Los Angeles... 

A soluble poison was first ai lied in the head-end process for highly enriched uranium-zirconium alloy fuel. The dissolver was basically a 324-mm-i.d. cylindrical slotted fuel .basket-charging chute enclosed in a pear-shaped dissolver shell which was 610-mm i.d. on the lower portion and 1041-mm I.d. on the top section. The shell was 2.52. m in height. This dissolver was essentially the same as used previously without soluble poison but with the appropriate safe mass loading. Use of... 

This paper discusses how the safe U mass and boron limits were determined for toe zirconium fuel dissolver at the Idaho Chemical Processing Plant (ICPP). This vessel, which has a S08-mm (20-in.)-o.d. cylinder with a complicated internal structure (Fig. 1), uses borated hydrofluoric acid to dissolve highly enriched uranium-zirconium alloy fuete. 

The operations and facilities include ore exploration (not included in NFCIS list), mining, ore processing, uranium recovery, chemical conversion to UO2, UO3, UF4, UFg, and uranium metal, isotope enrichment, reconversion of UF to UO2 (after enrichment), and fuel fabrication and assembly that are all part of the front end of the NFC. The central part of the NFC is the production of electric power in the nuclear reactor (fuel irradiation). The back end of the NFC includes facilities to deal with the spent nuclear fuel (SNF) after irradiation in a reactor and the disposal of the spent fuel (SF). The spent fuel first has to be stored for some period to allow decay of the short-lived fission products and activation products and then disposed at waste management facilities without, or after, reprocessing to separate the fission products from the useful actinides (uranium and plutonium). Note the relatively large number of facilities in Table 2.1 dedicated to dealing with the spent fuel. Also listed in Table 2.1 are related industrial activities that do not involve uranium, like heavy water (D2O) production, zirconium alloy manufacturing, and fabrication of fuel assembly components. 

Preparation of unstabilized zirconia. Zirconia is usually produced from zircon flour. Although the carbochlorination of zircon produces zirconium tetrachloride that can be oxidized to yield zirconia, such a method is only restricted to the production of zirconium metal (see Zirconium and Zirconium alloys). Therefore, to produce zirconia from zircon, the first step is to convert zircon to zirconyl chloride dihydrate. The process starts with the preparation of disodium metazirconate (Na ZrOj) by digesting zircon into molten sodium hydroxide as follows ... 

---