Specialized metallurgical processes – compositions for use therei – Processes – Producing solid particulate free metal directly from liquid...
Patent
1998-07-02
1999-09-28
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Processes
Producing solid particulate free metal directly from liquid...
75338, 75346, 75 1018, 75 1023, B22F 900
Patent
active
059581050
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method of producing metal beryllium pebbles, which are excellent not only in tritium emission power and anti-swelling properties, but also in crash strength and heat transmitting properties.
The metal beryllium pebbles produced according to the invention can be advantageously employed for moderators and reflectors of neutron, not to mention to speak of neutron multiplying materials of nuclear fusion reactor blankets, and further for aerospace structural materials and the like.
BACKGROUND ART
It has been highlighted that metal beryllium pebbles (pebble-like metal beryllium) are used for a neutron multiplying material in a nuclear fusion reactor blanket.
This is due to the fact that, in the nuclear fusion reactor blanket, although formation of one tritium requires one neutron, the collision of one neutron to metal beryllium causes two neutrons to be formed; therefore, use of metal beryllium pebbles for a blanket material enables tritium to be effectively multiplied, which results in expectation of advantageous improvement in nuclear fusion reaction fuel cycle.
Also, such metal beryllium pebbles are useful for moderators and reflectors of neutron in a nuclear fusion reactor blanket.
Further, such metal beryllium pebbles are expected to be employed for aerospace structural materials and the like, by utilizing the light weight and the high melting point properties.
As a method of producing such metal beryllium pebbles, there has been known a method of reducing beryllium fluoride by magnesium (hereinafter referred to as "magnesium reducing method").
The magnesium reducing method, which was developed in the United States of America and in other countries as a method of industrially extracting metal beryllium, is to produce pebble-like metal beryllium by the use of the following reaction formula:
In the above-mentioned magnesium reducing method, the pebble-like metal beryllium is formed in the beryllium fluoride solution, and then floats on the liquid surface of molten beryllium fluoride by the gravity concentration. Thus obtained metal beryllium pebbles are generally not less than 5 mm in particle diameter.
Besides, the metal beryllium pebbles produced by the magnesium reducing method are intermediate products obtained when the metal beryllium is industrially extracted, each of which includes various kinds of impurity elements. In particular, it includes fluorine, magnesium and the like as volatile impurities in large amounts, which possibly causes corrosive gasses to generate. Moreover, the shape of the pebble is not spheric at all, thereby lowering the packing density in the actual device, which reduces the neutron multiplying power to be satisfactorily expected.
Accordingly, in order to solve the above-mentioned problems in the magnesium reducing method, there has been developed a method called rotational electrode process (Japanese Patent Laid-open No. 3-226508, Japanese Patent Laid-open No. 6-228674, and the like).
The rotational electrode process comprises the steps of making an arc or a plasma between a plasma dissoluble electrode and a cylindrical column-like metal beryllium consumable electrode, both of which are disposed in a closed container filled with an inert gas, to thereby melt the leading end of the consumable electrode due to the heat generated by the above arc or plasma, while splashing beryllium droplets due to the centrifugal force caused by the rotation of the consumable electrode to thereby solidify the beryllium droplets in the inert gas atmosphere, providing spherical beryllium pebbles.
The beryllium pebbles obtained by the above process have various advantages. They are not only smaller and more uniform in particle diameter but they are also higher in purity and in sphericity, while being smoother in surface roughness, compared with those obtained by the magnesium reducing method.
Such metal beryllium pebbles effectively function as the neutron multiplying member, as described above; however, radiation of neutrons to the metal beryllium caus
REFERENCES:
patent: 3784656 (1974-01-01), Kaufmann
Ishitsuka Etsuo
Kawamura Hiroshi
Nishida Kiyotoshi
Sakamoto Naoki
Japan Atomic Energy Research Institute
Mai Ngoclan
NGK Insulators Ltd.
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