Vacuum and radiation-hardened gear motors and resolvers are utilized by
the Australian Nuclear Science and Technology Organization (ANSTO) on research
instruments at the organization's Bragg Institute research facility. To perform
reliably in the extreme conditions, all the organic materials used in the
standard motor design needed to be evaluated against specific radiation dose
requirements.
Everything from the magnets and bearings
to the glue and lubricants was analyzed. Radiation-resistant materials were substituted,
if required, to withstand the radiation generated to test materials and
equipment. Teflon motor lead wires, for example, don't perform well under
radiation and were replaced with a specialized material called peek to maintain
high system reliability.
In the final design, specialty motors and
resolvers from Empire Magnetics
are being used in ANSTO's TAIPAN and SIKA 3-axis spectrometers, its PELICAN
cold-neutron time-of-flight spectrometer and the QUOKKA small angle scattering
instrument. These instruments perform neutron scattering, and are essentially
scientific research tools for physicists, engineers and chemists. The
instruments allow the atomic, electronic, and magnetic structure of materials
to be analyzed on a resolution and depth not possible with any other
instruments.
The TAIPAN instrument is a triple axis
instrument used for measuring phonons or "solid state waves" which can give
scientists insight into processes such as high temperature superconductivity.
This instrument is closest to the core of the nuclear reactor and has a moment
of inertia of 15,000 kgm2. High torque, high inertia motors are
needed to function in a radion environment with a high degree of reliability
and quality.
In a nuclear research facility, all electrical
control components are subjected to extreme environmental conditions, including
gamma and neutron radiation. Components are embedded inside radiation shielding
that is keyed together in large monolithic slabs. If a motor fails, the instrument
is shut down and engineers wait up to a week for the radiation to die down. The
radiation shielding is then removed; the motor is replaced; and the shielding is
keyed back together, a process that can take up to two weeks.
Empire Magnetics' radiation-hardened motors
are available with continuous output torque ranging from 15 to 400 inch-lb (1.7
to 46 Nm) or momentary peak torque from 30 to 1000 inch-lb (3.4 to 113 Nm). Motors
are rated for a total standard accumulated dose of 2x108 rads (radiation
absorbed dose), with ratings to 1x109 rads available on a custom basis.
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