The Materials Testing Reactor Page: 6
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To remove the duneiy plug or experimental plug* which have boon irradiated present*
the problem of adequately shielding the equipment os it is withdrawn. Fc*» tM*
purpose a large handling cask filled with lead and mounted on a wheeled carriage la
provided. Although this cask weigh* about thirty tone It can be very accurately
aligned with the bean hole eo that the experiment or dunay plug can be easily
pulled out of the reactor and into the cask. After the cask has been loaded it
can be wheeled outside the reactor building and the radioactive equipment can be
stored In a shielded steel tube. Removal or Insertion of the radioactive plug is
performed manually by moans of a long rod* After the plug has been placed in the
e&sk radiation doors In both the beam hole and cask are closed before the cask is
pulled away from thj face of the reactor.
All control and safety signals pertinent to the operation of the reactor, regard-
less of where initiated, result finally in a movement of the control or shim rods.
In general, safety signals con request four things to happen2 l) slow setback,
2) fast setback, 3) reverse, and 4) scram. These are merely various methods of ef-
fecting a control of the power level, differing principally in the speed of response.
To start the reactor, first the process vator circulation and air exhaust systems
are placed in operation, then the control rods and shim rods are gradually with-
drawn from the lattice. Various interlocking time delay devices prevent the too
rapid withdrawal of control rods, *io that the flux buildup at any time can be kept
under close watch by the operator and the instruments. If the controls were with-
drawn too rapidly it ii possible that the reactor could become prompt critical tfm\
I _but all parts of the control systom are designed so that this
will not happen. Far example, the shim safety rods ore attached to the control
drive mechanl8n by electromagnets. If the rate of neutron multiplication becomes
too great the electromagnets are automatically deenergised, allowing the ehim rods
to fall into the lattice and scram the pile^ j Additional safety in
operation is also provided by an arrangement for monitoring the water which flows
past each fuel element. The monitor tubes measure the temperature and flow rate
of the water and collect a small sample of the each element, which is
then checked by an ionization chamber. If a fuel9; ^should warp and cut off the
water flow or if it should rupture and release fissionable materials into the water,
automatic devices will iaaediately warn the operator and shut down the reactor.
Safety devices rre also incorporated in the reactor cooling and air exhaust systems.
The water and air streams are automatically checked for flow rate and for radio-
activity and if the established quantities are not maintained tM instruments assume
control of the reactor to prevent damage.
Operation of the reactor involves the problem of disposing of the large amount of
heat which is generated. Most of the heat io removed in the primary process water
cooling system and a smaller portion is removed by air cooling. Process water
which circulates through the reactor in the primary system is never allowed to mix
with the secondary cooling water since contamination would otherwise result. Water
warmed in the reactor is circulated through flash evaporators and the beat is re-
moved by the secondary water stream which circulates through tubes in the evaporators,
A positive head of water is maintained on the inlet side of the reactor by an elevated
storage tank, with flow to the reactor controlled by a manually operated valve located
upstream. After passing through the reactor tank system the heated water enters a
seal loop, which is high enough to prevent draining of the reactor in the event of
water failure, and then into a seal tank in the process water building. A radia-
tion recorder is provided on this line near the entrance to the seal tank to check
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Weber, L. J. The Materials Testing Reactor, report, September 24, 1953; [Oak Ridge, Tennessee]. (https://digital.library.unt.edu/ark:/67531/metadc172781/m1/6/: accessed May 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.