SSC environmental radiation shielding Page: 4 of 105
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The environmental radiation shielding requirements of the SSC have been
evaluated using currently available computational tools that incorporate the well
known processes of energy loss and degradation of high energy particles into
Monte Carlo computer codes. These tools permit determination of isodose con-
tours in the matter surrounding a source point and therefore the specification
of minimum thicknesses or extents of shielding in order to assure annual dose
equivalents less than some specified design amount. For the general public the
annual dose equivalent specified in the design is 10 millirem, small compared to
the dose from naturally occurring radiation.
The types of radiation fall into two classes for the purposes of shielding
determinations-hadrons and muons. The sources of radiation at the SSC of
concern for the surrounding environment are the interaction regions, the spe-
cially designed beam dumps into which the beams are dumped from time to
time, and beam clean-up regions where stops remove the beam halo in order to
reduce experimental backgrounds. A final, unlikely source of radiation considered
is the accidental loss of the full beam at some point around the ring. Conservative
choices of a luminosity of 103 cm2s1 (ten times the design value) and a beam
current three times design (corresponding to 4 x 1014 protons in each circulating
beam) have been made in calculating the required shielding and boundaries of
the facility. In addition to determination of minimum distances for the annual
dose equivalents, the question of possible radioactivity produced in nearby wells
or in municipal water supplies is addressed. The designed shielding distances and
beam dumps are such that the induced radioactivity in ground water is safely
smaller than the levels permitted by EPA and international agencies.
A primary quantity resulting from this study is the recommended minimum
radius of 30 feet of light earth or similar shielding material outside of the 10-foot
diameter tunnel of the SSC. (The thickness may be less if the soil is denser.)
Another important distance in the plane of the accelerator is the recommended
secondary (muon) shielding, outward from the tunnel all around the ring. Near
the interaction regions and the beam dumps longer regions of land must be
reserved for muon shielding. The behavior of the muons is such that the land
above these regions may have shared use provided the plane of the tunnel is 50
feet or more below the surface.
The conclusion of the report is that, with appropriate land acquisition in
the neighborhood of the technical parts of the accelerator, the facility can be
operated in a safe manner with respect to environmental radiation exposure to
the general public.
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Jackson, J.D. SSC environmental radiation shielding, report, July 1, 1987; California. (https://digital.library.unt.edu/ark:/67531/metadc618504/m1/4/: accessed March 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.