Pre-conceptual design and preliminary neutronic analysis of the proposed National Spallation Neutron Source (NSNS) Page: 4 of 11
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Figure 1. Cutaway view of target facility
Therefore the peak displacement damage rate in the window of a
liquid target is greatly reduced compared to the peak value in a
solid target. Mercury was selected as the reference liquid target
material because it: (1) is a liquid at room temperature, (2) has
good heat transport properties, and (3) has high atomic number
and mass density resulting in high neutron yield and source
The mercury target shown in Fig. 2, has a width of 0.4 m, a height
of 0.1 m, and a length of 0.65 m. The mercury is contained within
a 316 stainless steel structure. Mercury enters from the back of the
target, flows along the two side walls to the front surface (proton
beam window), and returns through a rectangular passage in the
middle of the target. The target window, i.e., portion of the target
structure in the direct path of the proton beam is cooled by
mercury which flows through the passage formed between two
walls of a duplex structure. In this way, the window cooling and
transport of heat deposited in the bulk mercury are achieved with
separate flow streams. This approach is judged to be more reliable
and efficient (minimal pressure drop and pumping power) than
using the bulk mercury to cool the window. Also, the duplex
structure used for the window has significant structural
advantages that help to sustain other loads. Beside serving as flow
guides, the baffle plates used to separate the inlet and outlet flow
streams help to maintain the structural stability of the target. A
safety shroud is provided around the mercury target to guide the
mercury to a dump tank in the event of a failure of the target
container structure. The shroud is a water-cooled duplex
structure made from 316 stainless steel.
Figure 2. NSNS Mercury Target
Cryogenic Moderators -
water Cooled Shroud
Beam Ambient Temperature Modeator
Beryliu Iner eflelor
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Johnson, J.O.; Barnes, J.M. & Charlton, L.A. Pre-conceptual design and preliminary neutronic analysis of the proposed National Spallation Neutron Source (NSNS), article, March 1, 1997; Tennessee. (digital.library.unt.edu/ark:/67531/metadc674193/m1/4/: accessed February 17, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.