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The two important parts for the shielding in the MYRRHA design are the accelerator shielding and the target and subcritical core shielding. The shielding is designed in such a way that the dose to any body working around the shielding of the installation is lower than 1 mSv/year, the dose limit for the public. This means that the dose rate outside the shielding is smaller then 0.5 µSv.h-1, taking into account a working time for a non-exposed worker of 2000 h per year. |
A view of the linear accelerator shielding is given above. The accelerator is placed underground in a tunnel with concrete walls of 60 cm thickness. The dug out soil is used as a top shielding of 4.5 m height along the length of the high energy part of the beam line. |
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The cyclotron shielding needed to meet are requirements is 3 m concrete followed by 3 m soil shielding. A view of the cyclotron and its shielding is shown at the left. |
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The shielding of the spallation target and the sub critical core considers two aspects; the lateral and the top shielding. The lateral shielding is achieved by the lead bismuth eutectic followed by the concrete of the reactor block. The reactor is build underground excluding the possibility of human presence at the side shields. The radiation level after the lateral shield will be so that activation of the soil will be negligible. |
The top shielding is more difficult as the reactor lid is penetrated by the beam line. This provides a streaming path for the neutrons to the reactor hall. Dose levels in the reactor hall will be high excluding the presence of personnel in the hall during operation. The high neutron level will also lead to the activation of the components of the top lid. This together with the possible contamination risk has led to the development of the robotics approach to maintenance activities. |