Speaker
Description
The ISIS Endeavour programme is a mix of new and upgraded neutron and muon instruments at ISIS. Some instruments are completely new such as WISH-II, whilst others are upgrades ranging from minor changes to completely rebuilding large parts of the instrument such as HRPDX. The majority of the neutron instrument projects in the Endeavour programme include requirements for radiation shielding either to protect people and/or to reduce backgrounds.
New build instruments are an opportunity to ensure the shielding is not only fit for purpose but to also consider cost, environmental impact and longer-term reuse and disposal considerations. As an example, for both WISH-II and MUSHROOM instruments a common shielding design was used reducing design costs. We can follow the shielding design process from simplified simulation models focusing on bulk thickness to more detailed models considering penetrations and tolerance gaps. From this we can demonstrate how the shielding meets the dose requirements for the halls to remain supervised areas (<7.5 µSv/h) and that doses are As Low As Reasonably Practicable.
Upgrades have different challenges to new build instruments as there are more constraints such as space, interfacing with remaining parts of the instrument and limitations on materials. Additionally with an old facility such as ISIS the CAD models may not exist or may not match the real facility. There are also past dose rate surveys of the existing instrument and more often the shielding requirement for these projects is to match or improve the external dose rate. In the Sandals-II project space was heavily constrained. The design for the front of the instrument already exists and there are existing CAD models which are often very detailed compared with the new design areas. This resulted in a mismatch in the level of detail in the simulation model at the interface between the old and new design. This increased the complexity of the analysis and interpretation of results.
In this work, we describe the shielding design process at ISIS for the Endeavour programme from scenario definition, to concept design through to final design. We explain the tools used particularly best practices for the use of CAD conversion software. These developments provide a more efficient and traceable shielding design workflow, enabling faster and more reliable shielding analysis for ISIS instruments.