Speaker
Description
The European Spallation Source (ESS) Target Station is comprised of Neutron Factory (NF) and Remote Handling (RH) systems. Neutron Factory systems produce, moderate, and deliver neutrons to the instruments and include related infrastructure such as shielding and cooling. Operating the Neutron Factory creates significant inventories of nuclides in the target and nearby components, structures, and fluids. Remote Handling systems include the Active Cells Facility (ACF) and High Bay cask assemblies, which handle, process, and store highly activated monolith components. The ESS radiation safety analysis covers all Target Station areas and functions.
The Target Station radiation safety case is the result of applying a systematic 7-step process developed at ESS to identify, evaluate, and manage prompt, residual, and contamination hazards to the public and workers. The process begins with the facility description and concept of operation (Step 1). Radiological hazards during anticipated operations and maintenance are then characterized (Step 2) and safety provisions to protect the public and workers from these hazards are established (Step 3). These may be radiation safety functions (RSF), worker radiation safety functions (WRSF), or administrative measures (AM/WAM). Hazards due to events involving facility processes, failures, or external aggressors are evaluated (Step 4) and additional safety provisions are identified (Step 5). The structures, systems, and components (SSCs) implementing RSFs/WRSFs are classified in Step 6 according to their technical disciplines. Finally, relevant barriers are identified and the facility defence in depth strategy and implementation are evaluated in Step 7.
This analysis process is iterative in nature, allowing information from later steps to feed back to earlier steps, e.g. facility design or planned operations. The framework also allows for the incorporation of insights gained from experience during early commissioning, exposure to new perspectives, maturing understanding of the regulatory framework, and awareness of the wider impact and application of the safety analyses. As a result, the safety case has evolved over time, integrating new ideas and optimizing with respect to facility operations.
A summary of the current Target Station radiation safety case will be described, focusing on the Neutron Factory. Safety provisions for anticipated operations and maintenance, events that expanded the safety case, an overview of the classified SSCs, and fundamental defence in depth strategy will be explained. Insights into the evolution of the safety case over time will be presented, with emphasis on changes motivated by improvements to operational flexibility. In addition, ideas and strategies for developing a balanced safety case that facilitates flexible and efficient facility operations will be discussed.