Lee C. Cadwallader

The current fusion mission needs to demonstrate that fusion experiments and fusion power plants can be operated in a safe manner for the workers, local population, and environment. This paper describes some of the present issues and some solutions for personnel safety in magnetic fusion environments. Ionizing radiation, magnetic field exposure, chemical exposure, and radio frequency energy exposure are addressed. The present personnel protection limits are given and historical bases are used to speculate on the future of personnel protection limits as fusion research advances from experiments to the fusion power plants in the next decades.

Fusion design projects that reach the stage of design reviews typically require reliability, availability, maintainability and inspectability (RAMI) assessments. While many kinds of reliability and maintainability data are needed for a wide variety of fusion components to quantify a RAMI assessment, one of the types of components requiring data is the passive mechanical component. Passive mechanical components can be items such as metal plates, rods, shafts, brackets, bolts, and other items. Generally these passive components tend to have low failure rates since they are simple designs, have no or few moving parts, and do not need control signals to perform their design function. However, there are no widely recognized datasets for such components, so analysts must use multiple datasets and judgment for failure rates. This report gives recommended failure rates for various failure modes of these components, and gives suggested failure rate multipliers to apply to these failure rates if they reside in harsh environments. If the component resides far from the tokamak then typical industrial failure rates would suffice. Components near the tokamak find conditions can be demanding; similar to those in a fission reactor containment building. Some component failure rates can be modified if the components reside insidemore » the tokamak. « less

The Safety and Tritium Applied Research (STAR) facility provides the capabilities and infrastructure to support tritium research activities important to fusion research and development. Atmospheric tritium emissions are an expected byproduct of STAR laboratory operations and are monitored in accordance with federal regulations. This paper describes the STAR facility Stack Tritium Monitoring System, presents and discusses the annual STAR facility tritium emissions from 2004 to 2017, and briefly describes ongoing efforts to reduce atmospheric tritium emissions from the facility stack. Modeling calculations indicate that STAR facility atmospheric tritium emissions do not pose any health threat to the maximum exposed individual member of the public.

As fusion researchers look toward the future, there have been discussions on what the plant operation goals should be for a demonstration fusion power plant (DEMO). The U.S. Research Needs Workshop (ReNeW) in 2009 stated that power producers (the companies owning power plants) could not expect an ultimate fusion power plant availability of 80% or more if a DEMO reactor cannot demonstrate a 50% or higher availability. The ReNeW panel also stated that achieving 50% availability with a DEMO plant would be a huge accomplishment. Other recent DEMO design studies have given goals for plant availability as well. This technical note presents historical plant availability values of new technology fission power plants to compare fission achievements with the suggested goals for fusion DEMO plant designs. Demonstration fission plants that met or exceeded 40% average annual availability were generally considered to be successful. These data help to support the goal values that have been put forward in various studies.

Recently, Tritium Plasma Experiment (TPE), a unique high-flux linear plasma device that can handle beryllium, tritium and neutron-irradiated plasma facing materials, has undergone major upgrades in its electrical and control systems. The upgrade has improved worker occupational safety, and enhanced TPE plasma performance to better simulate extreme plasma-material-interaction (PMI) conditions expected in ITER, Fusion Nuclear Science Facility (FNSF) and demonstration fusion power plant (DEMO). The PMI determines a boundary condition for diffusing tritium into bulk plasma-facing components (PFCs) and plays critical role in in-vessel and ex-vessel safety assessments. Enhancing surface capabilities for tritium-contaminated and radioactive samples is crucial for the PMI sciences in burning plasma long pulse operation. The TPE Upgrade and improvement of surface diagnostic capabilities for tritium-contaminated and radioactive samples at STAR facility help enhance tritium and nuclear PMI sciences for the development of reliable PFCs and tritium fuel cycle in ITER, FNSF and DEMO.

This paper gives a brief overview of the Safety and Tritium Applied Research (STAR) facility operated by the Fusion Safety Program (FSP) at the Idaho National Laboratory (INL). FSP researchers use the STAR facility to carry out experiments in tritium permeation and retention in various fusion materials, including wall armor tile materials. FSP researchers also perform other experimentation as well to support safety assessment in fusion development. This lab, in its present two-building configuration, has been in operation for over ten years. The main experiments at STAR are briefly described. This paper discusses recent work to enhance personnel safety at the facility. The STAR facility is a Department of Energy less than hazard category 3 facility; the personnel safety approach calls for ventilation and tritium monitoring for radiation protection. The tritium areas of STAR have about 4 to 12 air changes per hour, with air flow being once through and then routed to the facility vent stack. Additional radiation monitoring has been installed to read the laboratory room air where experiments with tritium are conducted. These ion chambers and bubblers are used to verify that no significant tritium concentrations are present in the experiment rooms. Standby electrical power has been added to the facility exhaust blower so that proper ventilation will now operate during commercial power outages as well as the real-time tritium air monitors.