Elsevier

Fusion Engineering and Design

Volume 129, April 2018, Pages 259-262
Fusion Engineering and Design

Integrated radiation monitoring and interlock system for the LHD deuterium experiments

https://doi.org/10.1016/j.fusengdes.2018.02.067Get rights and content

Abstract

The Large Helical Device (LHD) successfully started the deuterium experiment in March 2017, in which further plasma performance improvement is envisaged to provide a firm basis for the helical reactor design. Some major upgrades of facilities have been made for safe and productive deuterium experiments. For radiation safety, the tritium removal system, the integrated radiation monitoring system, and the access control system have been newly installed. Each system has new interlock signals that will prevent any unsafe plasma operation or plant condition. Major interlock extensions have been implemented as a part of the integrated radiation monitoring system, which also has an inter-connection to the LHD central operation and control system. The radiation monitoring system RMSAFE (Radiation Monitoring System Applicable to Fusion Experiments) is already operating for monitoring γ(X)-rays in LHD. Some neutron measurements have been additionally applied for the deuterium experiments. The LHD data acquisition system LABCOM can acquire and process 24 h every day continuous data streams. Since γ(X)-ray and neutron measurements require higher availability, the sensors, controllers, data acquisition computers, network connections, and visualization servers have been designed to be duplicated or multiplexed for redundancy. The radiation monitoring displays in the LHD control room have been carefully designed to have excellent visual recognition, and to make users immediately aware of several alerts regarding the dose limits. The radiation safety web pages have been also upgraded to always show both dose rates of γ(X)-rays and neutrons in real time.

Introduction

The Large Helical Device (LHD) successfully started the deuterium experiment in March 2017, in which further plasma performance improvement is envisaged to provide a firm basis for the helical reactor design [1]. After agreements for the LHD deuterium experiment were concluded with the local governments, some major upgrades of facilities have been made for safe and productive deuterium experiments.

For high performance deuterium plasmas, upgrades of the plasma heating systems such as NBI, ECH, and ICRF, upgrades for plasma diagnostics systems especially for neutron measurements, closed helical divertor with an in-vessel pumping system [[2], [3], [4], [5]], and also some extensions for steady state data acquisition have been implemented. For radiation safety, the tritium removal system, the integrated radiation monitoring system, and the access control system for radiation controlled areas have been newly installed in LHD. The tritium removal system is operated to manage the tritium release less than 3.7 GBq/year by removing more than 95% of the estimated maximum tritium production of 37 GBq/year in the first six years and 55.5 GBq in the remaining three years [[6], [7], [8]].

Those newly installed radiation safety subsystems require a major extension of the central interlock system because of the increased number of interlock signals. They have been integrated as an important part of the newly developed integrated radiation monitoring and interlock system, and the central operation and control (COCO) system of LHD has provided some additional inter-connections to them [[9], [10]].

The LABCOM data acquisition and archiving system of LHD has already implemented the necessary functions to acquire and process 24 h every day (i.e. 24 × 7) continuous data streams. Therefore, endless radiation monitoring data can be handled by the same system and in the same way as the physics measured data for plasmas [[11], [12], [13]].

For a nuclear fusion experimental facility, radiation monitors such as γ(X)-ray and neutron measurements are required to provide nonstop operability against any device malfunctions [[14], [15]]. Therefore, all the equipment adopted in this system, such as sensors, controllers, data acquisition (DAQ) computers, network connections, and visualization servers and displaying clients, have been duplexed or multiplexed for redundancy.

In the following sections, newly implemented subsystems related to the LHD integrated radiation monitoring and interlock system will be explained with their functionalities and applied technology.

Section snippets

Integrated radiation monitoring system

Fig. 1 shows a photograph of the front view of the LHD control room. This room has been upgraded for the deuterium experiments. Some displays and a console have been additionally installed principally for the integrated radiation monitoring and interlock system. Newly added monitoring and interlock functions are implemented as an extension of the LHD central control and interlock system, as shown in Fig. 2.

The newly implemented radiation monitoring and interlock system consists primarily of six

HMI for plant automation and monitoring

For high efficiency development of the human–machine interface (HMI) programs, a .NET template and class library has been developed and used for implementing the LHD control subsystems. This is called SHMIT (Standard HMI Template) [26].

Fig. 6 shows the graphical view of the exhaust gas flow monitoring system, which is a typical example of the SHMIT-based plant monitoring HMI. The exhaust gas flow monitoring system has been also developed in close cooperation with the integrated radiation

Summary

For starting the deuterium experiments in LHD, major upgrades and implementations of new facilities were successfully completed by March 2017. For radiation safety, the integrated radiation monitoring system covers a number of interlock extensions for additionally implemented subsystems and also has inter-connections to the LHD central control system.

Indispensable fail-safe behaviors as a part of the safety interlock system have been verified before the beginning of the 2017 campaign, including

Acknowledgments

This work is performed with the support and under the auspices of the NIFS research program (NIFS17ULHH006, NIFS17ULII001, NIFS17UWIX002).

References (31)

  • M. Tanaka et al.

    Observations of the gas stream from the large helical device for the design of an exhaust detritiation system

    Plasma Fusion Res.

    (2016)
  • K. Yamazaki et al.

    Overview of the large helical device (LHD) control system and its first operation

  • H. Nakanishi et al.

    Real-time data streaming and storing structure for the LHD's fusion plasma experiments

    IEEE Trans. Nucl. Sci.

    (2016)
  • H. Nakanishi et al.

    Data acquisition system for steady-state experiments at multiple sites

    Nucl. Fusion

    (2011)
  • L. Giacomelli et al.

    Advanced neutron diagnostics for JET and ITER fusion experiments

    Nucl. Fusion

    (2005)
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