RAMI analysis of the collective Thomson scattering system front-end – Part2 – reliability block diagram analysis

Diogo Rechena*, Virgínia Infante, Elsa Henriques, Søren B. Korsholm, Axel W. Larsen, Bruno Gonçalves, Alberto Vale, Raul Luís

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


ITER is an experimental tokamak nuclear fusion reactor with the goal of achieving afusion energy gain factor of 10. Nuclear fusion presents an extreme environment for materials during operations while requiring continuous uninterrupted operation. The Reliability Block Diagram (RBD) is a graphic methodology for system reliability modelling which is constructed from the reliability-wise relations between different subsystems/components and their respective reliability and maintenance data. In this paper, we construct andanalyse the RBD for the Collective Thomson Scattering (CTS) front-end both in terms of fulfilling its functions and its effects in the ITER tokamak operations. Our RDB analysis results were then used to propose mitigation actions which include design changes and operational procedures to deal with the identified failure modes. Our initial results indicate that the system’s mean availability at the end of its lifecycle of 20 years is no greater than 82.55% which was due to low Mean Time Between Failures (MTBF) of a critical system component – theSplit Biased Waveguide (SBWG) – aswell as several thermally loaded components. After mitigation actions, which aimed at controlling the system’s exposure to heat loads, the MTBFs increased and the resulting mean availability achieved values over 97%, in conformity with design specifications. Furthermore, considering the CTS failure modes with impact on ITER operations, the expected value for the mean availability is of 99.995%. Therefore, we concluded that these failure modes did not require mitigation actions. In this article, we cover the second half of the RAMI analysis of the CTS diagnostic, the RBD analysis.

Original languageEnglish
Article number112593
JournalFusion Engineering and Design
Number of pages8
Publication statusPublished - 2021

Bibliographical note

Funding Information:
IPFN activities received financial support from “Fundação para a Ciência e Tecnologia” through projects UIDB/50010/2020 and UIDP/50010/2020.

This work was supported by FCT , through IDMEC, under LAETA, project UID/EMS/50022/2020.

The work leading to this publication has been funded partially by Fusion for Energy under the Framework Partnership Agreement F4E-FPA-393. This publication reflects the views only of the author, and Fusion for Energy cannot be held responsible for any use which may be made of the information contained therein.


  • RBD
  • RAMI
  • Collective Thomson Scattering
  • ITER

Fingerprint Dive into the research topics of 'RAMI analysis of the collective Thomson scattering system front-end – Part2 – reliability block diagram analysis'. Together they form a unique fingerprint.

Cite this