Radiation can damage or destroy electronic components or sensors, corrupt signals in analogue or digital circuits, corrupt data in memories, etc. These effects can appear progressively, due to cumulated ionization or cumulated atomic displacements, or instantaneously, due to a single highly ionising particle (the so-called Single Event Effects or SEE), or due to a strong blast of ionizing particles.
The ITER plant system will contain a large amount of electronics. Many of these parts will be, by necessity, located in areas exposed to radiation in the Tokamak Complex.
The purpose of the ITER Radiation Hardness Assurance is to ensure that for all ITER electronics exposed to radiation above alert thresholds, a radiation mitigation and/or a radiation qualification strategy is developed and implemented, in such a way that the electronics complies with its availability and reliability requirements.
Radiation Hardness Assurance (RHA) is a transverse integration activity which is set-up and coordinated by the ITER RHA Project Coordinator under the authority of DIP Head and CIE line management, and executed by the systems under the coordination of the System RHA coordinators, and by the DAs under the coordination of the DA RHA coordinators. This activity is coordinated through periodical RHA Coordination Meetings organized twice a month by the ITER RHA Project Coordinator, where the RHA policy and procedures are presented by the ITER RHA Project Coordinator, and where the systems and DAs plans, schedules and progress reports on RHA are presented by systems RHA coordinators and DAs RHA coordinators.
The ITER RHA Project Coordinator, assigned by IO, is Martin DENTAN (IO/CIE/PEI/SEAS).
The System RHA coordinators, assigned by the IO systems, and the DA RHA coordinators, assigned by the DA Heads, are identified in the List of RHA-CM members. They are also identified in the tab “Systems (DAs) RHA web sites”.
There is one ITER RHA Project Coordinator for the ITER Project. He belongs to CIE. He reports to the DIP Head through his line management.
His main role is:
The ITER RHA Project Coordinator works for and under the authority of DIP Head, and under the authority and guidance of his line management. He is the empowered arm of DIP Head for the definition, planning, scheduling and implementation of his IA by the Systems and by the DAs.
There is one System RHA Project Coordinator (DA RHA Project Coordinator) per ITER system (DA). He reports to the system RO (DA technical leader) through his line management. His main role is:
System RHA Project Coordinator (DA RHA Project Coordinator) works for and under the authority of his System RO (DA technical leader) and under the authority of his line management.
He is the empowered arm of his System RO (DA technical leader) for the definition, planning, and scheduling by his System (DA) of the RHA policy and procedures, and for the correct execution by his System (DA) of the IA plan and schedule defined by his System (DA) and accepted by DIP Head.
RHA-CM meets on a regular basis, every first and third Wednesday of each month. Its Terms of Reference define its objectives, its members, and the role and responsibility of its members.
The RHA-CM is the place where:
Each IA-CM meeting follows a standing agenda with progress reports presented by a limited number of systems or DAs. For instance, for a given IA, with two IA-CM per month, if each IA-CM includes 6 progress reports (of about 30 minutes each) given by 6 systems or DAs, a full cycle of progress reports (where all systems/DAs have presented one progress report) is achieved in about 3 months.
WORKING IN PROGRESS
To determine if their equipment will be exposed to radiation conditions above or below the alert thresholds, the ITER systems need the following simplified radiation maps (contour plots per decade):
Total Ionizing Dose rate (Gray/s) induced by photons plus neutrons (full energy ranges) in Si (not SiO2) during operation;
Total Ionizing Dose rate (Gray/s) induced by photons plus neutrons (full energy ranges) in Si (not SiO2) during cask transfer;
Neutron flux (1 MeV Si - equivalent (not SiO2 equivalent) neutron.cm2.s-1) during operation;
Neutron flux (1 MeV Si - equivalent (not SiO2 equivalent) neutron.cm2.s-1) during cask transfer;
Flat neutron flux (neutron.cm2.s-1 summed over the full energy range: 0 eV to 20 MeV) during operation;
Flat neutron flux (neutron.cm2.s-1 summed over the full energy range: 0 eV to 20 MeV) during cask transfer.
Simplified radiation maps will be appended to radiation simulation reports which describe the geometric model and radiation source(s) used to calculate radiation data and which summarizes the calculated radiation data.
See Minutes of meeting dedicated to RHA-CM action-08 (simplified radiation maps) (10-Sep-2013) (KQXDLS).
To calculate local shielding and to perform radiation tests, the ITER systems need the following detailed radiation maps:
Total Ionizing Dose rate (Gray/s) induced by photons and neutrons (full energy ranges) in Si (not SiO2) during operation;
Total Ionizing Dose rate (Gray/s) induced by photons and neutrons (full energy ranges) in Si (not SiO2) during cask transfer;
Neutron flux (1 MeV Si - equivalent (not SiO2 equivalent) neutron.cm2.s-1) during operation;
Neutron flux (1 MeV Si - equivalent (not SiO2 equivalent) neutron.cm2.s-1) during cask transfer;
Thermal neutrons:
“Medium” energy neutrons:
“High” energy neutrons:
Instructions for opening detailed radiation maps are provided in the document 01 - Radiation maps (KGEW3D).
PCRs taken into account for the 2013 revision of the radiation maps:
The table below, excerpted from the ITER policy on electronics exposed to radiation, gives the radiation thresholds above which:
Sub-system | Accumulated dose (Gray) | Neutron fluency (1 MeV SiO2 eq. n.cm-2) | Neutron flux (n.cm-2.s-1) | |
| 1 | Critical system with electronics | 1 | 108 | 10 |
| 2 | Non-critical system with electronics | 10 | 1010 | 102 |
| 3 | Critical system without electronics | 103 | N.A. | 104 |
| 4 | Non-critical system without electronics | 104 | N.A. | 105 |
Systems are considered as critical if they are classified Quality Class 1 or 2. This includes systems participating in nuclear safety functions, occupational safety functions, investment protection functions, and systems whose failure would result in a loss of plasma operation. Other systems are considered as non-critical.
JET courses on radiation effects on electronics:
Radiation Hard Electronics web sites:
Standard radiation test methods:
Other useful links:
