Projects / Programmes
Calculations to support neutron monitor calibration - JET fusion reactor example case
| Code |
Science |
Field |
Subfield |
| 2.03.02 |
Engineering sciences and technologies |
Energy engineering |
Fuels and energy conversion technology |
| Code |
Science |
Field |
| T160 |
Technological sciences |
Nuclear engineering and technology |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
Fusion, JET, Joint European Torus, fusion reactor, low carbon energy sources, sustainable energy, calibration of neutron detectors, Monte Carlo neutron transport, Monte Carlo variance reduction
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
27819 |
PhD Luka Snoj |
Energy engineering |
Head |
2011 - 2013 |
1,863 |
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0106 |
Jožef Stefan Institute |
Ljubljana |
5051606000 |
90,767 |
Abstract
Joint European torus (JET), presently the world's largest magnetic confinement nuclear fusion research facility, has gone under major refurbishment since 2009 and will start operating in 2011. The major change will be replacement of current reactor Carbon wall by the ITER-like wall (ILW) made of Beryllium, Tungsten and Carbon. This will most significantly affect the neutron yield measurements which are the basis for the determination of the absolute fusion reaction rate and the operational monitoring with respect to the neutron budget during any campaign.
After refurbishment, the neutron yield calibration will be ensured by direct measurements using a calibrated 252Cf neutron source deployed inside the JET vacuum-vessel. This measurement will allow direct confirmation of the time-dependent neutron yield detector calibration and provide the first direct calibration of the JET activation system. Time-dependent neutron diagnostics system KN1 consist of sets of fission chambers mounted on three JET transformer limbs, which provide the time-dependent neutron yield used to assess a JET pulse. The activation system pneumatically delivers capsules to positions just at the edge of the vacuum-vessel inside JET, where they are irradiated during the pulse, pneumatically retrieved, and the induced activity is counted to provide a time-independent absolute fusion yield measurement.
In order to significantly improve the accuracy of the calibration, a whole suite of calculations is required to support the JET neutron calibration project. Due to complex geometry of the fusion device and asymmetrical structure, the only reasonable method to be used for neutron transport calculation is the Monte Carlo method. As the detectors are very small compared to the tokamak one should use various Monte Carlo variance reduction techniques to speed up the calculations and reduce the statistical uncertainty of the calculated result. The type of method and the way the method is used, strongly depend on the type of problems under investigation, hence it is essential to verify the calculated results by comparison with benchmark experiments.
The scope of the project is to develop computational model of the JET tokamak, to choose and apply appropriate Monte Carlo variance reduction calculational methods, verify them by comparing the experimental values and use the calculations to support the calibration. Calculations will support the calibration process by evaluating all possible sources of errors, uncertainties and biases. This will then allow application of appropriate correction to the measurements, which will significantly improve the accuracy of the neutron yield measurements at JET. The results are useful also for other tokamak reactors. Moreover the knowledge and experience gained in the project is applicable also for neutron transport calculations in fission reactors.
Significance for science
Continuing JET operations depend upon good neutron yield measurements to stay within set operational limits and all the scientific Task Forces require sound fusion yield data to begin the characterisation of any JET pulse. In view of the planning for future tritium operations, it is especially important that the fusion yield measurements are well verified, starting with the current plans for D-T relevant calibrations. The deployment, measurement and calculational methods developed now will be extended to cover ITER’s D-T operations in the foreseen future and will certainly contribute to the foreseen ITER-related activities. In fact, knowledge, experience and methods developed during the project will be directly used in the recently started 14. MeV neutron calibration project, which will be even more complex. The project runs within H2020 The whole process of understanding & improving the knowledge of the neutron yield calibration for JET is of great interest for ITER, where the methods and procedures for calibrating the neutron yield monitors have yet to be finally defined. Knowing the fusion reactor power with great accuracy (which can be done only by neutron measurements, since they remove the bulk of the energy from the burning plasma) is of great importance for development of fusion as sustainable and environmentally friendly energy source. The evaluated experimental results will serve as the benchmark experiment for verification and validation of computational methods and nuclear data in fusion tokamaks and other similar systems, such as fission nuclear reactors, which feature similar materials and practically the same detectors. We will use the benchmark model for verification and validation of various variance reduction techniques used in Monte Carlo calculations and for validation of nuclear data libraries.
Significance for the country
From neutronic point of view, fusion reactors (e.g. JET or ITER) have many common features with classic fission nuclear reactors: similar materials - low activation alloys, same detector types - fission chambers, size of detectors compared to reactor size), etc.. Hence the results of our investigation can be applied also to: • calculation of response function of neutron detectors in classical fission nuclear reactors (very important for accurate and reliable reactor operation and measurements of reactor physics parameters) • accurate calculations of irradiation of reactor vessel (of key importance for determination of nuclear power plant (NPP) lifetime or prolongation of NPP lifetime) • accurate calculations of activation of materials outside the reactor vessel (important for determination of amount and type of radioactive waste at reactor dismantling) In nuclear power reactors the whole process of neutron calibration measurements and calculations with well-defined sources are practically impossible due to practical and economical limitations. Research reactors are too small and not complex enough to be representative for such measurements. Hence the experience and knowledge gained in experimental fusion reactors are priceless and very important also for classical fission reactors. By collaboration in the Joint European Torus, the world's largest nuclear fusion research facility, Slovenia will gain access to the state of the art knowledge on fusion technology and will be more actively involved in the European research projects. People involved in the project will benefit from immersion in a group of experts working in the fields of physics, experimental techniques and associated calculations for fusion neutron and gamma ray detection. The gained knowledge will be then passed on to the Slovenian scientists, professionals and students in the field of neutron detection and neutron transport calculations. The latter is especially important for conservation and improvement of knowledge on neutron and radiation science in Slovenia. Having an opportunity of collaborating in such important project is a big recognition to Slovenian science and a big promotion for Slovenia. The latter will be especially noticeable in the near future, when JET will reach fusion energy gain factor Q=1, which is an important milestone in the development of fusion as sustainable and environmentally friendly energy source. This proposed project is one of the important steps towards it. Collaboration within such an important project opened opportunities for collaboration in other European projects. Based on knowledge and experience gained in this project we were successful in obtaining a 5 year project (2014 – 2018) project on calculations to support JET DT calibration. The project will be performed within Eurofusion consortium within the H2020.
Most important scientific results
Annual report
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2012,
final report,
complete report on dLib.si
