29th Symposium on Fusion Technology (SOFT 2016)

I5.5 Nuclear fusion technology in conjunction with DT operations at JET in support of ITER

9 Sep 2016, 11:40

40m

Forum Hall 2nd floor (Prague Congress Centre)

Board: 5

Oral I5.5 P. Bastistoni

Speaker

P. Batistoni (EUROfusion Consortium)

Description

Within the framework of the EUROfusion programme, a work-package of technology projects (WPJET3) is being carried out in conjunction with the planned DT experiment at JET with the objective of maximising the scientific and technological return of DT operations in support of ITER. To this purpose, experiments, analyses and studies are performed in the areas of neutronics, neutron induced activation and damage in ITER materials, nuclear safety, tritium retention and outgassing in plasma facing materials, and waste production and characterization. This overview presents the results achieved since the project start in preparation of DT operations. Accurate calibration of JET neutron detectors at 14-MeV neutron energy is needed to measure the fusion power and plasma ion parameters during DTE2, and fully exploit the available neutron budget thus obtaining a full scientific return for the investment in DTE2. The 14-MeV neutron calibration of JET has been designed using a suitable 14-MeV neutron generator, to be deployed by the JET remote handling system, and fulfilling all challenging requirements imposed by physics, safety and remote handling. The portable neutron generator purchased for this purpose has been calibrated and fully characterized to the required accuracy at a standard neutron facility using different measuring techniques. The JET calibration strategy has also been developed to benchmark the calibration procedure envisaged in ITER where neutron detectors have to provide, with accuracy better than 10%, not only the fusion power but also the amount of tritium burnt for tritium accountancy. Neutronics benchmark experiments are carried out during and after every experimental campaign at JET, and will continue in DTE2, with the objective of validating the neutronics codes and tools used in ITER nuclear analyses, thus reducing the related uncertainties and the associated risks in the machine operation and maintenance. In the Neutron Streaming experiment, new streaming paths have been recently investigated by measuring the neutron fluence along and outside diagnostics channels in the JET biological shield. In the Shutdown Dose Rate experiment, the gamma dose rate has been measured during non-operational periods at ex-vessel positions. In both cases, results are compared with calculations performed with the codes used in ITER analyses and, in general, the comparisons show a satisfactory agreement within the experimental uncertainties. Two laboratory scaled facilities have been designed and are currently being constructed to study the tritium retention and outgassing in samples of ITER plasma facing materials (Be, W) under controlled conditions: the short term outgassing and the retention under plasma relevant conditions will be studied in the Tritium Loading Facility, using an ion sputter gun, whereas those resulting from torus relevant conditions, including torus venting, will be investigated in the Tritium Soaking Facility. In this overview, the progress in the development of other technology projects is presented as well. They include the development of neutron detectors and methods for ITER TBMs to be tested in JET, the collection of data on the occupational exposure, the preparation of measurements of neutron induced activity in ITER in-vessel materials, for the validation of numerical predictions of activation and dose rates in ITER, and of radiation damage in ITER functional materials up to 10-5 dpa during DTE2 with neutrons with a real fusion energy spectrum.