Investigations of pulsed heat loads on a forced flow supercritical helium loop – Part A: Experimental set up

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Abstract. The 4C code was developed to model thermal-hydraulics in superconducting magnet systems and related cryogenic circuits. It consists of three coupled modules: a quasi-3D thermal-hydraulic model of the winding; a quasi-3D model of heat conduction in the magnet structures; an object-oriented a-causal model of the cryogenic circuit. In the last couple of years the code and its different modules have undergone a series of validation exercises against experimental data, including also data coming from the supercritical He loop HELIOS at CEA Grenoble. However, all this analysis work was done each time after the experiments had been performed. In this paper a first demonstration is given of the predictive capabilities of the 4C code cryogenic circuit module. To do that, a set of ad-hoc experimental scenarios have been designed, including different heating and control strategies. Simulations with the cryogenic circuit module of 4C have then been performed before the experiment. The comparison presented here between the code predictions and the results of the HELIOS measurements gives the first proof of the excellent predictive capability of the 4C code cryogenic circuit module.

Section: Circuit Modelmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Verification of the predictive capabilities of the 4C code cryogenic circuit model

Zanino

Bonifetto

Hoa

et al. 2014

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“…1. This system is a scaled down model (1/20) of the auxiliary cold box of the JT-60SA cryogenic system [4]. It is composed of a closed supercritical helium loop driven by a cold pump which is connected to a saturated helium bath through 2 heat exchangers.…”

Section: Heat Load Smoothing Methodsmentioning

confidence: 99%

Experimental validation of advanced regulations for superconducting magnet cooling undergoing periodic heat loads

Lagier

Rousset

Hoa

et al. 2014

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Abstract. Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and the refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.

“…The vapor is compressed by the cold compressor connected to atmospheric pressure (8). The management of dynamic heat loads has been experimentally validated at CEA Grenoble in the HELIOS facility [3] [4]. The 4.3 K bath is sized such to act as a thermal damper and smooth the thermal loads arriving at the RCB.…”

Section: Cryogenic System Architecturementioning

confidence: 99%

Conceptual design of the JT-60SA cryogenic system

Lamaison

Beauvisage

Fejoz

et al. 2014

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Abstract. The superconducting tokamak JT-60 Super Advanced (JT-60SA) is part of the Broader Approach Programme agreed between Europe and Japan. Among other in kind contributions, CEA is in charge of supplying the Cryogenic System which includes a Warm Compression Station, the Refrigerator Cold Box, the Auxiliary Cold Box, a compressed air station and the vacuum systems. The cryogenic system requires a refrigeration capacity of about 8 kW equivalent at 4.5 K. It will supply cryopump panels at 3.7 K, superconducting magnets and cold structures at 4.4 K, HTS current leads at 50 K, and thermal shields between 80 K and 100 K. The contract for design, manufacture, installation and commissioning was signed between CEA and Air Liquide Advanced Technologies (AL-AT) in November 2012. The Cryogenic System shall be operational in 2016. The paper presents the main technical requirements and the limit of supply, the description of the process proposed by AL-AT, the main components, the preliminary layout and the interfaces at the JT-60SA Naka site.