Important Nuclear Fusion Reactor Component Tested In The Netherlands

Phil Black - PII Editor 12/10/2016

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NRG tests quality and operation of ‘First Wall’ in Petten High Flux Reactor

In the coming months NRG in Petten will test an important component of the nuclear fusion reactor that is currently being built by ITER in Cadarache in the South of France. In its High Flux Reactor (HFR) NRG is testing the operation, integrity and quality of the so-called ‘First Wall’ that is soon to shield the nuclear fusion process.

In this process, two hydrogen nuclei are fused to one helium nucleus and a neutron, releasing a tremendous amount of energy; the same process that takes place in the sun. The nuclear fusion takes place in a plasma at a temperature of 150 million degrees (Kelvin). As no material can withstand this kind of temperature, the plasma is held in place by a magnetic field.

The first shield that shields the core of the reactor is called the First Wall. This is exposed to the high-energy neutrons released during the process. The neutrons are not trapped by the magnetic field.

The fusion community has produced scale models, so-called mock-ups, representative of the First Wall of the fusion reactor in the South of France. Like the real first wall, these comprise beryllium tiles, welded on a subsurface of copper-chrome-zircon alloy, enclosed in a stainless steel construction.

The models are placed in the reactor core in Petten, where the material is exposed to neutrons. “This enables us to simulate the radiation environment and temperatures in ITER,” said Sander de Groot, nuclear expert at NRG.

The High Flux Reactor in Petten is used to produce medical isotopes and for nuclear research and is very suitable for testing this material. De Groot: “We can mimic the same conditions as in ITER, and the neutron density in the HFR is high. Within a short period we can use this to simulate radiation damage during the life span in the fusion reactor and determine how long components used in ITER can withstand the neutron radiation.”

After irradiation, the irradiated mock-ups are transported to Julich research centre, where they are exposed to extremely high heat flux and intense variable thermal radiation. This will demonstrate whether the irradiated material offers sufficient resistance to extreme heat load in the ITER system.

ITER is the largest international energy partnership in which the EU, Japan, South Korea, China, India, the US and Russia participate. A nuclear fusion reactor that produces 500 megawatt energy needs to be operational in the South of France by 2025. The most important objective is to demonstrate that nuclear fusion is an achievable energy form, without CO2 emissions and long-lived radioactive waste. Many components are still in construction, including the enormous magnets needed to keep the plasma in place.