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Chernobyl at 40 years: Looking back at Nuclear News
Sunday, April 26, at 1:23 a.m. local time will mark 40 years since the most severe nuclear accident in history: the meltdown of Unit 4 at the Chernobyl nuclear power plant in Ukraine, then part of the Soviet Union.
In the ensuing four decades, countless books, documentaries, articles, and conference sessions have examined Chernobyl’s history and impact from various angles. There is a similar abundance of outlooks in the archives of Nuclear News, where hundreds of scientists, advocates, critics, and politicians have shared their thoughts on Chernobyl over the years. Today, we will take a look at some highlights from the pages of NN to see how the story of Chernobyl evolved over the decades.
Xian-Zhu Tang, Zehua Guo
Fusion Science and Technology | Volume 71 | Number 1 | January 2017 | Pages 110-121
Technical Note | doi.org/10.13182/FST16-119
Articles are hosted by Taylor and Francis Online.
With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migration in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. It is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.