About the project

Reactor Physicist in the midst of nuclear fuel and reactor core modeling

Reaktorifyysikko Jussi Kumpula

We have opted to use reprocessed uranium (RepU) as the fuel in Hanhikivi 1. The RepU for the plant will be manufactured in Russia either by a MSZ plant in Elektrostal or the Novosibirsk Chemical Concentrates Plant (NCCP). In both plants, the manufacturing process covers all stages from the manufacture of fuel pellets to ready-made assemblies. At present, the only spent nuclear fuel reprocessing plant is RT-1 in Ozyorsk, Russia, but to our knowledge, a new reprocessing plant, RT-2, should be completed in 2025 in Zheleznogorsk, Russia. The fuel supply chain is regularly audited.

Manufacturing of the fuel for the initial core load will start a couple of years before the completion of the nuclear power plant. RepU is manufactured by separating unspent uranium from spent nuclear fuel by means of a chemical process. The process allows utilization of uranium that would otherwise go to waste. RepU is often confused with mixed oxide fuel (MOX) that contains plutonium. However, RepU only contains different uranium isotopes and no plutonium at all. RepU has been or is currently used in Europe in Switzerland, France, Germany, and Sweden, for example.

There will be a separate licensing process for the fuel once we have obtained a construction license for the plant. For the licensing process, we will submit a fuel suitability study to the Radiation and Nuclear Safety Authority. The suitability study will include a preliminary final disposal feasibility study of the fuel on which Posiva Solutions has been working since 2019. With these studies, we will demonstrate that the fuel meets all of the Finnish requirements for nuclear fuel and reactor core design.

We have reviewed and approved various reports submitted by the fuel supplier and compared their results with our own reactor physics calculations. Hence, we are already familiar with the properties of the fuel. In terms of mechanical design, the fuel is exactly the same as in the other VVER-1200 plants. The materials and mass of the fuel will be highly similar to the fuel of OL3, for example.

I have spent the first half of 2020 working with a completely new type of modeling for me, which has been extremely interesting. We have utilized a modeling program called Serpent, which is developed by VTT Technical Research Centre of Finland. With Serpent program we can model the quantity of fast neutrons hitting the reactor pressure vessel and its welds. The reactor pressure vessel and its welds must last the entire service life of the plant, which is 60 years. The justifications for the 60-year service life of the pressure vessel are provided by the plant supplier RAOS Project. We will perform our own calculations and analyzes in order to verify the accuracy of these calculations.  

The COVID-19 pandemic forced us all to work remotely since spring but otherwise it has not affected the progress of work in our plant safety unit. Both internal project meetings and external meetings with the plant supplier have gone quite smoothly with remote connections. What I have especially missed during this period is the shared coffee breaks at the office with our colleagues. 

We are expecting the plant supplier to submit the reactor chapter of the preliminary safety analysis report (PSAR) for our review in the fall. I will participate in the review of the nuclear fuel, reactor physics and thermo hydraulic design described in this chapter.  

Jussi Kumpula
Fennovoima's Reactor Physicist

Jussi Kumpula has a PhD in Engineering Physics from the Helsinki University of Technology TKK (current Aalto University). After his dissertation, Jussi also studied nuclear engineering at TKK. Jussi has worked as a Reactor Physicist at Fennovoima since September 2015. Jussi’s responsibilities include the computational modeling of the reactor core and nuclear fuel. After work Jussi turns to endurance sports, such as trail running. When the sea is not frozen Jussi also goes kayaking. Jussi is no stranger to kayaking in demanding conditions e.g. in the coast of England, Wales and Lofoten Islands in Norway. In addition, Jussi likes to solve various Rubik’s Cube types of puzzles.

Jussi Kumpula

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