atw - International Journal for Nuclear Power | 05.2021

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atw Vol. 66 (2021) | Issue 5 ı September DECOMMISSIONING AND WASTE MANAGEMENT 46 at the inner boundary of the canister from 1118 MPa (without cover) to 147 MPa (with cover) (Figure 8). Free fall of rock blocks First, preliminary pure elastic simulations using the VW canister were performed. Small rock pieces were considered with weights of 0.5, 1.0 and 2.0 kg, respectively. Drop height is 2.0 m (distance from the lowest rock piece point to the highest line of horizontally disposed canister). Simulation cases 1 to 4 generate dynamic line loads, case 5 to 7 lead to point loads (see Figure 9 (up)). Figure 9 (down) shows the maximum induced tensile stresses in a VW canister during impact for seven loading cases. Similar results were obtained for the other canister types. It becomes obvious from Figure 9 (down), that (a) even small rock pieces produce tensile stresses close to the strength of the SSiC material or even larger ones and (b) point loading loads to significant higher values compared to line loading. Rock weight [kg] D = 20 mm E = 800 MPa Such a pure elastic consideration is too conservative, especially because the limited strength of the rock pieces is not taken into account. It has to be expected that extreme high local stresses during impact at point or line contacts lead du massive fracturing of the rock pieces, so that stresses above the rock strength will not be reached. To investigate this phenomenon the rock pieces were set-up by numerous distinct elements, so that fracturing and disintegration can take place if strength of the rock is exceeded. Calibration was performed using typical rock parameters. Figure 10 shows results from a calibration process for claystone. Figure 10 reveals, that vertical splitting (tensile cracking) is dominating like typically observed during uniaxial lab tests. D = 20 mm E = 80 MPa 8 5 mm / 130 MPa 12 mm / 70 MPa D = 80 mm E = 100 MPa 40 17 mm / 70 MPa | Tab. 6. Maximum penetration depth and maximum induced tensile stresses inside a CANDU canister with soft cover of thickness D and Young’s modulus E during pure elastic collision with claystone rock piece (drop height 2 m, loading case 1 according to Fig. 16). | Fig. 10. DEM-model for claystone: up: stress-strain-curve from uniaxial compression test, down: DEM model at the time of failure indication cracking and disintegration. | Fig. 11. Top: claystone rock piece in point contact with CANDU canister; Bottom: sequence of rock splitting process during impact (drop height 2 m, weight 1 kg). | Fig. 12. Top: Maximum tensile stress inside the CANDU canister versus collision time for rock piece elements with edge length of 4 mm, 6 mm, or 10 mm; point contact according to Figure 9 (up) (drop height 2 m, weight 1 kg); Bottom: Maximum tensile stress inside the CANDU canister during impact with claystone rock pieces for loading case 1 (see Figure 9 (up)) versus volume ratio (volume of distinct elements to volume of rock piece) Decommissioning and Waste Management SSiC Nuclear Waste Canisters: Stability Considerations During Static and Dynamic Impact ı Yanan Zhao, Heinz Konietzky, Juergen Knorr and Albert Kerber
NUCLEAR ENGINEER EXPERIENCE IN COMPUTER MODELING, NEUTRONICS, CFD, ETC Our mission and your passion We are true believers in the necessity of sustainable green energy and we believe that there is an inextricable close tie between the abundance of accessible energy in the world, and the well being of our civilization. As a growth company we are looking for two nuclear engineers or physicists who have that same passion alongside several years of experience in computer modeling, neutronics, CFD, etc. We assume that you have experience with Serpent, OpenMC, MCNP, OpenFoam or similar and that you have a good understanding of molten salt reactors and how they are different from LWRs. Who are you? Curiosity is part of our culture and how we train every day as a team to become world champions of our mission. We are very curious of who you are and what purpose you have in life. What is your story and what are your dreams? As team players we depend on each other whether big or small projects and delivery. Hence, we make a huge effort to keep our promises and deadlines because it affects all of us. Our work pace can be intense at times due to our high ambitions, and errors can be expensive. However, if you like to be challenged Copenhagen Atomics might be the right place to work for you. Professionally we hope you have experience with 3D CAD drawings and meshing of such files. Preferably you also have knowledge in material properties and we are keen that you are skillful with Linux and programming experience with e.g. C++ or Python.. You can apply for this position at jobs@copenhagenatomics.com Please send your CV along with 10 - 20 lines about yourself and your experience with nuclear computer modeling and why you would like to work with MSRs. About Copenhagen Atomics Based in Copenhagen we’re an international growth team of 35 engineers, technicians and designers who are in the process of developing nuclear power plants to be manufactured on assembly lines in the future. We expect many new colleagues to join our company within the next 5 years as we expand our breath and capabilities even further. Copenhagen Atomics ApS, Maskinvej 5, 2860 Søborg, Denmark | copenhagenatomics.com
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