Dézsi, Tamás

Fischer, Ulrich

Nitti, Francesco Saverio

Qiu, Yuefeng

Simakov, Stanislav

English

KITopen

Be-7 deposition simulationGamma dose simulationInstitute for Neutron Physics and Reactor Technology (INR)Yuefeng Qiua*, Tamás Dézsib, Ulrich Fischera, Francesco Saverio Nittic, Stanislav SimakovaaKarlsruhe Institute of Technology, Karlsruhe (KIT), Germanyb Centre for Energy Research, Fusion Technology Department, / C3D Engineering Ltd., Budapest, Hungaryc ENEA Brasimone- I-40032 Camugnano, BO, Italy*Corresponding author: yuefeng.qiu@kit.edu  Assessment of the Be-7 radiation dose in the IFMIF-DONES lithium loopIntroductionBe-7 inventoryIFMIF-DONES, is an accelerator based neutron irradiation facility which aims at providing the irradiation data for theconstruction of a DEMO fusion power plant. It is a deuterium-lithium (d-Li) neutron source driven by a deuteronaccelerator (40 MeV and 125 mA) striking at the liquid Li target, and produces neutrons through stripping reactions.The radioactive isotope Be-7 is produced in the d-Li reaction. The deposition of Be-7 in the Li pipes, lead to highgamma doses, and raises a safety concern during maintenance. Therefore, a reliable assessment of the Be-7 dose inthe Li loop is required.Half-life 53.1 days; gamma energy 477 keV; Main pathways Li-6 (d, n ) Be-7, Li-7 (d,2n) Be-7The Be-7 production rate is estimated in [1], which is 0.75 g/year calculated for IFMIF-DONES.the Be-7 inventory (production + decay) at 1 fpy (full power year, 345 days for IFMIF-DONES) isabout 0.15 g.Recent re-evaluation [2] of the Be-7 production cross-section shows that the nuclear data in [1]provides reasonable estimation over other libraries, e.g. TENDL2017, FENDL3.1d, etc.[1]Simakov, S. P., Fischer, U., & Von Möllendorff, U. (2004). Assessment of the 3 H and 7 Be generation in the IFMIF lithium loop. Journalof Nuclear Materials, 329, 213–217.[2]Simakov, S., Fischer, U., & Konobeyev, A. (2020). Status and benchmarking of the deuteron induced Tritium and Beryllium-7 productioncross sections in Lithium. https://doi.org/10.5445/IR/1000120615Summarytime Be-7 activity1 h 99.95%10 h 99.46%1 day 98.71%2 days 97.43%4 days 94.93%10 days 87.79%20 days 77.07%Geometry and source modelingThe lithium loop model was simplified by considering only the heatexchanger (HX), cold leg and cold trap, where the Be-7 is deposited.Model converted using McCad, then integrated in to the main buildingmodelSource regions are subdivided into 16 segments associated with the Be-7activities on each segment, calculated Be-7 deposition analyses.Simulation with openModelica with Be-7 production rate of 0.75g/fpy, the mass transfersimulations have been performed with a parametric studies4x Cold leg tempature: 250, 275, 290, 300 °C3x ICS mass flow: 0.5%, 1.0%, 1.5%4x Cold leg mass transfer coefficients (MTC): 3.2E-4 , 3.6E-4, 3.8E-4, 4.0E-44x Trap efficiency: 100%, 60%, 40%, 0%The effect of the increased loop temperature (tested on 250, 275,290 and 300 degC) is significant, atheoretical total removal can be achieved, with some increased mass flow over ICS (eg. 1%).DONES Lithium loop Simulation model of lithium loop in openModelicaGamma dose (μSv/h) at 345 days operation, 0 second after shutdownCold Leg Temp.Hot Leg Temp.ICS mass flow [%]MTC CL MTC HX Trap eff. [%]U06S11W1E2 250 274 0.5 0.000328 8.29E-06 60U06S14W1E3300 324 1 0.000323781 300 40U06S14W1E4 300 324 1 0.000396 9.12E-06 0U06S11W1F2: HX1: 18.2% deposition, Cold leg: 74.0%, Cold trap: 7.7%U06S11W0E1Naming conventionModel IDMass flow ratio of ICS: 1 – 0.5%, 2 – 1%, 3 – 1.5%Cold leg temperture [degC]: 1 – 250, 2 – 275, 3 – 290, 4 - 300Nitrogen content: 1 – 10wppm, 2 – 30 wppmOptional Filter study: without - trao eff.1 - 100%, 2 – constant 60%, 3 – start on 60% and linearly decreases to 40% over the irradiation period, 4- 0%U06S14W1F3: Cold trap: 100% U06S14W1F4: HX1: 6.1% deposition, Cold leg: 93.9% , Cold trap: 0% HXCold legCold trapNeutron CAD model of the lithium loop Source region of the lithium loop (16 segments) MCNP model lithium loopcell lithium trapcell Simulation results of Be-7 deposition in the primary loopduring operationSimulations of all the cases were done using batch run of MCNP6 code with photon librarymcplib04. Results are tallied with mesh tallies and sphere tallies, and converted to the effectivedose (μSv/h).The dose map of three typical cases are shown, which the cases U06S11W1F1 as referenceparameter, U06S14W1F2 with 300 °C cold leg temperature, and U06S14W1F4 with 0% coldtrap efficiency.Without removing the Be-7 to the cold trap, the dose level in the lithium loop cell will reachseveral Sv/h. Therefore, 300 °C is considered a good operation temperature for the cold leg.The Be-7 deposition and radiation dose has been assessed through multi-physics simulations, including Be-7 mass transfer simulation and gamma transportsimulation. A parametric study has been done with in total 192 cases.The Be-7 results very strong radiation in the lithium loop cell. With 300 °C operation temperature, Be-7 can be confined in the lithium trap cell. The HX and coldleg need additional shielding in case of cold trap is not in duty.

Assessment of the Be-7 radiation dose in the IFMIF-Dones lithium loop

https://publikationen.bibliothek.kit.edu/1000124689/89938803

Assessment of the Be-7 radiation dose in the IFMIF-Dones lithium loop

Abstract

Similar works

Full text

Available Versions

KITopen