Periodic Reporting for period 1 - PATRICIA (Partitioning And Transmuter Research Initiative in a Collaborative Innovation Action)
Okres sprawozdawczy: 2020-09-01 do 2022-02-28
PATRICIA contributes to closing the nuclear fuel cycle by advanced recycling of spent fuel and waste burning in a dedicated accelerator driven system (ADS). In this way, together with multi-recycling of Pu for which technology exists, we can decrease the waste burden, optimize disposal and improve public acceptance. It will pave the way toward a sustainable carbon-free energy source.
PATRICIA works on recycling methods for minor actinides (MA) and the development of the MYRRHA ADS in four technical domains (DM): partitioning (recycling), transmutation, safety of the ADS driver fuel and safety of the ADS system.
PATRICIA works on recycling methods for minor actinides (MA) and the development of the MYRRHA ADS in four technical domains (DM): partitioning (recycling), transmutation, safety of the ADS driver fuel and safety of the ADS system.
DM1 develops new ways to separate Am from high-level liquid waste. WP1 produced and tested new water-soluble ligands to strip Am from the fuel selectively. It only has C, H, O and N (CHON) atoms so it only has gaseous combustion products, which reduces secondary waste. We studied extraction of several key fission products into the reference extracting-agent TODGA and the experimental needs to check the stability of above chemical systems under radioactivity. In WP2, we worked on the AmSEL process to recover Am from PUREX raffinate. Experimental results from single centrifugal contactor and batch distribution tests were used to create and calculate a new AmSEL flow sheet. The CHON-compatible ligand was also studied and data of a continuous counter-current process demonstration, selectively recovering Am and Cm, were evaluated, showing the validity of the new CHON-AmSEL process. In WP3, we studied a sol-gel process that uses internal gelation to convert the recycled material to usable fuel. The studies on Np showed that the Np(VI) system is a candidate for fabricating Np-bearing U fuel.
In DM2, we characterise irradiated MA bearing fuels to improve and test fuel performance codes (FPC’s). Migration of atoms and noble gas produced during irradiation can create a central hole and make the pellet swell. This enhances chemical and mechanical interactions between fuel and cladding. In WP4, we characterised these by non-destructive tests of previously irradiated fuel pins with destructive tests to follow. We also studied thermo-physical and -chemical properties of Am bearing to make a reliable thermodynamic database. In WP5 we intend to improve FPC’s applied to Am-MOX transmutation fuel. Main results were the implementation of an inter granular He migration model, including fuel grain size distribution, and extending the burn-up module with the derived He production correlation in the SCIANTIX code coupled to FPC’s. Thermo-physical properties modelling of Am-MOX fuel focussed on the specific heat and melting point. Here, FPC’s were extended as well using a model based on literature data. Work on integral fuel pin behaviour was started by assessing input settings and boundary conditions for the SPHERE irradiation experiment. Finally, a task force was set up to coordinate work on code benchmarking and code applications to set up scenarios for future experiments in MYRRHA. In WP6, we define future transient irradiation tests with Am bearing fuels. To optimise design of a transmutation target for MYRRHA, key options were fixed like fuel material, core configuration and experiment location. We selected several transient scenarios of interest realising that these also structure the design of future tests. In parallel, design work for future experiments in the HFR and BR2 was started together with an inventory and evaluation of in-pile and out-of-pile facilities for transient test available worldwide.
DM3 studies the safety of the MYRRHA core and driver fuel. WP7 includes a 7-pin heated bundle experiment simulating the MYRRHA fuel assembly conditions. The bundle was designed, made and installed in a lead bismuth eutectic (LBE) loop and first instrumentation tests were done. The full year test on corrosion as a function of time, temperature and pressure distributions along the bundle starts shortly. Secondly, samples of MYRRHA cladding tube are currently corroded in LBE for tests to correlate mechanical strength loss with clad thickness reduction. WP8 contains detailed post irradiation examination to gain extra information from fuel segments exposed to power transients. Fist profile data is available for exposed pins with different deformations. For selected pins, ovality measurements along the cylinder and a detailed profilometry was made using a laser method, revealing small deformations by pellet-clad mechanical interaction. Integrity checks of the cladding with eddy current scans and the study of crack patterns in the pellet by destructive analysis are ongoing. On the numerical side, thermal modelling was improved achieving better agreement with thermocouple temperature recordings. In WP9, we do thermal-hydraulic tests of the fuel pin bundle in abnormal conditions –a porous blockage and the case of a deformed pin- in both water and LBE. With experiments and numerical simulations, we will assess the temperature over the fuel pins and the associated failure risks. We used the first part of the project to design and implement the experimental set-ups.
DM4 works on the safety of the ADS system. In WP10, we aim to improve the accelerator reliability to a level of having less than 10 faults, longer than 3 seconds, over a fuel cycle of 90 days. As the accelerator is dominated by the Radio Frequency systems, the gain in availability of the accelerator with different fault compensation schemes was modelled on it by Monte Carlo codes to address the feasibility of the requirement. We also studied a break of the beam window separating the accelerator vacuum from the reactor in terms of radioelement release. We looked at fast and slow failures using various codes and compared results with experimental data. We found mercury to be an important contributor to pressure rise and that the migration of polonium upstream of the failed window is governed by the sticking factor on steel, close to room temperature. WP11 addresses thermal hydraulics of the reactor pool. Most effort went to preparing the transition-to-natural-circulation experiments in CIRCE and ESCAPE, planned for early 2023. In parallel, numerical models were made. In the work developing a heat transfer model, we implemented and validated the explicit and implicit CFD AHFM model against DNS data. In WP12, we plan to get a better grip on the chemical processes occurring in the coolant, and to develop better control methods. For this, we created computer models allowing simulating chemical reactions in the LBE. The code was developed, optimized and tested by comparing it to experimental data. We also studied phenomena and fundamental system properties related to the release of radioactivity, vital to the safety assessment of MYRRHA. Many optimizations of the experimental setups were made and samples were prepared. Also first experimental data on tellurium evaporation from LBE and calculations on the stability of gaseous tellurium-compounds were obtained.
In DM2, we characterise irradiated MA bearing fuels to improve and test fuel performance codes (FPC’s). Migration of atoms and noble gas produced during irradiation can create a central hole and make the pellet swell. This enhances chemical and mechanical interactions between fuel and cladding. In WP4, we characterised these by non-destructive tests of previously irradiated fuel pins with destructive tests to follow. We also studied thermo-physical and -chemical properties of Am bearing to make a reliable thermodynamic database. In WP5 we intend to improve FPC’s applied to Am-MOX transmutation fuel. Main results were the implementation of an inter granular He migration model, including fuel grain size distribution, and extending the burn-up module with the derived He production correlation in the SCIANTIX code coupled to FPC’s. Thermo-physical properties modelling of Am-MOX fuel focussed on the specific heat and melting point. Here, FPC’s were extended as well using a model based on literature data. Work on integral fuel pin behaviour was started by assessing input settings and boundary conditions for the SPHERE irradiation experiment. Finally, a task force was set up to coordinate work on code benchmarking and code applications to set up scenarios for future experiments in MYRRHA. In WP6, we define future transient irradiation tests with Am bearing fuels. To optimise design of a transmutation target for MYRRHA, key options were fixed like fuel material, core configuration and experiment location. We selected several transient scenarios of interest realising that these also structure the design of future tests. In parallel, design work for future experiments in the HFR and BR2 was started together with an inventory and evaluation of in-pile and out-of-pile facilities for transient test available worldwide.
DM3 studies the safety of the MYRRHA core and driver fuel. WP7 includes a 7-pin heated bundle experiment simulating the MYRRHA fuel assembly conditions. The bundle was designed, made and installed in a lead bismuth eutectic (LBE) loop and first instrumentation tests were done. The full year test on corrosion as a function of time, temperature and pressure distributions along the bundle starts shortly. Secondly, samples of MYRRHA cladding tube are currently corroded in LBE for tests to correlate mechanical strength loss with clad thickness reduction. WP8 contains detailed post irradiation examination to gain extra information from fuel segments exposed to power transients. Fist profile data is available for exposed pins with different deformations. For selected pins, ovality measurements along the cylinder and a detailed profilometry was made using a laser method, revealing small deformations by pellet-clad mechanical interaction. Integrity checks of the cladding with eddy current scans and the study of crack patterns in the pellet by destructive analysis are ongoing. On the numerical side, thermal modelling was improved achieving better agreement with thermocouple temperature recordings. In WP9, we do thermal-hydraulic tests of the fuel pin bundle in abnormal conditions –a porous blockage and the case of a deformed pin- in both water and LBE. With experiments and numerical simulations, we will assess the temperature over the fuel pins and the associated failure risks. We used the first part of the project to design and implement the experimental set-ups.
DM4 works on the safety of the ADS system. In WP10, we aim to improve the accelerator reliability to a level of having less than 10 faults, longer than 3 seconds, over a fuel cycle of 90 days. As the accelerator is dominated by the Radio Frequency systems, the gain in availability of the accelerator with different fault compensation schemes was modelled on it by Monte Carlo codes to address the feasibility of the requirement. We also studied a break of the beam window separating the accelerator vacuum from the reactor in terms of radioelement release. We looked at fast and slow failures using various codes and compared results with experimental data. We found mercury to be an important contributor to pressure rise and that the migration of polonium upstream of the failed window is governed by the sticking factor on steel, close to room temperature. WP11 addresses thermal hydraulics of the reactor pool. Most effort went to preparing the transition-to-natural-circulation experiments in CIRCE and ESCAPE, planned for early 2023. In parallel, numerical models were made. In the work developing a heat transfer model, we implemented and validated the explicit and implicit CFD AHFM model against DNS data. In WP12, we plan to get a better grip on the chemical processes occurring in the coolant, and to develop better control methods. For this, we created computer models allowing simulating chemical reactions in the LBE. The code was developed, optimized and tested by comparing it to experimental data. We also studied phenomena and fundamental system properties related to the release of radioactivity, vital to the safety assessment of MYRRHA. Many optimizations of the experimental setups were made and samples were prepared. Also first experimental data on tellurium evaporation from LBE and calculations on the stability of gaseous tellurium-compounds were obtained.
The work in PATRICIA is relevant for society as it contributes to a solution for spent fuel via a strategy of recycling and fuel reuse. Without treatment, spent fuel needs several hundred thousand years of storage in a geological depository. Societal acceptance can be improved and constraints are easier to achieve if the storage time can be significantly cut back and the storage volume reduced, independent of the technical status of the depository.