Stability of pyrolysis condensates during their high-temperature treatment

As part of a project dealing with the material use of waste plastics processed by pyrolysis, a method for the purification of primary pyrolysis gas at temperatures above the dew point of condensing components was proposed. In order to avoid the loss of liquid products, two procedures have been proposed to study this issue. The first procedure consists in separating the pyrolysis condensate from permanent gases and its subsequent evaporation and introduction into a high-temperature reactor where the purification takes place. The second procedure used the same equipment, but the pyrolyser was connected in series with a high temperature reactor by a heated tube. The function of the device is demonstrated on a pair of pure polymers, namely highdensity polyethylene and polypropylene. In practice, however, the device is used for testing waste plastics. The mass balance of liquid, gaseous and solid products of pyrolysis and subsequent vapour phase conduction through a high-tem-perature reactor was supplemented by data from chromatographic analysis. Experiments have shown that the separation of pyrolysis and subsequent evaporation of the condensate in an independent reactor causes the formation of an undesirable amount of fine aerosol (mist). Pyrolysis without any subsequent high-temperature step produced 85–90 % condensate. The inclusion of a separate high-temperature reactor reduced the yield of condensate to 44.5–47.5 %, at the expense of the above-mentioned mist. Its conver-sion back to liquid is difficult and makes the process inefficient for industry. In tests with the series-connected pyrolyser and the high-temperature reactor, the situation was significantly better. 68.5–73.5 % of condensate was obtained in this case. In addition to the formation of mist, the conduction of steam of condensing components through the high-temperature reactor also caused a slight change in the composition of the liquids obtained. There was a decrease in the proportion of C21–C29 hydrocarbons in products and, conversely, an increase in the concentration of C5–C15 hydrocarbons. Besides verifying a suitable approach to the high-temperature processing of pyrolysis products, the experiments showed that changing a single subparameter (in this case the separation of the two reactors) significantly altered the results of the experiments. During laboratory simulation of industrial processes, it is important not to approach simplifications, but to copy all conditions as much as possible.

Preliminary Analysis on Burnup Calculation of Several Arrangement of TRISO and Pebble inside an MCNP Model of HTR Core

Several studies related to simplifying the modeling of pebble bed High-Temperature Reactor core (HTR) has been developed before. From some calculation on several MCNP models with a fueled pebble to dummy ratio 57:43, using a combination of several types of TRISO (TRi-structural ISOtropic particle fuel) unit and Pebble unit is modeled to achieve its first criticality. In this paper, some MCNP model that uses 27000 pebbles with a 57:43 ratio and 100% fueled pebble is created to be used on burnup calculation and to compare its k-eff and nuclide inventory. From this burnup calculation, it could be seen that SC (Simple Cubic) TRISO unit has faster calculation time followed by the HCP (Hexagonal Close Packed) TRISO unit and then the FCC (Face-Centered Cubic) TRISO unit. The BCC (Body-Centered Cubic) pebble unit had some consistent deviation from another pebble unit, and it still needs more study to know more about the reason behind it. It could be seen that if there are some dummy pebbles inside the reactor, then the deviation would be higher than if there is just fueled pebble inside the reactor. On the 57:43 ratio, the absolute average deviation of k-eff on burnup calculation is lower than 2% and 10% for nuclide inventory (mass). On 100% fueled pebble, it’s below 0.15% on k-eff absolute deviation and below 8% on nuclide inventory deviation.

Preface

List of International Conference On High Temperature Reactor Technology 2021, Editorial Board And Reviewers, Design And Layout are available in this pdf.

Capability of Indonesian Hot cell Towards Pebble Bed Post Irradiation Examination

Post irradiation examination is one of the requirements to obtain licensing of nuclear fuel, and the purpose of this activity is to represent the performance of nuclear fuel itself. Currently, Indonesia is developing the 10 MWth high-temperature reactor type with its fuel in the form of pebble bed. Indonesia has a hot cell installation that has a function to do post-irradiated examinations. This hot cell mainly used for plate and rod type fuel. This paper wants to show this installation capability to perform the post-irradiation examinations based on its documents and current status. We also show the future possibility of performing pebble bed post-irradiation examinations. The hot cell installation in Indonesia, mainly divided into two areas. First areas are to perform the examinations in the intact form of fuel and second areas are to perform in the small specimen of fuel. For the future pebble bed examinations, Indonesian hot cell structure is possible to perform these examinations. These examinations are possible with limiting amount and stay time of fuel inside the hot cell. The current status gap with requirements for pebble bed tests such as handling tool, deconsolidation apparatus, simulation accident test apparatus also is described.

Prediction calculations for the first criticality of the HTR-PM using the PANGU code

The high-temperature reactor pebble-bed module (HTR-PM) is a modular high-temperature gas-cooled reactor demonstration power plant. Its first criticality experiment is scheduled for the latter half of 2021. Before performing the first criticality experiment, a prediction calculation was performed using PANGU code. This paper presents the calculation details for predicting the HTR-PM first criticality using PANGU, including the input model and parameters, numerical results, and uncertainty analysis. The accuracy of the PANGU code was demonstrated by comparing it with the high-fidelity Monte Carlo solution, using the same input configurations. It should be noted that keff can be significantly affected by uncertainties in nuclear data and certain input parameters, making the criticality calculation challenge. Finally, the PANGU is used to predict the critical loading height of the HTR-PM first criticality under design conditions, which will be evaluated in the upcoming experiment later this year.

Mixing Process of Two Component Gases by Natural Convection and Molecular Diffusion

A depressurization accident involving the rupture of the primary cooling pipe of the Gas Turbine High Temperature Reactor 300 cogeneration (GTHTR300C), which is a very-high-temperature reactor, is a design-based accident. When the primary pipe connected horizontally to the side of the reactor pressure vessel of GTHTR300C ruptures, molecular diffusion and local natural convection facilitate gas mixing, in addition to air ingress by counter flow. Furthermore, it is expected that a natural circulation flow around the furnace will suddenly occur. To improve the safety of GTHTR300C, an experiment was conducted using an experimental apparatus simulating the flow path configuration of GTHTR300C to investigate the mixing process of a two-component gas of helium and air. The experimental apparatus consisted of a coaxial double cylinder and a coaxial horizontal double pipe. Ball valves were connected to a horizontal inner pipe and outer pipe, and the valves were opened to simulate damage to the main pipe. As a result, it was confirmed that a stable air and helium density stratification formed in the experimental apparatus, and then a natural circulation flow was generated around the inside of the reactor.

Numerical Study on Multiscale Heat Conduction Problems in Very High Temperature Reactor Fuel Pebble Based on OpenFOAM

Pebble bed very high temperature reactor (VHTR) has been identified as one of six Generation-IV (Gen-IV) types of reactor which could operate at a high thermal power. The calculation of the temperature in the fuel pebble is a key part of VHTR thermal hydraulics numerical simulation. However, due to the special structure of the VHTR fuel pebble, the temperature calculation involves a multiscale problem. The multiscale heat conduction model includes mesoscale temperature of fuel pebble and microscale temperature of TRISO fuel particles calculation. To deal with the particularity of temperature calculation of the fuel pebble, this paper presents a multiscale heat conduction model based on an open source CFD package OpenFOAM. Firstly, the quasi steady state heat conduction method (QSSHC) and homogeneous layers method (HL) was verified by a simple multiscale model. The results show that the QSSHC method has a good ability of multiscale temperature prediction. Secondly, the mesoscale temperature distribution and the maximum temperature in the microscale of VHTR fuel pebbled are calculated with QSSHC method based on OpenFOAM. This multiscale solver will be couple with other solvers of OpenFOAM, to provide a new perspective of VHTR simulation.