Investigations on the Movement of Fuel Elements in the Core of a Pebble Bed Reactor

1969 ◽  
Vol 91 (2) ◽  
pp. 390-394
Author(s):  
D. Bedenig ◽  
C. B. v. d. Decken ◽  
W. Rausch
Keyword(s):  
Theoretical Model ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Experimental Equipment ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
The Core ◽  
Method Of Measurement ◽  
Fuel Elements ◽  
Type Fuel

For several years gas-cooled high temperature reactors have been developed in Germany, the main feature of which are their pebble-type fuel elements. The pebble bed is in the state of a continuous circulation process which is the reason for a series of nuclear and technical advantages. To make use of these advantages, comprehensive experimental studies on the flow behavior of a pebble bed were carried out. First, experimental equipment and the most successful method of measurement are described. Then typical results of parameter studies are reported as well as a theoretical model to calculate the pebble bed flow behavior. At last typical functions describing the flow behavior in the core of the THTR 300 MWe Prototype Reactor are reported.

scholarly journals Modeling of Fuel Elements Cycling System in Pebble Bed Reactor Based on Timed Places Control Petri Nets

2013 ◽  
Vol 05 (04) ◽  
pp. 510-516
Author(s):  
Hongbing Liu ◽  
Peng Shen ◽  
Dong Du ◽  
Xin Wang ◽  
Haiquan Zhang
Keyword(s):  
Petri Nets ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Cycling System ◽  
Fuel Elements

Fuel elements of the high temperature pebble bed reactor

1975 ◽  
Vol 34 (1) ◽  
pp. 93-108 ◽  
Author(s):  
L. Wolf ◽  
G. Ballensiefen ◽  
W. Fröhling
Keyword(s):  
High Temperature ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Fuel Elements

Optimization of a Radially Cooled Pebble Bed Reactor

2008 ◽  
Author(s):  
B. Boer ◽  
J. L. Kloosterman ◽  
D. Lathouwers ◽  
T. H. J. J. van der Hagen ◽  
H. van Dam
Keyword(s):  
Pressure Drop ◽  
Temperature Profile ◽  
Flow Direction ◽  
Outer Region ◽  
Fissile Material ◽  
Fuel Temperature ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
The Core ◽  
Power Profile

By altering the coolant flow direction in a pebble bed reactor from axial to radial, the pressure drop can be reduced tremendously. In this case the coolant flows from the outer reflector through the pebble bed and finally to flow paths in the inner reflector. As a consequence, the fuel temperatures are elevated due to the reduced heat transfer of the coolant. However, the power profile and pebble size in a radially cooled pebble bed reactor can be optimized to achieve lower fuel temperatures than current axially cooled designs, while the low pressure drop can be maintained. The radial power profile in the core can be altered by adopting multi-pass fuel management using several radial fuel zones in the core. The optimal power profile yielding a flat temperature profile is derived analytically and is approximated by radial fuel zoning. In this case, the pebbles pass through the outer region of the core first and each consecutive pass is located in a fuel zone closer to the inner reflector. Thereby, the resulting radial distribution of the fissile material in the core is influenced and the temperature profile is close to optimal. The fuel temperature in the pebbles can be further reduced by reducing the standard pebble diameter from 6 cm to a value as low as 1 cm. An analytical investigation is used to demonstrate the effects on the fuel temperature and pressure drop for both radial and axial cooling. Finally, two-dimensional numerical calculations were performed, using codes for neutronics, thermal-hydraulics and fuel depletion analysis, in order to validate the results for the optimized design that were obtained from the analytical investigations. It was found that for a radially cooled design with an optimized power profile and reduced pebble diameter (below 3.5 cm) both a reduction in the pressure drop (Δp = −2.6 bar), which increases the reactor efficiency with several percent, and a reduction in the maximum fuel temperature (ΔT = −50 °C) can be achieved compared to present axially cooled designs.

An Experimental Study of Thermohydraulic Processes in the Model of a Fuel Assembly with Micro Fuel Elements

Vestnik MEI ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 19-25
Author(s):  
Aleksandr V. Zakharenkov ◽  
◽  
Ivan A. Tupotilov ◽  
Kirill V. Zhuravlev ◽  
◽  
...  
Keyword(s):  
Fuel Assembly ◽  
Test Section ◽  
Pressure Loss ◽  
Experimental Studies ◽  
Internal Heat ◽  
Coolant Temperature ◽  
Geometrical Parameters ◽  
Pebble Bed ◽  
Flow Friction ◽  
Fuel Elements

The test section design of the TVS-MEI experimental setup intended for studying the hydrodynamics and heat transfer in a fuel assembly with micro fuel elements is developed, and the setup hydraulic circuit is modernized. The setup process characteristics correspond to the operational parameters of VVER-1000 reactor plants (a pressure up to 16 MPa and coolant temperature up to 350°C). The internal heat release in the bed of metal pebbles is obtained by high-frequency induction heating. A technology for compacting the test section made of high-strength alundum ceramics and a special clamping device for holding the bed were developed. The fuel assemblies with micro fuel elements have the outer geometrical parameters fully identical with those of the conventional assemblies with fuel rods. A technology for installing, wiring, and sealing thermocouples in the test section has been developed. Experimental studies aimed at determining the pressure loss and flow friction coefficient for a cylindrical pebble bed were carried with the following coolant operating parameters: P = (2--7) MPa and G = (0.05--0.5) kg/s. In processing the obtained experimental results, the dependences of pressure loss on the coolant mass velocity and the pebble bed flow friction on the Reynolds number were identified and plotted. The first experimental data on the temperature distribution in the pebble bed are obtained. The main objective of the experiments was to determine the possibility of heating the considered test section by using the chosen method.

The Re-Evaluation of the AVR Melt-Wire Experiment Using Modern Methods With Specific Focus on Bounding the Bypass Flow Effects

2008 ◽  
Author(s):  
Carel F. Viljoen ◽  
Sonat Sen ◽  
Frederik Reitsma ◽  
Onno Ubbink ◽  
Peter Pohl ◽  
...  
Keyword(s):  
Gas Flow ◽  
Coupled System ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Control Rod ◽  
Melting Temperatures ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects ◽  
The Many

The AVR (Arbeitsgemeinschaft Versuchsreaktor) is a pebble bed type helium cooled graphite moderated high temperature reactor that operated in Germany for 21 years and was closed down in December 1988 [1]. The AVR melt-wire experiments [2], where graphite spheres with melt-wires of different melting temperatures were introduced into the core, indicate that measured pebble temperatures significantly exceeded temperatures calculated with the models used at the time [3]. These discrepancies are often attributed to the special design features of the AVR, in particular the control rod noses protruding into the core, and to inherent features of the pebble bed reactor. In order to reduce the uncertainty in design and safety calculations the PBMR Company is re-evaluating the AVR melt-wire experiments with updated models and tools. 3-D neutronics thermal-hydraulics analyses are performed utilizing a coupled VSOP99-STAR-CD calculation. In the coupled system VSOP99 [4] provides power profiles on a geometrical mesh to STAR-CD [5] while STAR-CD provides the fuel, moderator and solid structure temperatures to VSOP99. The different fuel histories and flow variations can be modelled with VSOP99 (although this is not yet included in the model) while the computational fluid dynamics (CFD) code, STAR-CD, adds higher-order thermal and gas flow modelling capabilities. This coupling therefore ensures that the correct thermal feedback to the neutronics is included. Of the many possible explanations for the higher-than-expected melt-wire temperatures, flow bypassing the pebble core was identified as potentially the largest contributor and was thus selected as the first topic to study. This paper reports the bounding effects of bypass flows on the gas temperatures in the top of the reactor. It also presents preliminary comparisons between measured temperatures above the core ceiling structure and calculated temperatures. Results to date confirm the importance of correctly modelling the bypass flows. Plans on future model improvements and other effects to be studied with the coupled VSOP99-STAR-CD tool are also included.

scholarly journals GAMMA DOSE RATE ANALYSIS IN BIOLOGICAL SHIELDING OF HTGR-10 MWth PEBBLE-BED REACTOR

2019 ◽  
Vol 25 (1) ◽  
Author(s):  
Hery Adrial ◽  
Amir Hamzah ◽  
Entin Hartini
Keyword(s):  
Gamma Radiation ◽  
Dose Rate ◽  
Gamma Dose ◽  
Gamma Dose Rate ◽  
Minimum Thickness ◽  
Critical Height ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
The Core ◽  
Rate Analysis

GAMMA DOSE RATE ANALYSIS IN BIOLOGICAL SHIELDING OF HTGR-10 MWth PEBBLE BED REACTOR. HTGR-10 MWth is a high-temperature gas-cooled reactor. The fuel and moderator are pebble shaped with a radius of 3 cm. One fuel pebble consists of thousands of UO2 kernels with a density of 10.4 gram/cc and the enrichment rate of 17%. The core of HTGR-10 MWth is the center of origin of neutrons and gamma radiation resulting from the interaction of neutrons with pebble fuel, moderator and biological shield. The various types of radiations generated from such nuclear reactions should be monitored to ensure the safety of radiation workers. This research was conducted using MCNP-6 Program package with the aim to calculate and analyze gamma radiation dose in biological shield of HTGR-10 MWth. In this study, the biological shield is divided into 10 equal segments. The first step of the research is to benchmark the created program against the critical height of HTR-10. The results of the benchmarking show an error rate of ± 1.1327%, while the critical core height of HTGR 10 MWth for the ratio of pebble fuel and pebble moderator (F:M) of 52: 48 occurs at a height of 134 cm. The rate of gamma dose at the core is 3.0052E + 05 mSv/hr. On the biological shield made of regular concrete with a density of 2.3 grams/cc, the rate of gamma dose decreases according to an equation y = 0.0042 e-0.03x. Referring to Perka Bapeten no 4 of 2013, the safe limits for workers and radiation protection officers will be achieved if the minimum thickness of biological shield is 115 cm with gamma dose rate of 0 mSv/hour.Keywords: Gamma dose rate, HTGR 10 MWth, biological shield, pebble

Gas-Cooled Modular Reactors With Spherical Fuel Elements — Their Inherent Safety and Applications Not Just for Power Generation

2014 ◽  
Author(s):  
Walter Jaeger ◽  
H. J. Hamel ◽  
Heinz Termuehlen
Keyword(s):  
Power Generation ◽  
High Temperature ◽  
Reactor Design ◽  
Inherent Safety ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Pebble Bed Reactors ◽  
Fuel Elements ◽  
High Temperature Gas

The gas-cooled reactor design with spherical fuel elements, referred to as high-temperature gas-cooled reactors (HTGR or HTR reactors) or pebble bed reactors has been already suggested by Farrington Daniels in the late 1940s; also referred to as Daniels’ pile reactor design. Under Rudolf Schulten the first pebble bed reactor, the 46MWth AVR Juelich reactor (Atom Versuchs-Reactor Jülich) was built in the late 1960s. It was in operation for 22 years and extensive testing confirmed its inherent safety.

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