scholarly journals Axial Shuffling on Pebble Bed Reactor using PRAKTIK 3D-HTR

2021 ◽  
Vol 927 (1) ◽  
pp. 012012
Author(s):  
Muhammad Rizki Oktavian ◽  
Ganjar Putro Indratoro
Keyword(s):  
Critical Condition ◽  
Axial Direction ◽  
Reactor Power ◽  
Movement Speed ◽  
Diffusion Method ◽  
Thermal Reactor ◽  
Multiplication Factor ◽  
Pebble Bed ◽  
Core Diameter ◽  
Pebble Bed Reactor

Abstract With moving fuel, the pebble bed reactor (PBR) provides flexibility in the fuel management process due to the capability of online fuel refueling. This capability allows the reactor to operate at any given time without the need to shut down for refueling. The complexity of the depletion and burnup analysis requires the problem to be solved with sophisticated and robust computer codes that can handle the fuel shuffling. Since the fuel refueling is conducted from top to bottom, the shuffling and fuel movement in the axial direction should be modeled with acceptable accuracy. The purpose of the simulation is to obtain the equilibrium or even a critical condition of the reactor. The model used is based on the simplified pebble bed reactor with 200 MWt of thermal reactor power, 3 meters of core diameter, and 10 meters of core height. To model the axial shuffling on the reactor, a neutronic computer code called PRAKTIK 3D-HTR is used. The code utilizes the diffusion method in a three-dimensional cylindrical geometry to model the neutronic phenomena in the reactor. Moreover, PRAKTIK 3D-HTR is equipped with the burnup calculation and depletion analysis to be able to handle fuel movement. Finally, the axial shuffling mechanism is implemented using the once-through-then-out (OTTO) method. Implementing this method to the reactor, an equilibrium condition can be obtained. In this condition, the reactor condition in terms of criticality and flux shape is relatively constant. The critical condition can also be searched using PRAKTIK 3D-HTR to obtain the condition when the multiplication factor is equal to unity. The criticality search is conducted by changing the fuel movement speed. If the multiplication factor is less than 1, then the shuffling speed needs to be increased. Otherwise, if it is more than 1, the shuffling speed will be decreased.

scholarly journals Pebbles Making Waves

2008 ◽  
Vol 130 (02) ◽  
pp. 34-38
Author(s):  
Lee S. Langston
Keyword(s):  
South Africa ◽  
Power Plant ◽  
Packed Bed ◽  
Nuclear Fission ◽  
Reactor Power ◽  
Reactor Vessel ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
High Level ◽  
Reactor Power Plant

This paper describes various high-level nuclear researches including nuclear-fuelled pebbles that are being conducted across South Africa. The pebbles are ingenious industrial products, designed to passively limit the amount of heat unleashed by the nuclear fission reactions that drive the reactor. The spheres that give the pebble bed reactor its name enclose fissionable uranium inside layers that serve various roles, such as moderating fission, containing pressure, and accommodating deformation of the core. Nuclear-fuelled pebbles are introduced at the top of the reactor vessel and slowly wend their way down through the annular-packed bed under the action of gravity to the bottom of the reactor vessel. In a towering building at the headquarters of Nesca in Pelindaba, South Africa, reactor components are being tested for their ability to work with high-pressure helium. Those parts will go in the pebble bed modular reactor power plant to be constructed at Koeburg, near Cape Town. The plan of the pebble bed reactor power plant will use the helium coolant to run the turbine directly rather than heat a secondary fluid, as in a water reactor.

Preliminary neutronic study on Pu-based OTTO cycle pebble bed reactor

Kerntechnik ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. 643-647 ◽  
Author(s):  
T. Setiadipura ◽  
D. Irwanto ◽  
Zuhair
Keyword(s):  
Otto Cycle ◽  
Pebble Bed ◽  
Pebble Bed Reactor

Effect of bed configuration on pebble flow uniformity and stagnation in the pebble bed reactor

2014 ◽  
Vol 270 ◽  
pp. 295-301 ◽  
Author(s):  
Nan Gui ◽  
Xingtuan Yang ◽  
Jiyuan Tu ◽  
Shengyao Jiang
Keyword(s):  
Flow Uniformity ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Pebble Flow

scholarly journals A Safety Re-Evaluation of the AVR Pebble Bed Reactor Operation and Its Consequences for Future HTR Concepts

2008 ◽  
Author(s):  
Rainer Moormann
Keyword(s):  
Fission Product ◽  
End Of Life ◽  
Fission Products ◽  
Normal Operation ◽  
Primary Circuit ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Hot Gas ◽  
Design Basis ◽  
Gas Tight

The AVR pebble bed reactor (46 MWth) was operated 1967–1988 at coolant outlet temperatures up to 990°C. Also because of a lack of other experience the AVR operation is a basis for future HTRs. This paper deals with insufficiently published unresolved safety problems of AVR and of pebble bed HTRs. The AVR primary circuit is heavily contaminated with dust bound and mobile metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory. A re-evaluation of the AVR contamination is performed in order to quantify consequences for future HTRs: The AVR contamination was mainly caused by inadmissible high core temperatures, and not — as presumed in the past — by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot be equipped with instruments. The maximum core temperatures were more than 200 K higher than precalculated. Further, azimuthal temperature differences at the active core margin were observed, as unpredictable hot gas currents with temperatures > 1100°C. Despite of remarkable effort these problems are not yet understood. Having the black box character of the AVR core in mind it remains uncertain whether convincing explanations can be found without major experimental R&D. After detection of the inadmissible core temperatures, the AVR hot gas temperatures were strongly reduced for safety reasons. Metallic fission products diffuse in fuel kernel, coatings and graphite and their break through takes place in long term normal operation, if fission product specific temperature limits are exceeded. This is an unresolved weak point of HTRs in contrast to other reactors and is particularly problematic in pebble bed systems with their large dust content. Another disadvantage, responsible for the pronounced AVR contamination, lies in the fact that activity released from fuel elements is distributed in HTRs all over the coolant circuit surfaces and on graphitic dust and accumulates there. Consequences of AVR experience on future reactors are discussed. As long as pebble bed intrinsic reasons for the high AVR temperatures cannot be excluded they have to be conservatively considered in operation and design basis accidents. For an HTR of 400 MWth, 900°C hot gas temperature, modern fuel and 32 fpy the contaminations are expected to approach at least the same order as in AVR end of life. This creates major problems in design basis accidents, for maintenance and dismantling. Application of German dose criteria on advanced pebble bed reactors leads to the conclusion that a pebble bed HTR needs a gas tight containment even if inadmissible high temperatures as observed in AVR are not considered. However, a gas tight containment does not diminish the consequences of the primary circuit contamination on maintenance and dismantling. Thus complementary measures are discussed. A reduction of demands on future reactors (hot gas temperatures, fuel burn-up) is one option; another one is an elaborate R&D program for solution of unresolved problems related to operation and design basis accidents. These problems are listed in the paper.

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

scholarly journals Physical Analysis of the Initial Core and Running-In Phase for Pebble-Bed Reactor HTR-PM

2017 ◽  
Vol 2017 ◽  
pp. 1-6
Author(s):  
Jingyu Zhang ◽  
Fu Li ◽  
Yuliang Sun
Keyword(s):  
Physical Parameters ◽  
Physical Analysis ◽  
Fuel Management ◽  
Fuel Temperature ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Pebble Bed Reactors ◽  
Management Scheme ◽  
Typical Scheme ◽  
Scheme Evaluation

The pebble-bed reactor HTR-PM is being built in China and is planned to be critical in one or two years. At present, one emphasis of engineering design is to determine the fuel management scheme of the initial core and running-in phase. There are many possible schemes, and many factors need to be considered in the process of scheme evaluation and analysis. Based on the experience from the constructed or designed pebble-bed reactors, the fuel enrichment and the ratio of fuel spheres to graphite spheres are important. In this paper, some relevant physical considerations of the initial core and running-in phase of HTR-PM are given. Then a typical scheme of the initial core and running-in phase is proposed and simulated with VSOP code, and some key physical parameters, such as the maximum power per fuel sphere, the maximum fuel temperature, the refueling rate, and the discharge burnup, are calculated. Results of the physical parameters all satisfy the relevant design requirements, which means the proposed scheme is safe and reliable and can provide support for the fuel management of HTR-PM in the future.

scholarly journals Modeling stationary and moving pebbles in a pebble bed reactor

2015 ◽  
Vol 80 ◽  
pp. 52-61 ◽  
Author(s):  
Xiang Zhao ◽  
Trent Montgomery ◽  
Sijun Zhang
Keyword(s):  
Pebble Bed ◽  
Pebble Bed Reactor
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