scholarly journals KUGEL: a thermal, hydraulic, fuel performance, and gaseous fission product release code for pebble bed reactor core analysis

1981 ◽  
Author(s):  
B.I. Shamasundar ◽  
M.E. Fehrenbach
Keyword(s):  
Fission Product ◽  
Reactor Core ◽  
Core Analysis ◽  
Pebble Bed ◽  
Fuel Performance ◽  
Pebble Bed Reactor ◽  
Product Release ◽  
Gaseous Fission ◽  
Gaseous Fission Product

scholarly journals Evaporation Behavior of Non-gaseous Fission Products from UO2

1965 ◽  
Vol 20 (12) ◽  
pp. 1566-1568 ◽  
Author(s):  
J. Takagi
Keyword(s):  
Fission Product ◽  
Release Rate ◽  
Diffusion Constant ◽  
Fission Products ◽  
Post Irradiation ◽  
Product Release ◽  
Proportionality Constant ◽  
Gaseous Fission ◽  
Gaseous Fission Product ◽  
General Method

The evaporation behavior of non-gaseous fission products from UO2 was studied. The release rate of non-gaseous fission products during the post-irradiation annealing of UO2 was found to be controlled by the proportionality constant of evaporation, a, as well as the diffusion constant. The values of α for Ru, Ce, La, Mo and Te were determined at temperatures ranging 750 to 1600 °C and the general method of treating non-gaseous fission product release from UO2 was discussed.

scholarly journals Gaseous fission product release during storage at various temperatures for HTGR-type fuels

1978 ◽  
Author(s):  
C.L. Fitzgerald ◽  
R.J. Shannon ◽  
V.C.A. Vaughen
Keyword(s):  
Fission Product ◽  
Product Release ◽  
Gaseous Fission ◽  
Gaseous Fission Product

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.

Combined CFD and DEM Simulations of Fluid Flow and Heat Transfer in a Pebble Bed Reactor

2011 ◽  
Author(s):  
Xiang Zhao ◽  
Trent Montgomery ◽  
Sijun Zhang
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Discrete Element Method ◽  
Reactor Core ◽  
Turbulence Models ◽  
Discrete Element ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Packing Structure ◽  
Dem Simulations

This paper presents combined computational fluid dynamics (CFD) and discrete element method (DEM) simulations of fluid flow and relevant heat transfer in the pebble bed reactor core. In the pebble bed reactor core, the coolant passes highly complicated flow channels, which are formed by thousands of pebbles in a random way. The random packing structure of pebbles is crucial to CFD simulations results. The realistic packing structure in an entire pebble bed reactor (PBR) is generated by discrete element method (DEM). While in CFD calculations, selection of the turbulence models have great importance in accuracy and capturing the details of the flow features, in our numerical simulations both large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) models are employed to investigate the effects of different turbulence models on gas flow field and relevant heat transfer. The calculations indicate the complex flow structure within the voids between the pebbles.

ICONE19-43215 NUMERICAL RESEARCH ON THE THERMAL HYDRAULICS OF THE COOLANT IN A PEBBLE BED REACTOR CORE BY CFD

2011 ◽  
Vol 2011.19 (0) ◽  
pp. _ICONE1943-_ICONE1943
Author(s):  
Hua Li ◽  
Suizheng Qiu ◽  
Guanghui Su ◽  
Wenxi Tian ◽  
Youjia Zhang
Keyword(s):  
Reactor Core ◽  
Thermal Hydraulics ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Numerical Research

scholarly journals Study on the effect of various burnable poisons on pebble bed reactor with OTTO fuelling schemes using Serpent 2 Monte Carlo code

2021 ◽  
Vol 927 (1) ◽  
pp. 012018
Author(s):  
Nicholas Sidharta ◽  
Almanzo Arjuna
Keyword(s):  
Power Density ◽  
Power Distribution ◽  
Reactor Core ◽  
Monte Carlo Code ◽  
Volumetric Fraction ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Burnable Poison ◽  
Discrete Element Method Simulation ◽  
Upper Level

Abstract Pebble bed reactor with a once-through-then-out fuelling scheme has the advantage of simplifying the refueling system. However, the core upper-level power density is relatively higher than the bottom, producing an asymmetric core axial power distribution. Several burnable poison (BP) configurations are used to flatten the peak power density and improve power distribution while suppressing the excess core reactivity at the beginning of the burnup cycle. This study uses HTR-PM, China’s pebble bed reactor core, to simulate several burnable poison (BP) configurations. Serpent 2 coupled with Octave and a discrete element method simulation is used to model and simulate the pebble bed reactor core. It is found that erbium needs a large volumetric fraction in either QUADRISO or distributed BP to perform well. On the other hand, gadolinium and boron need a smaller volumetric fraction but perform worse in radial power distribution criteria in the fuel sphere. This study aims to verify the effect of BP added fuel pebbles on an OTTO refueling scheme HTR-PM core axial power distribution and excess reactivity.

Fission Product Release From HTGR Fuel Under Core Heatup Accident Conditions

2008 ◽  
Author(s):  
Karl Verfondern ◽  
Heinz Nabielek
Keyword(s):  
Fission Product ◽  
Technology Development ◽  
Normal Operation ◽  
Fuel Performance ◽  
Heating Facility ◽  
Product Release ◽  
Essential Input ◽  
Accident Conditions ◽  
Product Species ◽  
Htgr Fuel

Various countries engaged in the development and fabrication of modern fuel for the High Temperature Gas-Cooled Reactor (HTGR) have initiated activities of modeling the fuel and fission product release behavior with the aim of predicting the fuel performance under operating and accidental conditions of future HTGRs. Within the IAEA directed Coordinated Research Project CRP6 on “Advances in HTGR Fuel Technology Development” active since 2002, the 13 participating Member States have agreed upon benchmark studies on fuel performance during normal operation and under accident conditions. While the former has been completed in the meantime, the focus is now on the extension of the national code developments to become applicable to core heatup accident conditions. These activities are supported by the fact that core heatup simulation experiments have been resumed recently providing new, highly valuable data. Work on accident performance will be — similar to the normal operation benchmark — consisting of three essential parts comprising both code verification that establishes the correspondence of code work with the underlying physical, chemical and mathematical laws, and code validation that establishes reasonable agreement with the existing experimental data base, but including also predictive calculations for future heating tests and/or reactor concepts. The paper will describe the cases to be studied and the calculational results obtained with the German computer model FRESCO. Among the benchmark cases in consideration are tests which were most recently conducted in the new heating facility KUEFA. Therefore this study will also re-open the discussion and analysis of both the validity of diffusion models and the transport data of the principal fission product species in the HTGR fuel materials as essential input data for the codes.

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