Loop Studies Addressing the Hydraulic Impact From the Presence of Part-Length Fuel Rods Within a BWR Fuel Element, Using Water and Air-Water Mixtures at Room Temperature and Low Pressure

2008 ◽  
Author(s):  
Hamid Sadeghi ◽  
Jan Blomstrand ◽  
Guillermo Urrutia
Keyword(s):  
Fuel Element ◽  
Room Temperature ◽  
Low Pressure ◽  
Boiling Water ◽  
Theoretical Studies ◽  
Thermal Hydraulics ◽  
Fuel Rods ◽  
Water Reactor ◽  
Hydraulic Impact ◽  
Fuel Assemblies

There are a number of reactivity incidents which could possibly occur at low pressure in boiling water reactor (BWR) cores, and some of them may cause local boiling — entailing reactivity feed-back. Unfortunately, theoretical studies of events of this nature are somewhat hampered by the dearth of knowledge about the thermal-hydraulics involved. The research presented here addresses one particular aspect of this issue: how is BWR core thermal-hydraulics — at low pressure — affected in such fuel assemblies where some full-length rods have been replaced by part-length rods?

scholarly journals Measurement station for interim inspections of Lightbridge metallic fuel rods at the Halden Boiling Water Reactor

2018 ◽  
Vol 170 ◽  
pp. 04011 ◽  
Author(s):  
C. Hartmann ◽  
A. Totemeier ◽  
S. Holcombe ◽  
J. Liverud ◽  
M. Limi ◽  
...  
Keyword(s):  
Cross Section ◽  
Eddy Current ◽  
Boiling Water ◽  
Third Party ◽  
Boiling Water Reactor ◽  
Bonding Layer ◽  
Metallic Fuel ◽  
Fuel Rods ◽  
Water Reactor ◽  
Probe Geometry

Lightbridge Corporation has developed a new Uranium-Zirconium based metallic fuel. The fuel rods aremanufactured via a co-extrusion process, and are characterized by their multi-lobed (cruciform-shaped) cross section. The fuel rods are also helically-twisted in the axial direction. Two experimental fuel assemblies, each containing four Lightbridge fuel rods, are scheduled to be irradiated in the Halden Boiling Water Reactor (HBWR) starting in 2018. In addition to on-line monitoring of fuel rod elongation and critical assembly conditions (e.g. power, flow rates, coolant temperatures, etc.) during the irradiation, several key parameters of the fuel will be measured out-of-core during interim inspections. An inspection measurement station for use in the irradiated fuel handling compartment at the HBWR has therefore been developed for this purpose. The multi-lobed cladding cross section combined with the spiral shape of the Lightbridge metallic fuel rods requires a high-precision guiding system to ensure good position repeatability combined with low-friction guiding. The measurement station is equipped with a combination of instruments and equipment supplied from third-party vendors and instruments and equipment developed at Institute for Energy Technology (IFE). Two sets of floating linear voltage differential transformer (LVDT) pairs are used to measure swelling and diameter changes between the lobes and the valleys over the length of the fuel rods. Eddy current probes are used to measure the thickness of oxide layers in the valleys and on the lobe tips and also to detect possible surface cracks/pores. The measurement station also accommodates gamma scans. Additionally, an eddy-current probe has been developed at IFE specifically to detect potential gaps or discontinuities in the bonding layer between the metallic fuel and the Zirconium alloy cladding. Potential gaps in the bonding layer will be hidden behind a 0.5-1.0 mm thick cladding wall. It has therefore been necessary to perform a careful design study of the probe geometry. For this, finite element analysis (FEA) has been performed in combination with practical validation tests on representative fuel dummies with machined flaws to find the probe geometry that best detects a hidden flaw. Tests performed thus far show that gaps down to 25 μm thickness can be detected with good repeatability and good discrimination from lift-off signals.

Modeling of Fuel Assemblies in a Boiling Water Reactor for Seismic Analysis

2014 ◽  
Author(s):  
Yuichi Koide ◽  
Yoshihiro Goto ◽  
Yuki Sato ◽  
Shohei Onitsuka ◽  
Hirokuni Ishigaki
Keyword(s):  
Fuel Assembly ◽  
Seismic Analysis ◽  
Mass Matrix ◽  
Added Mass ◽  
Vibration Characteristics ◽  
Boiling Water ◽  
Boiling Water Reactor ◽  
Water Reactor ◽  
Excited Vibration ◽  
Fuel Assemblies

The purpose of this study is to develop a seismic analysis model of a group of fuel assemblies in a boiling water reactor and to confirm the validity of the developed model. Each fuel assembly was modeled as a beam on the basis of the finite element method. The mass matrix of the model includes an added mass matrix, which represents the coupled inertia effect caused by the coolant water, in order to simulate the coupled vibration of fuel assemblies. The added mass matrix was obtained by calculating the coefficient matrix of the acceleration vector and fluid force vector under the condition that each fuel assembly moves at unit acceleration. The validity of the model was confirmed by comparing the calculated results with experimental ones. The compared specimens for the experiments were full-scale mock-ups. The vibration characteristics of fuel assemblies in each case of 4 bodies and 368 bodies were compared. As a result of the comparison, the calculations of the frequency response were in agreement with the experimental results. Particularly, the calculation results on the resonance frequency were in good agreement, with an error of less than 2 percent, with the experimental ones. Furthermore, the calculated vibration characteristics of 368 fuel assemblies in the case of an earthquake, such as the excited vibration mode and phase characteristics, were in agreement with the experimental ones. We concluded that the developed model of fuel assemblies was applicable to seismic analysis of a boiling water core.

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