Abstract
The double-ended guillotine break (DEGB) of the horizontal coaxial gas duct accident is a serious air ingress accident of the high temperature gas-cooled reactor pebble-bed module (HTR-PM). Because the graphite is widely used as the structure material and the fuel element matrix of HTR-PM, the oxidation analyses of this severe air ingress accident have got enough attention in the safety analyses of the HTR-PM. The DEGB of the horizontal coaxial gas duct accident is calculated by using the TINTE code in this paper. The results show that the maximum local oxidation of the matrix graphite of spherical fuel elements in the core will firstly reach3.75⁎104 mol/m3at about 120 h, which means that only the outer 5 mm fuel-free zone of matrix graphite will be oxidized out. Even at 150 h, the maximum local weight loss ratio of the nuclear grade graphite in the bottom reflectors is only 0.26. Besides, there is enough time to carry out some countermeasures to stop the air ingress during several days. Therefore, the nuclear grade graphite of the bottom reflectors will not be fractured in the DEGB of the horizontal coaxial gas duct accident and the integrity of the HTR-PM can be guaranteed.
Highlights
The high temperature gas-cooled reactor has been considered as a candidate of the generation IV nuclear energy system technologies because of its advanced inherent safety properties [1]
In the air ingress accident analyses of high temperature gas-cooled reactor pebblebed module (HTR-PM), there are two kinds of air ingress accidents which are regarded as beyond design basic accidents (BDBA): one is the doubleended guillotine break (DEGB) of the horizontal coaxial gas duct which could result in large amount of air ingress into the primary circuit; the other is the simultaneous rupture of both upper and lower fuel discharging pipes connected to the primary loop which could cause large amount of air ingress due to the chimney effect [3]
The DEGB of the horizontal coaxial gas duct accident of HTR-PM is simulated by TIme Dependent Neutronics and TEmperatures (TINTE) code
Summary
The high temperature gas-cooled reactor has been considered as a candidate of the generation IV nuclear energy system technologies because of its advanced inherent safety properties [1]. Zone III is called the mass transfer controlled regime (BLDR), where the reaction temperature is high and the oxidation rate is dominated by the boundary diffusion mechanism. In this regime, the oxidation rate is much larger than that in CR and IPDR. Based on the calculation results, this paper mainly analyzed the oxidation of the matrix graphite of spherical fuel elements and the bottom reflector and further discussed the influence of bottom reflector oxidation on the integrity analyses in the DEGB of the horizontal coaxial gas duct accident
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
