This paper presents an experimental study dealing with the burning rate of pool fire in a confined and ventilated compartment within the framework of nuclear safety research. Based on full-scale pool fire experiments, it provides new information to improve understanding of burning rate mechanisms in confined and ventilated fire scenario. First of all, the paper describes the experiments conducted in both a free atmosphere and a compartment; the facility, instrumentation and fire source are detailed. Then, an analysis is made comparing free atmosphere and compartment burning rate for the same fire scenario (0.4 m 2 TPH pool fire). In compartment, burning rate versus time reveals three different periods: a first period when free atmosphere and compartment burning rate are identical, a second unsteady period, during which the burning rate is higher in a compartment than in a free atmosphere and a third steady period. From video-recorder and image analysis, a detailed description of the second unsteady region shows oscillating and periodic flame behaviour resulting in significant increase of the burning rate. The effects of the ventilation rate and the pool area on this phenomenon are demonstrated. The results provide new experimental information that contribute to improving understanding of burning rate in a compartment.
International audienceThe aim is to characterize the energy distribution of neutron fluence in the energy range 8 keV–5 MeV based on a primary standard: the LNE-IRSN/MIMAC microTPC. The microTPC is a time projection chamber. Time projection chambers are gaseous detectors able to measure charged particles energy and to reconstruct their track. The gas is used as a (n, p) converter in order to detect neutrons down to few keV. The neutron energy is reconstructed event by event thanks to proton scattering angle and proton ionization energy measurements. The scattering angle is deduced from the 3-D track. The proton energy is obtained by charge collection measurements, knowing the ionization quenching factor. The fluence is reconstructed thanks to the detected events number and the simulation of the detector response. The microTPC is a new reliable detector able to measure energy distribution of the neutron fluence without unfolding procedure or prior neutron calibration contrary to usual gaseous counters. The microTPC is characterized at the AMANDE facility, with neutron energies going from 8 keV to 565 keV. This work shows the first direct reconstruction of neutron energy and fluence, simultaneously, at 27.2 keV in a continuous irradiation mode
Summary
Repeatability of large‐scale fire test remains a key issue for code validation process. Most of the large‐scale experimental studies are based on single experiment, and the influence of repeatability is barely considered in the test analysis process. Due to the substantial cost, reproducing several trials of a given large‐scale fire scenario is not often performed. In the framework of the OECD PRISME 2 project, this topic has been identified, and a specific large‐scale fire test has been reproduced twice in the final goal of assessing the level of repeatability. The scenario is an oil pool fire in an enclosure mechanically ventilated and during which a water spray system is activated. The analysis consists in identifying a set of variables on which metrics is applied in order to quantify the levels of discrepancy between the two tests. A set of 27 variables are selected such as they characterize the whole fire scenario (the fire source, the gas phase, walls, the ventilation network, and the water spray system). The analysis points out that the repeatability levels are different depending on the type of variable. The gas temperature or species concentrations are more repeatable than gas pressure or air flow rate. In addition, a new methodology is proposed in comparing, for each physical variable, the variations due to repeatability (ie, the precision) and the uncertainty. A new metric is proposed helping modelers in code validation process.
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