Ignitability of hydrogen/oxygen/diluent mixtures in the presence of hot surfaces
- AECL Research, Whiteshell Laboratores, Pinawa, Manitoba (Canada)
In the licensing process for CANDU nuclear power stations it is necessary to demonstrate tolerance to a wide range of low-probability accidents. These include loss of moderator accidents that may lead to the formation of flammable mixtures of deuterium, oxygen, helium, and steam in the reactor calandria vessel. Uncovered adjuster or control rods are considered as possible sources of ignition when a flammable mixture is present. A knowledge of the minimum hot-surface temperature required for ignition is important in assessing the reactor safety. These hot surface temperatures were measured using electrically heated adjuster rod simulators in a large spherical vessel (2.3-m internal diameter). Whereas the effects of geometry on ignition temperature were studied in the large-scale apparatus, some of the effects, such as those produced by a strong radiation field, were studied using a small-scale apparatus. Investigations carried our over a range of hydrogen and diluent concentrations indicated that, although the ignition temperatures were fairly insensitive to the hydrogen concentration, they were strongly affected by the presence of steam The addition of 30% steam to a dry combustible mixture increased the minimum surface temperature required for ignition by approximates 100{degrees}C of the diluents investigated, steam had the most effect on ignition. The effect of initial temperature of the mixture on the ignition temperature was small, whereas the effect of initial pressure was significant. The effect of substituting deuterium for hydrogen on ignition temperature was small. The effect of a high-intensity gamma-radiation field on the minimum hot-surface temperature required for ignition was investigated using a 2-dm{sup 3} ignition vessel placed in a linear accelerator. Radiation had no measurable effect on ignition temperature.
- OSTI ID:
- 227180
- Journal Information:
- Nuclear Safety, Journal Name: Nuclear Safety Journal Issue: 1 Vol. 36; ISSN 0029-5604; ISSN NUSAAZ
- Country of Publication:
- United States
- Language:
- English
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