Scaling and design analyses of a scaled-down, high-temperature test facility for experimental investigation of the initial stages of a VHTR air-ingress accident

Journal Article · Wed Jul 01 00:00:00 EDT 2015 · Nuclear Engineering and Design

DOI:https://doi.org/10.1016/j.nucengdes.2015.03.007· OSTI ID:1188620

Arcilesi, David J. ^[1]; Ham, Tae Kyu ^[1]; Kim, In Hun ^[1]; Sun, Xiaodong ^[1]; Christensen, Richard N. ^[1]; Oh, Chang H. ^[2]

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1. The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program
2. Idaho National Lab. (INL), Idaho Falls, ID (United States)

A critical event in the safety analysis of the very high-temperature gas-cooled reactor (VHTR) is an air-ingress accident. This accident is initiated, in its worst case scenario, by a double-ended guillotine break of the coaxial cross vessel, which leads to a rapid reactor vessel depressurization. In a VHTR, the reactor vessel is located within a reactor cavity that is filled with air during normal operating conditions. Following the vessel depressurization, the dominant mode of ingress of an air–helium mixture into the reactor vessel will either be molecular diffusion or density-driven stratified flow. The mode of ingress is hypothesized to depend largely on the break conditions of the cross vessel. Since the time scales of these two ingress phenomena differ by orders of magnitude, it is imperative to understand under which conditions each of these mechanisms will dominate in the air ingress process. Computer models have been developed to analyze this type of accident scenario. There are, however, limited experimental data available to understand the phenomenology of the air-ingress accident and to validate these models. Therefore, there is a need to design and construct a scaled-down experimental test facility to simulate the air-ingress accident scenarios and to collect experimental data. The current paper focuses on the analyses performed for the design and operation of a 1/8th geometric scale (by height and diameter), high-temperature test facility. A geometric scaling analysis for the VHTR, a time scale analysis of the air-ingress phenomenon, a transient depressurization analysis of the reactor vessel, a hydraulic similarity analysis of the test facility, a heat transfer characterization of the hot plenum, a power scaling analysis for the reactor system, and a design analysis of the containment vessel are discussed.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1188620
• Report Number(s): INL/JOU-15-35654; TRN: US1500209
• Journal Information: Nuclear Engineering and Design, Vol. 288, Issue C; ISSN 0029-5493
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
AIR
REACTOR VESSELS
EXPERIMENTAL DATA
REACTOR ACCIDENTS
TEST FACILITIES
DESIGN
HELIUM
SCALING LAWS
GEOMETRY
TEMPERATURE RANGE 1000-4000 K
DEPRESSURIZATION
GAS COOLED REACTORS
HYDRAULICS
COMPUTERIZED SIMULATION
HEAT TRANSFER
DENSITY
MIXTURES
SAFETY ANALYSIS
CONTAINMENT
OPERATION
TRANSIENTS
VHTR