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Title: 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

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. Themore » 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.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
1188620
Report Number(s):
INL/JOU--15-35654
Journal ID: ISSN 0029-5493; TRN: US1500209
DOE Contract Number:
AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Engineering and Design; Journal Volume: 288; Journal Issue: C
Publisher:
Elsevier
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
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 SAFETY ANALYSIS; VHTR