Silver-indium-cadmium control rod behavior and aerosol formation in severe reactor accidents
Silver-indium-cadmium (Ag-In-Cd) control rod behavior and aerosol formation in severe reactor accidents are examined in an attempt to improve the methodology used to estimate reactor accident source terms. Control rod behavior in both in-pile and out-of-pile experiments is reviewed. A mechanistic model named VAPOR is developed that calculates the downward relocation and simultaneous vaporization behavior of the Ag-In-Cd alloy expected after control rod failure in a severe reactor accident. VAPOR is used to predict the release of silver, indium, and cadmium vapors expected in the Power Burst Facility (PBF) Severe Fuel Damage (SFD) 1-4 experiment. In addition, a sensitivity study is performed. Although cadmium is found to be the most volatile constituent of the alloy, all of the calculations predict that the rapid relocation of the alloy down to cooler portions of the core results in a small release for all three control rod alloy vapors. Potential aerosol formation mechanisms in a severe reactor accident are reviewed. Specifically, models for homogeneous, ion-induced, and heterogeneous nucleation are investigated. These models are applied to silver, cadmium, and CsI to examine the nucleation behavior of these three potential aerosol sources in a severe reactor accident and to illustrate the competition among these mechanisms for vapor depletion. The results indicate that aerosol formation in a severe reactor accident occurs in three stages. In the first stage, ion-induced nucleation causes aerosol generation. During the second stage, ion-induced and heterogeneous nucleation operates as competing pathways for gas-to-particle conversion until sufficient aerosol surface area is generated. In the third stage, ion-induced nucleation ceases; and heterogeneous nucleation becomes the dominant mechanism of gas-to-particle conversion until equilibrium is reached.
- Research Organization:
- EG and G Idaho, Inc., Idaho Falls (USA); Nuclear Regulatory Commission, Washington, DC (USA). Div. of Accident Evaluation
- DOE Contract Number:
- AC07-76ID01570
- OSTI ID:
- 6380030
- Report Number(s):
- NUREG/CR-4876; EGG-2501; ON: TI87010661
- Country of Publication:
- United States
- Language:
- English
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220400 -- Nuclear Reactor Technology-- Control Systems
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220900* -- Nuclear Reactor Technology-- Reactor Safety
36 MATERIALS SCIENCE
360104 -- Metals & Alloys-- Physical Properties
ACCIDENTS
AEROSOL MONITORING
AEROSOLS
AIR POLLUTION MONITORING
ALGORITHMS
ALLOYS
CADMIUM ALLOYS
COLLOIDS
COMPUTER CODES
CONTROL ELEMENTS
DATA
DISPERSIONS
EXPERIMENTAL DATA
FLOW MODELS
FORTRAN
INDIUM ALLOYS
INFORMATION
MATHEMATICAL LOGIC
MATHEMATICAL MODELS
MONITORING
NUCLEATION
NUMERICAL DATA
PERFORMANCE
PROGRAMMING LANGUAGES
RADIOACTIVE AEROSOLS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR SAFETY EXPERIMENTS
SENSITIVITY ANALYSIS
SILVER ALLOYS
SOLS
TEST FACILITIES
TRANSPORT THEORY
V CODES