Silver-indium-cadmium control rod behavior and aerosol formation in severe reactor accidents

Technical Report · Wed Apr 01 00:00:00 EST 1987

OSTI ID:6380030

Petti, D A

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
• Resource Relation: Other Information: Includes 2 sheets of 48x reduction microfiche
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
CADMIUM ALLOYS
CONTROL ELEMENTS
PERFORMANCE
REACTOR SAFETY EXPERIMENTS
INDIUM ALLOYS
RADIOACTIVE AEROSOLS
AEROSOL MONITORING
REACTOR ACCIDENTS
SILVER ALLOYS
ALGORITHMS
EXPERIMENTAL DATA
FLOW MODELS
FORTRAN
MATHEMATICAL MODELS
NUCLEATION
SENSITIVITY ANALYSIS
TEST FACILITIES
TRANSPORT THEORY
V CODES
ACCIDENTS
AEROSOLS
AIR POLLUTION MONITORING
ALLOYS
COLLOIDS
COMPUTER CODES
DATA
DISPERSIONS
INFORMATION
MATHEMATICAL LOGIC
MONITORING
NUMERICAL DATA
PROGRAMMING LANGUAGES
REACTOR COMPONENTS
SOLS
220900* - Nuclear Reactor Technology- Reactor Safety
220400 - Nuclear Reactor Technology- Control Systems
220502 - Nuclear Reactor Technology- Environmental Aspects- Radioactive Effluents
360104 - Metals & Alloys- Physical Properties