Development of the Monte Carlo-library least-squares method of analysis for neutron capture prompt gamma ray analyzers

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:6021366

Shyu, Chaurming

A new analysis principle called the Monte Carlo-Library Least-Squares (MCLLS) principle has been identified and investigated in a preliminary way for neutron capture prompt gamma-ray (NCPGR) analyzers. This method consists of: (1) generating the complete gamma-ray spectral resonse for a sample of known (assumed) composition by Monte Carlo simulation, (2) keeping track of the individual elemental responses within the Monte Carlo simulation for use as library spectra, (3) use of the (linear) library least-squares analysis method to obtain the elemental concentrations for any unknown sample spectrum, and (4) iterating these steps if the unknown concentrations are too far from the assumed composition originally used. An existing Monte Carlo model which simulated the analysis of coal on a conveyor belt using {sup 252}Cf and a Ge detector has been modified to predict these elemental library spectra. This Monte Carlo model includes several very efficient variance reduction techniques such as: (1) use of either expected value technique or discrete importance function to determine the interaction type, (2) forcing all prompt gamma rays to be emitted after an (n,{gamma}) event has occurred, (3) use of the direction biasing technique to biasing the emitting or scattering direction of primary and secondary photons toward the detector, (4) use of both deterministic estimator and statistical estimator to compute the unscattered detection probabilities of the primary photons and the subsequent secondary photons, (5) use of the correlated sampling method in order to study the sensitivity of the library spectrum shape to sample composition, and (6) use of the detailed detector response function to transform the detected photon spectra to pulse-height spectra.

• Research Organization: North Carolina State Univ., Raleigh, NC (United States)
• OSTI ID: 6021366
• Resource Relation: Other Information: Thesis (Ph.D)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
01 COAL, LIGNITE, AND PEAT
COAL
CHEMICAL ANALYSIS
GAMMA SPECTROSCOPY
DATA ANALYSIS
CALIFORNIUM 252
CONSTRAINTS
FEASIBILITY STUDIES
LEAST SQUARE FIT
MONTE CARLO METHOD
PROMPT GAMMA RADIATION
RECOMMENDATIONS
SPECTRAL RESPONSE
USES
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
CALIFORNIUM ISOTOPES
CARBONACEOUS MATERIALS
ELECTROMAGNETIC RADIATION
ENERGY SOURCES
EVEN-EVEN NUCLEI
FOSSIL FUELS
FUELS
GAMMA RADIATION
HEAVY NUCLEI
IONIZING RADIATIONS
ISOTOPES
MATERIALS
MAXIMUM-LIKELIHOOD FIT
NUCLEI
NUMERICAL SOLUTION
RADIATIONS
RADIOISOTOPES
SPECTROSCOPY
SPONTANEOUS FISSION RADIOISOTOPES
YEARS LIVING RADIOISOTOPES
400101* - Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
010600 - Coal
Lignite
& Peat- Properties & Composition