The seabed is envisaged to meet the increased future demands for
minerals from the rapidly growing industrialized societies of the world.
Shipboard analysis of cores can significantly reduce the cost and time
spent at the exploratory drilling stage by obviating the need to go back
to land for analysis. It can further speed the exploration process by
enabling a quick modification of the exploration plan based on the
results of the shipboard analysis.
A ²⁵²Cf-based analyzer utilizing the prompt gamma neutron
activation analysis technique has been designed. The analyzer is a
spherical iron shell with the source at its center. The seabed core is
passed through a hollow composite tube which is positioned a short
distance directly below the source and the resulting prompt gamma rays
are collimated to a HPGe detector. The rest of the sphere is filled
with paraffin. The gamma ray flux at the detector is converted into a
count rate by using a semi-empirical detector response function. This
count rate data are then used to determine the sensitivity and detection
limits for the chosen elements (Mg, Al, Ti, Cr, Mn, Fe, Ni and Cu).
Monte Carlo simulations using the Monte Carlo neutron photon
coupled transport code, MCNP, were carried out for a parametric study of
important variables influencing the design of the analyzer. These
parameters included the moderator type, source to sample distance and
sample porosity. MCNP was then used to model the analyzer and to
generate the neutron flux profiles in the sample and the prompt gamma
flux at the detector.
Due to the non-availability of the prompt gamma data for most of
the elements of economic interest in the ENDF/B-V cross section
libraries associated with MCNP, the point kernel photon transport code
ISOSHLD-II (modified for high energy gamma rays) was used to generate
the gamma flux at the detector for specific elements. The ISOSHLD-II
source term was calculated based on known gamma production data (thermal
capture only) and the thermal neutron flux in the sample obtained from
MCNP computations.
The sensitivity and detection limits obtained from the isotopic
source based analyzer were compared for the case of aluminum with values
reported from reactor facilities.
The results obtained indicate that the analyzer designed in this
work could prove suitable for the on-line analysis of many elements of
economic interest in seabed cores at the 1 weight percent level. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36235 |
| Date | 14 May 1991 |
| Creators | Anand, Ajay, 1961- |
| Contributors | Binney, Stephen E., Dodd, Brian |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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