NEUTRON ACTIVATION ANALYSIS SYSTEM

• US 3,781,556 A
• Filed: 09/08/1972
• Issued: 12/25/1973
• Est. Priority Date: 09/08/1972
• Status: Expired due to Term

• Current Assignee: John R. Rhodes, Morris C. Taylor
• Original Assignee: John R. Rhodes, Morris C. Taylor
• Inventors: Rhodes, John R., Taylor, Morris C.
• Primary Examiner(s): Borchelt, Archie R.
• Application Number:
  US05/287,310
• Time in Patent Office: 473 Days
• Field of Search: 250/83.1,83.3R,43.5D,43.5FC,43.5MR,16T,302,308,499
• US Class Current: 376/159
• CPC Class Codes: G01N 2223/0745 neutron-gamma activation analysis
• CPC Class Codes: G01N 2223/635 fluids, granulates
• CPC Class Codes: G01N 23/222 using neutron activation analysis [NAA]

Abstract

A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, includes two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors. Associated with the first loop is a neutron source that emits a high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gamma sources and detectors are arranged across a portion of each loop for determining the fluid density.

Claims

1. A system for the neutron activation analysis of fluid media which comprises:

a. A first activation analysis loop including a neutron source for generating a neutron flux that includes a substantial flux of thermal neutrons, a radiation detector for sensing gamma radiation produced as a result of activation by said neutron flux, and conduit means for circulating a first portion of fluid proximate to said neutron source and gamma detector;

b. A second activation analysis loop including a neutron source for generating a fast neutron flux that is substantially free of thermal neutrons, a radiation detector for sensing gamma radiation produced as a result of activation by said fast neutron flux, and conduit means for circulating a second portion of said fluid proximate to said neutron source and gamma detector; and

c. Pulse spectroscopy means for processing the outputs of said radiation detectors to determine the constituents of said fluid.

2. The neutron activation analysis system of claim 1 that includes gamma attenuation means for determining the density of said fluid, said gamma attenuation means including a gamma radiation source positioned to transmit a gamma beam through a portion of said conduit means in each of said loops, and a gamma detector oppositely disposed across said conduit means from said gamma radiation source for receiving said gamma beam.

3. The neutron activation system of claim 1 wherein said first activation loop includes a 252Cf neutron source and said second neutron activation loop includes a 238Pu-9Be neutron source having a layer of neutron absorbing material surrounding the outside surface thereof.

4. The neutron activation system of claim 1 wherein saId neutron source for generating a fast neutron flux includes a plurality of isotopic neutron sources each enclosed within a cadmium envelope.

5. The neutron activation system of claim 1 wherein said first activation loop includes a plurality of 252Cf neutron sources arranged in an axial array within a helical coil disposed within an enclosure of neutron moderating material.

6. A method for determining constituents within a cement slurry which comprises:

a. Irradiating a first portion of said slurry with a flux of slow neutrons including a substantial number of thermal neutrons to produce radioisotopes from stable elements of calcium, silicon, aluminum in accordance with the reactions 48Ca(n, gamma )49Ca, 28Si(n,p)28Al, and 27Al(n, gamma )28Al;

b. Quantitatively detecting radiation from 49Ca and 28Al to respectively determine the proportion of calcium in said slurry and an indicia of the combined proportion of aluminum and silicon in said slurry;

c. Irradiating a second portion of said slurry with a fast neutron flux, that is substantially free of thermal neutrons, to produce radioisotopes from stable elements of silicon and aluminum in accordance with the reactions 28Si(n,p)28Al, 27Al(n,p)27Mg and a small contribution of 27Al(n, gamma )28Al;

d. Quantitatively detecting radiation from said 27Mg and 28Al to respectively determine the proportion of aluminum in said slurry and a second indicia of the combined proportion of aluminum and silicon in said slurry; and

e. Resolving said first and second indicia in accordance with said proportion of aluminum to determine the proportion of silicon and to confirm said proportion of aluminum in said slurry.

7. The method according to claim 6 wherein said first and second slurry portions are recycled through said flux of slow and said flux of fast neutrons until sufficient radioisotopes are produced to perform said determination.