Functional test results are presented and comparative test results between the JBS gamma probe and the AlphaNUCLEAR Hi-Flux probe are evaluated. Future work is discussed for the use of Monte Carlo modeling and a high activity source to characterize the JBS gamma probe and achieve conversion of gamma counts to U3O8 grade.
Introduction
Thesis Objective
Cameco is working on preliminary plans to implement physical assay sampling downstream of the pilot hole to characterize the contaminant concentration and determine average grades per cavity. The penetrating nature of gamma radiation makes it possible to sample rock masses larger than the borehole itself; leads to a more accurate characterization of the uranium content and provides much faster results than chemical analysis [2].
Format of Thesis
Chapter 5 presents concept generation for each subsystem and constructs concept scoring matrices. At the end of the chapter, a morphological table is presented to show the selected design option for each subsystem.
Background
The deposit is in secular equilibrium as evidenced by the correlation between borehole gamma log uranium grade estimates and chemical test results. The mineral resource and mineral reserve geological interpretation model is the basis for the JBS cavity grade estimates and contains a combination of chemically tested boreholes and borehole radiometric data as shown in Figure 2.1 [4].
Mining Method
- Jet Boring Mining Method
- Project Motivation
The remainder of the pilot hole is drilled with a 1434 inch tri-cone drill, as shown in Figure 2.6, and the hole is examined with a gyroscope [5]. Before a cavity can be extracted, the blasting rods are inserted into the cased pilot hole, as shown in Figure 2.7, and the blasting sequence is initiated according to a blasting recipe.
Project Planning
- Opportunity Identification
- Mission Statement
Assumptions Data collection will be done automatically from a fixed position in the JBS lead hole drill rod. Normal functioning of the radiometric probe will have no impact on the JBS cycle time.
Costumer Need Identification
- Costumer Needs Lists Identification and Weighting
The device will be used in a rugged mining environment and will be exposed to high grade uranium ore. Minimal setup and initialization will be required, and data will be acquired using a standard PC.
Product Specifications
Product Description Develop a proof of concept for a gamma logger capable of determining ore grades and ore/waste contact while drilling the JBS pilot hole without affecting the JBS cycle time. 5 N7 JBS Gamma Probe data can be retrieved from the device. 5 N8 JBS Gamma Probe assembly can be mounted in the JBS pilot.
Technical Feasibility
Functional Decomposition
Radiation Measurement
- Radiation Interaction with Matter
- Equilibrium
- Z -effect
- Dead Time
Dead time is the time elapsed before the detector is able to detect another occurrence of radiation. Recovery time is the time elapsed before the detector produces a signal of high enough amplitude to generate a count from the discriminator [19].
Radiation Measurement Technologies
- Radiation Detectors Basics
- Gas Filled Detectors
- Scintillation Detectors
- Semiconductor Detectors
In the same way as an atom's discrete electronic energy states, a crystal has discrete energy bands as shown in Figure 4.19. The distribution of the electronic states is dictated by the Fermi distribution function, P(E) in equation (4.8) and illustrated in Figure 4.18.
Existing Patents
Concept generation and selection for the five subsystems of the JBS gamma probe are described in Section 5. US 7253401 B2 discloses a system for spectral logging of gamma rays during drilling for detecting gamma rays in a borehole. In this system, detectors are mounted on the periphery of the drill bit to increase sensitivity.
There is no indication that the plant would be suitable for the high flow environment present in the Cigar Lake mine orebody.
Concept Generation
- Radiation Detector Concepts
- High Voltage Power Supply Concepts
- Controller Concepts
- Battery Concepts
- Enclosure Concepts
The biggest disadvantage of this power supply is that it can only work from 0 ◦C to +70 ◦C;. The final power supply analyzed was the Matsusada TR Series TR-0.7P, a temperature-compensated high-voltage power supply capable of delivering up to 700 Vdc with <20 mVpp ripple from a 4.75 to 5.25 Vdc input. A matrix logger was chosen as the reference point because it is already in use at the Cigar Lake mine for well logging.
Designed in-house by alphaNUCLEAR for the PRISM Alpha monitoring system, this board is an area monitoring device for radon progeny built for the harsh underground mining environment.
Concept Selection
The AlphaNUCLEAR 597-PX3 logic board was selected as the controller because it was the highest ranked device from Table 5.3. The LiF eP O4 battery pack was chosen because it was identified as the best design in Table 5.4. The decision matrix in Table 5.5 identified the Hammond R-box as the most suitable to meet customer requirements.
The Hammond box was found to be three times more expensive than the Bud Industries AN1322 enclosure and required more machining to manufacture a bracket.
Implementation
- Hardware
- Firmware
- Software
The PRISM board components used in the JBS gamma probe board retain the original names. The radiation detection circuit of the JBS gamma probe is based on the original Hi-Flux probe shown in Appendix A.2. The JBS gamma probe firmware returns to a default date and time on first microprocessor initialization.
The user interface of the JBS gamma probe tool is shown in Figure 6.6 and connects to the JBS gamma probe via USB.
Form Generation
- Detector Box Design
- Readout Box Design
- Connection Terminal Module
The LEDs of the detectors have also been removed and replaced by the LEDs of the charger of the readout cabinet. The connection terminal module, shown in Figure 6.9, has been developed to provide easy maintenance and fast, reliable connection of the pins shared between the detector box and the interrogator box. To reduce costs, the detector terminal module and the readout box are designed as one board.
The first iteration of the JBS gamma probe had terminal blocks to connect each of the thirty-six cables from the detector box to the readout box.
Cigar Lake Alpha Testing Configuration
Data from the cleaning cycle cannot be used because no training logs have been recorded. This issue has been identified and will be addressed in due course by a previous shelved project that uses the height of the JBS drill table and the position of the drill clamp to determine the position of the drill head during the complete drilling cycle and cleaning. Once the position of the drill rods is tracked during the complete drilling cycle, at least four data points will be available for every 10 cm interval to increase confidence in the measurement.
The next chapter summarizes the laboratory tests performed on the JBS gamma probe, and the results from the Cigar Lake alpha tests are presented in Chapter 8.
Prototype Test Results
Immersion testing was done on Detector 1 when it still had cable glands as seen in Appendix A.4 and Appendix A.5. The design was changed soon after to main parts connectors to reduce moving parts, but the immersion test was not repeated before the alpha test. For testing purposes, the approximate time was programmed into the firmware as a temporary measure and had to be updated whenever the microprocessor lost power.
In addition, the detector did not need to be localized in the JBS pilot hole or prepared for alpha testing.
Laboratory Test Results
However, the readings are tightly clustered and the JBS gamma probe has consistently higher readings than the Hi-Flux probe. There was plexiglass between the bottom of the high flux probes and the source, which was not the case for the JBS gamma probe. Once again, the readings clustered closely with similar standard deviations with less consistency in the Hi-Flux probe readings.
Again the readings are closely grouped with similar standard deviations, but this time the JBS gamma probe readings are less consistent.
Discussion
- Circuit Board Testing
- Firmware Testing
- JBS Gamma Probe Configuration Utility
- Detector Box Testing
- Readout Box Testing
- Field Testing
- Lab Testing
Most of the elements on the JBS gamma probe are low power consumers, with the exception of the LCD screen and LEDs, which are not attached to the detector during drilling. The success of the JBS gamma probe depends on the integrity of the detector box. Housing Installation Test 3.2 ensured that the detector was securely mounted in a fixed location in the gamma probe drill rod.
Field testing of the JBS gamma probe was carried out by determining the location of the detector in the pilot well using test 7.1.
Results
The general trend of the JBS gamma probe corresponds to diamond borehole SF771 03 and the peak at the top of the cavity corresponds to SF766 04, as shown in Figure 8.3. The majority of counts are around 10 to 20 cps, which is consistent with the low quality expected in the cavity. The radiometric profile of the JBS gamma probe is consistent with diamond drill holes SF771 04 and SF766 04 and shows that the majority of the high-grade ore is located near the top of the cavity.
The JBG gamma probe readings indicate that the highest grade material in the cavity was located at the top of the cavity.
Discussion
- Numerical Modelling
Furthermore, analysis of the reported counts while the detector was stationary was highly consistent with an average standard deviation of less than 5% of the mean, comparable to the measurements obtained during laboratory testing on a single point source. In 765 025 E CV, the two counting peaks observed by the detector correspond to the radiometric data obtained from diamond borehole SF771 03. This was not proven because there is no drilling data to locate the detector in the pilot hole.
The detector showed a "No SD Card" error suggesting that the SD card had been unplugged due to vibration.
Summary and Contributions
A background on the Cigar Lake mine, an overview of the mine's unique challenges, and an overview of the Jet Boring mining method were provided. The prototype was presented and the discussion focused on the prototype PCB design and the presentation of the critical gamma detection circuits. The detector box design was presented as part of the detector shape design, followed by the readout box design.
The form function concluded with an introduction of the connection terminal module, which greatly simplified the design for the detector and readout box and allowed troubleshooting without special tools.
Future Work
Test Description: This test verifies that the power supply for the PIC controller and the USB connection is set to 3.3 volts. Test Description: This test verifies that the JBS gamma probe clock can be synchronized by the setup program. Test Description: This test will determine if the enclosure is watertight enough to accommodate the JBS range tonight.
Test description: This test checks whether the detector box is securely mounted in the JBS drill rod. Test Description: This test verifies that the sensor can be calibrated in frozen ground. Test Description: This test verifies the acquisition of time-stamped position data for the JBS pilot hole drilling.