IAEAInternational Atomic Energy Agency

Gauges and well logging

Overview

Day 6 – Lecture 3

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Objectives

• To give an awareness of the use of radioactive sources in gauging equipment

• To gain a basic understanding of how these gauges work

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Content

• What is a nuclear gauge ?• Applications of gauges in industry• Gamma gauges

• transmission

• Beta gauges• transmission and backscatter

• Neutron gauges• Well logging

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What is a Nuclear Gauge?

• Device used in numerous industries, mostly in process control and quality control.

• Consists basically of a shielded radiation source and a radiation detector

• The radiation interacts with the examined material before reaching the detector, supplying real-time data.

Detector

Material Flow

Shutter Control

ShieldingSource

Shutter(Closed)

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Applications of gauges in industry

Quality Control• Density: rubber, oils, fabric, paper, etc• Thickness: paper, glass, steel, plastic films• Level: beverages, cooking oil

Process Control• Density: cement, mud, liquids, chemical products• Level: vessels, silos, chemical products, minerals• Moisture: glass, cement, minerals

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Applications of gauges in industry

Film Thickness Paper Thickness

Beverage Level Oil Level

Quality control

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Applications of gauges in industry

Process Control

Mineral Weight

Liquid FlowMud Flow

Mineral Level

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Types of nuclear gauge

Gauges can be categorised by their mode of • operation

• transmission• backscatter

• type of radioactive source used• Gamma• Beta• Neutron

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Types of nuclear gauge

Transmission: the detector measures the amount of radiation that passes through the examined material

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Types of nuclear gauge

Backscatter: the detector is placed on the same side as the source, measuring the amount of scattered radiation

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Types of nuclear gauge

• Gamma• Beta• Neutron

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Gamma gauges

• Density gauge• Level gauge• All operate in transmission mode• Sources used

• caesium-137• cobalt-60• americium-241

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Density gauge

Detector

Typical source:1 GBq Cs-137

Source

For a known thickness of material, the density can be deduced by comparing the radiation signal at the detector with and without the material in the beam

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Point level gauge

High level alarm

Low level alarm

Typical source:10 GBq Cs-137

Sources Detectors

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Point level gauges

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Liquid fill height gauge

Typical source:3.7 GBq Am-241

Source Detector

Accept

Reject

Drinks can or bottle

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Liquid fill height gauge

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Beta gauges

• thickness gauge (transmission)• coating thickness gauge (transmission)• film thickness gauge (backscatter)• Sources used

• krypton-85 (encapsulated gas)• strontium-90 (foil source)• promethium-147 (foil source)

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Beta thickness gauge

detector

source

web

Typical sources:3.7 GBq Pm-14711.1 GBq Kr-85

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Beta thickness gauge

Can be used to measure: paint, oil, lubricating films, plastic, enamel, ceramic and phosphate coatings on metals and some non-metals

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Beta thickness gauge

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Beta coating thickness gauge

Detector 1

Source 1

web

Typical source:37 GBq Kr-85

coating

Source 2

Detector 2

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Beta backscatter gauge

GM counter

SourceMetal coating

Substrate

Typical sources:200 MBq Pm-147, Tl-204

Thicker the coating, the more backscatter

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Beta backscatter gauge

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Neutron gauges

• hydrocarbon detection gauge• moisture content gauge• usually operate in backscatter mode• Sources used

americium-241/berylliumplutonium-238/beryllium

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Moisture Gauging using Neutrons

Detector

Neutron shield

Neutron sourceHigh hydrogenconcentration

Low hydrogenconcentration

Typical source1.85 GBq Am/Be

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Neutron soil moisture gauge

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Nuclear Density Gauge

Am-241/Be

Cs-137

Typical sources:1.85 GBq Am-241/Be370 MBq Cs-137Neutron source

moisture measurement

gamma sourcedensity measurement

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Nuclear density gauge

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Well Logging Operations and Equipment

• Well logging• Drill to Stop• Measurement or Logging While Drilling

• Borehole logging• Sources used

• caesium-137 (gamma), typically 40 GBq• americium-241 / beryllium (neutron), typically

110 GBq

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Drill-to-Stop Well Logging Operation

Well Logging operation that requires all drilling operations to cease and requires that parts of the drilling apparatus are removed to provide access to the well bore. The well logging tool is then lowered into the well bore to obtain information.

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Drill-to-Stop Well Logging Operation

Well Logging tools without sources stored in transport vehicle

Well Logging tools without sources at storage facility

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Measurement While Drilling (MWD)

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Measurement while Drilling (MWD)

Well Logging operations that occur during the drilling of the well bore and do not require that the drill stem or other equipment be removed from the well. This type of operation requires that the well logging tool contains one or more sealed sources and be located above the drilling stem to obtain information through mud telemetry communications.

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MWD - Neutron Sub

Radioactive Source Port

Detectors

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MWD – Gamma Sub

Radioactive Source Port

Detectors

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Geological borehole logging

Geological logging is used to investigate the geological make-up of an area by lowering test tools into a borehole. The picture shows a logging tool containing a neutron source.

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Summary

• Overview of the types of nuclear gauges found in the workplace

• Brief description of well logging equipment and process