IAEA International 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

Shielding

Source

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 Flow Mud 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-147

11.1 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

Source Metal 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/beryllium

plutonium-238/beryllium

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Moisture Gauging using Neutrons

Detector

Neutron shield

Neutron source

High hydrogen

concentration

Low hydrogen

concentration

Typical source

1.85 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/Be

370 MBq Cs-137 Neutron source

moisture

measurement

gamma source

density

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

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