Gauges and well logging Overview Day 6 – Lecture 3

Objectives To give an awareness of the use of radioactive sources in gauging equipment To gain a basic understanding of how these gauges work Lecture notes: Instructions for the lecturer/trainer

Content What is a nuclear gauge ? Applications of gauges in industry Gamma gauges transmission Beta gauges transmission and backscatter Neutron gauges Well logging Lecture notes: Instructions for the lecturer/trainer

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)

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 Need examples

Applications of gauges in industry Paper Thickness Film Thickness Quality control Beverage Level Oil Level

Applications of gauges in industry Mineral Weight Process Control Mineral Level Mud Flow Liquid Flow

Types of nuclear gauge Gauges can be categorised by their mode of operation transmission backscatter type of radioactive source used Gamma Beta Neutron

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

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

Types of nuclear gauge Gamma Beta Neutron Lecture notes: Instructions for the lecturer/trainer

Gamma gauges Density gauge Level gauge All operate in transmission mode Sources used caesium-137 cobalt-60 americium-241 Lecture notes: Instructions for the lecturer/trainer

Density gauge 1 GBq Cs-137 Detector Source Typical 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 3

Point level gauge Sources Detectors Low level alarm High level alarm Typical source: 10 GBq Cs-137 High level alarm Sources Detectors Low level alarm 3

Point level gauges Sources only. Detectors out of view. Note no power supply needed, nor probes into the vessel.

Liquid fill height gauge Accept Source Detector Typical source: 3.7 GBq Am-241 Drinks can or bottle Reject 3

Liquid fill height gauge

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) Lecture notes: Instructions for the lecturer/trainer

Beta thickness gauge source web detector Typical sources: 3.7 GBq Pm-147 11.1 GBq Kr-85 web Describe typical industries using thickness gauges, ranging from tissue paper to steel sheet. detector 2

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

Beta thickness gauge

Beta coating thickness gauge Source 1 Source 2 coating web Detector 1 Detector 2 Typical source: 37 GBq Kr-85 2

Beta backscatter gauge Typical sources: 200 MBq Pm-147, Tl-204 GM counter Source Beta particles scattered back according to the thickness of the coating - thicker the coating, the more backscatter Metal coating Substrate Thicker the coating, the more backscatter 4

Beta backscatter gauge

Neutron gauges hydrocarbon detection gauge moisture content gauge usually operate in backscatter mode Sources used americium-241/beryllium plutonium-238/beryllium Neutrons are produced when alpha particles impinge upon any of several low atomic weight isotopes including isotopes of lithum, oxygen and carbon. As an example, a representative alpha-beryllium neutron source can be expected to produce approximately 30 neutrons for every one million alpha particles. Beryllium has a large scattering cross section for high-energy neutrons, thus effectively slowing the neutrons to the thermal energy range where the cross section is low (about 0.008 barn). The predominant beryllium isotope 9Be also undergoes a (n,2n) neutron reaction to 8Be, that is, beryllium is a neutron multiplier, releasing more neutrons than it absorbs. This nuclear reaction is: 94Be + n → 2(42He) + 2n Instructions for the lecturer/trainer

Moisture Gauging using Neutrons Typical source 1.85 GBq Am/Be Detector Neutron shield High hydrogen concentration Alpha (a) 5,443 (12.8%) & 5,486 (85.2%) KeV Neutron (n) - 4,500 KeV Neutron source Low hydrogen concentration

Neutron soil moisture gauge

Nuclear Density Gauge Neutron source moisture measurement gamma source Typical sources: 1.85 GBq Am-241/Be 370 MBq Cs-137 Neutron source moisture measurement Am-241/Be gamma source density measurement Cs-137

Nuclear density gauge

Well Logging Operations and Equipment 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

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.

Drill-to-Stop Well Logging Operation Well Logging tools without sources at storage facility Well Logging tools without sources stored in transport vehicle

Measurement While Drilling (MWD)

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.

Radioactive Source Port MWD - Neutron Sub Radioactive Source Port Detectors

Radioactive Source Port MWD – Gamma Sub Radioactive Source Port Detectors

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.

Summary Overview of the types of nuclear gauges found in the workplace Brief description of well logging equipment and process Lecture notes: Instructions for the lecturer/trainer