• Radiation Monitoring
• Nuclear Power Plant Radiation Monitoring
• Environmental and Plant Monitoring
• Radioactive Callibration Standards (PDF)
• Installations
• Electronic Personal Dosimeter

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MAJOR ASSEMBLIES

• Geiger Mueller Tube Detectors
• Ionization Chamber Detectors
• RM-80 Microprocessor/Customer Interface Junction Box

FEATURES Geiger-Mueller Tube Detectors Ranges: RD-10B, 10-1to 104mR/hr RD-11, 10-2to 103mR/hr RD-12, 100to 105mR/hr Built-in Cl36checksource (exempt quantity) Uniform energy response (±20%) from 0.8 to 3 MeV Internal amplification to drive signal up to 5,000 ft. Environmental cable connector Ionization chamber Detectors Ranges: RD-2A and RD-2B, 10-1to 104R/hr RD-8, 2 x 10-2to 2 x 104R/hr RD-23, 100to 108R/hr Built-in keep-alive source Uniform energy response (±20%) from 0.8 to 3 Mev Signal drive up to 1,000 ft MHV/BNC connectors (RD-2A and RD-2B) MHV/BNC connectors with nuclear-grade shrink sleeve (RD-8) HN connectors with nuclear-grade shrink sleeve (RD-23)

OPTIONS Equipment Extended-range configurations Multi-detector configurations RM-23A Control/Display Module RL-10 Local Indicator Lead shield for Process Monitoring application (for RD-2B, RD-10B, RD-11, and RD-12) Qualifications Seismic - IEEE 344-1975 Environmental - IEEE 323-1974 RM-80 Microprocessor Data acquisition and control Application-specific data base Front panel meter Local status indication Analog outputs External digital communications Multiple history files Continuous self-test Online diagnostics Operates as a stand-along system or may be integrated with a system configuration Internal 120 V ac power filter Outlet for test instruments NEMA-12 enclosures Customer Interface Junction Box Germinal blocks for field cable termination Cable entry from above through removable cover plate Wire trough for Customer Interface Junction Box to RM-80 Microprocessor cables Alarm lights NEMA-12 enclosures DOCUMENTATION Equipment Manual Operation and maintenance instructions Engineering drawings Parts lists

DESCRIPTION

Stand-alone G-M Tube and Ionization Chamber Detectors, coupled with an RM-80 Microprocessor, are used for monitoring within the plant and for monitoring process streams without withdrawing a sample. Area monitoring at lower radiation ranges is generally for plant personnel protection. Area monitoring at higher radiation ranges is generally for detecting breaches in process stream or containment boundaries. Process monitoring with stand-alone detectors is often applied to steam lines, high temperature process lines, and process lines with high concentrations.

GEIGER-MUELLER (G-M) TUBE DETECTORS

The aluminum housing around the thin-walled G-M Tube makes the RD-10B, RD-11 and RD-12 Detectors responsive to gamma radiation only. When a gamma photon interacts with the G-M Tube wall and a secondary electron reaches the internal gas, the gas goes into avalanche ionization. The tube current created causes the preamplifier to provide a positive output pulse. A small amount of halogen gas in the G-M Tube quenches the ionization. The G-M Tube is operated with a high voltage of 600 V dc.

At high radiation levels, a G-M Tube begins to saturate. The preamplifier board has a circuit which measures the G-M Tube's average dc current. This circuit provides a signal to the RM-80 Microprocessor when the G-M Tube exceeds its range and starts to undergo significant saturation. The RM-80 Microprocessor then maintains a full scale output for radiation levels up to 100 times the full scale rating of the G-M Tube.

A checksource function is provided by a fixed-position Cl³⁶ beta source (3 x 10⁵ yr half-life) with a solenoid-operated shutter. During normal operation, the aluminum shutter is between the Cl³⁶ source and the G-M Tube element. In a checksource mode, the RM-80 Microprocessor actuates the solenoid which moves the shutter and exposes the G-M Tube element to the Cl³⁶ source.

IONIZATION CHAMBER DETECTORS

Ionization Chamber Detectors are mounted in housings with mounted plates to facilitate installation. Insulating material between the housing and the chamber provides electrical isolation of the chamber.

Gamma photons interact with the walls; when secondary electrons reach the active region of the chamber, ion pairs are created which result in a dc current at the detector output. Ionization Chamber Detectors are operated at 1800 V dc (RD-2A, RD-2B, and RD-8) or 875 V dc (RD-23).

RM-80 MICROPROCESSOR/CUSTOMER INTERFACE JUNCTION

The RM-80 Microprocessor performs data acquisition and control functions, and provides alarm relays, analog outputs, and digital communications. The RM-80 Microprocessor can accept up to four G-M Tube Detector inputs or up to two Ionization Chamber Detector inputs. The RM-80 microprocessor data base, which can be programmed for specific applications as required by the user, contains the calibration constants for each detector, alarm setpoints, and history files (twenty-four 10-min averages, twenty-four 1-hr averages, and twenty-eight 24-hr averages).

Adjacent to the RM-80 Microprocessor is a Customer Interface Junction Box (CIJB) for termination of all field cables.

OPTIONS

Extended-range Configurations

System configuration with ranges which overlap between the G-M Tube Detector and the Ionization chamber Detector are available. A commonly used configuration for area monitoring combines the RD-2A Detector and G-M Tube Detector to provide the following ranges:

• RD-2A and RD-10B - 10^-1 to 10⁷ mR/hr
• RD-2A and RD-11 - 10^-2 to 10⁷ mR/hr
• RD-2A and RD-12 - 10⁰ to 10⁷ mR/hr

Another commonly used configuration for steam line process monitoring combines RD-2B Detectors, shield assemblies described below, and G-M Tube Detectors to provide the ranges listed above. Typically, the RM-80 Microprocessor uses Channel 1 for the G-M Tube Detector output and Channel 2 for the Ionization Chamber Detector output.

The RM-80 Microprocessor firmware has been programmed to provide a third composite channel covering the extended-range configurations. This third channel can drive meters and records and can be displayed continuously on an RM-23A Control/Display Module.

For steam line process monitoring applications, the relation between radioactive material concentration in the steam lines and dose rate at the detector can usually be calculated and used in determining the detector conversion factors for the RM-80 Microprocessor data base. The conversion factors enable each channel readout to represent radioactive concentration in units such as µCi/cm³ .

Multi-detector Configurations

The RM-80 Microprocessor can be configured to accept up to four G-M Tube Detector inputs and to provide the corresponding number of channels. The capacity for Ionization Chamber Detectors is two per RM-80 Microprocessor.

RM-23A Control/Display Module

An optional RM-23A Control/Display Module provides operator/monitor interface at a location remote from the RM-80 Microprocessor. The microprocessor-based RM-23A Control/Display Module communicates with the RM-80 Microprocessor over a shielded twisted-pair cable. The RM-23A Control/Display Module provides complete monitor control and allows display and alteration of channel and monitor items in the RM-80 Microprocessor data base. The measured radiation level of any channel can be presented on the numerical display continuously. Alarm lights indicate high (red), alert (amber), and operate status (green) for each channel. In addition, the RM-23A Control/Display Module provides alarm relay drivers and 4-to-20 mA analog outputs for peripherals such as a strip-chart recorder.

RL-10 Local Indicator

An optional RL-10 Local Indicator provides audible and visual alarms and a meter display of the changing reading. The front panel contains a green operate light, a horn acknowledge pushbutton, a horn, and an analog meter. The RL-10 Local Indicator can operate at higher temperatures and radiation levels than the RM-80 Microprocessor.

Detector-Shield Assembly

Some applications call for a 2L shield arrangement for the detector. Steam line process monitoring is a typical application. For the G-M Tube Detectors and RD-2B Ionization Chamber Detector, a shield providing 3-in. lead is available. The shield can be mounted as close as two inches from the outer surface of the structure to be monitored.

Detector	Approximate Weight (lb)	Range	Temperature (Max)
RD-2A, RD-2B	3	10-1 to 104 R/hr	165°
RD-8	10	2 x 10-2 to 104 R/hr	400°
RD-10B	1	10-1 to 104 mR/hr	165°
RD-11	1	10-2 to 103 mR/hr	165°
RD-12	1	100 to 105 mR/hr	165°
RD-23	11	100 to 108 R/hr	350°