Fixed Filter Particulate and Iodine Monitor

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Fixed Filter Particulate and Iodine Monitor

The Model RS-58D Fixed-Filter Particulate and Iodine Monitor is an offline continuous air monitor mounted on a skid frame. Its sampling equipment consists of a continuously operating motor pump, flow control valves, and piping that connects to the plant sample lines. A Model RD-58 detector sub-assembly provides two channels for continuous detection of radioactive particulates and I¹³¹. A microprocessor-based, digital Model RM-80 Signal Processor processes measured activity data, which are transmitted to a Model RM-23 Control/Display Module. Each detector has a checksource that can be remotely activated to verify detector operation.

SPECIFICATIONS

DETECTOR: Model RD-58 offline radiation detector assembly consisting of two separate scintillation detectors: fixed-filter particulate and iodine (see RD-58 data sheet)

SIGNAL PROCESSOR: Model RM-80 Signal Processor

ALARMS: Each of the two channels has two-level radiation alarms (alert and high) continuously and independently adjustable over full range; one failure alarm (operate status, where green = normally on, actuated by low-line voltage trip, loss of counts from detector, tolerance not within 85% of preset checksource count rate, or loss of sample flow); operation condition alarm for out-oftolerance flow rate. One dpdt relay contact per alarm (not per channel) rated 7.5 A at 120 V ac; relays in RM-80.

CONTROL/DISPLAY MODULE: Model RM-23 Control/Display Module mounted in control room for monitor information/controls

SELF TEST: Self-diagnostics of RM-80 and RM-23 electronics; remote controlled, solenoid operated checksources; automatic and manual purge

TEMPERATURE: 40° to 131°F (4° to 55°C) ambient POWER: Input 120 V ac, 50/60 Hz, 25 A, 1ø

WEIGHT: 1700 lb (771 kg) approximate

ELECTRICAL CONNECTIONS: One shielded, twisted-pair communication cable from RM-80 to RM-23 and alarm contact wiring through top plate of customer junction-box assembly. Input power for the entire assembly through top of power and control junction box

MECHANICAL CONNECTIONS: Condensate drain valves are provided and should be connected to a radioactive waste line. Separate installation instructions are available for monitors using isokinetic nozzles

PLUMBING: Type 304 or 316 stainless steel (except gaskets); maximum use of mechanical fittings to facilitate maintenance, removal, and/or component replacement

CUSTOMER PIPING INTERFACES: 1/2-in. (127-cm), 150-lb (68-kg), raised-face, stainless steel pipe flanges at sample inlet, purge inlet, and sample outlet

CABLING: All skid cabling complete and contained in metal conduit for electrical shielding

SAMPLE FLOW: 3 scfm (1400 cm³/sec) nominal

HUMIDITY: 95% RH at 90°F (32°C) max

THEORY OF OPERATION

In the particulate and iodine channels, the sample enters the detector chamber between the scintillation detector and the filter cartridge assembly. A beta-sensitive plastic phosphor detects radioactive particulates deposited on the filter face. In the next chamber, an NaI scintillation crystal and a photomultiplier tube detect gamma rays emitted by radioactive iodines adsorbed into an activated or charcoal or silver zeolite cartridge. The RM-80 Signal Processor reads current pulses and shows a corresponding rate for the two channels.

THE MODEL RM-80 Signal Processor performs signal processing and control functions for the monitor. The RM-80 database contains calibration constants for the RD-58 detector assembly, alarm setpoints, history (24 10-min averages, 24 1-hr averages, and 28 1-day averages), and other constants and control functions, including flow. It provides alarm relays and analog outputs. The RM-80 enclosure, rated NEMA 12, can operate at integrated radiation doses up to 10³ rad. The RM-80 is interrogated and controlled using an RM-23 Control/display Module (described below) It communicates with the RM-23 and with an RM-11 Console over shielded, twisted-pair cable.

THE MODEL RM-23 Control/Display Module provides the normal operator interface with the monitor. It allows the operator to display and alter the calibration constants, alarm setpoints, and all history contained in the RM-80 data base. The radiation exposure rate seen by the RD-58 detector assembly is continuously displayed as cpm or _Ci/cm³ in the IEEE standard

format X.XXE±XX. Calling up other information form the data base requires five keystrokes maximum. Alarm status is displayed on red (HIGH), amber (ALERT), and green (OPERATE) LEDs. The RM-23 mounts in a SE NIM bin (optional) that fits in a standard 19-in.-(48.3-cm-) wide instrument rack.

SERVICING

The Model RS-58D Particulate and Iodine Monitor requires minimal maintenance. Plug-in printed-circuit cards allow for quick replacement of faulty components. This monitor has a widely diversified software package that can perform self-diagnostics. In addition, the Model RD-58 Detector‘s particulate filter and iodine cartridge can easily be removed with no special tools.