Steam Line Monitor

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Steam Line Monitor

MODEL RS-42D
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The model RS-42D Steam Line Monitor is a process or effluent monitor that uses a lead-shielded gamma radiation detector (two shields, two detectors for extended range). A Model RM-80 Signal Processor with an operate status light and an integral customer interface junction box provides electronic support. Options include a Model RL-10 local analog display, a Model RM-23 digital control/display module, a stripchart recorder (Leeds & Northrup or equivalent), and a modified NIM bin with power supply. The monitor readily integrates into any SE digital radiation monitoring system and satisfies Reg. Guide 1.97 (2) requirements for detecting or assessing radioactivity in releases vented by steam generator safety relief valves or atmospheric dump valves.

SPECIFICATIONS

GENERAL:

RANGE: Customer specifies 5 decades from 10^-5to 10² R/hr (standard range); 10^-5 to ⁴ R/hr (extended range)

SYSTEM ACCURACY: Meets or exceeds Reg. Guide 1.97 (2)

QUALIFICATION: Environmentally qualified to design extreme conditions per IEEE 323-1974; seismically qualified to IEEE 344-1975

DETECTOR SHIELD:

MOUNTING: 2 in. (5 cm) min from steam line, mounted on solid surface, not directly on steam line

SHIELDING: 3-in. (7.6-cm) -thick 4π solid cast-lead to reduce background effects; steel detector window for viewing pipe

WEIGHT: 510 lb (230 kg) approx. (standard range); 1020 lb (460 kg) approx. (extended range)

DIMENSIONS: 17.5 in. (44.5 cm) high x 11 in.

(27.9 cm) wide x 7.5 in. (19.0 cm) deep (each detector)

MODEL RD-12, RD-11 AND RD-10B DETECTORS

Model RD-12 (typical required range), RD-11, or RD-10B Geiger-Mueller (G-M) tube with preamplifier in weather proof aluminum housing and Cannon MS-3102R20-27P connector for voltage input and signal output (standard range)

RANGE: 10^-3 to 10² R/hr (RD-12); 10^-5 to 10⁰R/hr (RD-11); 10^-4 to 10¹ R/hr (RD-10B)

SIZE: 3.75 in. (9.5 cm) diam x 6.5 in. (16.5 cm) length

CHECKSOURCE: 1 µCi Cl³⁶ (beta); half-life = 3 x 10⁵yr

ENERGY RESPONSE: Uniform (±25%) over 500 keV to 3 MeV

OUTPUT PULSE RATE: 10⁷ cpm max

POWER: +24 V dc at 200 mA max (checksource solenoid), +700 ±100 V dc at <1 mA (detector high voltage); power supplied by Model RM-80 Microprocessor

RADIATION LIFETIME: > 10³ rad, integrated dose

OPERATING RANGE: Temperature: 32º to 160ºF (0º to 71ºC). Humidity: to 95%

MODEL RD-2B DETECTOR:

Model RD-2B gamma ionization chamber made of stainless steel with two connectors: BNC and MHV (extended range)

RANGE: 10^-1 to 10⁴ R/hr

SIZE: 2.25 in. (5.7 cm) diam x 8.8 in. (22.3 cm) length

OPERATING RANGE: Temperature: 32º to 131ºF (0º to 55ºC). Humidity: to 100%

CHECKSOURCE (OPTIONAL): "Keep-alive" bias source

ENERGY RESPONSE: Uniform (±20%) from 80 keV to 3 MeV; responsive from 60 keV to 3MeV POWER: 1800 V dc standard setting at <1 mA; power supplied by Model RM-80

RADIATION LIFETIME: >10⁸ rad, integrated dose

SIGNAL PROCESSOR:

Model RM-80 Signal Processor; RM-80/customer interface junction box wall mounted in lowradiation area; signal processor 500 ft (152 m) max from detector

POWER: 120 V ac, 60 Hz, 1f, 2 A

RADIATION LIFETIME: 10³ rad, Integral dose

ALARMS: Two level alarms (alert and high) continuously and independently adjustable over full scale and one failure alarm (operate status); one dpdt relay contact per alarm at 7.5 A at 115 V ac; alarm relays in Model RM-80

ANALOG OUTPUTS: 4 to 20 mA (standard range); 0.0 to 1.0 V dc with 15-kW load impedance (extended range)

DIMENSIONS: RM-80/customer interface junction box assembly: 30 in. (76 cm) high x 44 in. (112 cm) wide x 13 in. (32 cm) deep

OPERATING RANGE: Temperature: 39º to 131ºF (4º to 55ºC). Humidity: To 95% RH at 90ºF (32ºC)

THEORY OF OPERATION

The Model RS-42D Steam Line Monitor uses a halogen-filled Geiger-Muller (G-M) tube detector (standard range) or both a G-M tube detector and an ion chamber detector (extended range). The three standard-range G-M tube detectors (Models RD-10B, RD-11, RD-12) each offers a five-decade range between 10^-5 and 10²mR/hr (see specifications).

The standard-range Model RS-42D consists of a G-M tube and a preamplifier in a waterproof, aluminum housing. When a gamma photon enters the G-M tube, the internal gas goes into avalanche ionization. The G-M tube causes a dc voltage pulse that is electronically conditioned before it reaches a pulse input circuit in the Model RM-80 Signal Processor. The extended-range Model RS-42D consists of two detectors: a G-M tube detector (low range) and a Model RD-2B detector (high range). Their combined range is seven, eight, or nine decades between 10^-5 to 10⁴ R/hr. in the high-range ion chamber (RD-2B), gamma photons generate ion pairs in the nitrogen fill gas. Charged electrodes collect these ion pairs, resulting in a net average dc current that is an input to the RM-80. Digital signal processing in the RM-80 smooths input data from the detectors before comparison to high- and alert-alarm levels in memory. Stored conversion factors automatically convert raw data to engineering units for display on the Model RM-23 Control/Display Module, recorders, or Model RL-10 local analog displays. An alarm horn and two indicating lights on the RL-10 signal an alarm condition. An acknowledge pushbutton on the front panel silences the horn.

In G-M tube detectors, an internal beta checksource verifies proper operation of the detector and signal processor. A small beta-sensitive region in the G-M tube assembly aligns with a fixed-position Cl³⁶ beta checksource. An aluminum shutter intercepts beta particles during routine operation and is withdrawn by a solenoid during checksource operation. In the ion chamber detector, an optional bias source generates an ~50 mR/hr sustaining signal ("keep alive"). A failure alarm sounds if the detector signal falls below this value.

THE MODEL RM-80 Signal Processor performs signal processing and control functions for the steam line monitor. Its database includes calibration constants for the detector assemblies, alarm setpoints, history files (24 10-min averages, 24 1-hr averages, and 28 1-day averages), and other constants and control functions. Alarm relays and analog outputs are also in the RM-80. The Model RM-80 and the customer interface junction box enclosures, rated NEMA 12, should be wall mounted where the integrated radiation dose is 10³rad or less. The RM-80 may be interrogated and controlled using an optional Model RM-23 Control/Display module. The RM-80 communicates with the RM-23 over a shielded, twisted-pair cable terminated in the customer interface junction box.

THE MODEL RM-23 Control/Display Module option provides routine operator/monitor interface. For safety-related applications, the Model RS42D has its own dedicated readout device (RM23) in the control room, to display or alter the calibration constant, alarm setpoints, or history information in the RM-80 Microprocessor data base. The radiation exposure rate seen by the detector assemblies is continuously displayed in IEEE standard format X.XXE±XX. Other information may be called up from the data base with no more than 5 keystrokes. Alarm status id displayed on red (HIGH), amber (ALERT), and green (OPERATE) LEDs. The RM-23 mounts in a modified NIM bin (optional) in a 19in. (48.3-cm) -wide instrument rack.

THE MODEL RL-10 Local Analog display option provides radiation alarm and indication signals. It can be wall mounted in a detector area, such as a reactor containment building, where sustained high temperatures and radiation levels in the containment could substantially degrade the performance of a Model RM-80 Microprocessor.

The Model RL-10 is basically a junction box containing lamp indicators, a logarithmic radiation meter, and a horn with an acknowledge pushbutton. When used, the Model RL-10 also houses the detector high-voltage power supply.