Fixed-Filter Particulate and Iodine Detector

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Fixed-Filter Particulate and Iodine Detector

Model RE-58
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The Model RD-58 is an offline radiation detector assembly for use on a process or continuous air monitor (CAM). It has two separate scintillation detectors: fixed-filter particulate and iodine. Both are contained in one compact 3-in.-thick 4π solid-lead shield, providing significant reductions in physical size, weight, and cost over earlier designs (which had two separate detector/shield assemblies) without reducing performance. Each detector can be easily and quickly serviced by just one person. Solenoid-actuated checksources are provided for each detector to verify proper operation. Various scintillator sizes are available, providing a choice of sensitivities and ranges.

Specifications

FILTERS: 1.9-in. (47-mm) –diam. HV LB5211 or equivalent (particulate); Scott TEDA-impregnated charcoal or silver zeolite filter cartridge (iodine)

SHIELDING: 3-in. (7.6-cm) full 4π solid cast-lead.

WEIGHT: 800 lb (364 kg) approximate

DETECTORS: 2-in. (5-cm) –diam. x 0.01-in. (0.03-cm) –thick beta phosphor, 2-in. (5-cm) –diam. photomultiplier tube (standard particulate detector); 2-in. (5-cm) –diam. x 2-in. (5-cm) –thick spectrometer-grade NaI (TI) crystal doped with Am241, optically coupled to a 2-in. (5-cm) –diam. photomultiplier tube (standard iodine detector)

CHECKSOURCES: <0.05 μCi Cl³⁶ (beta), particulate detector; < 9 μCi Ba¹³³ (gamma), iodine detector

SAMPLE PRESSURE: 15 lb/in.² (1.05 kg/cm²) gauge (max)

SAMPLE FLOW: 3 ft³/min (1400 cm³/min) nominal

SAMPLE TEMPERATURE: 35° to 120°F (2° to 49°C)

INLET/OUTLET: 0.5-in. (1.3-cm) –diam. stainless steel tubing

SAMPLER MATERIAL: Type 304 stainless steel or carbon steel except aluminum foil detector windows and selected other materials including O-ring seals

PRESSURE DROP ACROSS INLET/OUTLET: Approximately 4 in. (10-cm) Hg with clean filters at nominal flow

ELECTRICAL CONNECTORS (ON EACH DETECTOR): High voltage – MHV; signal – BNC

Calibration

The energy response curve for the particulate detector is shown below. The gamma spectrum of I¹³¹ below, shows how the major photo peak at 364 keV is monitored with a SCA window of 40 keV (~10%). Also shown is the Am²⁴¹ reference pulse for pulse height stabilization.

Channel	Phosphor Size [in. (cm)]	cpm*_abmient	cpm/mR/hr Co⁶⁰	Sensitivity (cpm/_Ci x 10⁵)/Isotope
Particulate	2 (5) diam x 0.01 (0.03) thick plastic	39	36	1.15/ 1.11/ 1.44/ Cs¹³⁷ Cl³⁶ Rh¹⁰⁶
Iodine	2 (5) diam x 2 (5) thick NaI(TI)	17	54	1.01/ — — I¹³¹

*Includes normal contributions from cosmic, natural, internal, and checksource backgournd

Minimum Detectable Activity (MDA) and Minimum Detectable Concentration (MDC)

Particulate Detector:

MDA and MDC for Cs¹³⁷ particulates in a 0.1-mR/hr Co⁶⁰ gamma field:

MDA: 2.46 x 10^-6 µCi (9.10 x 10^-1 Bq) Cs¹³⁷

MDC: 9.15 x 10^-14 µCi/cm³ (3.39 x 10^-3 Bq/m³) Cs¹³⁷

Iodine Detector:

MDA and MDC for I¹³¹ in a 0.1-mR/hr Co⁶⁰ gamma field:

MDA: 2.10 x 10^-5 µCi I¹³¹

MDC: 1.05 x 10^-12 µCi/cm³ I¹³¹

MDC = 1.30 x 10^-7 µCi/cm³ Xe¹³³