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Model RD-54
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The Model RD-54 is a beta scintillation, fixed-filter particulate detector assembly for use as an offline process monitor or a continuous air monitor (CAM). The shield assembly consists of a steel-jacketed, cast-lead, horizontal cylinder with a stainless steel sleeve through the center. The front end of the shield is capped by an easily removable lead plug and a particulate filter holder assembly. The opposite end is capped by a lead plug and a scintillator-photo multiplier tube assembly. The cylindrical shield and end plugs provide complete 4π shielding. Various shield thicknesses are available. Mounted internally to the shield is a beta-emitting checksource to verify detector operation. A solenoid assembly is located on top of the shield to actuate the checksource. There are various scintillator sizes available, providing a choice of sensitivities and ranges.

Specifications

FILTER: 1.9-in (47-mm) diam HV LB5211 or equivalent SHIELDING: 3-, 4-in. (7.6-, 10.2-cm) full 4π solid cast-lead WEIGHT: Dependent on shield thickness (see table of dimensions at end of data sheet) DIMENSIONS: 2-in. (5-cm)-diam x 0.01-in. (0.03-cm)-thick beta phosphor, 2-in. (5-cm)-diam photomultiplier tube (standard) CHECKSOURCE: <0.05 mCi Cl36 (beta) SAMPLE PRESSURE: 15 lb/in.2 (1.05 kg/cm2) gauge (max)

SAMPLE TEMPERATURE: 35° to 120°F (2° to 49°C) SAMPLE FLOW: 3 ft3/min (1400 cm3/sec) INLET/OUTLET: 0.5-in. (1.3-cm)-diam stainless steel tubing SAMPLER MATERIAL: Type 304 stainless steel, aluminum foil detector window, and selected other materials including “O-ring” seals PRESSURE DROP ACROSS INLET/OUTLET: 3.5 in. (9 cm) Hg vacuum at nominal flow with clean filter ELECTRICAL CONNECTORS: high voltage – MHV; signal – BNC

Calibration

Energy response curves at three flow rates for the fixed-filter particulate detector are shown below. These curves allow the determination of detector sensitivity for most isotopes of interest.

*Averages, rather than end point, beta energies better represent actual detector operation since beta particles from most isotopes are not monoenergetic. Using end-point beta energies would appear to result in improved, although perhaps misleading, performance.

Phospor Size (in.)	Lead Thickness (Model No.)	cpm* ambient	cpm/mR/hr Co60	cpm/_Ci (Deposited) Cs137	cpm/_Ci (Deposited) Cl136	cpm/_Ci (Deposited) Rh106
2.0 diam x 0.01 thick	3 in. (RD-54-30)	26	46	1.28 x 106	1.24 x 106	1.47 x 106
2.0 diam x 0.01 thick	4 in. (RD-54-40)	25	13	1.28 x 106	1.24 x 106	1.47 x 106

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

Minimum Detectable Activity (MDA) and Minimum Detectable Concentration (MDC) for RD-54-30.

Particulate Detector:

MDA and MDC for Cs¹³⁷ particulates in a 2.5-mR/hr Co⁶⁰ gamma field:

MDA= 4.92 x 10^-6 µCi (1.82 x 10^-1 Bq) Cs¹³⁷

MDC= 1.83 x 10^-13 µCi/cm³ (6.77 x 10^-3 Bq/m³) Cs¹³⁷