SPNDs (Self-Powered Neutron Detectors)

No need for power supply.
Simple and robust structure.
Relatively small mechanical “size” desired for in-core installation.
Good stability under temperature and pressure conditions.
Generate a reproducible linear signal.
Low burn-up (dependent on emitter material).

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SPND

Part Code: SPND

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Datasheet

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Details

Self-Powered Neutron Detectors are being widely used to monitor in-core neutron flux for control, safety, and mapping applications because of their small size, ruggedness and simplicity. These detectors use the basic radioactive decay process of neutron activation material to produce an output signal. As the name implies, no external source of ionizing or collecting voltage is required to produce the signal current. Depending on the response time, these detectors are broadly classified as prompt and delayed response detectors. Prompt response detectors as Cobalt and Inconel are used in reactor protection and regulation applications, whereas the delayed response detectors like Vanadium and Rhodium are being widely used for Flux Mapping System.

They have been effectively used as in-core flux monitors for over twenty-five years in nuclear power reactors worldwide. The typical SPND is a coaxial cable consisting of an inner electrode (the emitter), surrounded by insulation and an outer electrode (the collector).

Specifications

Description	Specification
Mechanical structure type	Integral, No integral
Emitter Material	Inconel 600, Rhodium, Vanadium, Cadmium, Platinum, Silver, Cobalt etc.
Insulation Material (for Detector section and lead cable section)	Magnesium Oxide (MgO), Alumina Oxide (Al₂O₃)
Collector Material	Inconel 600, Stainless Steel
Sheath Material of lead Cable section	Inconel 600, Stainless Steel
Lead material of Lead cable section	Inconel 600
No of lead	One or two
Emitter Diameter	Can be made upon request
Emitter length
Collector Diameter
Collector Length
Cable section Diameter
Cable Section length
Cable Lead Diameter
Collector and cable Sheath Thickness
Connector Type	LEMO Connector, BNC Connector, etc.
Insulation resistance at 20°C	≥ 10¹² Ω
Insulation resistance at 300°C	≥ 10⁸ Ω
Production Quality testing	Dimension Test Continuity Test Insulation Compaction Density Test Insulation Resistance Measurement Test at Room temperature and elevated Temperature Capacitance Measurement test Water Immersion Test for Sheath integrity Hydrostatic Pressure Test Radiography Examination Test Helium Leak rate Test Steam test (Autoclave test) Bend Test Weld joint Quality Test (liquid Penetration Test)

Key Features

Compared to other in-core detectors, they feature some advantages:

Need no power supply.
Simple and robust structure.
Relatively small mechanical “size” desired for in-core installation.
Good stability under temperature and pressure conditions.
Generate a reproducible linear signal.
Low burn-up (dependent on emitter material).

In addition, there are also some disadvantages:

Limited operating range due to relatively low neutron sensitivity.
Compensation for background noise required (for some emitters).
Delayed signal response (for some emitters).

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