ABOUT
Self-Powered Neutron Detectors (SPNDs)
Introduction
SPNDs leverage the radioactive decay of a neutron activation material (the emitter) to generate a current signal directly proportional to the neutron fluence rate (flux) requiring no external ionizing or collecting voltage. Tempsens manufactures high-quality self-powered neutron detectors (SPNDs) engineered for accurate, continuous in-core neutron flux monitoring in nuclear power reactors. Classified as either prompt response (Inconel 600, Cobalt, Platinum) or delayed response (Rhodium, Vanadium, Silver), Tempsens SPNDs are available in both Integral and Non-Integral (Modular) configurations, built for the demanding mechanical, thermal, and radiation environments of nuclear power plants.
About Self-Powered Neutron Detectors (SPNDs)
Characteristics and Features
- Coaxial construction: inner emitter electrode surrounded by Magnesium Oxide (MgO) or Alumina Oxide (Al₂O₃) insulation, and an outer collector electrode (Inconel 600 or Stainless Steel).
- The two types of SPND are integral SPND where the emitter is part of the lead wire, and nonintegral/modular SPND where the emitter is a separate device with a lead wire/cable assembly.
- Emitter materials include Inconel 600, rhodium, vanadium, cobalt, Hafnia, platinum, silver, and cadmium.
- Connector types: LEMO and BNC connectors; either one or two leads depending on requirements.
- Insulation resistance ≥ 100 GΩ at 20°C; ≥ 100 MΩ at 300°C.
Using SPND: Applications
- Monitoring of in-core neutron flux for reactor regulation (safety and control systems).
- Flux Mapping System — using delayed-response emitters (Vanadium, Rhodium).
- Reactor protection and regulation using prompt-response emitters (Cobalt, Inconel 600, Platinum, Hafnia).
- Nuclear power plant instrumentation requiring compact, rugged, and permanent in-core sensors.
Advantages of SPND
- No external power supply required — fully self-powered operation
- Simple, robust coaxial structure suited for harsh in-core environments
- Compact mechanical size enables direct in-core installation
- Excellent signal linearity and reproducibility across operating range
- Good stability under high-temperature and high-pressure reactor conditions
- Low burn-up rate (as low as 0.01%/month for Vanadium at 10¹³ nv)
Technical Specifications of SPND
| S. No. | Description | Specification |
| 1 | Mechanical structure type | Integral, No integral |
| 2 | Emitter Material | Inconel 600, Rhodium, Vanadium, Cadmium, Platinum, Silver, Cobalt etc. |
| 3 | Insulation Material (for Detector section and lead cable section) | Magnesium Oxide (MgO), Alumina Oxide (Al₂O₃) |
| 4 | Collector Material | Inconel 600, Stainless Steel |
| 5 | Sheath Material of lead Cable section | Inconel 600, Stainless Steel |
| 6 | Lead material of Lead cable section | Inconel 600 |
| 7 | No of lead | One or two |
| 8 | Emitter Diameter | Can be made upon request |
| 9 | Emitter length | |
| 10 | Collector Diameter | |
| 11 | Collector Length | |
| 12 | Cable section Diameter | |
| 13 | Cable Section length | |
| 14 | Cable Lead Diameter | |
| 15 | Collector and cable Sheath Thickness | |
| 16 | Connector Type | LEMO Connector, BNC Connector, etc. |
| 17 | Insulation resistance at 20°C | ≥ 100 GΩ |
| 18 | Insulation resistance at 300°C | ≥ 100 MΩ |
| 19 | Production Quality testing | 1. Dimension Test 2. Continuity Test 3. Insulation Compaction Density Test 4. Insulation Resistance Measurement Test at Room temperature and elevated Temperature 5. Capacitance Measurement test 6. Water Immersion Test for Sheath integrity 7. Radiography Examination Test 8. Steam test (Autoclave test) 9. Bend Test 10. Weld joint Quality Test (liquid Penetration Test). |
Why Tempsens for SPNDs?
- Over 35 years of manufacturing expertise serving numerous industries around the globe.
- Full in-house production quality testing suite covering dimensional, mechanical, electrical, and pressure integrity validations.
- Custom emitter materials, dimensions, and connector configurations available on request.
- Exported to 75+ countries, trusted by global nuclear instrumentation programs.
FAQ
Frequently Asked Questions
Find answers to frequently asked questions related to Self-Powered Neutron Detectors (SPNDs).
By initiating radioactive decay of the emitter material in the reactor’s core, neutrons create an electric current proportional to the neutron flux; therefore, there is no external power supply required.
SPNDs feature a compact design, are self-powered and stable under extreme reactor conditions, and provide linear and reproducible flux signals in real time for reactor regulation, as well as for precise flux mapping applications.
