CNCS BH3105E Portable Neutron Dose Equivalent Rate Meter

Overview

The CNCS BH3105E Portable Neutron Dose Equivalent Rate Meter is a precision-engineered instrument designed for real-time monitoring of neutron ambient dose equivalent rate (H*(10)) in mixed radiation fields. It operates on the principle of thermal neutron detection via the ⁶Li(n,α)³H exothermic reaction within a glass scintillator matrix, coupled with an optimized cadmium-absorber moderated polyethylene sphere. This design enables energy-dependent neutron moderation and selective absorption—specifically attenuating low-energy thermal neutrons (which contribute minimally to H*(10)) while preserving and thermalizing higher-energy neutrons (up to 14 MeV) that dominate biological dose weighting. The resulting light pulses are converted to electrical signals by a photomultiplier tube (PMT), processed through pulse shaping, amplitude discrimination, and digital counting under microcontroller control. Engineered for field deployment in high-radiation environments, the BH3105E delivers robust performance across seven decades of dose rate (0.1 µSv·h⁻¹ to 100 mSv·h⁻¹), with inherent compensation for angular incidence and strong rejection of interfering gamma radiation—critical for accurate neutron dosimetry where gamma fields exceed 10 mGy·h⁻¹.

Key Features

• High-sensitivity ⁶Li-glass scintillation detector with integrated PMT and low-noise analog front-end
• Cadmium-embedded spherical moderator enabling near-flat H*(10) energy response from thermal neutrons to 14 MeV fast neutrons
• Digital microprocessor-based signal processing with automatic background subtraction and real-time dose rate calculation
• Visual (LED) and audible (buzzer) alarm outputs triggered at user-defined threshold levels
• Hermetically sealed, lightweight, and ergonomic housing rated for operation in humid or dusty industrial environments
• Low power consumption (≤500 mW) supporting extended battery life during continuous field use
• Compliant with IEC 61005:2021 (Radiation protection instrumentation — Neutron ambient dose equivalent (rate) meters) and certified under China’s CMC metrological licensing system

Sample Compatibility & Compliance

The BH3105E is intended for use in gaseous media—primarily ambient air—and does not require sample collection or preparation. Its calibration is traceable to national neutron standards maintained by the China Institute of Atomic Energy (CIAE) and verified against reference neutron fields including ²⁵²Cf, Am–Be, and D–T sources. The instrument meets the performance requirements specified in IEC 61005 for neutron dose equivalent rate meters, including angular dependence (±25% over ±90°), linearity (±15% typical uncertainty), and gamma insensitivity (≤±10% added error in 1 mSv·h⁻¹ neutron field superimposed with 10 mGy·h⁻¹ ¹³⁷Cs gamma exposure). It is suitable for regulatory compliance in nuclear power plant surveillance, spent fuel handling areas, accelerator facilities, and emergency response operations where GLP-aligned documentation and audit-ready calibration records are required.

Software & Data Management

While the BH3105E operates as a standalone meter with direct digital readout, optional RS-232/USB interface modules support data logging and remote configuration via proprietary PC software. Logged parameters include timestamped dose rate values, alarm status flags, battery voltage, and accumulated counts. All firmware and calibration coefficients are stored in non-volatile memory with write-protection to ensure integrity during power cycling. The device supports configurable averaging intervals (1–60 s) and dual-threshold alarm settings. For laboratories operating under quality management systems (e.g., ISO/IEC 17025 or NRC-regulated environments), the instrument provides full traceability documentation—including factory calibration certificates, uncertainty budgets, and verification reports aligned with ISO/IEC 17025 Clause 5.10.

Applications

• Continuous neutron dose rate monitoring around pressurized water reactors (PWRs), boiling water reactors (BWRs), and research reactors
• Routine surveys in nuclear submarine compartments, reactor containment buildings, and spent fuel pool galleries
• Neutron well logging in oilfield geophysics and borehole radiation characterization
• Post-detonation assessment and civil defense radiological reconnaissance
• Shielding validation testing and neutron source characterization in accelerator laboratories
• Decommissioning and waste package monitoring at nuclear legacy sites

FAQ

What neutron energy range does the BH3105E cover?
The instrument provides compensated H*(10) response from thermal neutrons (~0.025 eV) up to 14 MeV, achieved through cadmium-filtered polyethylene moderation.
How is gamma interference suppressed?
By combining pulse-height discrimination with physical gamma attenuation in the moderator and PMT shielding, the BH3105E achieves a gamma rejection ratio exceeding 100:1 in a 10 mGy·h⁻¹ ¹³⁷Cs field.
Is the BH3105E suitable for personal dosimetry?
No—it is an area monitoring instrument designed for ambient dose equivalent rate (H*(10)), not individual dose assessment; it does not meet IEC 61526 personal dosimeter requirements.
Does it support external data acquisition?
Yes—optional serial interface modules enable integration with SCADA systems or centralized radiation monitoring networks using ASCII protocol.
What calibration standards apply?
Calibration follows IEC 61005 procedures and is traceable to the Chinese National Neutron Standard Facility at CIAE, with documented uncertainties compliant with ISO/IEC 17025.
Can it operate in high-humidity or outdoor conditions?
Yes—the IP54-rated enclosure ensures reliable operation in ambient temperatures from –10 °C to +50 °C and relative humidity up to 90% non-condensing.