Neutron Coincidence Collar, N2071

The ANTECH N2071 Neutron Coincidence Collar is used by international safeguards inspectors to verify the fissile material content of fresh nuclear fuel assemblies.

It conforms to a classic modular design with an adjustable cavity for different measurement arrangements.

The N2071 can perform active coincidence counting of 235U content in Pressurised Water Reactor (PWR) and Boiling Water Reactor (BWR) fuel assemblies, and passive neutron coincidence counting of the plutonium content in Mixed Oxide (MOX) fuel assemblies.




N2071 Datasheet


In its non-active configuration the ANTECH N2071 consists of four polyethylene detector panels that form a square collar around a fuel assembly. Six ³He tubes are embedded in the full length of each panel and connect to a junction box located at the top of the panel. Each junction box houses an Amptek A111 fast counting amplifier unit and the necessary low voltage, signal and high voltage distribution networks. The signals from the six ³He tubes are combined, amplified and output as a single pulse train.

When used in conjunction with suitable counting electronics (including most commercially available neutron coincidence and multiplicity counters) the system can be simply linked to a suitable computer and counting software such as INCC-32 with the interconnection cables supplied.

For active measurements one of the four detector panels is replaced with a panel that houses an americium/lithium source holder assembly rather than ³He detectors.

One of the panels is hinged to enable the fuel assembly to be inserted into the collar. The distance between the inner faces of the panels is adjustable according to whether a PWR or BWR fuel assembly is to be measured.

The system is supplied with its associated interconnection cables and a small spares kit, containing spare connectors, tools and fixings.

Features & Benefits


  • Easily removable cadmium panels
  • Amptek A111 amps
  • Non-interchangeable connector types prevent misconnection
  • Separate moderator panel supplied to accommodate americium/lithium source for active measurements. Source holder assembly fitted with source position indicator
  • Chamber can be configured for passive measurement of plutonium content in MOX fuel assemblies and active measurement of 235U in PWR and BWR assemblies


  • Hinged door to facilitate quick loading of fuel rod assembly
  • Scale on active source holder to establish orientation
  • Handles fitted to each panel for individual handling
  • Externally mounted N1081 De-Randomising Mixer Buffer Counter (DMBC) provides HV, LV and signal connections for each detector module, eliminates counting losses and reduces dead time, especially at high count rates (the collar can be used with an N1300 Neutron Counting OR Box as an alternative to the DMBC)
  • Can be used with most commercially available neutron coincidence and multiplicity counters
Outer dimensions (H x W x D) PWR configuration 571 mm x 432 mm x 432 mm (22.48 in x 17.01 in x 17.01 in)
BWR configuration 571 mm x 432 mm x 363 mm (22.48 in x 17.01 in x 14.29 in)
Chamber inner dimensions PWR configuration 235 mm x 235 mm (9.25 in x 9.25 in)
BWR configuration 235 mm x 165 mm (9.25 in x 6.45 in)
Maximum weight < 60 kg (< 132.28 lb) with Cd shield fitted
Junction box IP rating IP65
Operating range 5°C – 40°C, 20% – 60% RH
Storage range 5°C – 60°C, 20% – 80% RH
Power to junction boxes/amplifiers 5V DC ±10%
Maximum current LV – 0.3 A
Maximum high voltage HV – 2.0 kV
Safety Conforms to European Union Directive 72/23/EEC (EN61010-1:2001)
EMC Complies with 2004/108/EC
Detection efficiency BWR (passive, no cadmium) 17.5%
PWR (passive, cadmium) 13%
BWR (active, no cadmium) 13.5%
PWR (active, cadmium) 10%
Output channels 4 TTL output channels (SIGNAL), one per amplifier
Output pulse width 50 ns ± 5 ns
Sensitivity 5 x 104 electrons (nominal)
Period between consecutive pulses 500 ns