Berthold
LB 6414

Neutron Probe

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The neutron monitor LB 6414 is used for the search for plutonium contamination and the investigation of nuclear waste. It is a new portable neutron survey meter with extremely high sensitivity.

The energy-dependent response of the LB 6414 was maximized for fission neutrons and has a He-3 proportional counter tube in the centre of the moderator made of polyethylene (PE).  The neutron survey meter LB 6414 can be used in combination with (UMo II) LB 134  as a transportable instrument.

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Description

The LB 6414 is a new portable neutron survey meter with extremely high sensitivity. The energy-dependent response of the instrument was maximized for fission neutrons. There are several interesting applications amongst which is the search for plutonium.

Neutron Detection – Some applications in neutron detection require extremely sensitive instruments rather than flat energy response. In these cases, the LB 6414 neutron survey meter is superior to the conventional rem-counters, which have relatively low efficiencies.

Plutonium Detection – Plutonium is extremely dangerous and hard to detect over larger distances. The α-particles, γ’s and X-rays which are emitted by plutonium isotopes could easily be shielded by the material itself or by surroundings. Besides a few γ-rays, the only penetrating radiation emitted by plutonium samples are neutrons from the spontaneous fission of the even-numbered plutonium isotopes, especially from 240Pu. Thus a neutron detector that has maximum sensitivity for fission neutrons would provide an excellent tool for the detection of plutonium, even through shieldings.

Plutonium Contaminations – At close distances the neutron survey meter LB 6414 is capable of monitoring even smaller amounts of plutonium. This enables this instrument for the search and localization of plutonium contaminations for instance in glove boxes, pipes or elsewhere in plutonium processing facilities. Regions with relatively high plutonium concentrations can easily be identified. This is even true in the presence of shielding surrounding materials because neutrons are strongly penetrating.

Neutron Dose Rate Monitoring – As the LB 6414 is extremely sensitive it would sometimes also be useful in neutron dose rate monitoring. Especially in applications, where there is more need for high sensitivity than for flat energy response. For instance, in measuring low neutron radiation levels with a constant neutron energy spectrum it would be favourable to determine a user-specific calibration factor once and then benefit from good counting statistics.

The Universal Monitor (UMo II) LB 134  acquires the data from the neutron probe LB 6414 and provides easy-to-use data analysis, display of measured values, alarm indications, data storage, parameter setting and communication and service functions. The software uses sophisticated algorithms for the detection of changes in the observed counting rates. Therefore the instrument has excellent characteristics for the search for radiation sources.

For more details, please refer to datasheet.

Features:

  •  Search for illicit trafficking plutonium

  • Search for plutonium contaminations

  •  Measurement of 240Pu equivalent mass

  • Nuclear waste inspection

  • Measurement of 252Cf and other neutron sources

  • Monitoring of neutron radiation field intensities

Specifications

Neutron detector3He proportional counter tube in PE moderator
ElectronicsIntegrated preamplifier, discriminator and hv-supply
Fluence response26.4 cm2 for fission neutrons 10.7 cm2 for Am-Be
Detection limit (distance 1 m)75 g weapon´s plutonium in 5s (confidence level 95%)
Neutron energy rangeOptimized for 10 keV to 1000 keV
240Pu equivalent mass response0.2 cps per g of 240Pu at 1 m distance
Ambient dose equivalent res- ponse to H*(10) (Am-Be)27 counts/nSv or 0.13 μSv/h per cps
Ambient dose equivalent res- ponse to H*(10) (Cf-252)68 counts/nSv or 0.05 μSv/h per cps
Directional response100% at normal incidence, 78% side- ways, 60% frontal for Am-Be
Dimensions probe310 mm x 180 mm x 130 mm (Length x Width x Height)
Weight of probe3850 g
Typical background rate0.06 cps
Intrinsic detector background< 0.006 cps at total neutron flux φn < 2 x 10-4cm-2 s-1