LB 110 Tritium-Monitor

The LB 110 is a special measuring system for monitoring the tritium activity concentration in room and exhaust air.


  • Monitoring of 3H activity concentration in room and exhaust air
  • Direct and specific measurement
  • High sensitivity
  • Low interference of increased background levels or other gaseous nuclides than 3H
  • Two measuring channels
  • Compensation of other gaseous nuclides than 3H or background (optional)
  • Optimization for max. 3H sensitivity or low spillover
  • Detector with thermostat-controlled heating (optional)
  • Two different gas mixtures available: Methane (CH4), Argon-Methane (P10)
  • Two different data acquistion systems available: Data Logger LB 9000, Data Logger LB 5340

Device concept

Tritium (3H) in air is mostly available in the form of water vapor (H1H3O) or gaseous hydrogen (H1H3). Since the Beta particles emitted by Tritium have a very short range (only a few millimeters in air), windowless counter tubes must be used, i.e. the air to be measured has to be added to the counting gas. For a continuous measurement, the counter tube must therefore operate in the flow-through mode.

The air to be measured is mixed with a suitable counting gas and passed through a 1.3 liter volume proportional counter tube. Methane (mixing ratio air/gas 1:3) or Argon-Methane (P10, mixing ratio air/gas 1:4) are used as counting gas.

The distinction of Tritium pulses from those of other nuclides or from Gamma radiation – and hence the Tritium-specific measurement – is carried out using the pulse rise discrimination method, which offers major benefits as compared to the earlier used range discrimination (F. Berthold, Tritium-in-Air Measurements by Pulse Shape Discrimination Methods, in: Radiation-Risk-Protection Vol. III, Pages 1091 - 1094, FS-84-35 T, Verlag TÜV Rheinland, Köln 1984). This method yields better response sensitivity data, relative to the same gas consumption.

Rise time discrimination is based on the fact that the rise time in proportional counter tubes is dependent on differences in the drift time that electrons occurring in the primary ionization track need to get in the vicinity of counting wires. These drift time differences are dependent on the length and the course of the primary ionization track. In the case of Tritium, this track – due to the low particle energy – has to be regarded as point-shaped in contrast to the long ionization tracks caused by high-energy Beta or Gamma sources.

Device compontents

  • Pump and detector unit incl. operation electronics
  • Evaluation and display electronics (depending on measurement task)
  • Mixing and pump system (inside)
  • Flow-through counter tube (inside)

Counting gas control

The accuracy of the measurement is dependent on the constancy of the mixing ratio of air and counting gas. Due to that the LB 110 ensures a good and reliable gas-air control. Measuring air and counting gas flow are measured separately and kept at a constant level via a control circuit. The current gas and air flow rate is measured using an electronically controlled flow-through meter which operates according to the principle of thermal mass measure­ment.

An essential benefit of this principle is that the measurement is largely independent of pressure and temperature. Compared to volumetric principles, neither pressure nor temperature has to be measured in addition. The electronics integrated into the air and gas module is used to control and evaluate the signals modified by the flow-through controller. Gas and air supply are measured separately and kept on a constant level by one control circuit each.

Evaluation electronics

There are two evaluation units for the LB 110 Tritium-Monitor: The data loggers LB 5340 or LB 9000.

Mechanical Data
Dimensions counter tube LB 6225:   430 mm x Ø 80 mm
(active volume 1.3 l)                               
Dimensions / weight device LB 110:      500 mm x 420 mm x 335 mm
(L x W x H) / 20 kg




Calibration and Setting Data
Counting gas  




(90% Ar, 10% CH4)

Air-counting gas-mixture          1 : 3        1 : 4
Flow rate l/min    0.25 : 0.75 l   0.20 : 0.80 l
Measuring air contents in the
counter tube
0.325 l0.260 l                      
Efficiency for 3Happrox. 60%  approx. 55%
Calibration factor for 3H
(kBq/m³ per cps) 
5.1  7.0
Background in 3H channel0.4 to 3 cps
Measuring range                                    500 Bq/m³ - 20 MBq/m³

Spillover factor  

137Cs in 3H channel5 to 7 %     
85Kr in 3H channel3 to 5 %
14C in 3H channel23 to 25 %


Detection Limits for 3H in kBq/m³ at a background of 2 cps
Measuring time




(90% Ar, 10% CH4)

30 s3.65.0          
60 s2.53.4
600 s0.71.0
1 h0.20.4
24 h0.080.1


Gas and air connections (connection nozzle)
GasØ 7 mm                           
Measuring airØ 7 mm
Outlet for gas-air mixtureØ 7 mm
Power supply
Voltage  230 VAC 50 Hz or 115 VAC 60 Hz                 
Power consumption                            Max. 40 W                                           
Fuses230 VAC: 0.5 A, T  /  115 VAC: 1 A, T
Heating supply (optional)
Voltage  230 VAC 50 Hz or 115 VAC 60 Hz
Power consumption          Max. 82 W                                           
Fuses   230 VAC: 2 A, T  /  115 VAC: 3.15 A, T
Heating controller (front panel fuse)     230 V / 0.315 A, T
Ambient conditions
Operating temperature range       0 °C to 50 °C                               
Relative humidity                 0 to 90 %, no condensation
Protection typeIP32 in desktop housing
(according to DIN IEC 60529)














  • Biochemical research laboratories
  • Synthesis laboratories
  • Research laboratories for pharmaceutical industry
  • Neutron generators and accelerators
  • Nuclear technology and reprocessing
  • All Laboratories and factories where Tritium or Tritium-containing compounds and materials are manufactured, processed or stored
Format Size
LB 110 Brochure en PDF 1.9 MB