Model 1925


  • Low-level, real-time tritium in water monitor using automated liquid scintillation counting
  • Sensitivity: 100,000 pCi/L (3.7 kBq/L) in 9 minutes or less with 95% confidence
  • Resolution of 1.0 kBq/L or 0.02 µCi/L
  • Response time: 3 minutes for the beginning of the response and 9 minutes for the full value
  • Signal processing of coincident pulses for tritium specific wave shapes (height and duration)
  • Waste management: wastewater output lines with Swagelok® fittings are provided
  • Self-contained, mounted on a steel frame with lifting eyes for easy transport


The Model 1925 is automated, real-time tritium in water monitor designed for detecting ultra-low levels of tritium in water in the industrial environment of nuclear power plants.  The primary purpose is to detect the leak of heavy water (tritium) in nuclear power plants, however, it can also be used to monitor changes in tritium content of groundwater, rivers, lakes, or ocean currents.

The unit detects tritium decay via liquid scintillation counting with dual photomultiplier tubes (PMT) working in coincidence counting mode.  The use of highly effective PMTs, specially designed sampling cell to minimize cosmic radiation and Cherenkov effects, and 1” lead shielding provides for the low background noise of only one count per second with a counting efficiency of 30%.  MDA is 3.7 kBq/L with a 95% confidence level and a resolution of 1.0 kBq/L.

Model 1925 is a completely self-contained instrument mounted inside of a 200cm tall steel enclosure with reinforced anchoring feet and locked access.  The liquid scintillator is connected to the unit externally and it is stored inside of the polyurethane drum of 23 liters.  This quantity of liquid scintillator is sufficient for 60 days of continuous, 24/7 operation.

The main subassemblies are:

  1. Sample water input lines
  2. External cooling loop input/output lines
  3. Internal cooling loop complete with chiller, chiller pump and plumbing
  4. PRV and RV system with manifolds
  5. Water purification system (oil-in-water and micron filter)
  6. Sample water pump
  7. Detection module
  8. Data acquisition electronics module
  9. System control module
  10. Wastewater output line, RV output line, and sample bypass output lines

Response time:  Can be configured for 1 to 6 inputs for sampling up to 6 individual lines.  The response time from when sample enters the system until the unit starts to respond is 3 minutes, and in 9 minutes the full value of tritium concentration in the sample is displayed on the screen. If selecting multiple inputs, each sample line is sampled for 10 minutes so that the effect of residual activity from the previous line is minimized.

Pressure Regulating Equipment: The pressure of input sample streams can be up to 103 kPa. This pressure is immediately reduced to 2-3psi via Pressure Regulating Valves (PRV). Each PRV is associated with Pressure Relieve Valve set to open at 100 kPa, therefore, the pressure in the system can never be more than 100 kPa, which makes it safe to handle. This also makes the instrument a Class 6 Nuclear Device.

Cooling:  In order to have a maximum efficiency of the liquid scintillator, a solution that is tested inside of the sample cell is kept between 12°C and 20°C. This is achieved by an internal cooling loop system, which is a closed-loop cooling system with its own pump and chiller unit. If the unit operates in extreme temperatures (more than 45°C) external cooling loop is provided, where the user shall provide chilled water from its own source.

Routine Maintenance:  Scheduled maintenance of consumables is required. The liquid scintillator needs to be replenished every 2 months and sample water filters need to be replaced. Also, a periodic check of the efficiency and background is recommended if there is a possibility of increased background contamination and due to the standard lifecycle of electronics components.

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