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:
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.
|MEASUREMENT RANGE||3.7 to 130 kBq/L|
|MINIMUM DETECTABLE LIMIT||3.7 kBq/L at a confidence level of 95%|
|DISPLAY||LCD Color Touch Screen; units of display user-settable|
(i.e., kBq/L, μCi/L)
|RESPONSE RATE||3 minutes– beginning of response |
9 minutes full valued displayed
|MEASUREMENT METHOD||Liquid scintillation counting|
|DETECTOR||Dual PMT coincidence counters surrounded by multi-element shielding|
|SIGNAL PROCESSING||Electronic signal processing of coincident pulses for tritium|
specific wave shapes (height and duration)
|ALARM SETPOINT||Can be manually adjusted|
|DATA RECORDING/OUTPUT||Insertable USB flash drive; Data communication via TCP/IP. |
Standard data output is Ethernet and USB.
|SAMPLING/MIXING SYSTEM||Dual head, low flow rate pump. Liquid scintillator and sample mixed at the sample cell.|
|SAMPLE CELL||Stainless steel cell, volume 5cc with fused silica windows and Viton O-rings for sealing.|
|WASTE MANAGEMENT||Unused water output lines with Swagelok® fittings are provided, user to provide recycling system or waste collection system.|
|TEMPERATURE||0°C to 50°C|
|HUMIDITY||0 to 95 % R. H.|
|SEISMIC||Withstands modest shock|
|ELECTRICAL||Power 110/230VAC, 5A|
|MECHANICAL||Self contained, mounted on a steel frame with lifting eyes for easy transport.|
|DIMENSIONS||31.5in x 23.6in x 84.0in
(800mm x 600mm x 2133mm)
|WEIGHT||1100 lb (500 kg)|