Zeus-4G Plastic Scintillator Option

Features

• Two large plastic scintillators (23 x 15 x 2 in. each) installed on the door behind the main front panel of alpha/beta detectors
• One smaller plastic scintillator (14 x 4.5 x 2 in.) installed in place of the top-of-shoe alpha/beta detector
• Lead shielding 9.5 mm (0.375 in.) surrounding five sides of each of the above detectors
• Lead shielding wall (81 x 36 x 1 in.) consisting of painted lead ingots which can be user installed on site in an attached frame
• Each of the three plastic scintillator detectors has its own photomultiplier and pre-amp. These have been designed specifically to allow the detectors to accurately report counting data through the same computer system as the 25 regular alpha/beta detectors. This ensures that all the data is presented in the same format regardless of whether the contamination is alpha, beta or gamma

Description

This option to a standard alpha/beta or beta only monitor provides enhanced gamma sensitivity by adding several large plastic scintillators behind the sealed or flow proportional detectors. These scintillators are extremely close to the person's body and yield excellent counting efficiencies. Independent tests and factory tests show conclusively that by combining the capability of flow or sealed detectors to monitor for alpha and/or beta with plastic scintillator detectors to monitor for gamma combines to have the "best of both worlds" in a single combined monitor. Since the subject has to stand and count to allow for alpha/beta detection it makes good sense to do this for gamma at the same time and save both the space and cost of having two monitors with the added benefit of reduced maintenance using a single combined monitor.

Performance
This unit was subjected to independent tests at a US nuclear power plant during which its performance was measured in normal backgrounds and with an artificially increased background. The tests involved the placement of a ⁶⁰Co point source attached to various different parts of the body including the torso, face, feet and hands.

During this test the Argos-4AB was also tested for its capability to successfully detect a 5000 DPM beta point source; it passed 100%, which is to be expected since this monitor is in use in many nuclear plants throughout the world.

In a "normal" background of 8 µR/hr the monitor successfully detected a source of 22.5 nCi (50 000 DPM) located at all body locations in a count time of 6 s.

In an "inflated" background of 14 µR/hr the monitor successfully detected a source of 22.5 nCi (50 000 DPM) located at all body locations in a count time of 8 s.