The Model 2241-4 is a portable neutron REM meter. This instrument combines Ludlum's microprocessor-based digital Ratemeter/Scaler Model 2241 electronics with a Model 42-31H Neutron Detector. This system is sensitive to neutrons from thermal to 12 MeV with a response approximating the inverse RPG curve for neutron dose.
Data is presented on a four-digit LCD with a moving decimal point. Two additional digits are employed for the Scaler mode. A three-position switch labeled "Off/Ratemeter/Scaler" selects the desired operating mode for the instrument. Other controls include Audio On/Off switch, Fast/Slow Response switch, LCD Backlight pushbutton, Count Reset pushbutton, and Scaler Count/Stop pushbutton.
This instrument incorporates independent adjustable alarms for the ratemeter and scaler operating modes. Audible alarms may be silenced (acknowledged) by depressing the RESET switch. The scaler count time, alarm values, and backlight on time are pre-programed values. This instrument can be programmed via its RS-232 port, which can also be utilized to output its readings at two-second intervals.
NCRP Report #151 redefines the need to evaluate not only new Linac installations but also equipment that has been upgraded for higher energies and broader capabilities, like IMRT and rotational beam systems, which may be beyond what original shielding designs had recommended