SLIDE 39 Whole-body counter. was a 28 cm diameter, The detector chosen for field use +; Brookhaven personnel 10 cm thick, sodium iodide thallium activated scintillation crystal NaI(T1). It is optically coupled to three low background magnetically shielded photomltiplier tubes connected in parallel through a summing box with the combined output routed to an amplifier and then to a microprocessor~based computer and pulse height analyzer (PHA). The PHA data is stored on a magnetic discette, and results are analyzed in the field and at BNL using a matrix reduction, minimization of the sum of squares techniques. 207 The gamma emitting nuclides observed have been 6570, 137¢, 609 and Bi, Additionally, naturally occurring ““K is present in normal amounts. typical counting time is 15 minutes and a typical minimum detection limit is 100 Bq (3 nCi). The whole-body counting system is currently standarized against a human like phantom. A