. ag ort i y ere 2 TAOS eg et 4 ay ee U.S. PUBLIC HEALTH SERVICE, DIVISION OF RADIOLOGICAL HEALTH PHOTO FIGURE 13.— Monitoring for external gamma radiation near the Nevada Test Site by U.S. Public Health Service personnel. FIGURE 14.—High volume air sampler. The large glass fiber filter is for collection of particulates. Behind the filter is placed an activated charcoal cartridge to coliect gases such as radioiodines. instruments(fig. 13), chamber survey instruments, fallout trays and additional air samplers and recorders. Each vehicle was equipped with two-way voice radio communication. The number of teams used for each event was determined in advance by the predicted radiological situation, howeverfive to ten teams was the usual number deployed. Up to 20 teams could be organized within a short time, but were not normally maintained ona standbybasis. Mobile ground monitoring teams arestill maintained on a standby basis and used when needed. Air Sampling There were and are 30 permanent air sampling stations in operation 24 hours per day in the area surrounding the NTS at distances up to 180 miles. The air samplers used are high volume units, drawing air through an 8" x 10” glass fiber filter (fig. 14). When deemed de- sirable, a secondary activated charcoal cartridge is added for the collection of gaseous fission products. Flow rates are approximately 50 cubie feet per minute(c.f.m.) for the glass fiber filter alone and 25 c.f.m. with the charcoal cartridge added. 40 Glass fiber filters are counted for gross beta activity in the proportional region. All charcoal cartridges, and any glass fiber filters with gross beta activity significantly above background levels are assayed with a 400 channel gamma scintillation spectrometer, using a steel shield for a 4” x 4” Nal (T1) crystal with a Cs!%7 peak resolution of eight percent for identification of specific gamma-emitting isotopes. Film Badging Film badges were distributed to hundreds of locations around the Test Site and to as many as 1,600 persons during certain operations. Presently there are about 50 locations with some 200 persons wearing film badges. Film badges were and are collected and processed monthly. In the event that radioactivity was found in the area by the mobile monitoring teams, film badges were collected from these locations and from people living in the area; new film badges were distributed. Additional stations and people were included if the situation required more extensive monitoring. 4]