John J. Griffin'
Memorial school Hull, Massachusetts 02045 and Joseph R. Driscoll Boston College Chestnut Hill, Massochusetts 02167
I
I I
Junior High ~chool/~niversity cooperative Experiment Collection and analysis of fresh nuclear debris
The nuclear test by the People's Republic of China on March 18, 1972 provided an excellent opportunity for a seventh grade Science class a t the Memorial School, Hull, Massachusetts to participate in a scientific experiment of a timely nature. With the cooperation of the Nuclear and Radiochemistry Laboratory at Boston College, the class undertook the project of monitoring the atmosphere over their school for fresh radioactive debris. Several days after the United States Atomic Energy Commission had announced that a Chinese nuclear device had been exploded at Lop Nor, China, the seventh grade science students placed a commercial, home type, vacuum
Radioactive Isotopes Identified by Ge(Li) Gamma Ray Spectroscopy from 20-hr Air Filtration Sample of March 26-27.1972
Isotope
Half Life
Gamma Energy (keV)
Decay product of 232Th natural series. Cosmic ray produced isotope.
Figure 1 . Autoradiograph
composte photograph
Air nit-
cb
k*
cleaner on the roof of their school. The vacuum cleaner was run continuously in an attempt to collect particles from the nuclear explosion as the debris passed over the area. The hose inlet of the vacuum cleaner had been modified to accommodate a filter paper which was changed and analyzed each day in order to obtain a time profile of the passage of radioactivity from the March 18 explosion. Almost all of the radioactivity found appeared to have passed over within a 20-hr period of time between 11 a.m. March 26 and 7 a.m. March 27 as shown by the composite photograph (Fig. 1). A gamma ray spectrum (Fig. 2) of the radioactivity of this filter paper (after ashing) demonstrated the presence of over 15 different radionuclides as shown in the table. The presence of short-lived fission products indicated an origin from a recent nuclear explosion. From the announced date of the explosion and the date of peak period of radioactivity, the students in the class calculated, to a rough approximation, the velocity with which the debris travelled. With this information the students then calculated a timetable for the return of the radioactive cloud over their school. I t has been observed2 that nuclear debris from an atmospheric explosion are detectable after circling the earth as many as three times. Efforts to collect radioactivity from the cloud during its calculated second passage over the school were in vain, probably because of the small ( < 1 ft3/min) flow rate of the vacuum cleaner and the reduced quantity of available radioactive debris. The experiment motivated in the students a high degree of interest in learning the methods of radioactive debris 'Current Address: Hull High School, Hull, Massachusetts 02045.
ENERGY IMEVI
Figure2. Ge(Li) gamma ray spectrum of 26/27 March. 1972 air filter.
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/Journal of Chemical Education
'Baugh, J. O., Yoshikawa, K., and Kurada, P. K., Science, 155,1405, (1967).
generation during a nuclear explosion. At the same time the students in t h e class became more aware of the importance of limiting nuclear testing in the atmosphere. Related materials showing t h e dangers of inhaled and ingested radioactivity were discussed a t this time. T h e experiment demonstrated t h a t a topical event could be introduced into t h e science class with a good deal of success. In this case, lack of equipment was compensated b y initiative and cooperation with a local university, Boston College. Experimental
A Lewyt vacuum cleaner, Model 66, was modified for the experiment by placing an aluminum funnel with a maximum diameter of 7 em over the hose inlet. Several strips of plastic label tape were placed across the opening of the funnel to support the filter paper. Whatman No. 41 filter paper was taped in place over the top of the funnel. The filter paper was changed daily and tested for radioactive content after the decay of natural activities with a portable hand monitor (Baird Atomic G.M. Survey Meter, Model 420). A 30 cm3 Ge(Li) detector system at the Boston College Nuclear and Radio-
chemistry Laboratory was used to identify the gamma ray emitting isotopes present on the filter paper exposed for the 20-hr per i d between the 26th and 27th of March 1972. The autoradiograph was made as follows. Each filter paper was carefully ashed in a porcelain crucible over a Bunsen burner. The ash from each filter paper was suspended in 95% ethanol and filtered onto separate 2.4-cm filter papers. Each of these filter papers was then mounted on a brass or a polyethylene disc. Five mounted samples corresponding to the day of maximum activity and the two days before and after were placed on Kodak X-Ray no screen film and left undisturbed for 37 hr. The film was developed with standard Kodak X-Ray solutions. A composite negative was prepared by transferring "transfer lettering" to a clear sheet of acetate film and aligning the developed X-ray film to correspond to the proper caption. Photographic paper was placed under the composite negative and the exposure was made by light from an overhead enlarger to produce the photographshown in Figure 1. Acknowledgment
T h e authors wish t o t h a n k Irving J. Russell, Sheila Griffin and Shih-Lieh Fang for their assistance i n conjunction with this work.
Volume 50,Number 6, June 7973 1 439
