i EDUCATION Special Irradiation Facility ~ \
Scientist is placing a control rod guide tube in t h e core of General Atomic's TRIGA reactor. This model of the 10-kw. training, research, and isotope-producing reactor is being set up a t GA's San Diego, Calif., laboratories. I t is due to go critical next month. First TRIGA for school use will be installed at the University of Arizona this summer
TRIGA Trains, Produces Isotopes Newself-controlling fuel rods allow design of a safe isotope reactor for training and research X RIGA, A TRAINING, RESEARCH ISOTOPE
REACTOR, created b y General Atomic Division, General Dynamics, will go critical at GA's San Diego, Calif , l a b oratories next month. Key to GA's success in building a truly safe reactor that operates a t 10 to 30 kw. is a n e w fuel-moderator element. GA developed TRIGA's fuel rods of solid homogeneous uranium-zirconium hydride. An alloy of uranium, 209c enriched, provides the fuel, and zirconium hydride, which has high hydrogen content combined with metallic properties, serves as moderator. About 60 of these rods are used in each reactor. Safety features of the reactor are related to the fuel-moderator composi tion: When t h e rods heat u p , reactivity decreases and neutron intensity falls. Thus, temperature changes, within t h e core, control t h e reactor. Safety is built in and does not depend on electronic or mechanical devices. GA says at least 2% excess reactivity can be sud76
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denly introduced into this type core without causing any damage. T h e solid form of TRIGA's aluminum-clad fuel rods lends a second safety factor to the reactor, GA adds: Fission products are always encased within the reactor proper with no chance of leakage. Heat is removed from the core by water cooled below room temperature. Because it is safe at all stages of operation, GA says TRIGA can be used freely by teachers, researchers, and students. It can also b e installed without the expense of special containment. TRIGA is designed for installation at the bottom of an aluminum tank, 20 feet deep b y six feet in diameter. Some 16 feet of water in the tank above the core shields the reactor. The core and control rods are visible through the water and can b e seen while t h e reactor is operating. A graphite reflector 12 inches thick, covers sides and bottom of t h e reactor
Diagram of TRIGA shows reactor parts and facilities provided for isotope production and for educational and research uses of the equipment
core. Six-inch thick graphite on t o p of the fuel rods provides a reflector over the core. Space around and above the reflector is useful for irradiating large or odd-shaped specimens. Three control rods located in the core are used to regulate t h e power level and shut off the reactor, which can be operated by hand or by a servocontrol system. Critical mass, according to GA, is 2.2 kg. of U 235 , and excess reactivity available is less than that required to make the reactor critical. • Arizona Will Get First TRIGA. First TRIGA for educational use will be installed at t h e University of Arizona, Tucson, ready for operation next fall. It will become t h e center of a broad program of research a n d teaching in nuclear science at the school. Reactor engineering, isotope production and application, and instrumentation using isotopes will b e included. UA's departments of chemistry, physics, bacteriology, agriculture, zoology, and botany also expect to use the reactor for research. TRIGA will provide UA with three main facilities in and around the reactor core for nuclear science studies and isotopes production—the "lazy susan," a "rabbit tube," and a "glory hole."
T h e lazy susan is a rotary specimen rack which holds 4 0 specimen contain ers. A drive shaft extending to the top of t h e reactor pit turns the rack for loading and unloading. Thermal neu tron flux at t h e rack, GA says, is 10 1 1 neutrons p e r sq. cm.-sec. A pneumatically operated rabbit tube is used for producing isotopes with short half lives. This consists of two concentric tubes running from the t o p of t h e tank t o the edge of the reactor core. Specimens a r e fed in by gravity through the inner tube a n d ejected b y a carbon dioxide line through t h e outer tube. Neutron flux at this position is also given as 1 0 1 1 neutrons per sq. cm.-sec. T h e glory hole is a l 1 / 2 - i n c h diam eter tube located i n the core of the re actor at the point of maximum flux and maximum statistical weight. I t is use ful, GA finds, for isotope production, pile-oscillator experiments, and dangercoefficient experiments. GA says i t chose the 10-kw. power for general operation of TRIGA because it is high enough to produce a large number of radioisotopes. Useful quan tities of 62 of the first 8 3 elements can be obtained. Besides producing isotopes, and par ticularly short-lived ones, G A says TRIGA is a powerful tool for traceelement determination by activation analysis. F o r example, i t adds, as small a quantity as Ι 0 - 1 0 gram of manganese can be detected i n a biological sample. Other radiochemical work, including hot atom chemistry, GA says, can also be carried o u t with TRIGA.
NOW
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Too Many Students Teach Concern for t h e quality of teaching in college general chemistry has led William Ε Caldwell of Oregon State College to ask other schools w h o teaches their course. Before t h e present rush of students in freshman chemistry a n d before pro fessors spent so much of their time on research, career instructors taught gen eral chemistry. Now Caldwell finds graduate students teach more and more of these classes—both lab and recitation sections. H e even finds schools that use undergraduates to teach chemistry or graduate students from other d e partments such as botany, pharmacy, and horticulture. This situation, Caldwell says, exists only in chemistry. It does not occur in teaching other sciences a n d engi neering, English, or math.
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5, I 9 5 8
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77
EDUCATION Caldwell told the the A C S Division of Chemical Education, meeting in San Francisco last month, he believes n o t more than 60% of teaching in general chemistry should b e left to graduate students. His reasons: T h e r e is n o efficiency in using graduate students to teach chemistry. They a r e inexperi enced and teaching is a secondary in terest to them. G r a d u a t e students seldom teach more than t w o years. They take research jobs as soon as possible. Replies from five schools surveyed by Caldwell show:
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• Graduate students teach l a b a n d recitation sections in all these schools. One school that used student teachers was criticized so strongly for t h e prac tice it now has a full-time staff instruc tor in charge of each lab section. Grad uate students still assist the instructor. • Graduate students also lecture in some schools. In these instances, t h e staff usually prepares the lectures, • The only staff help given teaching students in most schools is in a weekly meeting. One school tries to get its teaching graduate students t o start work on July 1 for training before t h e fall semester. It also insists t h a t these teachers attend the lectures their stu dents attend. • All five replies express agreement with Caldwell on t h e need for more staff participation in the general chem istry course, especially in supervising the students' lab work.
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Recruiting at colleges for t h e 1958 crop of engineers and scientists is slower this spring than it was In either 1956 or 1957, says Engineers and Sci entists of America. The slack is most noticed in schools in the East and t h e South (C&EN, April 28, p a g e 21). Data t h a t ESA gathered in a survey of the 148 colleges and universities ac credited b y the Engineers' Council for Professional Development show only eight schools with recruiting activity higher than last year; 34 schools say recruiting continues at the 1957 level, and 59 indicate a drop in activity. With few exceptions, E S A says, schools in the eastern part of t h e coun try have fewer recruiters than usual so far this spring. In the Midwest and Far West, though, recruiting at some colleges seems to be heavier.
A number of the schools surveyed by ESA say, although t h e y h a v e r e cruiters on campus, m a n y of t h e m a r e just looking at possible candidates. They have no openings n o w , b u t h o p e to h a v e some by June. Recruiters are also m o r e selective this year, the schools report. Some companies, they say, are considering only the u p p e r 10% or t h e u p p e r 2 5 % of t h e graduates for any job. G e n e r ally, however, t h e schools find industry following its usual pattern—looking for research a n d d e v e l o p m e n t personnel among the top 2 5 % but covering t h e total group for production a n d sales engineers.
• University of Michigan has surveyed its 5 9 4 accredited high schools ( 8 0 % of all Michigan high schools) to see h o w students a n d teachers a r e progressing in science. It reports: • Of total enrollment, 2 0 % are study ing biology, 1 0 % chemistry, 9 % gen eral science, and 5% physics; 3 8 % a r e taking algebra, geometry, trigonometry, or advanced m a t h ; a n d 1 7 % are study ing applied m a t h . • Among this year's 55,000 gradu ates, more than 1 2 % will h a v e com pleted four years of m a t h b y J u n e ; 9 0 % of this group will have at least o n e year of both science and m a t h . • Over t w o thirds d ï t h e science a n d math teachers in t h e U M - a c c r e d i t e d schools have h a d at least 20 semester hours of college science a n d m a t h . • Chemical microscopy, crystallography, and fusion methods will b e covered in courses, d e s i g n e d for industrial personnel, t o be given this year b y Walter C. M c C r o n e Associates, 5 0 0 East 33rd St., Chicago 16, 111. T h e three courses, t w o weeks each, will r u n consecutively starting July 7. • University of Dayton last month dedicated a n e w chemistry and chemical engineering building—Wohlleben Hall—planned t o take care of these d e partments until school enrollment reaches 4 0 0 0 full-time s t u d e n t s . Besides 14 classrooms, 2 6 laboratories, a n d 37 offices, Wohlleben Hall boasts a lecture hall e q u i p p e d with wide-screen motion picture facilities.
