Symposium
From the chemistry of responsible environmentalism to environmentally responsible chemistry
Successes and Techniques Associated with Teaching the Chemistry of Radioactive Wastes Donald H. Williams Hope College, Holland MI 49422-9000 Greg ChopI n the October 1994 issue of THIS JOURNAL, pin presented a n interesting article, "Aspects of Nuclear Waste Disposal of Use i n Teaching Basic Chemistry" ( I ) . That paper was part of the 207th National ACS Meeting where a symposium was held on "Nuclear Chemistry, The State of the Art for Teaching." Herein is described a program that takes that idea a large step forward. Here the challenge of radioactive wastes (radwastes) becomes the central theme for a chemistry course, "The Chemistry of Radwastes". The subject is very rich in environmental implications and i t provides more than enough chemical connections to fill a semester. The chemistry principles that can he taught around this topic are truly extensive and include redox, equilibrium, kinetics, the periodic chart, and more. Cooperative learning and group learning activities also seem to evolve natnrally. Furthermore, this topic is well suited to those unafraid to teach citizenship a n d environmental issues and to address controversial issues and even moral choices. In the discussion of radwaste disposal, there is no avoiding the idea that the class will confront many value-laden questions. This seems to appeal to many students. I t has been found that students become quite interested in the relevant chemical specifics in the process. Furthermore, many students report that they appreciate the opportunity to see their chemical insights put to a good and clearly moral use. They realize that we have radwaste and that the issue is about what to do with i t i n the context of competing financial demands. "The Chemistry of Radwastes" is presently a popular option for nonscience students who are required to take a t least one science course at Hope College. Parts of that course and items from that course are used in our beginning chemistry course for science majors. Both the topic itself or parts of this theme are well received in either situation. The popularity of the topic, especially for the nonscience majors, can be found in four areas a s summarized from student evaluations: 1. The problem of the safe isolation or disposal of radwaste presents a fresh challenge, one that has not yet been
Truly, many students are attracted to the sciences because they have discovered the opportunity to work on a timely, relevant, and important problem. The disposal, or safe isolation, of radwastes presents exactly t h a t challenge. The newspapers continually remind us that as the world recovers from the cold war era, huge sums of money will be spent to clean up defense establishments. A whole chemistry course can be taught around the science that must he employed if weapons grade uranium or plutonium is to be recycled and turned into power plant fuel or permanently poisoned. I n fact, one could build a whole chemistry course around the fuel reprocessing that is practiced in parts of Europe and Japan. But this is not my central theme. The fact that the United States generates nearly a quarter of its electrical supply .+a nuclear fission also means that another consequence must be faced, that of handling spent nuclear fuel (SNF). And finally, a s our hospitals and labs make increased use of nuclear or radiological processes, still another quantity of radwastes is generated. In fact, examples exist of hospitals curtailing radiological procedures because they have not solved the radwaste issue. Even if such a move by a hospital is more political than technical, i t allows the students to face squarely the costs associated with benefits that have accrued, or may accrue. to them. This is a moral issue that students find very interesting. The disposition of radwaste has many different aspects and serious envirnnmtmt:il c~nsequences.13ecnuse the ramificatiimi are extensivt~,it has h w n found hest to focus on just one aspect of the situation. I focus upon the disposition of SNF, the fission products of electrical power production. It is to be noted here that every nuclear power producing country has independently chosen deep geological disposal for HLW. This means that burial is to be the ultimate fate of either SNF or the reduced volume of radioactive material that comes from the reprocessing of SNF. Regardless of how one feels about nuclear power, there is no denying that a s a country, we can do something better that letting the waste accumulate a t 108 different power plants. Power plants are usually located near population centers and their cooling water supplies are often also the source for local drinking water.
met well. 2. The challenge of radwaste disposal is a problem that will be with students far all of their lives and the lives oftheir
offspring. 3. The subject of radwaste appeals positively to those students with a sense of history, political science or ecanomio. 4. The environmental theme is attractive in itself, hut stu-
dents report that they have renewed respect for the eomplicated nature of any environmental problem and the tradeoffs that must be considered,
Nuclear Context I n order to assure that all students have the same foundation, some facts are shared about nuclear power prodnction. Across the United States, 23% of electricity is produced via fission. This i s second to the burning of coal (about 55%) as a primary energy source. (This is about 7% of America's primary energy sources.) The benefits and negative consequences of all alternate energy sources are Volume 72 Number 11 November 1995
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discussed. includine the onnortunities lost a s rivers are dammed, b i i~s burnid and &forth. Time constraints mean focusine on coal and nuclear comnarisons. The costs of coal are discussed clearly i n an arti'cle by Robert Cullen (2). Much chemistrv can be taueht about the chemical notential of coal. Themost comm& conclusion is that whiie SNF and all nuclear waste must be handled with great care, its volume i s very small compared to t h a t generated from burning coal. The table summarizes comparative data from ~ & a r d Cohen (3).I t is very instructiGe for students to consider the stoichiometric calculation associated with the fact hat "my" nearby power plant hums 72 lh ofcoal a second and to calculatr the COLoutput which then results. Comparative Power Plant Wastes Nuclear Approximately 2.0 yd3/y
Coal 7 lb Sods 17 lb ashls 500 lb COnIs
One could just as well build a chemistry course around coal burning. One could study the effects of acid rain on the environment, the disposition of fly ash and bottom ash or the technoloeies evolvina to reduce the nroduction of nitrogen oxides in coal burning power plants. There are many interestine trace elements and radioisotones nut into our environm&t by the burning of coal. My s t u d e h respond more positively to the challenge of radwaste isolation than to what they perceive a s the repeated doom and gloom of studvine a n old environmental nroblem. The nuclear " power technology is newer and more interesting to them. Mv students review The Nuclear Waste Policv Act of 198i (NWPA) (41,which renews the Federal ~ o v e k e n t ' s responsibility for High Level Waste (HLW) consisting of SNF and Defense Wastes (TRU's-Transuranic Element primarily). That law gives States or groups of States the responsibility of Low Level Radwastes (LLW). The NWPA also gives the responsibility of handling SNF to the Office of Civilian Radioactive Waste Management (OCRWM) in w (DOE). (For the nonscience the U S Denartment of E n e r-. . student, thk extensive use of acronyms i n areas outside chemical symbols is usually revealing.) Class attention then moves to the 1987 amendment of the NWPA that concentrates OCRWM attention on Yucca Mountain, Nevada a s the only site being carefully studied a s a possible deep geologic repository for HLW, mostly SNF from commercial reactors (5).Yucca Mountain is a ridge of welded volcanic ash called tuff that is located about 100 mi northwest of Las Vegas. The politically inclined are shown that the amendment also forbids the consideration of a a n ite as a host rock for a repository. They are remindezthat the eastern half of the United States where most nuclear power plants and voters are located is located on granite. There mav not be much chemistw evident in studvine . the seismic situation and the volcanism associated with Yucca Mountain. But, there is much chemistry in the study of the possible zeolytic nature of tuff and the hydrology of the area. Students are not likely to ever forget the etymology of the word ion after a good discussion of this chemistry. (Copies of the Site Characterization Plan for Yucca Mountain are free from OCRWM but the list of experiments to be done there comnrises 6600 naees and weiehs 37 lb!) ~ i final e asdec; of the n u z e a r situation that interests students ereatlv is the first nart of the storv. the histow of s nuclear power and the atomic bomb. ~ a ~ b e t hisi because atomic weapons represent the defining image of this age. Literature majors are intrigued by the references to atomic power that appeared in popular science fiction writings a t the very time that Rutherford was establishing the nuclear
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atom. I recommend the book by Richard Rhodes on the history of the atomic bomb (6). The Lisa Meitner story and her introduction of the term nuclear fission eets the attention of all students. On this subject, I recommend a particular video (7).Students i n our current classes must learn about the atmosphere prevailing i n August 1945 from their grandparents. The Atoms for Peace Program and the original intention to put SNF in a n abandoned salt mine near Lyons, Kansas is news to all of the class (8). Chemical Implications The teaclung of the nuclear atom, the mass defect and the bind~neenermare very evidently related LOthe theme ofradwaste.-The l&tory su&oundingthose discoveries is equally appropriate and all these subjects are introduced a t the same time in my course for the nonscience majors. This is also the time to put energy outcomes in perspective, chemical and nuclear. The impact of the mass to energy change is an unusual way to teach the conservation of energy and mass but i t seems to work well. It has been my experience that the teaching of radioactivity should occur in two distinct nhases. the first to teach about the basic emissions of a,p, a i d "rap." There is little difference between teachine chemical eauation writine and that of nuclear equation wricng. This firit phase is al; when halflives and the mathematics of firsborder kinetics are introduced. Even science majors seem to appreciate a fresh look a t the electromaenetic spectrum and the nlace of X-rays in it. The second phase orradioactivity that emphasize"s its effects is more comfortablv taught if one waits until the students have worked with-covagnt bonds and molecules. The idea of a free radical is alien without this context. But a student who is anxious about the effects of radiation on the human body is very inclined to learn about the various bondingforces that h o l d ~ ~ ~ t o ~ e t h e r . After discussing nuclear fission and the idea of chain reactions, the periodic chart is introduced with the notion that in SNF one can find nearly 1000 isotopes with every element rep resented. The periodic table and some obvious descriptive chemistry are meaningful topics to anyone contemplating the vears (the safe isolation of this material for the next 10.000 , time requirement in the NWPA). There are three links to the periodic chart that I employ The first deals with the eventual consequences of the 100 elements on the periodic chart. Most elements are metallic and will become wandering cations on the oxidizing planet that we inhabit. I t is obvious that redox chemistrv is taueht here as well as the reactivity and general behavio; of'cations. The reason for the hope that the substrata for anv . geolocic - rcposi. tory are zeolytic now becomes very clear. The second link to the periodic chart comes i n a discussion of general bond types that are found among various elements. This is needed for the covalent chemistry that will occur when radiological effects are introduced. The third link to the chart comes with the discussions about snecific radioisotones. esneciallv those of bioloeical or environmental importance. My students respond well to knowi n e whv iodide tablets are stockpiled a t nuclear installations and exactly why Cs-137 or ST-90 are so feared. There is room for almost any wecific chemical interest to be advanced when the peribdie table is before the class. Among other scientific and chemical aspects of this situation that can be addressed include calculating the volume needed to contain the 40,000 metric tons of SNF expected to be accumulated by the year 2020. One must considerjust how much heat is given off and how densely packed this material should be. students can wrestle with t h e fate of inert gases produced and other possible uses of materials in the HLW. One only needs to know that this is a topic of interest to the students. It takes little effort to become informed on the sub-
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ject and to find chemical applications and insights related to it. The OCRWM in the U.S. DOE has an abundant supply of educational material available a t no cost to those who call them.' One good starting point is a set of 66 lessons suitable for high school students complete with a study guide for teachers. They can also direct one to a free database containing the make up of the fuel rods in each nuclear power plant in the United States. This database allows one to calculate the isotopic makeup of that material into any time in the future. Summary "The Chemistry of Radwastes" has worked well for me in several contexts. The material is not all chemical but richly so. The material presented can all be scientific but students seem to learn more chemistry when it is related to the associated politics, history, and economics that surround this controversial topic. I do not avoid the valueladen questions. Personal Notes My syllabus is available upon request. I n it I recommend a book that did not made the list in the ACS Symposium referred to in the first paragraph (9).Much personal satis-
faction comes with tackling a tough problem and feeling that perhaps I have helped to create a n educated citizenry that will help to solve this problem. Hope can be found in a brand new work by Barry Rabe, Beyond Nimby: Hazardous Siting (10).I know from sad personal observation that those working on this task need both moral support and constant supervision. I recall a n article by John Ahearne in The Chronicle of Higher Education noting that scientists must help deal with the hazards of the nuclear era (11).I urge you to join in the effort. Literature Cited 1. Choppin, G R . J Chem. Educ. 199471,826429. 2. Cullen, R.T h e True Cost o f Coal,"Harpers 1993112),38.
3. Cohen, B.L.ThPNucleor Enorgy Option; Plenum: New York. 1990, p 17P175. 4. EL. 97-425. ThaNucleor Waste Policy Act of1982. Janualy 7, 1983. 5. TLUe V o f P L . 1ML203, Nuclear Wasfa Amendmenfs, Deeemkr 22. 1 9 8 7 . 6 ~ 7 1 . 6.Rhodes, R.The Moking of the Atomic Bomb; Simon and Schuster: New York. 1986. 7. "Who Found the Missing Link?" Peeodic Toble and the Human Element Series, Films for the Humanities & Sciences: Princeton,NJ. 8. Carter, L. Nudeor I m p e m l i ~ ~and s Public D u d : Deoliw with Radiooclivo Waste; Resources for the Future: Washington. DC. 1987. 9. Mumay R.L.Understonding Rodimcliu. Wosfs, 4th ed.; Battelle: Richland, 1994. 10. Rabe, 0 B. Beyond NIMBY Hazardous WasB Siting in Canodo and the United State, Bmokings Institution: Washington. DC. 1994. 11. Aherne J. F Chmn. Hggher Educ 1992 (June24). A40.
'OCRWM can be reached at 800-225-6972and at P.O. Box 44375. Washington. DC 20026.
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