AND KRYPTON-85 ATOM COUNTING

IN THE DISPOSAL OF HAZARDOUS WASTES, ATTENTION MUST BE DIRECTED NOT ONLY TO THE PROBLEMS OF SAFE COLLECTION, TRANSPORTATION AND STORAGE, BUT ALSO TO THE PROBLEM OF ISOLATING THE HAZARDOUS MATERIAL FOR A LONG TIME. THIS IS ESPECIALLY TRUE FOR RADIOACTIVE WASTES, WHICH NEED TO BE ISOLATED FOR MANY THOUSANDS OF YEARS. UNDERGROUND DISPOSAL IS AN OPTION THAT SHOW CONSIDERABLE PROMISE IF ASSURANCES CAN BE MADE TO ITS LONG-TERM SAFETY. A MAJOR CRITERION IN IDENTIFYING A SUITABLE SITE IS FOR THERE TO BE LITTLE WATER CIRCULATION TO PREVENT WIDESPREAD AND RAPID DISPERSAL IF THE STORAGE CONTAINERS ARE BREACHED. LOW CIRCULATION MAY BE ASSURED IF THE GROUNDWATER IS VERY OLD. THERE ARE MANY METHODS OF ESTIMATING GROUNDWATER AGES, BUT ATMOSPHERIC RADIONUCLIDES ARE, PERHAPS, THE MOST DIRECT AN MOST ACCURATE. TANDEM ACCELERATOR MASS SPECTROMETRY HAS RECENTLY MADE 36C1 (3.1X105 YR.) AVAILABLE AS A WATER DATINGTECHNIQUE. ANOTHER RADIONUCLIDE, 81KR (2.1X105 YR.), SHOWS GREAT PROMISE AS A WATER DATING METHOD AND HYDROLOGICAL TRACER. 81KR WILL COMPLEMENT INFORMATION GAINED FROM 36C1 AND OTHER DATING TECHNIQUES, AND BECAUSE OF THE CHEMICAL INERTNESS OF KRYPTON, MAY SIMPLIFY INTERPRETATION OF THE RESULTS. 81KR CANNOT BE MEASURED WITH TAMS. RESONANCE IONIZATION SPECTROSCOPY (RIS) INVOLVES THE STEPWISE EXCITATION, IONIZATION, AND COUNTING OF ATOMS OF A PRE-SELECTED ELEMENT. BECAUSE NARROW-BAND LASERS ARE USED, SUFFICIENT OPTICAL POWER ENABLES ALL OF THE ATOMS OF THE SELECTED ELEMENT TO BE IONIZED, WHILE THE INTERFERENCE FROM OTHER ELEMENTS REMAINS NEGLIGIBLE. THE IONS FORMED ARE EXTRACTED AND PASSED THROUGH A MASS SPECTROMETER, THEREBY ACHIEVING ISOTOPIC SELECTIVITY. BECAUSE OF THE VERY HIGH ISOTOPE RATIOS IN 81KR COUNTING, SEVERAL ENRICHMENT STEPS ARE REQUIRED BEFORE COUNTING BY RIS. IT IS THE PURPOSE OF THIS PROGRAM TO DEVELOP 81KR COUNTING TO ENABLE ROUTINE MEASUREMENTS OF THIS IMPORTANT ENVIRONMENTAL TRACER. PHASE I WILL CHARACTERIZE EXISTING ENRICHMENT PROCEDURES AND MAKE RECOMMENDATIONS FOR PRACTICAL ENRICHMENT SYSTEMS. AS A TEST, THE 81KR CONTENT OF ATMOSPHERIC KRYPTON WILL BE MEASURED. PHASE II WILL DEVELOP THE ENRICHMENT SYSTEM AND TAILOR THE RIS ATOM COUNTING SYSTEM TO 81KR. MEASUREMENTS WILL BE MADE OF WELL CHARACTERIZED HYDROLOGICAL SAMPLES FOR COMPARISON.