1. Dongnam Institute of Radiological and Medical Sciences, Research Center Busan 619-953, Korea
2. Kyungpook National University, Department of Physics Daegu 702-701, Korea
3. Dong-A University, Department of Physics Busan 604-714, Korea
4. Rensselaer Polytechnic Institute, Department of Mechanical, Aerospace, and Nuclear Engineering Troy, New York 12180-3590
5. Bechtel Marine Propulsion Corporation, Knolls Atomic Power Laboratory P.O. Box 1072, Schenectady, New York 12301