An analysis of fission product release during the Three Mile Island Unit 2 (TMI-2) accident has been initiated to provide an understanding of fission product behavior that is consistent with both the best estimate accident scenario and fission product results from the ongoing sample acquisition and examination efforts. ''First principles'' fission product release models are used to describe release from intact, disrupted, and molten fuel. Conclusions relating to fission product release, transport, and chemical form are drawn. 35 refs., 12 figs., 7 tabs.

In response to the accident at Three Mile Island Unit 2 (TMI-2), the United States Nuclear Regulatory Commission (USNRC) initiated a series of Severe Fuel Damage tests that were performed in the Power Burst Facility at the Idaho National Engineering Laboratory to obtain data necessary to understand (a) fission product release, transport, and deposition; (b) hydrogen generation; and (c) fuel/cladding material behavior during degraded core accidents. Data are presented about fission product behavior noted during the second experiment of this series, the Severe Fuel Damage Test 1-1, with an in-depth analysis of the fission product release, transport, and deposition phenomena that were observed. Real-time release and transport data of certain fission products were obtained from on-line gamma spectroscopy measurements. Liquid and gas effluent grab samples were collected at selected periods during the test transient. Additional information was obtained from steamline deposition analysis. From these and other data, fission product release rates and total release fractions are estimated and compared with predicted release behavior using current models. Fission product distributions and a mass balance are also summarized, and certain probable chemical forms are predicted for iodine, cesium, and tellurium. An in-depth evaluation of phenomena affecting the behavior of the high-volatility fission products - xenon, krypton, iodine, cesium, and tellurium - is presented. Analysis indicates that volatile release from fuel is strongly influenced by parameters other than fuel temperature. Fission product behavior during transport through the Power Burst Facility effluent line to the fission product monitoring system is assessed. Tellurium release behavior is also examined relatve to the extent of Zircaloy cladding oxidation. 81 fig., 53 tabs.

The Three Mile Island and Chernobyl nuclear incidents emphasized the need for the world-wide nuclear community to cooperate further and exchange the results of research in this field in the most open and effective manner. Recognizing the roles of heat and mass transfer in all aspects of fission-product behavior in sever reactor accidents, the Executive Committee of the International Centre for Heat and Mass Transfer organized a Seminar on Fission Product Transport Processes in Reactor Accidents. This book contains the eleven of the lectures and all the papers presented at the seminar along with four invited papers that were not presented and a summary of the closing session.

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The Three Mile Island and Chernobyl nuclear incidents emphasized the need for the world-wide nuclear community to cooperate further and exchange the results of research in this field in the most open and effective manner. Recognizing the roles of heat and mass transfer in all aspects of fission-product behavior in sever reactor accidents, the Executive Committee of the International Centre for Heat and Mass Transfer organized a Seminar on Fission Product Transport Processes in Reactor Accidents. This book contains the eleven of the lectures and all the papers presented at the seminar along with four invited papers that were not presented and a summary of the closing session.

The accident at the Three Mile Island Unit 2 (TMI-2) reactor, now 10 years old, remains as the United States' worst commercial nuclear reactor accident. Although the consequences of the accident were restricted primarily to the plant itself, the potential consequences of the accident, should it have progressed further, are large enough to warrant close scrutiny of all aspects of the event. TMI-2 accident research is being conducted by the US Department of Energy (DOE) to provide the basis for more accurate calculations of source terms for postulated severe accidents. Research objectives supporting this goal include developing a comprehensive and consistent understanding of the mechanisms that controlled the progression of core damage and subsequent fission product behavior during the TMI-2 accident, and applying that understanding to the resolution of important severe accident safety issues. Developing a best-estimate scenario of the core melt progression during the accident is the focal point of the research and involves analytical work to interpret and integrate: (1) data recorded during the accident from plant instrumentation, (2) the post-accident state of the core, (3) results of the examination of material from the damaged core, and (4) related severe-accident research results. This paper summarizes the TMI-2 Accident Evaluation Program that is being conducted for the USDOE and briefly describes the important results that have been achieved. The Program is divided into four parts: Sample Acquisition and Plant Examination, Accident Scenario, Standard Problem Exercise, and Information and Industry Coordination.