The critical hazards generated from operation of a melting facility for metal radioactive waste are mainly assumed to be such as vapor explosion, ladle breakthrough and failure in the hot-cell or furnace chamber using remote equipment. In case of vapor explosion, material containing moisture and/or enclosed spaces may, due to rapid expansion of gases when heated, cause an explosion and/or violent boiling. The rapid expansion of gases may lead to ejection of molten radioactive metal from the furnace into the furnace hall. If there is a large amount of liquid the explosion may damage or destroy technical barriers such as facility walls. The consequences for the facility ranges from relatively mild to very severe depending on the force of the explosion as well as the type of waste being melted. Nonradiological consequences may be physical damage or destruction of equipment and facility barriers, such as walls. Due to the radiological consequences a longer operational shutdown would likely be required. Cleanup efforts would include cutting of solidified metal in a problematic radiological environment requiring use of remote technology before damage and repair requirements can be assessed. Even though there is a risk for direct physical harm to operators for example in the control room and hot-cell, this analysis focuses mainly on the radiological impact. The extent to which remote equipment could be used in the decontamination effort will largely determine the health consequences to the workers. It is reasonable to assume that there will be a need for workers to participate manually in the effort. Due to the potentially large dose rates and the physical environment, it is possible that the maximum allowable dose burden to a worker will be reached. No major consequence for the environment is expected as most of the radioactivity is bound to the material. In case of ladle breakthrough, a ladle breakthrough involves loss of containment of the melt due to damage of the ladle. This may be caused e.g. by increased wear due to overheating in the melt, or from physical factors such as mechanical stress and impact from the waste. A ladle breakthrough may lead to spread of molten metal in the furnace hall. Molten metal coming into contact with the surrounding cooling equipment may cause a steam explosion. The consequences of a ladle breakthrough will depend on the event sequence. The most severe is when the molten metal comes into contact with the cooling system causing a vapor explosion. The basic consequences are assumed to be similar to those of the vapor explosion above. While the ejection of molten metal is likely more local in the ladle breakthrough scenario, the consequences are judged to be similar. In case of failure in the hot-cell or furnace chamber using remote equipment, the loss of electric supply or technical failure in the furnace causes loss of power supply. If not remedied quickly, this could lead to that the melt solidifies. A melt that is solidified due to cooling after loss of power cannot be removed nor re-melted. This may occur especially fast if there is not melted material in the furnace. An unscheduled replacement of the refractory in the furnace would be required. It could be unknown to what degree remote equipment can be used to cut a solidified melt. It is therefore assumed that personnel may need to be employed. This event could not have any impact on environment

Working with molten metal has always been and will always be a dangerous workplace. No matter how carefully equipment is designed, workers are trained and procedures are followed, the possibility of an accident can occur in melting workplace. Some primary causes of melt splash and furnace eruptions include wet or damp charge material, dropping heavy charge into a molten bath, wet or damp tools or additives and sealed scrap or centrifugally cast scrap rolls. Induction melting brings together three things (water, molted metal and electricity) that have the potential for concern if the furnace is not properly working. Induction furnace must have a water cooling system built into the coil itself. Water picks up the heat caused by the current as well as heat conducted from the metal through the refractory. The water carries the heat to a heat exchange for removal. Spill pits serve to contain any molten metal spilled as a result of accident, run out or dumping of the furnace in an emergency. If a leak is suspected at any time, cease operation and clear the melt deck area of all personnel and empty the furnace. Molten metal fins can penetrate worn or damaged refractory and come into contact with the coil. A furnace or a close capture hood which suddenly swings down from a tilted position will cause injury or death. Whenever workers are working on a furnace or close capture hood when it is in the tilted position, be sure that it is supported with a structural brace that is strong enough to keep it from dropping if hydraulic pressure is lost. In theory refractory wear should be uniform, however, in practice this never occurs. The most causes of lining failure are improper installation of refractory material, inadequate sintering of refractory material, failure to monitor and record normal lining wear, allowing the lining to become too thin, installation of the wrong refractory, improper preheating of a used cold lining, failure to properly maintain the furnace the sudden or cumulative effects of physical shocks or mechanical stress, and excessive slag or dross buildup. Pouring cradles provide bottom support for crucibles. A crack in the crucible occur below the bottom ring support, the bottom of the crucible can drop and molten metal will spill and splash, possibly causing serious injury or death. To reduce this danger, a pouring cradle that provides bottom support for the crucible must be used. Power supply units must have safety locks and interlocks on all doors and access panels. Workers who work with low voltage devices must be made aware of the risk posed by high levels of voltage and current. The most causes of accidents are introduction of wet or damp material, improper attention to charging, failure to stand behind safety lines, coming into contact with electrically charged components and lack of operator skills and training. Only trained and qualified personnel are to have access to high risk areas. Safety lockout systems are another effective measure to prevent electrical shock