Foundries can be a source of mercury contamination,when thermometers and other such equipments are mixed with the stainless steel scrap and melted. In normal industrial use this may not pose a threat,however in nuclear applications,if this contaminated stainless finds its way through,it could be disastrous.It is felt that mercury can vaporize easily,and then later the mercury ions can cause damage if these vapors reach central core region of the reactor. Hence as an utmost precaution,mercury free stainless steel is recommended.
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"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year