Help locating a book.

[Dhmcd]

I had this SF short story paperback YEARS ago, but due to the lapse of time, aging brain cells, and CRS, the details of the plot are vague. Forgive me if this is the wrong forum to ask.

Here's what I recall. The beginning of the story revolved around a disgruntled worker at a power plant (nuclear, I think) who, in his garage shop, built a thermite / chemical type device inside the thermos that he carried in his lunch to work every day. One day he hid this thermos on top of a critical coolant pipe, which was time-fused to detonate after a period of time, thus putting the plant into melt-down. Or that was the plan. The rest of the story was a race of time to find this thing before the unthinkable happened.

Any ideas? I owned this book YEARS ago, and would like to find it again to re-enjoy it.

Thanks in advance

dhmcd