It’s set in a TV studio and these scientists are showing off this new wonder tool, which can basically blow up anything. At first it’s shown off as this great thing that can help mankind, then it becomes clear this thing can vaporise entire tank columns and the presenter orders the film feed to be cut, but it’s too late and designs for this thing are all over the world, and we’re left unsure if the world will be a better place, or be destroyed by Tuesday.
Sounds to me like Frank Herbert's Short Story "Committee of the Whole".
William R. Custer, a representative of farmers from Oregon, uses the public hearing for amendments to Taylor Grazing Act of 1934 to showcase a weapon with enough power to "cut the planet in half". The live broadcast of the hearing, during which Custer explains the details on how to build such a weapon, ensures that restraint becomes the key to survival of the human race, making threats and any form of slavery among humans obsolete, while also sending humanity in a new direction that may lead to its maturity.
The tool itself, as Custer describes it in the story, can be constructed out of simple components such as copper wiring and easily-obtainable electronic components, and cost next to nothing. He presents it at first as a general work cutting tool, and its application as a weapon of mass destruction becomes inherent only after a detailed description of its construction has been broadcast live.
The story ends with several government men worrying about how they could stop/silence people who saw the broadcast, and restrict general access to these components, and basically realizing these things would be impossible, and that if mankind were to survive having such a device being so ubiquitous, we'd have to learn to simply be responsible and trusting in each other, lest we all be destroyed.