Nuke particles escaping bounce node with geometry input
This looks like a bug in Nuke's ParticleBounce node. The geometry input is new to Nuke 9, which was released pretty recently.
That said, the bug seems to manifest only in this idealized environment of two spheres. The first sphere (radius 1) emits the particles, and the second sphere (radius 3) kills them. It is likely because of the exact alignment between vertices that causes it to penetrate.
Rotating one of the two spheres 0.1 degrees on each axis solves the problem
In theory, the &quot;real world&quot; wouldn't see this bug as frequently, but I've submitted this bug report to The Foundry.

Response from The Foundry

Thanks very much for providing reproduction script, we can see the
problem easily. Your comments and script are logged:
Bug 47417 - ParticleBounce - Leaks with static primitive geometry
input in some cases
We recommend checking upcoming release notes for updates on this
issue.