If a player builds a reactor too close to the core. That reactor gets destroyed and the player gets a warning in chat.
Auto kick is by default disabled but you can enable it in the server console using antinuke-kick <on/off>.
If this option is enabled the player gets kicked and a servermessage gets send to all the players on the server.
No panic sometimes when a player is to stubborn and keeps spamming nuclear reactors a Nullpoint exception occurs. No panic your server is fine.
But it is wise to kick/ban that player.
gradlew jar / ./gradlew jar
Output jar should be in build/libs.
Simply place the output jar from the step above in your server's config/plugins directory and restart the server.
List your currently installed plugins by running the plugins command.