| backdraft |
| backflow |
| backpressure |
| backseat (valves) |
| backup (noun or adj), back up (verb) |
| BOP | balance-of-plant |
| bbl | barrel(s) |
| bbl/d | barrel per day |
| base load |
| basemat |
| baseplate |
| BEPZ | basic emergency planning zone |
| bedrock |
| BOL | beginning of life |
| beltline |
| beyond-design-basis (accident) |
| biaxial |
| bidirectional |
| BeV | billion electron volts |
| bistable |
| biweekly |
| blowdown |
| blueprint |
| BN | Board Notification |
| B&PV | Boiler and Pressure Vessel (Code) |
| bp | boiling point |
| BWR | boiling water reactor |
| boiloff |
| BCMS | boron concentration measurement system |
| BCMS | boron concentration monitoring system |
| BIT | boron injection tank |
| BHP | brake horsepower |
| BTP | Branch Technical Position (NRC) |
| breakwater |
| Btu | British thermal unit |
| bldg | building |
| buildup (noun or adj), build up (verb) |
| built-in (adj) |
| burnup (noun or adj), burn up (verb) |
| bypass |
