| TER | Technical Evaluation Report (NRC) |
| TMS | Technical Maintenance Services |
| TRG | Technical Review Group |
| TS, Tech Spec | Technical Specification |
| TSIP | Technical Specification Improvement Program |
| TSC | Technical Support Center |
| TCV | temperature control valve |
| TI | temperature indicator |
| TAM | thermal anchor movement |
| TDC | thermal diffusion coefficient |
| TEMP | Thermal Effects Monitoring Program |
| TC | thermocouple |
| TLD | thermoluminescent dosimeter |
| TLC | thin-layer chromatography |
| k | thousand |
| keV | thousand electron volts |
| three-step |
| time-history |
| to date |
| ton (spell out) |
| tpd | tons per day |
| tpy | tons per year |
| TSAR | Topical Safety Analysis Report |
| tornado-borne |
| TDH | total dynamic head |
| TEDE | total effective dose equivalent |
| TZ | Transaction Zone |
| TSP | tube support plate |
| tubesheet |
| TIG | tungsten inert gas (welding process) |
| TB | turbine building |
| TBS | turbine bypass system |
| TG | turbine generator |
| TPS | turbine protection system |
| TDAFW | turbine-driven auxiliary feedwater (pump) |
| turnover |