Instrument Surveillance Testing and Technical Specification Compliance

Why Instrument Surveillance Testing Matters

Nuclear power plants rely on safety-related instrument channels to detect off-normal conditions, initiate automatic protective actions, and give operators the information they need to make safe decisions. Because these instruments must work correctly when they are needed most, federal regulations and each plant's Technical Specifications (Tech Specs) require that they be tested on defined schedules. Performing these tests accurately—and knowing exactly what to do when a channel does not meet acceptance criteria—is one of the most safety-critical tasks a non-licensed operator or radiation protection technician performs.

What a Surveillance Test Is

A surveillance test is a periodic, procedure-driven check that verifies a safety-related component or channel remains operable. The test frequency, method, and acceptance criteria are all established in the plant's Technical Specifications, which are legally binding documents approved by the U.S. Nuclear Regulatory Commission (NRC). Missing a surveillance or failing to act on a failed result is a reportable event under federal regulations.

Three types of surveillance are commonly performed on instrument channels:

• Channel Check: The most frequent and simplest test. The operator compares the reading of the instrument channel to an independent indication of the same parameter—another instrument, a calculation, or observable plant conditions—and confirms they are consistent. A channel check verifies the instrument is reading and responding; it does not confirm calibration accuracy.
• Channel Functional Test (CFT): Verifies the entire channel—sensor signal path, bistable trip logic, and output relay—responds correctly when a test signal is applied. The CFT is performed less frequently than a channel check.
• Channel Calibration: A full verification that the instrument reads within its required accuracy band across its operating range, using traceable standards. Calibration is the least frequent of the three and typically requires taking the channel out of service briefly.

The surveillance frequency for each type is set by the Surveillance Frequency Control Program or directly in the Tech Spec Surveillance Requirements (SRs). Frequencies are based on the importance of the instrument, its failure history, and regulatory guidance.

Performing a Channel Check

Channel checks are performed following a written, approved procedure—never from memory. The general sequence is:

1. Obtain the current procedure revision and verify you have the correct procedure for the channel being checked.

2. Review precautions and limitations listed at the front of the procedure before taking any action.

3. Verify plant conditions are appropriate for the surveillance (e.g., the reactor is at the required power level).

4. Read and record the channel reading from the designated indicator, exactly as specified.

5. Read and record the independent indication (the reference parameter).

6. Apply the acceptance criterion: the procedure will state an allowable difference or a qualitative consistency check.

7. Record results on the surveillance data sheet, including date, time, your name, and any observations.

8. Sign and date the data sheet and submit it per plant administrative procedures.

Never skip steps or change their order. Procedure adherence is a fundamental nuclear safety behavior.

Technical Specification Action Levels

If the channel check result does not meet the acceptance criterion, the channel is considered not operable (failed). The Tech Spec Limiting Condition for Operation (LCO) associated with that channel then applies immediately. LCOs define:

• Required Actions: Specific steps the shift supervisor or operator must take (e.g., place the channel in trip, notify the shift manager, restore the channel within a defined Completion Time).
• Completion Times: The maximum time allowed to restore operability or take the required action before a more restrictive action—such as a power reduction or plant shutdown—is required.
• Condition Statements: Logical conditions (e.g., "One required channel inoperable") that trigger specific Required Actions.

If a channel fails, you must:

1. Stop the surveillance and notify the shift supervisor immediately.

2. Identify the applicable LCO condition.

3. Initiate a Condition Report per the plant's corrective action program.

4. Do not attempt to repair or adjust the instrument without a separate, approved work order.

Safety Behaviors in the Lab and in the Field

• Procedure use at every step: Hold the procedure and perform a concurrent verification (two-person check) for safety-critical steps when required.
• PPE: In radiological areas, wear dosimetry and any additional PPE specified on the Radiation Work Permit (RWP) before entering the area where the instrument is located.
• ALARA: Minimize time near radioactive components; know your dose rates before beginning.
• Lockout/Tagout awareness: Some instrument channel tests require defeating an interlock or lifting a lead. These activities require an approved LOTO or jumper/lifted-lead log per plant procedures—never defeat a circuit without written authorization.
• Communicate clearly: Use repeat-back (three-way communication) when recording readings over the phone or radio. Misread values have caused reportable events.

Connecting to Your Credentials

The NRC Non-Licensed Operator and Reactor Operator license exams test knowledge of surveillance requirements, Tech Spec compliance, and required actions. The NEI NUCP Uniform Curriculum specifically includes instrument surveillance as a core competency. Accurate data recording and corrective action program entry also appear on the NRRPT examination for radiation protection technologists.