Radiation / NDT Safety

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Overview

Industrial radiography uses gamma sources or X-rays to inspect welds; the guiding principle is ALARA.

Time, Distance and Shielding govern every job, backed by a controlled area, dosimetry and a licensed crew.

The three protections

Time — minimize time spent near an exposed source.
Distance — inverse-square law; double the distance, quarter the dose.
Shielding — collimators, lead and structural mass to absorb radiation.
Source accountability — counted in and out of its container every time.

Step-by-step procedure

Plan RT for off-shift / night and clear the area of other workers.
Cordon the controlled area to the boundary dose rate (commonly 7.5 µSv/h).
Post warning signs and set up flashing lights and an audible alarm.
Crew wear dosimeters (TLD/film badge), carry a survey meter and pocket alarm.
Survey to confirm no one is inside the cordon before exposing the source.
Expose the source for the calculated time, monitoring throughout.
Fully retract the source and survey it back into its shielded container.
Stand down the area, record doses, and account for and transport the source.

Dose limits & monitoring

Radiation workers — typically 20 mSv/year averaged over five years.
Public — 1 mSv/year; the controlled-area boundary protects them.
Each crew member's dose is recorded and reviewed against the limits.

Roles & responsibilities

Role	Responsibility
Radiographer / RSO	Runs the exposure, sets the controlled area, accountable for the source.
Site Supervisor	Coordinates the area clearance and confirms no conflicting work.
Other Workers	Stay clear of the cordon and obey signs, lights and alarms.

Common mistakes to avoid

Setting the cordon too small so the boundary dose rate is exceeded.
Assuming the source is retracted without confirming with a survey meter.
Doing RT during the day with other crews still working nearby.

Legal requirements (Thailand)

Occupational Safety, Health and Environment Act B.E. 2554 (2011) — the governing workplace-safety law in Thailand.
Nuclear Energy for Peace Act B.E. 2559 (2016); licensing and control by the Office of Atoms for Peace (OAP).

Frequently asked questions

What is Radiation / NDT Safety?

Industrial radiography uses gamma sources (Ir-192, Co-60) or X-ray equipment to inspect welds for defects. The radiation is invisible, gives no warning at the time of exposure, and can cause serious harm. The work is therefore tightly controlled around one idea — keep dose As Low As Reasonably Achievable (ALARA).

Who is responsible?

Radiographer / RSO: Runs the exposure, sets the controlled area and is accountable for the source.; Site Supervisor: Coordinates the area clearance and confirms no conflicting work is taking place.; Other Workers: Stay clear of the cordon and obey warning signs, lights and alarms.

What are the most common mistakes to avoid?

Setting the cordon too small so the boundary dose rate is exceeded. Assuming the source is retracted without confirming it with a survey meter. Doing RT during the day with other crews still working nearby.

References — IAEA BSS & ALARA; Thai Nuclear Energy for Peace Act B.E. 2559 and OAP licensing; OSH Act B.E. 2554.