Radionuclide laboratory type A, B or C: what drives the classification – and what it triggers in construction

01The classification follows a calculation, not a label

Anyone working with unsealed radioactive sources above the licensing limit requires a working area under the Radiological Protection Ordinance (RPO): a separate room reserved solely for this purpose within a controlled area. Art. 81 RPO classifies it according to the activity handled per operation or per day – measured in multiples of the nuclide-specific licensing limit LA from Annex 3.

• Type C – 1 to 100 LA
• Type B – 1 to 10 000 LA
• Type A – from 1 LA up to an upper limit defined in the licensing procedure

For storage, the supervisory authority may increase the values by up to a factor of 100; for handling operations with a low risk of incorporation, exceptionally by up to a factor of 10.

02The fallacy: counting becquerels

The licensing limit is fundamentally set such that a single inhalation of this activity results in a committed effective dose of 5 mSv. It therefore reflects how hazardous a nuclide is inside the body – and this differs by orders of magnitude.

800 Bqlicensing limit for actinium-225 – compared with 70 MBq for fluorine-18

One hundred megabecquerels of a short-lived PET nuclide lie just above the licensing limit; for an alpha emitter, the same activity corresponds to a hundred thousand times the limit. For the positron emitter, shielding against external radiation is the priority; for the alpha emitter, incorporation. If several nuclides are handled, their combined effect must be clarified with the supervisory authority. What matters, therefore, is not the largest number, but the most demanding nuclide in relation to its limit.

03Three classifications that do not mean the same thing

The working area type describes the room. The controlled or supervised area governs access and monitoring – every working area is at the same time a controlled area. Persons, in turn, are classified by the enterprise into categories A or B according to the possible annual dose. A type A laboratory and a category A person have nothing in common except the letter.

04What the type triggers in construction

The FDHA Ordinance on the Handling of Radioactive Material (UraM) sets minimum requirements for each type – not for each trade. Every working area is a separate fire compartment. A single decision therefore shifts several trades at once.

05What this means for your project

• Determine the activity per nuclide and room per operation, separately for storage and handling – not the annual quantity
• Define the type for each room early and agree it with the supervisory authority: FOPH for medicine, research and teaching, Suva for industry and trade
• Show the working area type, controlled area and person category separately
• Clarify the consequences for each trade before the preliminary design: fire compartments, ventilation and negative pressure, access, waste water, decay storage
• Involve radiological protection experts early

Deriving the classification properly avoids both: an oversized type A laboratory – and an under-planned type B laboratory that has to be retrofitted during the licensing procedure.

Takeaway

It is not the label “radioactive” that determines the laboratory, but the activity in relation to the licensing limit – and each type leaves its mark on every trade.

SEDC AG · Article from our internal training series “Technik Praxis”, abridged for clients and users.