Crushed Corner and Powder at a Freight Terminal
At 02:40 a warehouse handler finds a 40 kg fibreboard box on a pallet with a crushed lower corner and a fine pale-yellow powder scattered across the pallet and about 30 cm of concrete floor. The label is Category II-YELLOW with TI 0.8; the consignment note reads UN 2915, RADIOACTIVE MATERIAL, TYPE A PACKAGE, non-special form, 1.2 GBq, contents: uranium compound. A handheld meter reads 25 µSv/h at 1 m from the box and 3 µSv/h at 2 m. The terminal has one other worker on shift, no fenced compound, and a collection driver due in 20 minutes for the pallet. The terminal's dangerous goods plan is locked in an office and the supervisor is not answering the phone.
1. Set out the immediate actions and justify the size of the controlled area from the measured numbers.
Read the worked answer
The dominant hazard here is contamination, not external dose - and the numbers prove it.
A worker standing 1 m away for half an hour receives about 12.5 µSv. That is a trivial external dose. The powder on the pallet and floor is the actual problem: a uranium compound that can be inhaled or ingested, spread on boots, or carried out on a jacket is a committed-dose and cross-contamination pathway that the survey meter reading tells you nothing about.
Immediate actions:
- Do not open, do not tip, do not move the pallet unless it is necessary to prevent a worse outcome. Movement re-suspends powder.
- Cordon an area large enough to control spread, which means covering the powder and the likely walking path rather than drawing a circle at an arbitrary radius. A radius of a few metres around the pallet, plus a controlled entry point, is proportionate given the low external dose rates.
- Stop the collection driver. The pallet must not leave the site, and the driver must not enter the cordon.
- Protect the floor path: plastic sheeting over the powder and over the route already walked, and restrict the two workers to a defined area until their boots and hands are checked.
- Call the RPO or the on-call radiation protection number now, and get the plan out of the locked office or use the emergency contact sheet - a plan nobody can reach at 02:40 is a finding to be fixed afterwards.
Turning away the collection driver will upset a customer; letting a leaking package into an unmonitored vehicle will not be recoverable.
2. The meter reads 25 µSv/h at 1 m while the label implies about 8 µSv/h. What are the plausible explanations, and what do you do about them?
Read the worked answer
Do not assume the package is worse than declared, and do not assume the meter is right. Investigate.
Plausible explanations, roughly in order of likelihood:
- Instrument response. Uranium compounds emit low-energy gamma radiation that many survey meters under- or over-read badly depending on energy response and calibration. A meter calibrated on a caesium source can be substantially wrong here.
- Measurement geometry. TI is a defined quantity at 1 m; holding the meter at 1 m from the nearest surface while other material sits behind the box gives a different number from the declared value.
- Background and neighbouring sources. The terminal may hold other consignments.
- Contents redistribution. A crushed corner means the contents may have shifted, moving material closer to the surface. That is consistent with both the higher reading and the spilled powder.
Response: re-measure with a suitable instrument, take background readings before and after, record distances explicitly, and treat the higher of the credible readings as the working value until resolved. Report the discrepancy to the consignor - a package whose measured radiation level does not match the declared TI is a package whose declared contents cannot be relied on, and that matters far more than the 17 µSv/h difference itself.
3. The supervisor wants the pallet loaded onto the waiting vehicle with a note to the consignee. What is wrong with that, and what should happen instead?
Read the worked answer
A damaged package with spilled contents is not a package in transport condition.
A Type A package that has been breached may no longer meet its design requirements, and the powder outside the package is a loss of contents. Loading it would convert a contained local event into a moving contamination source with no monitoring, no placarding consistent with the actual condition, and a driver who has not been told anything.
What should happen instead:
- Hold the consignment on site in a controlled position, covered and marked, under the terminal's procedures.
- Notify the consignor so they can decide on recovery or repackaging; the consignee does not get a surprise.
- Notify the competent authority in accordance with the applicable reporting requirements for a damaged package with loss of contents; retain the survey records, photographs and a timeline.
- Decontaminate under radiation protection supervision - no ordinary vacuuming, which would exhaust contamination into the warehouse air; wet methods with disposable materials, surveyed afterwards, and the debris consigned as radioactive waste.
A note to the consignee is not a containment measure. The judgement being tested is whether commercial pressure to keep the freight moving is allowed to override the physical condition of the package.