Note: This advice relates solely to radiation hazards
Depending on the pipe/duct, other hazards may exist including, for example, biological agents, mercury, sharps and asbestos. Departments should seek necessary advice and take appropriate actions to address those hazards.
All pipes and ductwork along which radioactive waste is carried should display a radiation warning sign at appropriate intervals and at obvious access panels such that no-one should be able to break into the pipe/duct without being faced with the following warning:
All departments currently undertaking work with radioactivity will have an appointed senior radiation protection supervisor (SRPS) who must be contacted before any attempt is made to break into the pipe/duct. If the warning is historical, relating to previous radioactive waste disposals in a building that is no longer used for work with radioactivity, the University Radiation Protection Officer should be contacted in lieu of an appointed SRPS. The SRPS must consult the URPO regarding any requests to access an active fume hood duct.
Before permitting the work, the SRPS should first confirm what isotopes have been disposed along the waste run and, by considering their half-life and the most recent disposals, determine whether a radioactive contamination hazard is expected. With the exception of disposal of very short lived isotopes, it should always be assumed that a contamination hazard may exist and therefore internal contamination monitoring must be undertaken at the outset. The SRPS or nominated deputy should be present at the initial stages of the work to perform this monitoring. Where practicable, pipe-work should be flushed with Decon solution prior to dismantling.
Appropriate PPE (disposable gloves, lab coats/overalls and protective eyewear) should be worn at all times.
Pipes should be drained of water as far as possible prior to breaking in. In the presence of the SRPS, building maintenance staff should careful break into the pipe using coupling points where possible, rather than sawing. Where the work involves removal of a section that will retain water (ie a U-bend), the section should be removed over a bucket to catch any spills. The waste water should be disposed of down a sink connected to a separate drain run. The inside of the pipe should then be dried with paper towels. All solid waste generated by the work should be bagged for subsequent disposal depending on the outcome of the contamination monitoring.
Typically, use of hand held radiation monitoring instruments is not possible inside drain runs. Therefore, contamination monitoring should be performed by wipe test and liquid scintillation counting. The only exceptions to this rule are likely to be waste runs where only photon emitting isotopes have been disposed. In any case, wipes must always be performed where pipes/ducts have been used for the disposal of 3H and 14C waste. Wipes should be made of the internal surfaces of removed sections and at either side of the break. Work must not continue until the results of the liquid scintillation counting are known.
If radioactivity is not detected on the wipes, work can proceed without any special consideration of radioactivity. However, if radioactivity is detected, the SRPS should supervise the entire job until the break in the pipe has been replaced. Dismantling should be carried out by removing complete sections where possible; reconnecting replacement sections using standard couplings. All waste must be disposed of as solid low level radioactive waste in accordance with departmental waste disposal procedures. This will require identification of the constituent isotopes and an estimate of the activity in the waste. The URPO should be consulted for advice as necessary.
On complete reassembly, the drain run should be confirmed to be free of leaks before any aqueous waste disposals are permitted.