Dilution of radioactive waste

Dilution of radioactive waste:-
the slenderest of threads prevents it
and RWMAC is snipping at that thread

First some background

If you define waste in terms of concentrations, rather than in terms of total amounts you automatically encourage potential polluters to dilute their wastes to reduce the concentration, especially when disposing of radioactive waste has such vast political and financial costs.

The Basic Standards Directive (BSS) contains absolutely no reference to preventing such dilution, so this has been a major part of our responses to it.

In the UK only one thing stops dilution; it is the wording of the Substances of Low Activity Exemption Order usually known as SoLA1.

In setting the waste limit the pivotal phrase is that the substance in question has to be less than 400 Bq/Kg "... at the point at which it becomes waste ... ". This phrase is the only measure in UK law stopping waste being diluted to bring it below the SoLA threshold. (As far as we know SoLA has never been the subject of democratic debate.)
Responding to the DETR on transposing the BSS Directive, we predicted that SoLA would be too fragile, and we wanted something more robust built into the Radioactive Substances Act.

RWMAC's attack

RWMAC's case sounds reasonable:-

Disposal: the technetium-99m clinical waste issues

7.74 Technetium-99m (Tc-99m) is the most widely used short half-life (six hours) radionuclide in nuclear medicine. Like a small number of other radioisotopes with relatively short half-lives, Tc-99m can be "decay stored" until its level of activity is close to zero.

7.75 Management of Tc-99m contaminated wastes is causing difficulties for Scottish Small Users. In England and Wales, once Tc-99m contaminated waste has decayed to close to zero levels of activity, EA allows its incineration as clinical waste. In Scotland, however, SEPA does not allow its reclassification, even after a similar period of decay storage, from radioactive waste to clinical waste. Because of the difficulty of disposing of these wastes in Scotland (owing to a lack of incinerator facilities), decayed Tc-99m is moved to England and Wales for burning as radioactive waste, hence incurring a higher disposal cost for Scottish Small Users than if it were classified as clinical waste.

RWMAC view

7.76 EA and SEPA need to consider whether they are able to agree a common policy for regulating decayed Tc-99m. The current, inconsistent, approach, described above, is confusing for Small Users and results in Scottish waste disposers incurring additional costs that could reasonably be avoided. SEPA has indicated that the problem lies in legislation, in particular, in the Substances of Low Activity EO (SOLA). It is in favour of revising SOLA, as part of the review of the EO system, to remove this inconsistency.

RWMAC's proposal effectively threatens to remove the phrase "... at the point at which it becomes waste ... " from the SoLA Exemption Order.
We have established that this wording has significance far beyond the disposal of short-lived hospital wastes.
We have made robust representations to DETR to ensure that wording of SoLA [or whatever replaces it] will continue to guard against intentional dilution. We have received some reassurance and are keeping an eye on developments.

All 17 Exemption Orders are being revised. Here is a link to our recommendations.


1 Radioactive Substances (Substances of Low Activity) Exemption Order: SI 1986 No 1002 and (amending order) 1992 No 647

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