Will Exemption Orders prevent nuclear pollution?

Will Exemption Orders prevent nuclear pollution?
They are under review

In the UK there are 17 orders intended to allow undertakings which use or hold small amounts of radioactivity to be exempt from regulation under the Radioactive Substances Act. They were put in place many years ago and some are felt to be out of date. The Department of the Environment, Food and Rural Affairs is reviewing them. LLRC is making representations.

We are concerned about two areas:-

  1. the Substances of Low Activity Order (SoLA) and
  2. "Naturally Occurring Radionuclides" (NOR).

1. SoLA

The SoLA exemption value of 400 Becquerels per Kilogram has long been used as a definition between what is regarded as radioactive and what is not. This function crucially includes disposal - i.e. material below 400 Bq/Kg can be disposed of as clean.

Despite its origin as a Small Users' exemption level SoLA is being used for Clearance of large volumes of material and waste from decommissioning and even for delicensing land. SoLA was never intended for such large amounts of material. It seems reasonable to have separate regimes for Clearance and delicensing land.


SoLA should only apply to small quantities.
It should also have an explicit ban on diluting waste to bring it below exemption levels. [See this link for our caveats on dilution]

2. "Naturally Occurring Radionuclides" (NOR)

DEFRA proposes to replace six Exemption Orders for NOR and to lump all the NOR industries together under one EO. This is not rational and goes against the tide of radiobiological debate.

There are different types of radiation exposure involved in various industries.

NOR regulatory practice varies in different countries, and there is a strand of opinion which holds that each concerned industry should be able to present its case, and industry-specific decisions on regulation should be made on the basis of specific types of exposure.


The UK Government should commission a review of regulatory approaches world wide as a first step towards industry-specific regulation including industry-specific EOs.

They could well begin with:-

the Natural Gas Supply Industry

There are problems with DEFRA's modelling of radiation doses from natural gas
  • It does not differentiate between gases and fine particulates
  • It assumes that "gases" include particles
  • It assumes that most of the discharges are expected to be in particulate form.
This silliness is based on NRPB's assumption that radiation doses will be evenly distributed across large volumes of tissue. It's just not valid to treat particles as if they were gas; they lodge in lungs and lymph nodes, and deliver very high doses to tissue within range of their decays. DEFRA does not know how big the particles are, nor what chemical and physical form they are in. They believe that only sub-micron particles will be able to reach the houses of the critical group, but local dose from even a 0.2 micron Uranium particle equals natural background, so there are no grounds for complacency. Dust particles this size are highly mobile, and more radioactive species than Uranium are involved.

Modelling particulate emissions as if they were gases is irrational, and DEFRA has far too little information about what is being or will be released into the environment from the Natural Gas Supply Industry.


Before the new NOR EO is finalised DEFRA should commission NRPB to study:

  1. particulates in emissions currently or previously classified as "gaseous" from a representative sample of undertakings and classes of practice to determine the particulate content, the physical and chemical composition of any particles, and their size and activity;
  2. the mobility and geographical distribution of particulates from emissions.

More on Natural Gas ...

.... exposures from decommissioning, Clearance, and disposal of scales

The Netherlands, Germany, UK, and Norway are using different formulas to calculate the total activity of radioactive scales and sludges, due to differences in including daughter radionuclides for the calculations. These inconsistencies must be resolved.

Radium comes before radon in the decay series and the scale will certainly contain radionuclides below radon as well as radium (radon itself is a short-lived gas, so it won't be a big component of doses from scale). But some radon daughters are quite vigorous Second Event emitters and there will also be considerable amounts of complex radioactive organo-metallic compounds incorporated into the scale. The potential biological activity of these compounds means that we need to know what is there before it can be written off as below regulatory concern.

Amounts of radioactivity in scale will vary down the supply route, as gas is refined in stages between off-shore platforms and the final consumer.

DEFRA assumes that a large amount of metal will arise from decommissioning gas supply plant (1.8 million tonnes from off-shore; unknown quantity of on-shore). This means that recycling is a certain disposal route with a wide variety of exposure pathways.

Irrespective of whether or not natural gas supply industry has its own Exemption Order, the industry should work with NRPB to publish a radiological and chemical analysis of scales, pipe scrapings and the contents of filters at various points in the supply network before it is disposed of or "Cleared".

Calculation of internal doses. [This has special significance for the natural gas supply industry, but that is not the only source of particulate doses]

DEFRA assumes that highest doses are to lungs and bone surfaces. This is based on questionable assumptions. Briefly, it overlooks lymph tissue - known to be a critical organ for leukaemia. NRPB's analysis of this kind of exposure is completely bogus:- see this report.


Before the new NOR EO is finalised (whether or not gas supply is excluded)

  1. NRPB should redefine the critical groups in light of the results of studies in Recommendations C1 and C2
  2. NRPB should calculate organ and tissue doses to critical groups with special reference to tracheobronchial lymph nodes (TBLNs ) specifying the weight of tissue assumed for TBLNs (tissue weights to be specified as "wet weight").

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This page was last updated 10th June 2001