Radiological

To confirm that the site is performing in accordance with the radiological risk assessment Augean undertakes radiological analysis of groundwater, surface water, leachate, gas and dust.

A number of technical terms and reference to units of measurement are used in this section.  Definitions of the terms and units are presented at the end of the section.

Radiation in context
All matter on earth is radioactive. We are continuously exposed to radiation from space, from the ground and in our food. The average natural radiation exposure in the UK is 2.2mSv/a (Sv = Sievert) which provides a measure of effective exposure taking into account fatal and non-fatal outcomes, the effect on unborn babies, effects on all age groups (including children and the elderly), the cumulative effect on all organs and effects from external and internal irradiation.

In parts of the UK due to the geology there is the potential for additional exposure from radon gas which is released from underlying rocks. In Cornwall for example the average annual exposure to natural radiation is 7.4mSv/a. Some areas of Northamptonshire have an average annual exposure to natural radiation of 3.6mSv/a. The potential for exposure occurs principally in the valleys where deposits such as clay are not present over the underlying rocks. In areas covered in clay such as at ENRMF the radon levels are very low. At the request of the Kings Cliffe Liaison Group Augean produced a report on radon in the local area. 
This report can be accessed here .

We also receive radiation from a range of common activities and sources for example:

100g of Brazil nuts 0.004 mSv
1L per day bottled water - up to 0.024mSv
Return flight to the USA 0.1 mSv
Chest x-ray 0.02 mSv
Medical Abdominal CT Examination 10 mSv


Potential for exposure from low activity LLW disposal at ENRMF
The design limit of public exposure from the ENRMF is 0.02mSv/a which is less than 1% of the average natural background level in the UK. As exposure declines exponentially with distance the potential exposure at nearby villages is many orders of magnitude less.

Risk assessments are undertaken to ensure that the acceptance of the waste will not result in exceedence of the design limits. Risk assessments are the standard tool and approach used for all forms of environmental management. This is not just a series of theoretical mathematical models. Risk assessments are based on well understood processes such as the fate and transport of individual contaminants, groundwater flow, air dispersion and acceptable exposures. Where there is uncertainty, conservative or worst case assumptions are made. Where the effectiveness of a protection measure is not clear, it is assumed that the protection measure is not present. Risk assessment therefore generates a conservative assessment of the maximum impact.

There are three main types of radiation that must be considered in assessing risk; alpha, beta and gamma. The environmental monitoring requirements include all three types of radiation.

If you wish to know more about radiation you might find the following sources of information helpful:

  • Living with radiation – It is available in hard copy only. We have a number of copies which we should be pleased to send on request.
  • Public Health England website

Radiological monitoring
In accordance with good environmental practice radiological monitoring in the site and around the site is undertaken to confirm that the site is behaving the way that is predicted in the risk assessments. In the unlikely event the results of monitoring show a variance with the assumptions in the risk assessment action can be taken at an early stage to ensure this does not result in significant impact.

The Environmental Permit requires monitoring of the behaviour of the site in all media. As with the chemical data there is a large amount of information. Key selected data is presented relating to:

  • Groundwater
  • Dust
  • Surface soils
  • Ambient air
  • Personal monitoring of site staff

Full monitoring commenced on receipt of the first loads of LLW in December 2011. The results are being submitted to the Environment Agency. On approval by the Agency key selected data will be presented on this web site.

The monitoring points for these environmental media are at or beyond the boundary of the site. The Environment Agency is undertaking radiological monitoring of the environment around the site.

Before accepting LLW Augean undertook background monitoring at the site. The results of this background monitoring show that, as expected, radiation such as tritium is naturally present at the site but is generally below detection limits. The data can be viewed here .

Post LLW monitoring
The graph below displays the analytical results of Tritium in groundwater at the ENRMF, including both background data and post LLW monitoring data.  Tritium is a good indicator as it migrates relatively quickly and would be the first isotope to be found if there was a problem.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The graph shows that no significant levels of Tritium have been detected in down-gradient boreholes since low- level radioactive waste has been accepted at the ENRMF site. All post LLW monitoring data for surface soils, groundwater, site perimeter dose rate monitoring and deposited dusts can be viewed here .

The post LLW radiological monitoring data shows that all analytical results were almost identical to the background data, with the majority of results showing that levels were below or equal to the Limit of Detection (LOD) of the test method used for the parameter listed at the time of analysis.

Horsewater Spring located in the Kings Cliffe village, is also monitored annually by the Environment Agency. Total alpha, total beta, tritium and gamma spectrometry analysis showed that all radiological parameters were below the limit of detection (LOD) in the February 2013 sample.

Definition of Radiological Terms

Exposure is the amount of radiation received by a human or living thing.

A measured dose is the amount of exposure received by a human or living thing over a specified period of time.

Dose exposure is measured in Sieverts (Sv/hr or Sv/a).  As the doses associated with the ENRMF are low (well below natural background levels of 2.2mSv/a) the doses are expressed in millisieverts per hour (mSv/hr). In accordance with the ENRMF’s procedures, a dose limit of 0.01 mSv/hr at a metre from the Low-level waste (LLW) in its container is assigned to all incoming LLW loads, before they can be accepted for disposal and burial in a designated area of the landfill.

Activity is the amount of radioactive decay occurring in a particular substance for example in a soil disposed of in the site. Activity is calculated in Becquerels per litre (Bq/l) or Becquerels per gram (Bq/g) depending on whether the substance being analysed is a gas, liquid or solid.

A radionuclide (an atom with an unstable nucleus) goes through the process of radioactive decay. These are also known as radioactive isotopes. For example Tritium is a well-known radioactive isotope of hydrogen. Tritium can combine with oxygen to produce Tritiated Water (HTO), meaning it has rapid rate of transport through a substance. Therefore, Tritium is analysed as a good indicator of the movement of radioactivity within the landfill. 

Radionuclides undergoing radioactive decay emit gamma rays and/or alpha and beta particles.

Alpha particles consist of two protons and two neutrons. Radionuclides including Americium-241, radium-226 and Thorium-232 are some of the key alpha emitters. Due to their slow movement, alpha particles are unable to penetrate paper and can reach only the very outer layers of human skin. They can also pass through only a few centimetres of air due to their rapid loss of energy.  Alpha radiation cannot pass through the packaging used to transport and dispose of waste at ENRMF.

Beta particles are high-energy electrons. Radionuclides including Caesium-137, Carbon-14, Cobalt-60. Lead-210 and Tritium (H-3) are all beta emitters. Despite their high energy, beta particles can be stopped by solid materials including cardboard, however they are slightly more mobile in air than alpha particles and can travel up to several feet. Beta particles are also more harmful than alpha particles as they can penetrate skin and tissue further which can result in more widespread cellular damage.  Beta radiation is significantly attenuated by the packaging used to transport and dispose of waste at ENRMF.

Gamma radiation (also known as gamma rays) is high energy ionising radiation. Gamma photons can travel significant distances in air due to their high energy and can also pass through many materials including human tissue.  However the dose declines rapidly with distance due to energy loss.   Lead is one of the materials that can significantly prevent movement of gamma rays. Radionuclides including Caesium-137 and Cobalt-60 are gamma emitters. Both Caesium-137 and Cobalt-60 are commonly used in the treatment of cancer, whilst Cobalt-60 is also utilised in the sterilisation of medical apparatus.  

Personal dose
Doses received by all staff involved with the admittance and disposal of LLW are measured using personal “Body TLD” (Thermoluminescent) dosemeters provided by the Public Health England (PHE). These are attached to the wearer’s overalls as a badge. They measure doses to the whole body and skin received by the wearer.

A “Body TLD” comprises of a TLD card, wrapper and holder. The TLD card contains two pellets of specially-doped Lithium Fluoride (LiF: Magnesium (Mg), Copper (Cu) and Phosphorus (P). The thicker element is used for the analysis of the doses emitted from the strongly-penetrating radiation and the thinner element is used for the analysis of the doses from both weakly and strongly penetrating radiation. (HPA, 2010).

When an LLW load arrives onto site, all operators involved in its monitoring and its subsequent disposal must immediately attach their individually identified TLD to their overalls and they must remain attached until the disposal process is completed.

All TLDs are then returned to Public Health England (PHE) for analysis after the completion of the 3-monthly wear period.

Personal dosemeter results for the period December 2013 to March 2014
The results show that site personnel have not received any detectable radiation dose while operating at the site. To view the results click here.

ENRMF - LLW

If you have any queries relating to this information or would like to be kept informed of developments at ENRMF please contact us at consultation@augeanplc.com or telephone us on 01904 654989 to be added to our register of stakeholders.