On Friday morning, Sellafied Ltd. instructed its non essential employees not to report for work, due to “elevated readings at a perimeter monitoring point”. This understandably created huge interest in the media both locally and nationally. By the end of the day it was announced that “investigation and analysis confirmed that the elevated readings at that perimeter monitoring point were due to naturally occurring radon”.
It is commendable that the company released this information and responded immediately and in doing so they have also clearly drawn attention to themselves. That is probably a better course of action than simply covering up the unusual reading and taking no action. However, there are questions about the radon incident that need answering.
Radon is indeed a common natural radioactive element and could well have shown elevated levels at the northern perimeter of the site where it was measured. This UK national map shows it to be a potentially very high zone of soil gas radon. This is presumably linked to underlying limestone at that locality.
There are some relevant questions. Firstly, is the reading an accurate reflection of radioactivity levels or could the detector have malfunctioned? We need to know whether the detector has been tested and other meters installed to ascertain if the high reading has been replicated. Will Sellafield Ltd. release the measurement sets from this detector during the 12 hours either side of the elevated reading?
Assuming the elevated reading is correct, what has caused it? Any leakage of radon would normally be expected to be dispersed into the atmosphere very rapidly. It is possible that the high readings are due to radon release from the underlying groundwater. This could be caused by a low pressure weather system causing a decrease in pressure or temperature overnight or an upwards flow of groundwater caused by heavy rainfall to the east moving through the aquifer and returning through the well-known upwards flow of groundwater towards the surface in the Sellafield region. This is, of course, one of the primary reasons why disposal of radioactive waste at much deeper levels is not suitable in this region of the UK.
These ideas are just possibilities and hopefully Sellafield Ltd. will investigate further and inform the public of the real reasons behind the “elevated readings”.