Radiation: How to Protect Against an Invisible Threat

28th May, 2019
    Lucy MurrayPhD Student

When most people hear the word radiation they may think of Chernobyl, Fukushima or the atomic bombings of Hiroshima. These catastrophic events in recent history have ingrained a deep-seated fear of radiation into the public psyche. Factors such as the type of radiation, the dose of radiation or the type of exposure are considered irrelevant: radiation is danger. So why don’t we just avoid it? That doesn’t seem like a hard task to accomplish for most of society. However, the truth is that the utilisation of radiation is not avoidable, and it is now considered that the fear of radiation is in fact more harmful to the progression of society than radiation itself. Some of the applications of radiation and nuclear technology have unparalleled benefits which undoubtably outweigh the risks posed; health care, materials engineering and energy production are but a few of the sectors advancing due to employing radiative materials. In those cases where we accept that the benefits outweigh the risks, we must employ the most cutting-edge technologies in order to negate the potential danger to that sector of society for which exposure is not entirely avoidable

Perhaps the most prominent use of nuclear technologies today, in both research and industry, is developing a solution to the energy crisis. It is an undisputable fact that our current means of producing electricity are not sustainable: we will run out of fossil fuels. Renewable energy is an alternative however we do not currently have the battery technology to store and distribute it as is needed for certain parts of the world. Here is where nuclear power is the answer. The map below labels the existing nuclear reactors in the world today, more than most would assume, and this number will only increase in coming years as fossil fuels are depleted. Due to the progressive and expanding nature of this technology, future generations will see a much larger sector of society having to work in nuclear environments. Therefore, we need to be progressive in our approach to radiation protection for the safety of these workers, this is where my research project will come into play.

The basic mechanism behind the harmful nature of radiation is this: the radioactive material emits high energy ionizing ‘radiation’, if this ionizing radiation encounters the human body it can cause cell mutations which in turn can lead to cancer. The body can easily recover and repair damage from low doses of radiation but if exposed regularly over a long period of time the risks of cancers increase dramatically. The International Commission on Radiation Protection (ICRP) have gathered data from huge amounts of research to produce an annual recommended dose limit for which a worker such that they will be at no more risk of cancer than any other member of the public. This is built into most countries’ laws. This method is controlled by the use of dosimeters, which can be used to ascertain the dose (amount) of radiation a person has received. The only problem with this is that for most dosimeters the reading can only be taken by post-processing and so if the worker has received more than their annual dose limit it is already too late. So, wouldn’t it be better if we could know the radiation dose a person would potentially be receiving before they enter the environment? Well, to an extent, we can. VRdose is a piece of software developed by the Institute for Energy Technology (IFE) in Norway designed to do just that.

The user models the geometry and material properties of the environment and the source(s) of radiation. A worker can be inputted into this scenario and a planned maintenance procedure can be recreated, VRdose then uses a point kernel approximation method to determine the dose uptake of the worker for each stage of the work and the total dose accumulated over the scenario. The image below shows an example of this software in operation, a risk maps overlays the environment showing areas of high and low dose uptake and the plot shows the calculated dose uptake of the virtual person moving around in the environment. At a glance this software seems to solve our problem, but how are we to know we can trust the outputs? Can we just take this at face value and use it for real life planning? No…we need to know the uncertainties and that’s where my project in the institute for risk and uncertainty comes in. After all, what is a value without an associated uncertainty? Meaningless.

Radioactive decay by its very nature is random and so one output value from a simulation will, with practically 100% certainty, never be true. Therefore, what we really need is a range of values which we can, with confidence, predict the real-life dose uptake value to fall within. The main part of my project will be to link VRdose software with Cossan, an uncertainty analysis tool developed by the University of Liverpool. So instead of a map of discrete values for dose uptake we will instead gain an uncertainty map with upper dose limits to be used in planning. This way we can plan with maximum efficiency and certainty that the worker will be at no more long-term risk than you and I.