Safeguarding miners against radon gas using the AlphaGUARD
14th June 2023
The AlphaGUARD radon monitor by Bertin Instruments has delivered accurate real-time readings of radon gas at the Bath Stone Group's Stoke Hill Mine.
The Bath Stone Group have been using the radon monitor to implement safe working practices in their limestone mine
The Bath Stone Group in South West England has been using the AlphaGUARD radon monitor by Bertin Instruments to safely manage the radioactive gas inside the shaft. The mine has been in operation since 1982, although the mine workings date back to the 1500s.
Matthew Hawker is the Mine Manager and Radiation Protection Supervisor who joined the mine in 1996. He explained the difficulty that the company had in properly monitoring radon in the mine for many years before using the AlphaGUARD, which delivers high detection efficiency with a wide measurement range of between 2 and 2,000,000Bq/m³ with long-term stable calibration.
Historic radon monitoring using third-party contractors
Matthew began by recounting how the mine was originally monitored. “We knew radon was a potential hazard, but we didn’t have a real understanding of it ourselves or how it should be managed other than it should be below 400Bq per annum. Originally, monitoring was carried out by a single contractor every three months who would take spot measurements in different areas of the mine to give us an average reading. Based on these historical readings, we were classified as a supervised area under IRR17 with annual doses above 1mSv, although we were never above 6mSv which would have designated us as classified workers.
“When that contractor retired, we needed to find a replacement. We hired another contractor to begin testing and our readings were higher than they had been previously, which raised a lot of questions. I approached Public Health England (PHE) who began passively monitoring the mine every three months, and their readings showed an average of over 2000Bq, which was high due to the anomaly of the passive monitors being present 24 hours a day. This included when the ventilation system was stopped during the off shift and this figure couldn’t easily be reconciled.
“I have colleagues here that I’m responsible for and I needed to accurately and consistently quantify the radon levels whilst we tried to improve the gas readings to ALARP. We began a planned and phased process of sealing the entrances to old workings and directing the fresh air from the main fan as far into the mine as was practicable. The issue that we faced, however, was getting quick and accurate readings to prove the efficacy of that work.
Miners of the Bath Stone Group in the Stoke Hill Mine, southeast of Bath.
Accurate real-time readings using the AlphaGUARD
"Our RPA from PHE visited the mine with their own department Alphaguard. The AlphaGUARD was the only piece of kit that could give us give results in real-time, good or bad. We’d previously relied on contractors and PHE’s three-month passive monitoring, but with the AlphaGUARD, we had a handle on the problem immediately.
“When I had to hand the AlphaGUARD back to PHE, the first thing I wanted to do was get my own, which is why I got in touch with Southern Scientific. The service that we’ve had is so helpful and so comprehensive. I recommend it wherever I possibly can, and I genuinely mean it because without the AlphaGUARD we would not be able to effectively manage a safe working environment. It’s robust, it’s simple. I’ve never had an issue but whenever I’ve had a question, the team at Southern Scientific has been on it so quickly.
“With the assistance of Southern Scientific, our long-term ventilation consultants, PHE, and the hard work of our team, we have reduced our Radon gas levels to ALARP. We are no longer a controlled area, our operatives have been de-classified, and the gas levels are monitored and recorded each hour, 24 hours per day.
“We’ve been so impressed with the AlphaGUARD that we’ve just ordered the smaller portable AlphaE for personal radon monitoring.”
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