 To develop a cancer of some kind is a fact that one in two people on average can look forward to. Although tragic, developing the disease in the modern day is probably the best time in history to get the big C. Your chance to survive all are probably the best they have ever been. Don't get me wrong it's still rubbish being diagnosed because even though treatment is loads more effective now than it has ever been in human history, it's still very intrusive and not a guarantee that you'd survive. One such form and the one covered in this video is breast cancer. Treatment can involve surgery which permanently alters the body and as such can cause significant psychological trauma. Chemo is another heavy one for treatment and another is radiotherapy. Radiotherapy is a fascinating subject and it uses a beam of radiation to kill cancer cells. The machines are complex and today's subject is about when that complexity causes a disaster. In our case today sadly the machine used in the hope of treatment will end up causing far more suffering. The L-Stock radiotherapy overexposure event. Forward. So today's video will be based on the IAEA report into the incident. If you'd like to go into a further deep dive into the figures then check out the report and as always the link will be in the description below. I won't go too much into the history of radiotherapy today which is only because if I do then the video will be way too long but I will touch lightly on the particular machine involved. Right, let's get started. Bialstock. So this is Bialstock. Going on population is the 10th biggest city in Poland. Like most big cities it has an extensive healthcare network which deals with many things including with those who have cancer. This was dealt with by the Bialstock Oncology Centre which I'll call the BOC from now on to minimize your exposure to my abysmal attempt at Polish. Anyway the BOC is as described by the IAEA as reasonably well equipped and staffed. The centre treated in the early 2000s over a thousand patients per year in its tele therapy department using its three tele therapy machines. But for today's video we'll only be looking at one, this one to be precise, a Neptune P10. A domestically produced machine under licence from France by the nuclear centre in Swerk. It is a linear particle accelerator. This type of tele therapy machine accelerates charge some atomic particles into a radiation beam which is then fired at the patient. The dose level is vital as too much can actually cause more damage than good. This is achieved by two transmission chambers inside the radiation head at the exit of the beam. They monitor the dose to see if the beam's flatness and symmetry are in spec. The signal from the two chambers is fed into the machine's control system which will then make sure the actual dose matches the pre-selected dose amount. The Neptune machine control system offers five different dose rates. The power for these vital transmission chambers is supplied from one power supply in which the current runs for a fuse. It will later be found that the defective fuse could cause abnormal readings from the transmission chambers which in turn could make the tele therapy machine give a dose higher than anticipated by driving the filament voltage to its maximum. But for the time being this was not known during the machine's operation. Now starting up the Neptune machine requires multiple steps to ensure its safe operation. First of all once switched on a minimum of five minutes is needed to pass to allow for proper warm-up. Then a check process begins. This involves the operator pressing certain buttons to initiate each system's self-check. After the step is complete a green light is displayed on the control panel and the next step can be initiated. Of course one of the checks is of the dose monitoring system. If it fails then the signal is sent to an interlock which will stop the initiation of the radiation beam. The signal sent to the interlock uses a diode. However this system has a flaw. If for any reason there is a break in the diode's wiring the signal is not sent to the interlock and bizarrely will give a green light allowing the next check to be undertaken. This leads the machine to be able to administer a dose of radiation without the proper checks. Anywho after startup an output measurement should be taken and this includes even after an emergency shutdown. The Neptune's manual stated a number of reasons for a complete startup checkup. This mainly covered events relating to equipment malfunctions but not for the case of a power cut. Now remember that for later on. So the BOC when treating patients always had at least two radiographers on shift at the radiation unit and at the beginning of any radiation treatment program an oncologist and physicist are also present. The overexposure. On the 27th of February 2001 the centre would be operating as normal. During the treatment of a patient the BOC experienced a power cut. The patient who was lying down on the treatment couch at the time was being dozed with 2.5 grey. This would be a total of 155 monitor units. But at the moment of the power cut had only received 5 monitor units. Now power cuts were a semi regular event at the BOC and as such wasn't seen as too much of a serious issue. Although the Neptune tele therapy unit would need to undergo the restart process. Previously the machine had operated just as good as pre power cut keeping the selected dose rates. The operator of the tele therapy machine called his boss the chief physicist and they restarted the machine. After the warm up time had passed he did some checks with the panel and power supply and these seemed to come back okay. But a full check including an output measurement wasn't undertaken because the power cut wasn't listed in the manual. The patients remaining 150 monitor units were administered however a small asymmetrical radiation field was noticed. So the patient completed their treatment and the next one was set up for their dose. She as well was due to receive a couple of greys in dose. During her treatment the chief physicist was called out for an emergency in another part of the centre. The next three patients received their doses and each reported skin irritation around the treatment site. The last of the three raised concerns with centre staff after experiencing severe itching. Something that shouldn't have happened after only a couple of greys. The patients were examined by the radiation oncologist and they discussed their concerns with the chief physicist and the decision was made to stop treatment and investigate. A Siemens dosimeter was used to check the output of the machine and it read 37 times higher than the selected amount for an 8 MeV electron beam and 17 times higher for the 10 MeV electron beam. Obviously something was not right and further investigation would be needed. It was disassembled on the 28th and an engineer discovered a failed fuse in the AC to DC power supply and on top of that the diode responsible for sending a signal to the interlock was also faulty. These were replaced and afterwards the machine's output tested within spec. It was rather confusing but the freakstorm of two fail components had caused the overexposure. Clearly a more in-depth investigation was required and this would result in the IAEA being called in. So after the overexposure the IAEA were informed. This is the International Atomic Energy Agency. They are called in for these types of incidents to assist local authorities in their investigation. So let's first of all talk about the patients. All five had received many times the prescribed radiation dose. They were initially prescribed vitamins. By May they had been re-examined and it was initially thought that they may not need to have surgery. However the progressions of ulcers into necrosis on their bodies would change this. Eventually all five would require surgery in 2002. Three remaining in Poland and two being sent to the Institute Curry in France and this was to remove decaying affected areas. All experienced reduced blood cell counts and severe discomfort and sickness. Their exposure was severe but survivable albeit with a reduced life expectancy. The IAEA set about trying to reconstruct the series of failures that led to the overexposure. They found that if the diode had failed and a fuse had also failed that the output monitors would fail to correctly read the radiation beam causing the filament control voltage to rise and cause doses up to 100 grey over the course of a treatment of 150 monitor units. Well over the 2.5 grey that was intended. It would seem that the shortcomings in the machine's design in which it wouldn't fail safe was a pretty big oversight. This failure could have still been caused if a more robust restart process was in place that would have required a dosimeter check. This would have caught the high dose of radiation but sadly missing this resulted in five serious overexposures. So it's the time for my new disaster scale. No one died. Thankfully. So it's going to be the most serious in the lower end of the scale at a number two. Do you agree? This is a Plainly Evcourt production. All videos on the channel are created because we can share our license. Plainly Evcourt videos are used by me John in a currently wet and windy corner of southern London UK. I have YouTube membership as well as Patreon membership so fancy feel free to go over there to financially support the channel. 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