Entering SKALA codes during RBMK operation. (Credit: Pripyat-Film studio)Running a nuclear power plant isn’t an easy task, even with the level of automation available to a 1980s Soviet RBMK reactor. In their continuing efforts to build a full-sized, functional replica of an RBMK control room as at the Chornobyl Nuclear Power Plant – retired in the early 2000s – the [Chornobyl Family] channel has now moved on to the SKALA system.Previously we saw how they replicated the visually very striking control panel for the reactor core, with its many buttons and status lights. SKALA is essentially the industrial control system, with multiple V-3M processor racks (‘frames’), each with 20k 24-bit words of RAM. Although less powerful than a PDP-11, its task was to gather all the sensor information and process them in real-time, which was done in dedicated racks.Output from SKALA’s DREG program were also the last messages from the doomed #4 reactor. Unfortunately an industrial control system can only do so much if its operators have opted to disable every single safety feature. By the time the accident unfolded, the hardware was unable to even keep up with the rapid changes, and not all sensor information could even be recorded on the high-speed drum printer or RTA-80 teletypes, leaving gaps in our knowledge of the accident.(Credit: Chornobyl Family, YouTube)Setting up a genuine RTA-80 teletype is still one of the goals, but these old systems are not easy to use. Same with the original software that ran on these V-3M computer frames, which was loaded from paper tape (the ‘library’), including the aforementioned DREG program. This process creates executable code that is put on magnetic tapes, with magnetic tape also used for storage.(Credit: Chornobyl Family, YouTube)The workings of the SKALA system and its individual programs including KRV, DREG and PRIZMA are explained in the video, each having its own focus on a part of the RBMK reactor’s status and overall health. Interacting with SKALA occurs via a special keyboard, on which the operator enters command codes to change e.g. set points, with parameters encoded in this code.Using this method, RBMK operators can set and request values, with parameters and any error codes displayed on a dedicated display. There is also the Mnemonic Display for the SKALA system which provides feedback to the operator on the status of the SKALA system, including any faults.Although to many people the control system of a power plant is just the control room, with its many confusing buttons, switches, lights and displays, there is actually a lot more to it, with systems SKALA and its associated hardware an often overlooked aspect. It’s great to see this kind of knowledge being preserved, and even poured into a physical model that simulates the experience of using the system.The long-lived nature of nuclear power reactors means that even today 1960s and 1970s-era industrial automation system are still in active use, but once the final reactor goes offline – or is modernized during refurbishing – a lot of the institutional knowledge of these systems tends to vanish and with it a big part of history.