Beside the Padma River in Pabna, a 1,080 megawatt reactor built over eight years reached its first chain reaction, and the milestone makes Bangladesh the world’s newest nuclear power producer
A reactor hall on the Padma River just made nuclear history.
At a few minutes past three in the afternoon, neutrons inside a core of fresh uranium fuel began splitting each other apart fast enough to sustain themselves without outside help.
No alarms sounded.
The unit still needs to prove itself at rising power levels, and grid connection is expected by the end of November, the next concrete milestone the plant must hit.
No lights dimmed in Dhaka, 100 miles away.
Nothing visible happened at all.
But inside that steel reactor vessel, a self sustaining chain reaction had just started for the first time in the country’s history, and that instant is where the next question begins.
What actually happens inside a reactor at first criticality
A reactor reaches criticality the moment the uranium atoms splitting inside its core produce exactly enough new neutrons to keep the reaction going on their own, with no external source required. Operators reach that point by slowly withdrawing the neutron absorbing rods that keep the core shut down, a few inches at a time.
Each small withdrawal is followed by a pause, a measurement and a comparison against predicted values. That patience is the whole point, since a core that goes critical too fast, or in an unpredicted way, has stopped behaving like the models say it should.
So the moment itself is almost anticlimactic by design. Instrument readings tick upward on a chart rather than anything a visitor could see or hear, and the real drama happened in the decade of construction that made it possible.
Thirteen years on the same stretch of riverbank
The site itself has a longer memory than the reactor does. Construction began on October 2, 2013, with about 30,000 local and foreign workers cycling through the site since, turning a farming district into what local reporting describes as a round the clock company town.
The country’s first railway junction had put Ishwardi on the map more than a century earlier, in 1915, long before anyone there imagined a reactor dome rising beside it.
The unit now carrying that history is a VVER V-523, a pressurized water design supplied by Russia’s state nuclear contractor. The 1,080 MW reactor unit achieved first criticality at 15:34 on October 11, capping eight years of pouring concrete and testing systems on one patch of riverbank.
Even so, criticality is not the finish line. The unit still needs to prove itself at rising power levels, and grid connection is expected by the end of November, the next concrete milestone the plant must hit.
Why this number matters more than the megawatts
Bangladesh has spent more than six decades waiting for this moment. The Rooppur site was first selected for a nuclear plant back in 1963, and successive governments floated and shelved the idea for generations before a firm commitment finally came in 1999.
That long delay makes the hard numbers from this stage worth noting carefully. The project’s estimated construction cost runs to about $12.65 billion, financed overwhelmingly through a Russian state loan.
Officials say the completed facility will help diversify the energy mix and build lasting baseload capacity, with Rooppur projected to supply over 10 percent of national demand once both reactors run. That is a heavy load to place on two units, which is exactly why each commissioning step gets logged in public rather than folded into one later announcement.
The fuel assemblies now sitting inside a working core
Getting to criticality required loading real uranium fuel assemblies into the vessel, a step that followed years of dry runs with no fuel present at all. The sister effort at Palisades in Michigan, where crews are racing to return a shuttered American reactor to service, shows how delicate that loading stage can be even for an experienced operator.
A tilted fuel assembly there forced regulators into an emergency review just last week. Rooppur’s own path was not free of friction either, with regional reporting tracking years of schedule slippage, cost disputes and a publicized procurement scandal over worker housing furnishings.
That kind of friction dogs almost every first of a kind build. None of it changed the physics inside the core on October 11, but it shaped how skeptically outside observers greeted the news.
Rooppur’s second unit is still working through its own schedule, years behind the first. The broader regional picture, where a far older design recently returned to service after a lengthy outage, shows how long a reactor’s working life can stretch once it starts producing power.
What still has to happen before the lights actually change
Reaching criticality tells engineers the core behaves as predicted at essentially zero power, nothing more. The real test comes over the following weeks, as operators raise output in stages and check turbines, generators and safety systems before the grid connection happens.
That grid will need to absorb a single source capable of supplying a meaningful share of the country’s electricity. Regional grid operators elsewhere have sometimes struggled when a large new source comes online at once, and Bangladesh’s planners have months yet to prepare.
Industry trade coverage of the startup, including World Nuclear News, reported that power start up is scheduled for November 20, with a series of tests and checks still to come before output rises in stages. For now, the milestone that matters is the one already measured and logged, a sustained chain reaction inside a core beside the Padma River on one specific afternoon in October. Everything still to come, the grid connection, the commercial operation, the second unit trailing behind it, will be judged against how predictably that first afternoon went.
Hugo is an engineer with strong technical expertise. Multilingual from an early age, his writing combines technical clarity with a strong interest in science and energy.
