Bangladesh’s Rooppur 1 reaches first criticality

Bangladesh’s first nuclear power reactor, Rooppur Unit 1, achieved its first self-sustaining nuclear chain reaction on 11 October, opening the low-power testing phase at the country’s first nuclear plant. The milestone brings the 1,200-megawatt unit closer to operation, but it is not yet producing electricity for the grid.

Key facts

• Rooppur 1 achieved criticality at 15:34 local time on 11 October, according to World Nuclear News, which cited the project’s official account.
• Bangladesh’s regulator gave the go-ahead three days before the criticality milestone, World Nuclear News reported.
• Rooppur 1 is a VVER-1200 pressurized-water reactor rated at 1,200 MWe gross.
• The project’s two reactors together have 2,400 MWe gross capacity.
• Rosatom’s in-house publication gave 20 November 2026 as the planned power start-up date; the date remains a target pending tests and regulatory steps.

What happened

Criticality is the point at which fission in the reactor core sustains a continuing chain reaction. Rooppur 1 reached that state at 15:34 on Sunday, 11 October, after Bangladesh’s national atomic regulator authorized the step earlier in the week. World Nuclear News attributed the milestone to a statement on the project’s official account. NNN has not located a directly accessible regulator or operator release confirming the precise time, so the timing and sequence here are attributed to that report.

This is a commissioning milestone, not a switch from construction to ordinary commercial operation. The reactor now has to be tested at low, controllable power, with plant systems and equipment checked before operators can raise output. According to the project statement quoted by World Nuclear News, grid supply will advance in stages only after the required criteria and safety verification are completed.

Rosatom’s in-house publication, Strana Rosatom, reported a planned power start-up date of 20 November. That schedule should be treated as a target. Criticality by itself does not demonstrate that the unit has passed the remaining tests, received permission to supply the grid, or reached commercial operation.

Why it matters

Rooppur is Bangladesh’s first nuclear power plant, and its first unit has now moved from fuel loading and pre-start checks into the phase where a controlled chain reaction is maintained and tested. The milestone is consequential for the country’s electricity system, but the actual contribution to supply depends on the next stages going as planned.

The scale is substantial for a first project: the site is designed for two VVER-1200 reactors. The International Atomic Energy Agency’s account of the project describes two pressurized-water units, each with 1,200 MWe gross capacity. Unit 1’s progress therefore carries practical weight, while the second unit remains a separate construction and commissioning undertaking. A first criticality announcement should not be mistaken for both reactors being ready or the full site capacity being available.

The distinction matters because commissioning language can blur milestones that have different meanings. First criticality confirms a sustained reaction. Subsequent power ascension and testing establish how the plant performs across operating conditions. Grid connection and commercial operation require further technical and regulatory milestones. For readers tracking Rooppur, those later authorizations and the actual start of electricity delivery are the next useful markers.

Background

The Rooppur site is in Pabna district, northwest of Dhaka, on the Ganges River. The two-unit project is being built for the Bangladesh Atomic Energy Commission with Russia’s Rosatom. Construction of Unit 1 began in November 2017, while work on Unit 2 began in July 2018, according to the World Nuclear Association’s country profile. The long schedule reflects the scale of the project and the sequence of construction, fuel loading, licensing and commissioning work required before an operating plant can supply power.

Rooppur’s current stage has parallels with other commissioning stories, though the designs and licensing regimes differ. NNN previously reported that Akkuyu Unit 1 in Turkey completed hydraulic testing, a system-check milestone that also preceded further commissioning work. In the United States, Westinghouse’s eVinci test reactor reached zero-power criticality, a distinct research-reactor achievement that illustrates why “criticality” describes a reactor state, not commercial electricity production.

What’s next

The next test phase at Rooppur 1 will check equipment and safety systems at minimum controllable power before output can increase in steps. The project’s reported 20 November power start-up target is one date to watch, but the more conclusive evidence will be any subsequent regulatory authorization and a confirmed grid supply milestone. Until those are reported, Rooppur 1 should be described as having achieved first criticality, not as operational or commercially generating electricity. That careful wording also keeps a scheduled target separate from an event that has actually happened.