# Is Haiyang 4 Now Ready for the Next Construction Phase?

The CB20 containment water tank module — the last large module — has been installed at unit 4 of China's Haiyang nuclear power plant, State Power Investment Corporation (SPIC) announced on July 2, 2026. The milestone marks the completion of large-scale modular installation at the Shandong province site, clearing the path toward civil works completion and eventual systems commissioning.

This is a meaningful construction checkpoint. The [containment structure](https://smrintel.com/glossary/containment) at a pressurized water reactor serves as the final passive barrier against fission product release — the CB20 water tank module specifically supports passive safety functions, providing gravity-fed coolant inventory that can suppress pressure and manage [decay heat](https://smrintel.com/glossary/decay-heat) without active pumping during off-normal events. Getting this module seated and structurally integrated is a prerequisite for the pressure boundary work and internal systems installation that follows.

Haiyang is located in Shandong province on China's eastern coast. Units 1 and 2 at the site are operating AP1000s — the same Westinghouse-derived design that informs much of the passive safety architecture seen in the newer units under construction. Unit 4's progress under SPIC represents a continued scaling of China's domestic nuclear construction cadence, which remains the most aggressive of any country globally.

## What the CB20 Module Installation Signals

The sequencing of large module installation is a reliable proxy for overall construction progress at Chinese nuclear sites. Once the final large module is placed, the construction schedule shifts toward precision-fit mechanical and electrical installation — piping, instrumentation, reactor internals, and fuel handling systems. These phases are more labor-intensive but generally carry less schedule risk than heavy lift operations, which depend on crane availability, weather windows, and dimensional tolerance verification.

The CB20 designation — containment water tank — identifies this as part of the passive safety system architecture. In AP1000-family designs, the in-containment refueling water storage tank (IRWST) and associated passive cooling water inventory are core to the defense-in-depth strategy. The fact that this is described as the last *large* module is notable: it suggests all major structural and safety-system modules have now been set, and the site is transitioning to the next construction phase.

SPIC's public announcement, accompanied by installation photographs per the World Nuclear News report, follows standard Chinese nuclear operator communications practice around milestone completions. The company has been expanding its nuclear portfolio and Haiyang 4 is part of a broader multi-unit build program.

## Industry Context: China's Construction Cadence vs. Western Timelines

China's ability to sequence large module installations at pace continues to stand apart from Western nuclear construction experience. Where [first-of-a-kind (FOAK)](https://smrintel.com/glossary/foak) Western projects have encountered multi-year schedule slippage driven partly by modular fabrication challenges, Chinese constructors have iteratively refined their modular assembly processes across successive units.

For Western developers — including [Westinghouse Electric Company](https://smrintel.com/companies/westinghouse), which supplies the AP1000 technology underlying Haiyang's design — the Chinese build program functions as an operational learning library. The passive safety systems being installed at Haiyang 4, including the CB20 water tank, are directly relevant to ongoing AP1000 and AP300 deployment discussions in the US, UK, and Central Europe.

The pace differential also has implications for levelized cost of energy ([LCOE](https://smrintel.com/glossary/lcoe)) competitiveness. A multi-unit site with a mature construction workforce and localized supply chain compresses per-unit costs in ways that single-unit Western builds structurally cannot replicate without sustained policy support and a committed build program.

For uranium markets, continued Chinese construction progress sustains long-term demand fundamentals. Each unit that advances through major construction milestones toward fueling represents confirmed future uranium offtake, relevant to analysts tracking producers including [Cameco Corporation](https://smrintel.com/companies/cameco) and [NexGen Energy Ltd](https://smrintel.com/companies/nexgen-energy).

## What Comes Next at Haiyang 4

Following large module completion, the typical sequence at a Chinese PWR site moves through:

- **Reactor pressure vessel installation and internals fit-up**
- **Steam generator and pressurizer connection**
- **Primary circuit pressure testing**
- **Fuel load preparation and criticality approach**

No commissioning date for Haiyang 4 was provided in the source announcement. The construction timeline from this point will depend on how far advanced the parallel systems work has been running — Chinese sites typically prosecute civil, mechanical, and electrical work on overlapping schedules to compress the overall program.

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## Key Takeaways

- **SPIC has installed the CB20 containment water tank module** at Haiyang 4, completing large-scale modular installation at the Shandong province site.
- **The CB20 is a passive safety system component**, providing gravity-fed coolant inventory for decay heat management without active pumping — a core feature of AP1000-family design architecture.
- **Large module completion marks a construction phase transition** from heavy lift operations to precision mechanical, electrical, and instrumentation installation.
- **No commissioning date was announced** in the source material; schedule to fuel load depends on parallel systems work progress.
- **China's multi-unit construction cadence** continues to outpace Western programs, with direct implications for LCOE benchmarks and supply chain learning curves that Western developers reference.
- **Uranium demand fundamentals** are reinforced by each construction milestone that confirms future fuel requirements.

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## Frequently Asked Questions

**What is the CB20 module at Haiyang 4?**
The CB20 is the containment water tank module — the last large module to be installed at unit 4 of China's Haiyang nuclear power plant. In AP1000-family designs, this module forms part of the passive safety system, providing a gravity-fed water inventory to cool the reactor and suppress containment pressure during off-normal events without requiring active pumps or operator action.

**Who operates the Haiyang nuclear power plant?**
Haiyang is operated under State Power Investment Corporation (SPIC), one of China's major state-owned nuclear and power groups. The site hosts multiple AP1000-derived units in Shandong province.

**What construction milestones follow large module installation?**
After large modules are set, construction advances to reactor pressure vessel and internals installation, steam generator connection, primary circuit pressure testing, and ultimately fuel loading and pre-criticality testing. These phases are more labor-intensive and generally carry lower schedule risk than heavy lift operations.

**Why does China's nuclear construction pace matter to Western developers?**
China operates the world's most active nuclear construction program and has iterated its modular assembly processes across dozens of units. Western developers building AP1000-family or new SMR designs reference Chinese construction data for cost benchmarking, supply chain strategy, and passive safety system integration experience.

**What does Haiyang 4's progress mean for uranium markets?**
Each unit that advances through major construction milestones represents confirmed future uranium demand. Construction progress at sites like Haiyang 4 is a leading indicator of mid-term fuel procurement requirements, which uranium producers and analysts track as a demand signal.