ITER Baseline Schedule (Project Baseline 2024)

Overview

The ITER baseline schedule is the official, integrated project plan that defines the timeline, milestones, resource allocation, and critical path for the construction and operation of the International Thermonuclear Experimental Reactor. As a first-of-a-kind global collaboration in fusion energy, the schedule is a fundamental management tool for coordinating the complex interplay between the central ITER Organization (IO) and the seven domestic agencies (DAs) responsible for providing in-kind contributions. It dictates the sequence of manufacturing, delivery, assembly, and commissioning of millions of components, culminating in the achievement of key project goals such as First Plasma (FP) and Deuterium-Tritium (DT) operations.

The schedule's integrity is critical for maintaining project momentum, managing budgets, and aligning the expectations of member governments and the scientific community. Re-baselining, the process of formally updating the schedule, is a significant undertaking prompted by accumulated delays, technical challenges, or external factors. The most recent major update is the proposed Project Baseline 2024 (PB24), which seeks to replace the 2016 baseline. This new schedule accounts for significant delays encountered in the manufacturing and assembly of critical components, most notably the vacuum vessel sectors and toroidal field coils, as well as the impacts of the COVID-19 pandemic. The PB24 proposal represents a shift towards a more realistic, risk-informed project timeline.

Mechanism

The ITER schedule is managed using integrated project management principles tailored for a large-scale nuclear construction project with a complex international supply chain. The core mechanism is critical path analysis, which identifies the longest sequence of dependent tasks that determines the overall project duration. For ITER, the critical path has historically run through the fabrication, delivery, and assembly of the main machine components: the vacuum vessel, the superconducting magnets (toroidal and poloidal field coils), and the cryostat.

The project is structured in a staged approach with distinct, verifiable milestones:

Construction and Assembly Phase: This involves civil engineering for the tokamak complex buildings, manufacturing of components by the DAs, and their subsequent on-site assembly by the IO. The complexity is magnified by the in-kind procurement model, where components built in different countries must meet exacting tolerances to be integrated successfully in France.
First Plasma (FP): This is the first major operational milestone, defined as the successful creation of a magnetically confined plasma inside the tokamak. It verifies the integrated performance of the vacuum vessel, the magnet systems, cryogenics, control systems, and essential power supplies. It does not involve nuclear fusion reactions and is typically performed with hydrogen or helium gas.
Pre-Fusion Power Operation (PFPO): A period of integrated commissioning and operational testing following First Plasma. This phase is used to optimize plasma control scenarios, test diagnostics, and prepare the machine for nuclear operations without using tritium.
Deuterium-Tritium (DT) Operation: The ultimate goal of the project. This phase involves introducing tritium fuel to achieve significant fusion power, aiming for a plasma energy gain of Q_plasma ≥ 10. This milestone marks the beginning of ITER's full scientific mission to demonstrate the feasibility of fusion as a large-scale energy source.

The 2024 baseline revision was necessitated by delays in the first phase, directly impacting the achievable dates for all subsequent operational milestones. The schedule's mechanism must account for the intricate logistical dependencies; for example, a delay in a vacuum vessel sector from one DA prevents the installation of toroidal field coils from another, halting the entire machine assembly sequence.

Historical development

The ITER project's schedule has undergone several major revisions since the signing of the ITER Agreement in 2006. The original, highly optimistic schedule targeted First Plasma as early as 2016.

By the early 2010s, it became clear that the initial timeline was untenable. Delays stemmed from the finalization of the complex design, the establishment of the seven DAs and their industrial supply chains, and the challenges of manufacturing first-of-a-kind components to unprecedented specifications. An independent review led by Director-General Bernard Bigot culminated in the 2016 Baseline. This was a comprehensive, bottom-up rescheduling of the entire project. It established a new, fully-integrated plan with First Plasma in December 2025 and the start of DT operations in 2035. For several years, the project made significant progress against this revised schedule, meeting 25 consecutive project milestones through 2019.

However, beginning around 2020, several critical issues began to exert pressure on the 2016 baseline. The COVID-19 pandemic caused widespread disruption to global supply chains and on-site work. More significantly, major technical challenges emerged with key components. Dimensional non-conformities were discovered in the vacuum vessel sectors being manufactured in Korea and Europe, requiring extensive on-site repairs after delivery. Additionally, stress corrosion cracking was identified in the thermal shields, and issues with the continuity of the superconducting joints in the toroidal field (TF) coils required remediation. These issues, concentrated on the machine's critical path, made the 2025 First Plasma target impossible.

In response, the ITER Organization, under Director-General [/scientists/pietro-barabaschi](Pietro Barabaschi), initiated a comprehensive review of the project status, leading to the development of the Project Baseline 2024 (PB24) proposal. This new baseline was formulated throughout 2023 and 2024 and presented to the ITER Council for review.

Current status

As of early 2026, the Project Baseline 2024 is the operative, though not yet fully approved, schedule for ITER. The ITER Organization presented the new baseline to the ITER Council at its 35th meeting in November 2024. The Council acknowledged the revised timeline as a realistic assessment of the project's status, effectively accepting that the 2016 goals were no longer achievable. However, it deferred a formal decision on the full schedule and the associated cost and resource implications, pending further review by the members.

The proposed PB24 timeline indicates a significant delay. While official dates are pending formal approval, public statements and reports suggest First Plasma is now anticipated in the early 2030s, with DT operations following in the late 2030s. The immediate focus of the project is on completing the necessary repairs and modifications to the affected first-of-a-kind components, particularly the vacuum vessel sectors and TF coils. Assembly of the main tokamak has been re-sequenced to accommodate these repairs without completely halting progress in other areas. Construction of plant systems and buildings continues, with over 80% of the total construction scope completed.

The project is currently operating under a provisional plan aligned with the PB24 proposal, prioritizing the critical repair work and advancing non-critical-path assembly tasks where possible. The final approval of PB24 by the ITER Council, expected in 2026, will formalize the new timeline and budget, providing a stable planning basis for the next phase of the project.

Notable implementations

The ITER baseline schedule is a singular entity governing one project. Its implementation is managed by the ITER Organization in collaboration with the seven domestic agencies:

Europe (F4E): Responsible for the largest share of contributions, including the tokamak buildings, five vacuum vessel sectors, and half of the TF coils. Delays in its vacuum vessel fabrication have been a primary driver of the schedule revision.
Japan (QST): Providing the technologically complex TF coils and the central solenoid's conductor. The performance of its industrial partners, like Mitsubishi and Toshiba, is critical to the magnet system timeline.
United States (US-ITER): Contributing key systems such as the central solenoid magnet, plasma diagnostics, and pellet injection systems. The US Department of Energy conducts rigorous annual reviews of the project's progress against the baseline.
Russia (RF-DA): Responsible for 25 major systems, including the powerful gyrotrons for plasma heating and the superconducting conductors for magnets.
China (ITER-CN): Providing electrical systems, magnet feeders, and thermal shields. Its manufacturing has generally proceeded on schedule.
South Korea (K-DA): Fabricating four vacuum vessel sectors and the thermal shields. The discovery of dimensional non-conformities in its vacuum vessel sectors upon delivery necessitated significant on-site repair work, a key factor in the schedule slip.
India (ITER-India): Responsible for the massive cryostat, which has been successfully fabricated and installed, as well as cooling systems and diagnostics.

The coordination among these DAs, each with its own industrial and regulatory frameworks, is the central challenge in executing the ITER baseline schedule.

Open challenges

Executing the revised Project Baseline 2024 presents several formidable challenges:

Component Repair and Rework: The highest-priority challenge is the successful repair of the non-conforming vacuum vessel sectors and the remediation of the TF coil conductor joints. These are complex, first-of-a-kind engineering tasks that must be completed on-site to exacting nuclear-grade standards. The duration and success of these repairs represent the largest uncertainty in the new schedule.
Maintaining Project Momentum and Morale: A schedule delay of several years can impact staff morale and political support. The IO must manage the project effectively through this period of rework, demonstrating tangible progress to maintain the confidence of the ITER members and the public.
Cost and Resource Management: Significant delays invariably lead to increased costs. The final cost-to-complete under PB24 is still being assessed. Securing the necessary additional funding from all seven members in a coordinated manner is a significant political and financial challenge.
Supply Chain and Manufacturing Integration: As assembly continues, the project remains vulnerable to any further delays in the manufacturing or delivery of the thousands of remaining components from the international partners. Maintaining quality and schedule adherence across dozens of global suppliers is a persistent challenge.
Nuclear Licensing and Regulation: As ITER moves closer to its nuclear phase (DT operations), it must meet all requirements of the French nuclear safety authority, ASN (Autorité de Sûreté Nucléaire). The schedule must accommodate a rigorous commissioning and licensing process that could introduce further delays if unforeseen issues arise.

Outlook

The credible 5- to 15-year trajectory for the ITER project is now framed by the proposed Project Baseline 2024. The immediate outlook for the next five years (2026-2031) is dominated by the on-site repair of the vacuum vessel and magnet components, followed by the resumption of the main tokamak assembly sequence. The primary goal will be to complete the closure of the tokamak cryostat, a major milestone signifying the completion of the core machine assembly.

Based on the PB24 proposal, First Plasma is credibly expected in the early 2030s. Following this milestone, a multi-year phase of integrated commissioning and plasma experiments (PFPO) will commence. This will be a critical period for the scientific and engineering teams to learn how to operate the machine and prepare it for its ultimate mission.

The start of Deuterium-Tritium operations, the point at which ITER will begin its campaign to demonstrate a net energy gain, is now projected for the late 2030s. This places the key scientific results from ITER, which are intended to inform the design of a demonstration power plant (DEMO), in the 2040s. While the revised schedule represents a significant delay, its adoption is seen as a necessary step to place the project on a more robust and achievable footing for its eventual completion and operation.

References

35th ITER Council Meeting (IC-35) — ITER Organization (2024)
ITER project status: a realistic and robust path forward — ITER Organization (2024)
ITER's new boss confronts delays and welding problems — Science (2023)
ITER Council endorses updated project schedule — World Nuclear News (2016)
ITER Director-General Bernard Bigot submits an updated schedule for the ITER Project for the Council’s approval — ITER Organization (2016)
ITER Home Stretch — Nature (2024)
Fusion project ITER to be delayed by years, internal documents show — Reuters (2024)
ITER Status — U.S. Department of Energy Fusion Energy Sciences Advisory Committee (2023)

ITER baseline schedule (Project Baseline 2024)