Nuclear Energy Companies in the UK: 24 Active Firms (2026)
Nuclear energy companies in the UK develop, operate and support civil nuclear power generation, fuel-cycle services and specialist engineering.
Buying centres tend to sit around site operations, asset-life extension, decommissioning and waste, fuel-cycle support, and safety-critical engineering assurance. Buyers are usually regulated energy operators, infrastructure owners, public-sector-adjacent bodies and industrial customers that cannot tolerate generic delivery models. Engagements tend to be framework-led or project-packaged, with qualification, security and documentation requirements doing much of the supplier filtering before price is discussed. The cohort therefore leans towards specialist operators and technical services firms, rather than generalist consultancies or broad industrial contractors that only touch nuclear work at the margins.
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The UK cohort contains 24 actively trading companies, with reported employment of 499 people. Only 8 sit above £5M in turnover, and just 1 has been incorporated since 2022, so the market reads as mature and tightly qualified rather than start-up heavy. That shape is consistent with civil nuclear procurement: suppliers need established assurance processes, relevant technical permissions and evidence of delivery in safety-critical settings. It also means the list is not a proxy for the whole low-carbon energy supply chain; it is a narrow civil nuclear slice.
Civil nuclear suppliers operate inside a permission-heavy market structure. Work tied to licensed sites, fuel handling, decommissioning or safety-critical modification usually involves safety cases, radiological protection controls, quality documentation, security vetting and long audit trails. Procurement can therefore favour firms that already understand nuclear-site governance, even where the task looks like conventional engineering from the outside. Defence-adjacent work adds another layer of access control and confidentiality, while industrial support contracts often depend on the ability to maintain traceable processes over long asset lives.
New entry appears constrained by the time it takes to earn buyer confidence, qualify for controlled work and build delivery references in safety-critical settings. The sector therefore tends to refresh through spin-outs, adjacent engineering teams moving deeper into nuclear, and small specialist practices becoming embedded in long programmes. Demand has been steadier than in more discretionary technology markets, but supplier expansion is still likely to be uneven. Firms with narrow technical competence may remain small by design, while broader engineering groups may absorb niche capability where project risk and assurance requirements make ownership useful.
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One row per company, 50+ columns — everything below plus each company’s verified directors, from Companies House filings.
Company data
Verified directors — included
Active director count is the full Companies House board, so it can be higher than the number of names listed — we leave out nominee and formation-agent directors, who aren’t worth contacting. It’s blank for the small number of companies whose officers we haven’t fetched yet.
You’re charged per business, not per row. Where a business trades through several registered companies you get every one, and the Group Primary column marks one row per business — filter to those and the count matches your invoice. Rows sharing a website are not automatically one business: franchises and multi-site operators each count separately, and where names don’t prove a relationship we count them apart rather than guess.
24
Active firms
2026
8
Above £5M
Annual revenue
1
Since 2022
New incorporations
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Key facts
About 33% of the trading cohort reports turnover above £5M (8 of 24 firms) — the rest sits below that revenue band.
4% of the cohort was incorporated since 2022 (1 firms), so a sizeable share is in its first few filing cycles.
Civil nuclear activity in the UK centres on long-cycle infrastructure rather than high-volume company formation.
The market spans generation, fuel-cycle services and specialist engineering, so suppliers tend to sell into project-led procurement rather than short buying cycles.
A narrow set of assets and supply chains shapes buyer relationships, with operators and engineering contractors sitting close to technical service providers.
The mix of operating businesses, project vehicles and engineering services firms makes the sector less uniform than software or professional services lists.
Top UK Nuclear Energy companies
Financial sub-scores
Computed from 5 filingsProvides mechanical engineering design, fabrication and installation services, producing ventilation and pipework systems, pressure vessels, structural steelwork and waste containers, with testing…
Serves B2B clients in civil nuclear decommissioning, oil and gas, defence, energy, pharmaceutical and renewables sectors, including organisations commissioning bespoke engineering and fabrication…
Financial Health
StrongStrong · Growing, Hiring · 2% CAGR over 4y
Location
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Computed from 4 filingsProvides engineering design and consultancy services for high‑assurance sectors including nuclear, fusion energy and subsea. Supplies embedded engineers, develops remotely operated systems for…
Serves operators, project teams and public-sector research bodies in high-assurance industries, including nuclear, fusion energy and subsea/offshore sectors, with technical challenges in hazardous…
Financial Health
StrongStrong · Growing, Hiring · 16% CAGR over 3y
Location
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Develops fusion energy technology based on spherical tokamak reactors and designs high‑temperature superconducting (HTS) magnet systems. Conducts research, engineering and commercialisation of…
Serves B2B and public-sector partners in fusion energy, superconducting technology, government research and defence programmes, alongside energy-sector stakeholders interested in commercial fusion…
Location
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Computed from 5 filingsDesigns and integrates industrial control and safety systems for energy, utilities and manufacturing sectors. Provides hardware and software engineering, cybersecurity, fire and gas safety…
Serves B2B operators and engineering teams in energy, utilities and regulated manufacturing, including renewables, oil and gas, nuclear, national infrastructure, food and beverage, chemicals and…
Financial Health
HealthyHealthy · Hiring · 8% CAGR over 5y
Location
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Provides engineering and technical consulting services for energy and infrastructure sectors, including asset management, risk management, human factors, grid connection studies, nuclear advisory,…
Serves B2B clients in energy, utilities and process industries, including oil and gas operators, power and renewables developers, nuclear, petrochemical, pharmaceutical, marine and infrastructure…
Location
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- Stowen11274915
Financial sub-scores
Computed from 3 filingsProvides engineering and technical services for energy and industrial sectors, including inspection and integrity testing, non‑destructive testing, construction support, project management, and…
Serves major international energy corporations, EPC contractors, consultants and OEMs in onshore/offshore renewables, oil and gas, marine and nuclear sectors.
Financial Health
HealthyHealthy · -5% CAGR over 2y
Location
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- Core Power12262063
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Computed from 5 filingsDevelops advanced nuclear energy technology and commercial models for ocean transportation and heavy industrial assets, focusing on long‑cycle nuclear power systems designed to provide low‑emission…
Targets maritime operators, ocean transportation companies, and heavy industry businesses seeking advanced nuclear energy solutions for industrial assets.
Financial Health
StrongStrong · 14% CAGR over 3y
Location
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Computed from 5 filingsProvides fabrication and construction services for energy infrastructure, including high‑pressure process pipework in exotic alloy materials and associated structural steelwork. Delivers turnkey…
Serves B2B clients in wind, oil and gas, nuclear, thermal power, water and hydro, and process industries, including operators and contractors managing safety-critical construction and fabrication…
Financial Health
HealthyHealthy · -2% CAGR over 4y
Location
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Computed from 5 filingsProvides metal fabrication, structural steelwork and piping for onshore and offshore projects. Offers decommissioning support, ship repair and modification, and skilled labour supply for oil and gas,…
Serves B2B clients globally in oil and gas, decommissioning, renewable energy, nuclear, maritime and structural steel sectors, including operators needing offshore/onshore fabrication, labour supply,…
Financial Health
HealthyHealthy · Hiring · 11% CAGR over 4y
Location
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Computed from 4 filingsProvides engineering and construction services including project management, process pipework fabrication and installation, electrical and instrumentation work, plant installation, maintenance, and…
Serves B2B industrial operators and project owners in pharmaceutical, chemical, oil and gas, process, nuclear, power and wind power sectors, including teams needing on-site engineering support,…
Financial Health
DistressedDistressed · -23% CAGR over 3y
Location
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Computed from 5 filingsProvides engineering and technology consulting services for energy and industrial sectors. Offers engineering design and drafting, HSE and risk consulting, energy transition support, digital twin and…
Serves B2B clients in high-hazard and regulated industries, including renewables/offshore wind, power and energy, oil and gas, refineries and petrochemicals, hydrogen, nuclear and defence, and food,…
Financial Health
StrongStrong · Growing, Hiring · 6% CAGR over 4y
Location
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Computed from 5 filingsProvides electrical engineering consultancy, design and project support, alongside mechanical and electrical contracting, power connections, installation, commissioning, and operations and…
Serves B2B clients in renewable energy, marine electrical, nuclear, utilities and building sectors, particularly organisations delivering electrical power systems, network connections and energy…
Financial Health
WeakWeak · -69% CAGR over 4y
Location
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Computed from 5 filingsProvides engineering consultancy and project support for energy and marine sectors including green hydrogen, nuclear, and oil and gas. Services include concept and detailed design, procurement…
Serves B2B project owners, operators and EPC contractors in green hydrogen, nuclear power, oil and gas, and marine sectors needing engineering project support.
Financial Health
StableStable · -66% CAGR over 4y
Location
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Computed from 3 filingsDesigns and manufactures fire and blast protection systems, including blast walls, heat shields, ducts and thermal defence products. Provides steel fabrication, modular structures and engineering…
Targets industrial operators, EPC contractors and project teams in the oil and gas, nuclear, renewable energy, chemical and petrochemical sectors worldwide.
Financial Health
StableStable · Profitable, Hiring · 5% CAGR over 2y
Location
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Computed from 3 filingsFacilitates transactions in nuclear fuel markets and provides pricing data and market risk technology. Trades environmental market products and low‑sulphur marine fuels, and supplies renewable fuels,…
Serves B2B participants in nuclear fuel, carbon and environmental markets, marine fuels, hydrogen, battery and biofuel sectors, including energy producers, industrial buyers, traders and…
Financial Health
WeakWeak · -90% CAGR over 2y
Location
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Computed from 2 filingsDevelops inertial fusion energy technology, focusing on the design and testing of fuel targets that enable fusion reactions. Uses simulation, data science and experimental platforms to support fusion…
Serves fusion energy developers, public-sector research bodies and industrial partners in the energy sector, with near-term commercial markets in materials science and space applications.
Financial Health
WeakWeak · -1% CAGR over 1y
Location
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- STP Group08712184
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Computed from 5 filingsProvides fabrication, welding, and precision machining services for the offshore energy sector, supporting nuclear, oil and gas, renewable energy, and decommissioning projects with manufactured…
Serves B2B customers in the offshore energy sector, including oil and gas, renewables, nuclear and decommissioning operators, contractors and engineering firms.
Financial Health
HealthyHealthy · -7% CAGR over 4y
Location
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Computed from 5 filingsProvides high‑voltage electrical engineering services for transmission and distribution networks, including commissioning at 400kV and 275kV, protection and control system testing, factory acceptance…
Serves B2B clients in electrical transmission and distribution, including transmission system operators, renewable and nuclear generation projects, offshore wind farms, substations and high-voltage…
Financial Health
HealthyHealthy · Hiring · 6% CAGR over 4y
Location
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Computed from 5 filingsProvides environmental consultancy for energy infrastructure projects including offshore wind, power cables and nuclear developments. Services include environmental impact assessment, habitat…
Serves B2B clients developing and operating major energy infrastructure projects, especially offshore wind, power cables and nuclear. Targets UK and international project developers, operators and…
Financial Health
StrongStrong · Growing, Hiring · 41% CAGR over 4y
Location
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Computed from 5 filingsProvides engineering, construction and maintenance services for offshore and onshore energy projects. Activities include inspection, fabrication, electrical and instrumentation work, rope access,…
Sells to businesses in renewables, oil and gas, nuclear, construction and marine sectors, particularly operators, asset owners and project teams running offshore and onshore engineering, maintenance,…
Financial Health
StableStable · -6% CAGR over 5y
Location
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Computed from 5 filingsProvides project management and project development consultancy for infrastructure and energy projects, including solar, wind, storage, hydrogen and nuclear. Also supports aviation and defence…
Serves organisations delivering complex energy, infrastructure, aviation and defence projects, including major energy companies, solar developers and asset owners needing project management support.
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StrongStrong · Growing, Hiring · 61% CAGR over 4y
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Computed from 5 filingsProvides engineering and technical services for energy and industrial facilities, including design and upgrade of PLC and HMI control systems, SCADA and DCS integration, turbine and rotating…
Serves B2B industrial end users and operators in oil and gas, power generation, hydroelectric, nuclear and renewable energy sectors, including plants, remote stations and facilities with turbine,…
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HealthyHealthy · -5% CAGR over 4y
Location
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Computed from 4 filingsManufactures power generation and industrial equipment and provides energy engineering services. Activities include wind, solar, gas and nuclear power systems, power transmission and distribution…
Serves B2B and public-sector customers in energy, utilities, manufacturing, infrastructure and environmental sectors, including power generators, grid operators, industrial plant owners and…
Financial Health
StrongStrong · Hiring · 10% CAGR over 3y
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How UK Nuclear Energy companies work and how to sell to them
What they do
Civil nuclear firms earn revenue through asset operation, fuel-cycle support, decommissioning packages, engineering assurance, site services and specialist consultancy. Commercial models are usually a mix of framework call-offs, fixed-price work packages, time-and-materials engineering support and retained advisory work. Some revenue is tied to physical infrastructure or controlled materials, but many suppliers sell documented expertise: safety cases, inspection regimes, design review, maintenance planning and evidence packs for controlled environments. Gross margins can depend less on software-like scale and more on utilisation, qualification depth, liability allocation and the ability to keep qualified staff on long programmes.
Who they sell to
Most customers are regulated energy operators, infrastructure owners, public-sector-adjacent bodies, defence-adjacent programmes and industrial buyers with safety-critical sites. Buying committees tend to include site directors, programme managers, heads of engineering, safety-case owners, quality leads, procurement and finance. Sales cycles are usually slow because qualification, audit evidence, security checks and framework access sit ahead of commercial negotiation. Smaller advisory jobs may start through direct relationships, but material work is commonly routed through tendered frameworks, approved-supplier lists or project-level procurement exercises. A credible proposal usually has to show delivery method, assurance controls and relevant personnel before pricing becomes persuasive.
What they buy
Most nuclear energy firms tend to spend on quality management, document control, project controls, asset management, field-service tooling, workforce scheduling, training, audit preparation, cyber security and finance systems that can support traceable work. Recruitment and contractor supply are recurring needs, particularly for safety-case, radiological protection, quality, project management and specialist engineering roles. Professional services spend often covers legal review, insurance, accounting, bid support, technical writing and external assurance. Infrastructure purchases are more cautious than in less controlled markets: hosting, identity management, collaboration tools and analytics are normally assessed through security, retention and evidence requirements rather than user convenience alone.
Why and how to sell to them
Buying interest tends to rise when firms win framework places, mobilise new site work, absorb a specialist team, face an audit, update a safety case or carry more controlled documentation than existing processes can handle. Common pain points are qualification burden, rework caused by poor evidence trails, scarce technical staff, cost control on long programmes and the need to prove that subcontractors follow the same procedures as the prime contractor. Outbound messages land better when they are specific to controlled delivery: reduced audit preparation time, clearer document ownership, lower handover risk, faster onboarding for qualified workers, or better visibility across live work packages.
How this list is built
Data sources
This list is built from UK Companies House filings, XBRL accounts data, and semantic analysis of each company's public website. Revenue and headcount figures come from the most recent filed accounts; where the company has not filed, values are estimated using a model trained on filed history and peer benchmarks and are labelled as estimates.
Classification
Rather than relying solely on SIC codes, Firmbase classifies each company semantically: the company's website is crawled, an AI model reads what the company actually sells, and the company is placed into the relevant industry and subsectors. SIC codes are used as one signal but not the only one. This means a company that registered under a generic SIC code but pivoted into (for example) fintech is correctly identified as fintech, not as its original SIC category.
Freshness
The underlying company data is refreshed from Companies House continuously; filings appear in the list within days of submission. The curated list ordering is regenerated when the underlying data moves meaningfully (company count changes by more than 5%, a new company enters the top-ranked segment, or the filed-revenue numbers for the top firms change). You can see the last-updated timestamp near the top of the page.
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Frequently asked questions
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