MIT Spinoff Apollo Atomics Raises $31M to Shrink Nuclear Reactors by 40x
Apollo Atomics, an MIT spinoff developing compact nuclear reactors, has raised $31 million in seed funding as it works to make nuclear power smaller, faster to manufacture and easier to deploy.
The Cambridge, Massachusetts-based startup was founded in 2025 by Assil Halimi and Drew Walker. The funding round was led by FCVC and includes $26 million in equity and $5 million in debt, with backing from investors including Y Combinator, Telesoft Partners, Alumni Ventures, Robinhood Ventures and Nucleation Capital.
Unlike many nuclear startups developing entirely new reactor technologies, Apollo is building on the established pressurized-water reactor design. Its key innovation is a redesigned steam generator, one of the largest components in a conventional nuclear power plant.
Apollo says its new steam generator achieves around 10 times the power density of conventional systems, allowing the overall reactor footprint to be reduced by approximately 40 times. The compact design could enable reactors to be manufactured in factories, transported to sites and assembled significantly faster than traditional nuclear plants.
The company is developing three reactor models: the 10-megawatt A-10, 50-megawatt A-50 and 300-megawatt A-300. Apollo says it has received letters of intent representing more than 20 gigawatts of potential demand.
The new funding will support the development of its 1-megawatt A-1 demonstration facility, long-duration reliability testing, manufacturing capabilities and regulatory work with the U.S. Nuclear Regulatory Commission.
Apollo has already built a reactor-system demonstrator at MIT and says its commercial fuel configuration has achieved full-power criticality.
The startup is targeting commercial deployment in 2028, with ambitions to make nuclear power more competitive with conventional energy sources while meeting growing electricity demand from data centers, industry and other large-scale users.
If successful, Apollo’s factory-built approach could mark a significant shift from nuclear power’s traditional megaproject model toward smaller, standardized and rapidly deployable reactors.
AI Accounting Startup Rillet Becomes a Unicorn With $100M Series C Led by ICONIQ
AI accounting startup Rillet has raised $100 million in a Series C funding round led by ICONIQ, taking the company’s valuation to $1 billion and making it the latest AI startup to achieve unicorn status.
Rillet is building an AI-native enterprise resource planning platform designed to modernize accounting and financial operations for growing businesses. Its software automates a range of finance workflows, helping companies manage accounting, reporting and other core financial processes through a unified platform.
The latest funding comes roughly a year after Rillet secured $70 million in its Series B round. The company has now raised more than $200 million in total funding as demand for AI-powered business software continues to grow.
Rillet was founded by Nicolas Kopp and Stelios Modes, who saw an opportunity to rethink traditional accounting systems that often require significant manual work and rely on fragmented software. Instead, the company is developing an ERP platform with AI built into its core rather than added as an extra feature.
The startup has reported rapid growth over the past year, with its annual recurring revenue doubling repeatedly as more companies adopt its platform. Rillet now serves more than 600 customers, ranging from startups to rapidly expanding technology companies.
The company has also strengthened its enterprise presence through partnerships with major professional-services firms, helping businesses integrate AI into their finance and accounting operations.
Rillet’s latest fundraise highlights the growing investor appetite for AI applications that tackle critical business functions. While much of the AI boom has focused on consumer applications and foundation models, enterprise software is increasingly becoming another major area of investment.
With its new unicorn valuation, Rillet will use the fresh capital to expand its product, grow its team and accelerate adoption among larger businesses.
The company now faces competition from established ERP providers and a growing number of AI-native accounting startups. Its ability to maintain rapid growth while handling increasingly complex enterprise financial operations will determine whether Rillet can turn its billion-dollar valuation into a lasting position in the accounting software market.
Etched Raises $700M Led by Jane Street, Doubling Valuation to $21B
AI chip startup Etched has raised $700 million in a new funding round led by Jane Street, reportedly doubling its valuation to $21 billion. The massive investment highlights growing confidence in specialized AI hardware as demand for computing power continues to accelerate.
Founded in 2022, Etched is taking an unusual approach to the AI chip market. While major semiconductor companies develop multiple types of processors designed for different applications, Etched is focused on building a single category of chip known as an application-specific integrated circuit, or ASIC.
The company’s strategy is built around specialization. Etched is designing its chip specifically for transformer-based AI models, the architecture behind many of today’s most widely used generative AI systems. By focusing on a particular workload, the startup believes it can deliver faster and more efficient AI inference than more general-purpose hardware.
The latest funding gives Etched significant financial firepower to expand its engineering teams, strengthen its hardware and software ecosystem and scale its commercial operations. The company is also competing in an increasingly crowded AI accelerator market, where startups are attempting to challenge the dominance of traditional GPU-based computing.
Etched’s valuation is particularly striking because the company has remained highly focused rather than developing a broad portfolio of chips. That narrow strategy could ultimately become one of its biggest advantages or risks.
If transformer-based models continue to dominate AI workloads, a chip designed specifically for them could offer major performance and efficiency benefits. However, rapid developments in AI could also create new architectures and workloads that require different hardware.
The funding round reflects a broader trend in the technology industry: investors are increasingly willing to place large bets on specialized infrastructure that can support the next phase of AI growth.
With $700 million in fresh capital and a $21 billion valuation, Etched has emerged as one of the most valuable AI chip startups. Its next challenge will be proving that a company making essentially one kind of chip can compete in a market evolving at extraordinary speed.
Temporal in Talks to Raise $500M at $12B Valuation
Temporal, the software infrastructure startup known for helping developers build reliable applications and workflows, is reportedly in talks to raise $500 million in a new funding round at a pre-money valuation of $12 billion.
If the deal goes through at the reported terms, it would more than double Temporal’s valuation in just six months, highlighting the growing investor interest in software infrastructure powering artificial intelligence and other large-scale applications.
Temporal provides a platform for building and managing complex workflows that can run reliably over long periods. Its technology allows developers to create applications that can recover from failures, resume interrupted processes and coordinate multiple services without requiring teams to build these capabilities from scratch.
The company’s technology has become increasingly relevant as businesses deploy more sophisticated software systems and AI applications. Modern AI-powered products often require multiple steps, tools and services to work together, creating a greater need for reliable systems that can manage these processes.
The proposed $500 million investment would give Temporal significant capital to expand its technology, grow its workforce and strengthen its position in the infrastructure market. It could also help the company accelerate its push into AI-related workloads as businesses increasingly rely on autonomous software and AI agents.
The reported $12 billion pre-money valuation would make Temporal one of the most highly valued private infrastructure software companies. The sharp increase also reflects the broader enthusiasm surrounding companies that provide the foundational technology needed to support the AI boom.
However, Temporal is not alone in the market. It faces competition from established cloud providers and other infrastructure startups seeking to capture demand for workflow automation and orchestration.
The potential transaction is still under discussion, meaning the final amount and valuation could change.
If completed, the deal would nevertheless mark a major milestone for Temporal. More importantly, it would demonstrate how quickly investor expectations are shifting toward infrastructure companies that could become essential to the next generation of AI-powered software.
Former SpaceX Engineers’ Castelion Raises $1B at $13B Valuation
Castelion, a defense technology startup founded by former SpaceX engineers, has raised $1 billion in new funding at a reported valuation of $13 billion, marking a major milestone for the young company and highlighting growing investor interest in next-generation defense technology.
The company was founded by a team with backgrounds in aerospace and advanced engineering, including experience at SpaceX. Castelion has attracted attention for its focus on developing advanced defense systems and bringing commercial-sector approaches to a traditionally slower-moving industry.
The latest funding round represents a significant increase in the company’s value and gives Castelion substantial financial backing as it expands its operations. The investment comes amid a broader surge in private capital flowing into defense and aerospace startups, driven by rising government demand and increasing geopolitical tensions.
Castelion’s approach is centered on applying modern engineering, software and manufacturing philosophies to defense development. The company has positioned itself as a technology-focused alternative to established defense contractors, seeking to move from development to production more rapidly.
The $13 billion valuation places Castelion among the most valuable private companies in the emerging defense technology sector. Its rapid rise also demonstrates how investors are increasingly viewing defense as a major technology market rather than a sector dominated exclusively by traditional contractors.
The company is expected to use the new capital to expand its workforce, infrastructure and overall development efforts while pursuing contracts and partnerships within the defense ecosystem.
Castelion’s growth comes as governments seek to strengthen domestic defense capabilities and accelerate the development of advanced systems. Startups with experience in commercial aerospace and technology are increasingly being viewed as potential sources of innovation in this effort.
However, the company will face significant challenges as it scales, including regulatory requirements, complex government procurement processes and the difficulties associated with turning ambitious technology programs into reliable products.
With $1 billion in fresh capital and a $13 billion valuation, Castelion has emerged as a major player in the defense startup landscape. Its progress will be closely watched as private investment continues reshaping the aerospace and defense industry.
