It's Monday. The nuclear industry has spent decades arguing about where to put a reactor and what to do with it afterward. One startup's answer to both is the same hole.
In today's edition:
🔬 Big Story: DOE clears a reactor design meant for a mile underground
⚡ Quick Hits: China's 12.8 GWh cluster, a utility's own LTE network, Wednesday's eclipse
💰 Capital: Spain funds co-located storage
📋 Policy Watch: a court upholds queue reform, a polysilicon tariff lands
📊 Chart of the Day: US batteries clear 52 GW
The Big Story
DOE approves the safety design for Deep Fission's mile-deep reactor.
Deep Fission, a California company founded in 2023, said on August 6 that the Department of Energy signed the Nuclear Safety Design Agreement for its Gravity Nuclear Reactor, a pressurized water reactor built to sit in a borehole a mile underground. The agreement sets the safety framework for the design and moves the company to the next segment of DOE authorization under the Reactor Pilot Program. It is not an NRC license. Each unit is rated at 15 MWe, and the company says ten produce 150 MWe on a fraction of the land a surface plant needs. Work is underway at Parsons, Kansas, where Deep Fission broke ground in December 2025 and has drilled to 6,000 feet.
This approval is a major step forward for Deep Fission. We believe our mile-deep design gives us the ability to move faster in the stages ahead.
Fuel assemblies and power controls are conventional PWR, and the company says hydrostatic pressure from a mile-deep water column supplies the 160 atmospheres a surface plant has to engineer.
Heat moves to a steam generator at depth, and according to Deep Fission non-radioactive steam rises to a standard surface turbine, with cables that let the reactor be raised for inspection.
The company said the Kansas unit is not planned as a one-time criticality test, and that it intends the reactor to become a fully NRC-licensed, commercially operating unit after initial testing.
Source: POWER Magazine
Quick Hits
Technology milestones from across the grid
Four from across the stack, from a record Chinese battery cluster to a grid planning around Wednesday's eclipse.
Envision brought what CleanTechnica calls the world's largest battery storage cluster, 12.8 GWh at the Jingyi Chagan Hada station, into commercial operation after grid verification testing, with AI algorithms running inside the battery management systems. CleanTechnica
Tampa Electric picked Ericsson, OneLayer and Burns & McDonnell for a private LTE network for grid field communications, adding SIM lifecycle management as utilities move critical traffic off leased carrier service. Data Center Dynamics
OPENTUNITY, an EU-backed grid modernisation project, entered live testing of a digital environment meant to let transmission and distribution operators and prosumers exchange flexibility data on common interfaces. Enlit World
Solcast and DNV modelled the August 12 eclipse and put its solar ramp rates in front of European and US operators, a scheduled test of how much fast reserve a solar-heavy system needs. pv magazine
The Capital Stack
Spain puts €360 million behind batteries that share a solar connection.
Spain's Ministry for the Ecological Transition awarded €360 million to 1.14 GW of solar PV co-located with battery storage, according to Energy-Storage.news. The award is structured around the pairing rather than either technology alone, and co-location reuses a grid connection and a permitted site, the two things interconnection queues are shortest of. The subsidy is aimed at the connection point as much as the capacity.
Source: Energy-Storage.news
Also in the capital stack:
Naked Energy won £7 million from Great British Energy inside an £8.9 million round, an early direct equity position for the state-owned company in a solar thermal maker. Enlit World
Policy Watch
The DC Circuit Court of Appeals upheld FERC Order 2023, leaving in place the first-ready, first-served process that RTOs have spent two years rebuilding their queues around. Energy-Storage.news
President Trump signed an executive order imposing a 15% tariff on polysilicon effective December 6, which Data Center Dynamics reports lands on semiconductor and solar supply chains through the same feedstock. Data Center Dynamics
GridX's Scott Engstrom argues in Utility Dive that legacy billing systems constrain new rate designs, since a tariff a utility cannot bill is a tariff it will not offer. Utility Dive
Chart of the Day
US battery storage cleared 52 GW halfway through 2026.
Operators added 8.3 GW of nameplate battery storage in the first six months of the year, on top of 43.6 GW running at the end of 2025, capping three years of 70% average annual growth. Another 54 GW is planned through 2028.
Source: EIA Today in Energy · August 7, 2026
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