The First Reactor Permit at a U.S. Chemical Plant Is About Steam. A Ton of Glycol Can Take 5.5 Tons

Most people picture a reactor as a power station: a turbine, a transmission line, a city on the other end. The permit the NRC issued on 9 November for Dow’s site on the Texas Gulf Coast is about something less visible. A chemical plant runs on steam: steam to heat reactors, steam to drive distillation columns, steam to boil water out of products that were made in water. The four reactors in the Seadrift permit are designed to make that steam, and electricity, on the same site that uses it.

This article sets out what the NRC approved, what Seadrift makes, and why a chemical site can need that much heat, using ethylene glycol, the molecule in antifreeze, as the worked example. It takes no position on nuclear power, on the project’s economics or on the licensing process; it reports the decision as the NRC record, X-energy, Dow and the American Nuclear Society describe it. Where a number is our own arithmetic, we say so.

What did the NRC approve for Dow?

A construction permit, not an operating license, for the Long Mott Generating Station: four Xe-100 high-temperature gas-cooled reactors at Dow’s UCC Seadrift Operations site, held by Dow’s subsidiary Long Mott Energy. X-energy’s 9 November release describes the scope: the NRC “has approved the Construction Permit Application (“CPA”) for the proposed construction of four Xe-100 advanced small modular reactors at Dow’s UCC Seadrift Operations site in Texas.” The American Nuclear Society’s report the next day gives the reason the decision is unusual: “It is the first time the NRC has issued a construction permit for a nuclear reactor on an industrial site.”

The same release lists the other firsts: “Issuance marks the first NRC CPA approval of a high-temperature gas-cooled reactor in nearly 60 years, the first-ever pebble-bed HTGR approval and the first-ever for a nuclear industrial deployment.” On timing, ANS reports that “Monday’s issuance means a permit decision was reached within 18 months of the review commencing, a target NRC officials set for the process.”

Why does a chemical plant want a reactor?

For steam first, electricity second. X-energy’s release states the purpose: “The proposed plant is intended to provide both electricity and high-temperature steam to Dow’s site, replacing existing energy and steam assets near their end-of-life.” That is the ordinary reason any plant rebuilds its utilities. What is new is the heat source.

Steam is the chemical industry’s main carrier of heat. The U.S. Department of Energy’s energy footprint of the chemicals sector (2006 data, the most detailed public breakdown) says of the fuel that plants burn on site: “A significant proportion of fuel use, 70%, is used to generate onsite steam and electricity in this sector.” It adds that “The chemicals sector has the largest amount of steam output from CHP units of any of the manufacturing sectors, 416 TBtu.” CHP is combined heat and power: one plant making both electricity and steam, which is what Long Mott is designed to do.

The reactor design suits that job. ANS describes the Xe-100 as “an 80-MWe, 200-MWt HTGR that can be deployed in configurations of four to 12 units.” The gap between the two numbers is the point: each unit makes 200 MW of heat (800 MWt for four, our arithmetic), and only 80 MW of it becomes electricity if all of it goes through a turbine. Heat that goes straight to the process as steam skips that conversion step. X-energy’s reactor page says the Xe-100’s “steam generator produces steam at temperatures up to approximately 565°C”, which is hot enough for the high-pressure steam headers that drive a large chemical site.

What does Seadrift make?

Plastics, glycols and the family of chemicals made from ethylene oxide. Dow’s site page describes it this way: “UCC Seadrift Operations is the second largest Dow facility in Texas, spanning about 4,700 acres and employing more than 1,200 people.” Among the products it lists: “Glycols for antifreeze, polyester fabrics and bottles”, and oxide derivatives for medicines, shampoos, soaps, detergents, window cleaners, brake fluids and paint.

Ethylene oxide is the common thread. It is a three-atom ring, two carbons and an oxygen, under strain, and that strain is why it reacts with almost anything that has a hydrogen to give. Open the ring with water and you get ethylene glycol. Open it with ammonia and you get the ethanolamines, starting with monoethanolamine (MEA). Open it with ethanol and you get 2-ethoxyethanol, sold as Glycol Ether EE. Each of those reactions gives off heat; the steam bill comes afterwards, in separating the product from everything that was added to steer the reaction.

One strained ring, three products

Ethylene oxide opens with water, ammonia or ethanol. Pick a partner; drag to turn the molecules.

+ water+ ammonia+ ethanol

Ethylene oxide + water → ethylene glycol

Our report on ethylene oxide exposure limits covers why the intermediate itself is handled so tightly. Buyers rarely see it: what leaves an oxide site are the derivatives.

How much steam does it take to make a ton of ethylene glycol?

On the conventional route, about five and a half tons. The figure is in a Mitsubishi Chemical patent for an ethylene glycol process (EP0776890, priority date 1995), and it comes from water, not from the reaction itself.

The reaction is simple: one molecule of ethylene oxide and one of water give one molecule of ethylene glycol. The difficulty is that ethylene glycol also reacts with ethylene oxide, giving diethylene glycol, then triethylene glycol. The patent explains the fix: “The larger the ratio of water to the ethylene oxide, the higher the selectivity of ethylene glycol becomes.” So plants flood the reactor: “an excess amount of water, i.e. 10 - 25 times the molar quantity of ethylene oxide, is often supplied for hydration reaction.” The result is a weak solution: “the concentration of the ethylene glycol obtained after completion of the reaction is at most around 10 - 20 % by weight.”

Every kilogram of that surplus water then has to be boiled off. The patent puts a number on it for a 20-to-1 feed: “when water in a molar quantity 20 times that of ethylene oxide is supplied, the heat necessary for removing by evaporation the unused water in a molar quantity about 19 times that of ethylene glycol, is 170 kcal per mole of ethylene glycol.” And then the line that matters to a site’s utility planner: “That means about 5.5 tons of steam is consumed for 1 ton of ethylene glycol.”

The patent’s numbers check out against molar masses. Ethylene glycol is 62.07 g/mol and water 18.015 g/mol (PubChem). The rest of this table is our arithmetic.

The water evaporated and the steam consumed come out at almost the same mass, about 5.5 tons each, which is what you would expect if one kilogram of condensing steam boils off roughly one kilogram of water. Real plants do better than that one-for-one with multiple-effect evaporators, which reuse the vapour from one stage to heat the next, and the patent itself is a design for using less energy. Catalytic routes that run with less water exist too. The 5.5-ton figure is the baseline those designs are measured against, not a number for any particular plant, Dow’s included.

Is glycol made this way the same as the glycol in a drum of antifreeze?

Yes. Ethylene glycol is one molecule, HOCH₂CH₂OH, whatever heated the evaporator. Steam from a reactor, a gas boiler or a waste-heat recovery unit leaves no trace in the product. Our report on Eastman’s methanolysis award shows glycol recovered from PET is the same molecule too. What differs from lot to lot is purity: water, diethylene glycol, aldehydes and trace metals. That is a matter for the certificate of analysis, not the energy source.

The patent also explains why the higher glycols exist as products at all. The diethylene and triethylene glycol that the excess water is there to suppress never fall to zero, so every glycol plant makes some, and they are sold on their own. Our ethylene glycol complete guide covers the grades and coolant blends, and our propylene glycol versus ethylene glycol guide covers when the other glycol is the better choice. Ethylene glycol is toxic if swallowed, and its sweet taste is why antifreeze is kept away from children and animals.

What this means on a specification

Seadrift’s permit changes nothing on a certificate of analysis. It is a reminder that three chemicals buyers treat as unrelated, a coolant base, an amine and a solvent, come off the same ethylene oxide chemistry. The table matches the work to the grades as they are named on our storefront.

Two handling notes. Glycol Ether EE (2-ethoxyethanol) carries reproductive-toxicity hazard statements on its safety data sheet, so read the SDS and use ventilation, gloves and eye protection. MEA is corrosive to skin and eyes. Our guide to monoethanolamine and guide to glycol ethers cover uses and handling. For the water side of a steam system, see how deionized water is made and sodium bisulfite for boiler corrosion control.

About supply. This article reports a licensing decision and the companies’ stated plans as published by X-energy, Dow and the American Nuclear Society, and works through the chemistry from a public patent, DOE data and PubChem. Alliance Chemical has no connection to Dow, X-energy or the Long Mott project. The article makes no claim about ours: it does not say where the ethylene glycol, MEA or glycol ether we list is made, or how this decision touches the supply or price of any of them. Prices are on the product pages and change with pack size.

Common questions

What did the NRC approve at Dow’s Seadrift site?

A construction permit, issued on 9 November 2026, for the Long Mott Generating Station: four X-energy Xe-100 high-temperature gas-cooled reactors at Dow’s UCC Seadrift Operations site in Texas. It is the first NRC construction permit for a reactor on an industrial site. An operating license is still needed before fuel loading, and Dow expects to consider a preliminary investment decision in 2027.

Why would a chemical plant want a nuclear reactor?

For steam as much as for electricity. Chemical plants use steam to heat reactors, run distillation and evaporate water. X-energy says the Long Mott plant would supply electricity and high-temperature steam to the site, replacing existing energy and steam assets near the end of their life. Each Xe-100 makes 200 MW of heat and steam at up to about 565°C.

How much steam does it take to make ethylene glycol?

A Mitsubishi Chemical patent (EP0776890) gives about 5.5 tons of steam per ton of ethylene glycol for a conventional process fed with 20 moles of water per mole of ethylene oxide. On our arithmetic that matches about 5,514 kg of surplus water evaporated per ton of glycol. Modern evaporator designs and catalytic routes use less.

Why do ethylene glycol plants use so much water?

To stop the glycol reacting further. Ethylene glycol reacts with ethylene oxide to make diethylene and triethylene glycol, so plants feed 10 to 25 times as much water as ethylene oxide, which favours the single glycol. The reactor product is only about 10 to 20% glycol by weight, and the rest of the water has to be boiled off.

What chemicals are made from ethylene oxide?

Ethylene glycol (with water), the ethanolamines such as monoethanolamine (with ammonia) and glycol ethers such as 2-ethoxyethanol, sold as Glycol Ether EE (with an alcohol). Dow lists glycols and oxide derivatives among the products made at Seadrift, alongside polyethylene.

Does the Seadrift permit change ethylene glycol or MEA supply?

The reporting does not say, and this article makes no forecast for the price or supply of any chemical. The permit allows construction to proceed; Dow has not yet made an investment decision, and X-energy’s stated timeline for first delivery is the early 2030s.

What we stock

Ethylene Glycol ACS Grade

For lab work, polymer research and analytical standards.

100% Ethylene Glycol Inhibited

Concentrate for heat-transfer loops, mixed on site.

Monoethanolamine (MEA) Technical Grade

For gas sweetening, pH control and formulation. ACS grade also listed.

Glycol Ether EE Technical Grade

2-Ethoxyethanol solvent for coatings, inks and resins. ACS grade also listed.

Key numbers and sources