HTR-PM – Nuclear-heated gas producing superheated steam

The first HTR-PM (High Temperature Reactor – Pebble Module), one of the more intriguing nuclear plant designs, is currently under construction on the coast of the Shidao Bay near Weihai, China.

This system uses evolutionary engineering design principles that give it a high probability of success, assuming that the developers and financial supporters maintain their steady progress. Considering the fact that the plant is a logical follow-on to a successful prototype that has been operating since 2000 and that it is being developed by long-term thinking Chinese engineering and constructors there does not appear to be much development risk. Since the project appears to have the solid backing of the Chinese government, there does not appear to be much risk of sudden funding removal.

Here is a link to an April 2014 update presentation given to the IAEA – HTR Progress in China.

It does a good job of describing the technical foundations of the plant design and the reasons why the system is considered to have a high degree of inherent safety.

In basic layout, the power plant will share a number of features with the second stage of a modern combined cycle power plant. In a combined cycle power plant, the exhaust gases from combustion turbines are directed to a heat recovery steam generator (HRSG).

Those combustion product gases enter the HRSG at a temperature somewhere close to 750 C and leave that HRSG at a temperature of about 250 C. On the other side of the HRSG heat transfer tubes, feed water enters and boils, leaving the HRSG as superheated steam with a temperature somewhere close to 565 C and a pressure of 13-15 MPa. In most cases, the steam output of two or more gas turbine/HRSG modules is combined to drive a single steam turbine train, which might include both a high pressure and a low pressure turbine.

Interestingly enough, those are the same conditions produced in the HTR-PM.

For the demonstration plant, two reactor modules, each producing 250 MWth in a large, low power-density pebble bed reactor produce high temperature gas that enters the reactor at 250 C and leaves the reactor at 750 C. That hot gas (helium in the case of the HTR-PM) is moved by a circulator (the gas equivalent of a pump) into a steam generator that has feed water coming in and steam going out. The steam conditions are 565 C and 13.2 MPa. The output of the two steam generators is combined to drive a single 210 MWe steam turbine.

As described in the literature, this demonstration configuration was chosen to gain experience with multiple modules with the full intention of eventually producing larger output power plants by using more reactor/steam generator modules connected to larger steam turbines.

There are conceptual designs for 4, 6, 8 and even 10 reactor modules all connected to a single steam turbine. The designers are sticking with smaller power output reactors. Calculations tell them that if they keep total output power less than 300 MWth they can make a testable claim of inherent safety. No conceivable event can lead to a situation where the temperature in any part of the core exceeds the 1600 C design temperature for the TRISO particle fuel.

If no accident leads to temperatures that can cause fuel damage, there is no need to devise additional safety systems or features to remove heat.

HTR-PM Reactor Vessel and Steam Generator  (via Next Big Future)

HTR-PM Reactor Vessel and Steam Generator
(via Next Big Future)

There are several evolutionary paths available based on this design advancement. One path would be to implement a phased replacement of coal fired boilers with HTR-PM reactor/steam generator modules. China has a large and rapidly growing inventory of modern steam plants that currently require burning about 3.5 billion tons of coal per year, resulting in places where the air is almost too foul to breathe.

Moving all of that coal from the source to the power plant is also a major burden on the country’s straining rail and barge transportation network. Replacing coal boilers with nuclear heat sources would eliminate the main drawbacks of the power plants while fully using the rest of the installed infrastructure of cooling water, steam plant, transmission lines, and trained operators/maintenance staffs.

Another direction available is to gradually increase the temperature capability of the pebble bed to the point where the gas is hot enough to drive a direct cycle gas turbine whose exhaust can then be directed to the steam generator for a higher efficiency, higher power output combined cycle system.

The Chinese purchased their initial TRISO fuel manufacturing capability from the Germans and their designs have a great deal in common with the HTR program being pursued in Germany up until the end of the 1980s. In that program, demonstrated gas temperatures reached 950 C with future plans of hitting 1100 or 1200 C as the manufacturing techniques improved.

As demonstrated in the German program, TRISO fuel particles do not have to be UO2, a wide variety of actinide compounds including UC, PuO2, and ThO2 have been tested and are available for future use.

One of the things that I find incredibly invigorating about nuclear technology is the almost endless horizons and options for creatively using energy dense, ultra-low emission fuel sources to create useful heat that does not require wholesale reengineering of our basic infrastructure. We can reuse a large portion of what we have already built and already learned how to effectively operate and maintain.

If you are as interested in high temperature reactors as I am, you might want to learn more about HTR-2014, The 7th International Topical Meeting on High Temperature Reactor Technology. It is being held in China in Weihai, close to the HTR-PM construction site, from October 27-31. Tours of the site will be offered as part of the conference program.

Additional reading

Next Big Future (April 2013) HTR-PM High Temperature Pebble-Bed Modular Status in China March 2013

Fission is an elegant way to heat a gas

What if it was possible to combine the low capital cost, reliability, and responsive operations of simple cycle combustion gas turbines with the low fuel cost and zero-emission capability of an actinide (uranium, thorium, or plutonium) fuel source? Machines like that could disrupt a few business models while giving the world’s economy a powerful new […]

Read more »

Nuclear-Powered Trans-Ocean Shipping – 3rd place in New York Advanced Energy contest

I received an update from Benjamin Haas, the SUNY Maritime student who has been working on nuclear powered ship designs from a complete systems perspective for the past three semesters. He and his team have not just focused on the technical aspects of designing a power plant and a ship that could take full advantage […]

Read more »

B&W mPower cover story about lack of interest is bogus

Update: (June 20, 2014) Here is the chart of B&W’s stock price during the past year. It is interesting to note the 10% drop between May 9, 2014 and May 18, 2014 and the fact that the stock continues to trade in a range centered around the new, lower price established after that drop. End […]

Read more »

SMRs – Why Not Now? Then When?

I have shamelessly borrowed the title of one of the talks given during the first day of the Nuclear Energy Insider 4th Annual Small Modular Reactor (SMR) Conference as being representative of both the rest of the agenda and the conversations that I had in the hallways during the breaks. For the past five years, […]

Read more »

Westinghouse’s Roderick shifts resources from SMR to AP1000

NuScale was the sole winner in the latest round under the DOE’s Funding Opportunity Announcement (FOA) for small modular reactors (SMR). The DOE announced its decision in December 2013. As a result of that decision, Westinghouse has shifted internal resources from working on a 225 MWe SMR to focus more on continued refinements and completion […]

Read more »

Accelerator Driven System promoters are playing to irrational antinuclear fears

By Ed Pheil I mentioned at the Thorium Energy Conference 2013 that accelerator driven systems (ADS) were likely to hurt the nuclear industry more than help it with the following discussion. The ADS proponents are justifying their participation, including with thorium, on the basis of two concepts that cater to the anti-nuclear crowd. A) ADS […]

Read more »

Fantasy Crossfire debate: Ed Lyman versus Rod Adams on fast breeder reactors

CNN has done a masterful job of seizing the opportunity provided by Robert Stone’s thought-provoking Pandora’s Promise to generate a passionate discussion about the use of nuclear energy — a vitally important topic — at a critical time in American history. The decision makers at that somewhat fading network should be congratulated. Of course, generating […]

Read more »

I want a nuclear plant in my backyard. So do some of my neighbors

  Watch more video from the CNN channel on Frequency   Though I sometimes suffer from the blues, I am not crazy — I swear. Even though I am just a guy who often blogs in my PJs, I’m also pretty sure that I am not a nobody. In fact, none of us are nobodies, […]

Read more »

On Plutonium, Nuclear War, and Nuclear Peace

By NNadir I trust — and I hope I am justified in this — that no one wants a nuclear war. I know I don’t. We already have a set of environmental problems that are worse than a limited nuclear war, and may be facing an environmental crisis that might be as dire as a […]

Read more »

Big bets in energy technology from “Beyond Petroleum”

As an energy industry observer with a long memory, I was somewhat bemused by a recent interview aired on Platts Energy Week. Bill Loveless sat down with David Eyton, BP’s head of technology, to talk about the exciting new technologies that his company is developing. The company is making substantial investments; in June 2013, BP […]

Read more »

Open letter to Ralph Nader from Timothy Maloney – Atomic energy is much better than you think

By Timothy Maloney, PhD Editor’s note: Timothy Maloney has written a number of text books about electrical circuits, electricity, and industrial electronics. The below is a copy of a letter that he wrote to Ralph Nader in response to an opinion piece published by CounterPunch under the headline Why Atomic Energy Stinks Worse Than You […]

Read more »