Soviet Supercritical Water Reactors?

[Delta Force]

The Soviet Union constructed at two AMB series supercritical water reactors at Beloyarsk in the late 1950s, AMB-100 (Beloyarsk 1) and AMB-200 (Beloyarsk 2). They apparently achieved a mid-30% conversion efficiency, on par with more modern nuclear power stations and much better than the efficiencies observed in the Magnox units and at Shippingport. Does anyone know of a good source for more information on the AMB series reactors? Did the Soviet Union carry out any additional research on nuclear applications of supercritical water technology?

 

[Delta Force]

I know supercritical water is considered an advanced reactor technology even now. Were there any issues with the Soviet reactors that led them to pursue alternative designs, or was it more that the VVER and RBMK designs were a simpler way to do the same thing?

 

[etudiant]

The Soviets tried several unconventional designs, including one which used a lead bismuth alloy in molten form as the reactor coolant..
Here and also in the critical water design, the problem was that the materials technology.was inadequate to the task.
The molten metal coolant began to dissolve the reactor internals. I'd expect the supercritical water was similarly challenging, but have not seen any summary reports.

 

[Astronuc]

Here is a paper published through IAEA.
IAEA-CN-164-5S12, V.A. Yurmanov, V. N.Belous, V. N.Vasina, E.V. Yurmanov, "Chemistry and Corrosion Issues in Supercritical Water Reactors," (cites some references).

and presentation http://www-pub.iaea.org/MTCD/publications/PDF/P1500_CD_Web/htm/pdf/topic5/5S12_V. Yurmanov_PM.pdf

from IAEA International Conference on Opportunities and Challenges for Water Cooled Reactors in the 21st Century
26-30 October 2009, Vienna

One may wish to acquire a copy of the papers from the International Workshop on
SUPERCRITICAL WATER AND STEAM IN NUCLEAR POWER ENGINEERING: PROBLEMS AND SOLUTIONS
22-23 October 2008, NIKIET, Moscow
(24 papers)

The Wikipedia page reports electrical generation capacity for both units:
AMB-100 108 MWe
AMB-200 160 MWe

and later in the article, it states, "In 1977 half of the fuel rods melted down in the ABM-200 reactor. Operators were exposed to severe radiation doses, and the repair work took more than a year." No reference is cited for this, but I'm curious, so I'll look around.

There is this page - http://sosnycompany.com/performed-projects/preparation-of-the-amb-100-and-amb-200-reactor-snf-for-transportation-and-reprocessing-at-mayak-pa.html - in which it is reported, "About 40% of the SFAs at the Beloyarsk NPP is stored in carbon steel leaky baskets, and most of the SFAs in the baskets have corroded." Could be galvanic corrosion in SFP, but I don't know if this is inherent in SCWR fuel.

I saw some presentations on SCWR fuel cladding materials back in 2006. I noted high corrosion rates, but that was in unirradiated conditions, i.e., without the effects of neutron and gamma radiation in the cladding alloy or radiolysis in the water. Adding a radiation field can increase corrosion rates by factors of 2 or 3 at least, as compared in non-irradiation conditions. Erosion-corrosion is an issue.

It looks like the AMB reactors were graphite moderated, as opposed to water moderated (a problem for high temperature water), as is the case for conventional LWRs. Some SCWR concepts have considered hydride fuel or metal hydride moderators. So the neutronic aspects of moderation and reactivity distribution and control have been challenges.

 

[Delta Force]

Thank you for these sources Astronuc. Could you clarify some of the issues raised in the first presentation?

On Page 6 the AM reactor is mentioned. AM-1 was the Obninsk reactor, which Wikipedia further claims was the forerunner to the RBMK series. There are some similarities in design between the RBMK and AMB series designs (graphite moderated water light water cooled designs), so might RBMK and AMB have been different branches of development from a common AM reactor ancestor?

On Page 8 there are some diagrams of the AMB-100 and AMB-200 loops. Can you explain what's going on in them? The AMB-100 diagram looks vaguely like a pressurized water reactor, while the AMB-200 diagram looks vaguely like a boiling water reactor.

On Page 9 it mentions that ammonia was added to the reactor coolant to prevent hydrolysis. Ammonia-water mixtures are one of the mixtures used for the Kalina Cycle, might there have been any findings relating to that? I've wondered if the Kalina Cycle has ever been considered for nuclear power plants.

On Page 10 "crud deposition" is mentioned, and "fuel crud" on Page 12. Is that something similar to how carbon deposits would build up on reactor surfaces in some organically cooled reactors? Organic contaminants are even mentioned as an issue to be aware of in Page 17. How did organic contamination occur?

On Pages 19-21 it mentions the possibility of developing fast breeder reactors using supercritical water technology (something Wikipedia mentions as a possibility here as well). Aren't water cooled/moderated reactors limited to being thermal breeders? Does graphite moderation allow for fast breeding? Also, given the risks of water cooled graphite moderated reactors, is there any elevated risk using a supercritical water cooled graphite moderated fast breeder reactor?

Thank you once again for the sources. I hope these questions make sense, I'm not trained in reactor physics or engineering so these might be basic questions for those fields.

 

[Astronuc]

. . . these might be basic questions for those fields.

All good questions. I'll attempt to answer as best I can.

As to the first question about the succession of AM-1 to AMB-100 and AM-200, it does appear that the concepts demonstrated in AM-1 were the foundation for RBMK and later AM units. In paper, http://www.nikiet.ru/eng/images/stories/NIKIET/Publications/Conf/mntk_nikiet_2014/P-1_en.pdf , it states:

In 1957 in loop-type facilities of the AM reactor a nuclear production of superheated steam was carried out for the first time ever. Conditions for water boiling in evaporation channels and for steam superheating in superheating channels for the designed AMB-1 and AMB-2 reactors of Beloyarsk NPP were validated.

Subsequently in the paper:

Pressure tube line of power reactor building gained its further development in the USSR in the middle 1960-s, when the objective of a development of a large NPP unit with a pressure tube boiling water reactor was set in order to increase electric power production in the European part of the USSR. The requirement was for the reactor allowing for production of its main equipment at existing machine-building plants.

In 1965-1969 this challenge was met by the development team from IAE named after I.V. Kurchatov (scientific leader), NIKIET (chief designer), VNIPIET/AEP (general architect engineer). In the 1973-1990 period there were 15 power units with RBMK-1000 constructed within Russia and Ukraine, and 2 power units with RBMK-1500 in Lithuania.

I'll have to study the diagrams of the AMB-100 and AMB-200 to understand where the fuel is in relation to the SCW.

Hydrogen is added to cooling water in LWRs in order to reduce free oxygen which attacks stainless steel by stress-corrosion cracking. Ammonia is one way. As for the Kalina cycle, I've seen proposals of using the Kalina cycle as a bottoming cycle in NPPs. I'll have to look in my library for the details.

Crud is inherent in any power system which uses water. Basically, one is struggling with the tendency of the metal alloys to oxidize, i.e., revert back to their natural state of being oxides/hydroxides. Crud occurs as metal cations move from metal surfaces (dissolution) to heated surfaces and in the process become oxides, oxyhydroxides or hydroxides, and settle on heated surfaces, especially where boiling occurs. One controls crud deposition by controlling water chemistry, i.e., pH and electrochemical potential in the coolant.

Carbon deposition in organic systems is a bit different in that it involves radiolysis of organic compounds, whereby free carbon or perhaps methylene (CH₂) forms. Methylene can dissociate in a radiation environment to form C and H₂.

In supercritical water, the density of the water is reduced, which hardens the neutron energy spectrum, i.e., the fast neutron component increases while the thermal component decreases. Fast spectrum is desirable for breeding Pu from U-238. Graphite reactors tend to be epithermal, i.e., the average neutron energies shift into eV range rather than fractions of eV.

There are risks with any power system, and it is incumbent upon the designer to understand where the risks lie and design accordingly to mitigate the risks. In other words, one must identify the 'Achilles heel' or potential failure points and select appropriate design remedies, e.g., material composition, microstructure, geometry, and environmental conditions.