BN-800_Nuclear

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Chapter 17 Backup Plan - BN-800 NUCLEAR BOILER Directory
The purpose of the page is to identify a more-mature but less suitable substitute for the thorium-fueled molten salt reactor.

Backup Plan - BN-800 NUCLEAR BOILER
The thorium-fueled molten salt reactor is not a well-proven technology.

The Russian Rosatom BN-800 is a fully mature fast-neutron, sodium cooled power plant.

The BN-800 is rated to produce 880 megaWatts (e) (OKBM Afrikantov design being built at Beloyarsk 4 and due to start up in 2014). It has 3 independent internal steam generators that produce superheated steam which, in turn, heats steam generators, producing the various types of high-pressure steams - saturated, superheated, and reheated - needed to power turbogenerators. A successor to the BN-600, which went on line in 1980 (and is still running), this is a mature product, is currently under construction in Russia, and is scheduled to come on-line in 2014. A BN-1200 is on the drawing boards, scheduled to be running by 2020.

The author suggests that possibly the 3 high-pressure steam generators could be replaced with three unpressurized liquid sodium-to-liquid HITEC salt heat exchangers instead for both greater efficiency and greater safety.

Fast-neutron reactors take a huge initial load of fissile fuel. Global nuclear fuel supply limitations mean only a few can be brought on-line each year, severely limiting the possibility that this type of reactor will ever be able to make a significant contribution in the struggle against Global Warming.

Two additional BN-800s (with a different core configuration) were sold to China in 2010. If there were a market for it, the BN-800 could be in mass production very quickly. As things stand now, the Russians have made many engineering improvements to the BN-800 and the BN-800 is now considered a prototype for a successor, the BN-1200, scheduled to go on-line in 2020. A fast-neutron reactor, the BN-800 could be configured as a breeder reactor thereby reducing its need for uranium fuel by a factor of more than 50. Unlike the Thorium-Fueled Nuclear Boiler, the BN-800 cannot go more or less automatically for 30 years between refueling. Click for larger, sharper view.

Plan "B's" reactor is designed to be as inexpensive as possible. Over half of the world's supersized coal-burning power plants are on navigable water so this one comes on what, at first sight, seems to be a poorly-proportioned Panamax (Max Size: 106'W, 965'L, 39'D) barge. The nuclear boiler is guesstimated to weigh about 500 tons, standard ocean-going barges typically can carry as much as 3,000 tons. The dotted line indicates how a "Parking Slip" would be cut into the beach next to the power plant. Once the barge is parked on its pilings (not shown), the slip is then filled with dirt to hold the barge in place.

The configuration shown above would use unpressurized molten HITEC heat transfer salt rather than unpressurized molten metallic sodium as the secondary coolant to carry the BN-800's heat to the steam generators. Since the BN-800 produces only 910°F heat, natural gas-fired booster stages in the both the superheater and reheater would boost the steam to the 1,000°F required by the original power plant's turbogenerator. This is necessary to keep the steam from cooling so much it turns into turbine blade and bucket-damaging fog as it reaches the lower pressure and temperature ends (large end) of the high and intermediate pressure turbine stages.

The Reactor Barge would be mass-produced in the world's shipyards where precision computer controlled heavy steel plate cutters and welders can produce the highest quality product for the lowest cost. Then the Reactor Barge is towed to its power plant and connected to its steam turbogenerator. Since it is a Russian product, it would be part of their "Take-Back" system where, like milkmen, they come around every 18 months renewing the fuel rods, taking the worn-out fuel rods back to their recycling plants in Russia. No accumulation of spent fuel rods at the power plant site occurs under this program. When the reactor is worn out, it is re-floated and taken back also, leaving no residual radiation at the power plant site.

In addition to maximum cost reduction and convenience, the concrete barge confers a substantial number of safety features. In the event something radioactive is spilled, the barge acts as a catch basin preventing the spread of whatever was spilled. Being on navigable water, in the not unlikely event a hurricane or typhoon storm surge overflows the power plant, the 40 foot height of the barge keeps the typically ten foot or so storm surge from entering the barge. In the unlikely event of an earthquake, the barge will "float" on the unsteady earth beneath it as if the earth were water.

The Russian Rosatom BN-800 "Hot Tub" fast-neutron, sodium cooled 880 megaWatt (electrical) nuclear boiler.

This reactor is an upgrade of the very successful BN-600 "Hot Tub" reactor that went on-line in 1980 and is still running.

Like the BN-600, the BN-800 has three heat exchangers and a circulating pump arranged in a circle around the reactor's core - not unlike four people sitting in a hot tub. The sodium primary coolant is unpressurized so it is incapable of making a powerful steam explosion as is the concern with conventional pressurized water reactors.

At 1,000°F the pressure of the steam in the reactor's heat exchangers would be over 2,000 psi.

In the above sketch, the BN-800's three heat exchangers are joined together to provide heat for the new preheater, evaporator, superheater, and reheater.

To keep costs down and minimize the danger of steam explosions, the heat exchangers are of the "shell and tube" type with both the reactor's water and the boiler's water being in tubes running through unpressurized shells. The heat would be carried between the tubes via molten "HITEC" heat transfer salt. The salt goes solid at room temperature so it should be drained into the heated blue drain tanks beneath the heat exchangers before it cools.

Originally, in the early 1980's, Soviet Russia planned to build five BN-800s. Now Russia is currently building a BN-800 next door to the BN-600. They have also sold two BN-800s to China, which is now building them in the Sanming City area. Evolved from the same sized 600 megaWatt (e) BN-600, the 880 megaWatt (e) BN-800 has been improved in many ways. Now, on paper, the BN-800 has been superseded by the BN-1200, scheduled to come on line about 2020.

The BN-800's fuel rods are a bit different than conventional fuel rods. Like conventional fuel rods, they are thin zirconium tubes, but instead of being filled with enriched uranium oxide pellets, they are filled with either uranium or MOX granules. Other fast-neutron reactors, such as the Integral Fast Reactor, use a solid metal fuel rod. Solid fuel rods provide better conduction of heat to the core's primary coolant.

Russia's Power Machines Company has built and successfully tested the lead steam turbine, a K-800-130/3000 of 885 MW capacity, for the fourth unit with BN-800 reactor under construction at Beloyarsk nuclear power plant. The company noted that Beloyarsk-3 with BN-600 already operated three 210-megawatt turbines produced by the power machines. The fourth unit will utilize one large capacity turbine linked to a hydrogen-free turbine generator of high efficiency, heating power margins and substantially greater safety level.

OJSC “Power Machines” and JSC “Engineering Company “ZIOMAR” have entered into a contract for supply of power generating equipment for the new 800 MW power unit construction project of Beloyarskaya NPP. http://www.power-m.ru/eng/Default.aspx

Under the contract Power Machines will perform the design and engineering work, the manufacturing and supply of the 800 MW steam turbine K-800-130/3000 and supplementary equipment as well as of the 890 MW turbogenerator T3B-890-2УЗ. Also Power Machines will perform the erection supervision of the equipment and will supervise the starting works

The first BN-800, a new more powerful (880 MWe gross, 2100 MWt) FBR from OKBM with improved features is being built at Beloyarsk. It has considerable fuel flexibility - U+Pu nitride, MOX, or metal, and with breeding ratio up to 1.3. It has much enhanced safety and improved economy - operating cost is expected to be only 15% more than VVER. It is capable of burning 2 tonnes of plutonium per year from dismantled weapons and will test the recycling of minor actinides in the fuel. The BN-800 has been sold to China, and two units are due to start construction there in 2012.

However, the BN-800 is likely to be the last such reactor design built (outside India’s thorium program), with a fertile blanket of depleted uranium around the core. Further fast reactors will have an integrated core to minimize the potential for weapons proliferation from bred Pu-239. Beloyarsk-5 is designated as a BREST design.

Russia has experimented with several lead-cooled reactor designs, and has used lead-bismuth cooling for 40 years in reactors for its 7 Alfa class submarines. Pb-208 (54% of naturally-occurring lead) is transparent to neutrons. A significant new Russian design from NIKIET is the BREST fast C,°neutron reactor, of 300 MWe or more with lead as the primary coolant, at 540 and supercritical steam generators. It is inherently safe and uses a high-density U+Pu nitride fuel with no requirement for high enrichment levels. No weapons-grade plutonium can be produced (since there is no uranium blanket - all the breeding occurs in the core). Also it is an equilibrium core, so there are no spare neutrons to irradiate targets. The initial cores can comprise Pu and spent fuel - hence loaded with fission products, and radiologically 'hot'. Subsequently, any surplus plutonium, which is not in pure form, can be used as the cores of new reactors. Used fuel can be recycled indefinitely, with on-site reprocessing and associated facilities. A pilot unit is planned for Beloyarsk by 2020, and 1200 MWe units are proposed.

Market Qualms Make Safer Reactor Designs Slow In Coming, Experts Say.
In an "Ingenuity Of The Commons" blog entry for Forbes (4/22), Jeff McMahon wrote, "Safer nuclear reactors have been available for years, but the energy market prefers less expensive conventional designs, a nuclear energy expert from Argonne National Laboratory said Thursday." Argonne Nuclear Energy Division director Hussein Khalil said that there is a "tremendous incentive" to develop "new reactors that have more inherent, intrinsic safety features, and we've been doing this for some time at ANR" and while they have "been developed to a fairly high degree of technical maturity, but none of them have been successfully commercialized yet because it appears they can't yet compete on an economic basis with the existing technology." Khalil said, "liquid-metal and sodium cooled reactors are examples of safer reactor designs," but noted they haven't been selected because it's easier and cheaper to repeat older designs than risk the "'regulatory uncertainty' faced by power companies that risk new designs."