Category Archives: Science & Technology

China Planning Exports Nuclear Reactor III+ Generation

By the end of the year, Chinese companies will begin international marketing of a 1,400 megawatt power reactor based largely on the Westinghouse AP1000.

In return for the right to sell the AP1000 in China, Westinghouse agreed to help Chinese firms use its generation III pressurized water reactor as a template to develop domestic Chinese designs. One is the CAP1400, which is slated for construction in Rongcheng this year. State Nuclear Power Technology Co. President Gu Jun announced Friday that the coming months would also see the beginning of efforts to export the CAP1400, People’s Daily reported.

The marketing will take place in cooperation with Westinghouse, according to the Communist Party newspaper, and the Pennsylvania-based Toshiba subsidiary might also generate business from sales of CAP1400s abroad. In the same press conference, SNPC Chairman Wang Binghua also announced that development of a larger reactor called the CAP1700 would begin this year.

The AP1000 is a two-loop pressurized water reactor planned to produce a net power output of 1117 MWe.It is an evolutionary improvement on the AP600, essentially a more powerful model with roughly the same footprint.

The design is less expensive to build than other Generation III designs partly because it uses existing technology. The design also decreases the number of components, including pipes, wires, and valves. Standardization and type-licensing should also help reduce the time and cost of construction. Because of its simplified design compared to a Westinghouse generation II PWR, the AP1000 has:

  • 50% fewer safety-related valves
  • 35% fewer pumps
  • 80% less safety related piping
  • 85% less control cable
  • 45% less seismic building volume

The AP1000 design is considerably more compact in land usage than most existing PWRs, and uses under a fifth of the concrete and rebar reinforcing of older designs.

Probabilistic risk assessment was used in the design of the plants. This enabled minimization of risks, and calculation of the overall safety of the plant. According to the NRC, the plants will be orders of magnitude safer than those in the last study, NUREG-1150. The AP1000 has a maximum core damage frequency of 5.09 × 10−7 per plant per year.

Used fuel produced by the AP1000 can be stored indefinitely in water on the plant site. Aged used fuel may also be stored in above-ground dry cask storage, in the same manner as the currently operating fleet of U.S. power reactors.

Power reactors of this general type continue to produce heat from radioactive decay products even after the main reaction is shut down, so it is necessary to remove this heat to avoid meltdown of the reactor core. In the AP1000, Westinghouse’s Passive Core Cooling System uses multiple explosively-operated and DC operated valves which must operate within the first 30 minutes. This is designed to happen even if the reactor operators take no action. The electrical system required for initiating the passive systems doesn’t rely on external or diesel power and the valves don’t rely on hydraulic or compressed air systems.

The design is intended to passively remove heat for 72 hours, after which its gravity drain water tank must be topped up for as long as cooling is required.

In April 2010, Arnold Gundersen, a nuclear engineer commissioned by several anti-nuclear groups, released a report which explored a hazard associated with the possible rusting through of the containment structure steel liner. In the AP1000 design, the liner and the concrete are separated, and if the steel rusts through,

there is no backup containment behind it” according to Gundersen. If the dome rusted through the design would expel radioactive contaminants and the plant “

could deliver a dose of radiation to the public that is 10 times higher than the N.R.C. limit” according to Gundersen. Vaughn Gilbert, a spokesman for Westinghouse, has disputed Gundersen’s assessment, stating that the AP1000’s steel containment vessel is three-and-a-half to five times thicker than the liners used in current designs, and that corrosion would be readily apparent during routine inspection.

Edwin Lyman, a senior staff scientist at the Union of Concerned Scientists, has challenged specific cost-saving design choices made for both the AP1000 and ESBWR, another new design. Lyman is concerned about the strength of the steel containment vessel and the concrete shield building around the AP1000. The AP1000 containment vessel does not have sufficient safety margins, says Lyman.

Potentially the most damaging critique of the AP1000 comes from John Ma, a senior structural engineer at the NRC.

In 2009, the NRC made a safety change related to the events of September 11, ruling that all plants be designed to withstand the direct hit from a plane. To meet the new requirement, Westinghouse encased the AP1000 buildings concrete walls in steel plates. Last year Ma, a member of the NRC since it was formed in 1974, filed the first “non-concurrence” dissent of his career after the NRC granted the design approval. In it Ma argues that some parts of the steel skin are so brittle that the “impact energy” from a plane strike or storm driven projectile could shatter the wall. A team of engineering experts hired by Westinghouse disagreed,

In 2012, Ellen Vancko, from the Union of Concerned Scientists, said that “the Westinghouse AP1000 has a weaker containment, less redundancy in safety systems, and fewer safety features than current reactors”.

Source :

http://www.nuclearstreet.com

http://www.wikipedia.com