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Friday, March 25, 2011

Decommissioning Scenario for Fukushima Dai-ichi

Credit: TEPCO - Fukushima Dai-ichi
Two weeks after the 9.0 earthquake and tsunami that damaged the nuclear power plant Fukushima Dai-ichi the Japanese government and Tokyo Electric have mentioned the likely decommission of the nuclear plant when the current crisis has been overcome.

Decommissioning of Nuclear Power Plants

The process of decommissioning of a nuclear facilities is regulated and includes many administrative and technical actions such as all clean-up of radioactivity and progressive demolition of the plant. Once a facility is decommissioned, there should no longer be any danger of a radioactive accident or to any persons visiting it. After a facility has been completely decommissioned it is released from regulatory control, and the licensee of the plant no longer has responsibility for its nuclear safety. 
The International Atomic Energy Agency (IAEA) has defined three options for decommissioning, the definitions of which have been internationally adopted: Immediate Dismantling (Early Site Release/DECON in the US), Safe Enclosure (SAFSTOR) or Entombment (ENTOMB).

According to the
World Nuclear Association to date, about 80 commercial power reactors, 45 experimental or prototype reactors, over 250 research reactors and a number of fuel cycle facilities, have been retired from operation. Some of these have been fully dismantled. Most parts of a nuclear power plant do not become radioactive, or are contaminated at only very low levels. Most of the metal can be recycled. Proven techniques and equipment are available to dismantle nuclear facilities safely and these have now been well demonstrated in several parts of the world. Decommissioning costs for nuclear power plants, including disposal of associated wastes, are reducing and contribute only a small fraction of the total cost of electricity generation. Some examples of decommissioning are folowing below. 


Safe Enclosure Japan: The Tōkai Nuclear Power Plant (1966-2018) 
One of the first decommissioning projects in Japan was the Tōkai Nuclear Power Plant, the first nuclear power plant in Japan, built in the early 1960s to a 160 MWe British Magnox design, and generated power from 1966 until it was decommissioned in 1998. The plant has passed decommissioning phase SAFSTOR (1998-1999) and DECON will end in 2018. The decommissioning cost was estimated to yen 93 Billion (Euro 660 Million) by the OECD in 2003. JPY 35 billion for dismantling and JPY 58 billion for waste treatment which will include the graphite moderator (which escalates the cost significantly).

Safe Enclosure USA: Three Mile Island (1979-2036)
Credit: CMU 
After the Three Mile Island, Unit 2 (TMI-2) accident on March 28, 1979, which resulted in severe damage to the reactor core, TMI-2 has been in a non-operating status since that time. The licensee conducted a substantial program to defuel the reactor vessel and decontaminate the facility. All spent fuel has been removed except for some debris in the reactor coolant system.
The first robotics vehicle to enter the basement of Three Mile Island after the meltdown, was Remote Reconnaissance Robot 1983 developed by CMU roboticist William L. ''Red'' Whittaker. The robot worked four years to survey and clean up the flooded basement. The CoreSampler, 1984, was a remote vehicle drilling core samples from the walls of the TMI basement to determine the depth and severity of radioactive material that soaked into the concrete at the site.
The plant defueling was completed in April 1990. The removed fuel is currently in storage at Idaho National Laboratory, and the U.S. Department of Energy has taken title and possession of the fuel. TMI-2 has been defueled and decontaminated to the extent the plant is in a safe, inherently stable condition suitable for long-term management. This long-term management condition is termed post-defueling monitored storage, which was approved in 1993. There is no significant dismantlement underway. The plant shares equipment with the operating TMI - Unit 1. TMI-1 was sold to AmerGen (now Exelon) in 1999. GPU Nuclear retains the license for TMI-2 and is owned by FirstEnergy Corp. GPU contracts with Exelon for maintenance and surveillance activities. The licensee plans to actively decommission TMI-2 in parallel with the decommissioning of TMI-1. The current radiological decommissioning cost estimate is $836.9 million. The current amount in the decommissioning trust fund is $576.8 million, as of December 31, 2009. Estimated Date For Closure: 12/31/2036.
Entombment USSR/Ukraine: Chernobyl Case (1986 - 2065)
Credit: Wikipedia - Chernobyl
The worst nuclear power plant accident in history, the only one classified as a level 7 event on the International Nuclear Event Scale, is the Chernobyl nuclear disaster on 26 April 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian SSR (now Ukraine). After a 1991 fire in Reactor 2, this reactor was taken offline, and decommissioned in 1996.

First in 1999, after the End of the Cold War, reconnaissance robot Pioneer entered the radiated plant for structural analysis of the Unit 4 reactor building. Even this robot was developed by CMU roboticist William L. ''Red'' Whittaker and his company RedZone Robotics. The robot was a teleoperated mobile robot for deploying sensor and sampling payloads, with a mapper for creating photorealistic 3D models of the building interior, a coreborer for cutting and retrieving samples of structural materials, and a suite of radiation and other environmental sensors.
Credit: CMU/RedZone Pioneer

Reactor 3 was switched off in 2000 to close the plant. In early 2002 the European Commission paid the first installment of its promised €40m additional Shelter Fund. The fund was paid in four installments from 2001–2004. It helped to support the decommissioning work at the site.

In 1997 the Chernobyl Shelter Fund was established at the Denver 23rd G8 summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition by means of stabilization of the sarcophagus followed by construction of a New Safe Confinement (NSC). While the original cost estimate for the SIP was US$768 million, the 2006 estimate was $1.2 billion. The SIP is being managed by a consortium of Bechtel, Battelle, and Electricité de France, and conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus.
New Safe Confinement 2013
On 7 January 2010, the Ukrainian Government passed a state law to transform the Chernobyl shelter facility into an environmentally safe system in order to protect the surroundings from radiation. The programme will be executed in four stages. In the first stage, nuclear fuel will be moved to a storage facility, which will be completed by 2013. In the second stage which will be completed by 2025, all the reactors will be deactivated. The third stage involves maintaining the reactors until radiation drops to an acceptable level and is envisaged to be completed by 2045. The fourth and the final stage involves dismantling the reactors and clearing the site, which is expected to be completed by 2065.

Novarka is a French consortium for the construction of the new safe confinement over the Chernobyl shelter. Members of the consortium are Vinci, Bouygues (France), Nukem (Germany/UK), Hochtief (Germany) and some Ukrainian companies. In 2007 the Ukrainian authorities announced Novarka as winner of the $ 453 Million contract. Check the video animation below.



Demolition Robots at Dounreay plant, UK 
Credit: NDA - Brokk 40
In the UK robots have been used to take over from human staff to dismantle the uranium fuel reprocessing plant at Dounreay. The plant is too contaminated with radiation for human workers to carry out the work, so the site has turned to specialist demolition firm Brokk to supply the remotely-operated equipment that can work inside cells and a pond. Staff are drilling through the concrete that surrounds the plant to let the electric powered demolition robots move inside and begin dismantling it. The robots which are mounted on tracks like a construction excavator have been fitted with specially-designed tools.

Fukushima Dai-ichi 2011-20??
Depending on further crisis development and the final status of nuclear reactors at the power plant the decommissioning process and the recovering of the surroundings will take many years and cost billions of yen. Fukushimas will forever be remembered with the nuclear disaster caused by the earthquake and devastating tsunami on March 11, 2011. 

4 comments:

-MG said...

With great respect to Mr. Whittaker and his students, nevertheless IAEA bulletin, Autumn 1985 p33 indicates the DOE's SISI robot was in use for photographing and monitoring radiation at Unit 2 in August 1982, and in spring 1983, another (apparently DOE-sourced) robot Fred used a "high-pressure water spray...to decontaminate the walls and floor of a pump cubicle in the auxiliary building basement". So Rover (RRV) was not the first robot to enter the plant. Rover-2, however, seems to me to be the first to remove any material from the plant, namely concrete sameples the robot extracted with a borer; see IAEA Bulletin Winter 1985 p21.

Infonaut AB said...

Swedish Demolition Robots arrive now at Fukushima nuclear plant.
http://robotland.blogspot.com/2011/05/swedish-demolition-robots-arrive-at.html

Mari said...

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Radiological Decontamination and Decommissioning