Life cycle of any reactor consists of design, construction, operation and decommissioning stages. After the design life is over, reactor should be transformed into nuclear safety condition and decommissioned. Termination of operation can be caused by other reasons including economic, operational, technological ones and because of the accidents.

According to “General provisions on safety assurance during the process of decommissioning of NPPs and research reactors” (approved by the decree of Ministry for Environmental Protection and Nuclear Safety of Ukraine №2 of January 9, 1998) there are introduced following definitions:

Decommissioning – a set of measures after the process of nuclear fuel removal and operation termination of installation that makes it impossible to use for the purposes for which it was constructed and provides safety of personnel, population and environment.

Termination of operation – the final stage of installation operation that is performed after the making a decision about its decommissioning and in the course of which this facility is brought to the state when nuclear fuel is absent at its territory or being within this territory, is located in spent fuel storages (SFS) that are intended for a long-term safe storage.

Reactors closed following an accident or serious incident

Country
Reactor
Type
MWe net
Years operating
Shut down
Reason
Germany
Greisfwald 5
VVER-440/V213
408
0.5
11/1989
Partial core melt
Gundremmingen A
BWR
237
10
1/1977
Botched shutdown
Japan
Fukushima Daiichi 1
BWR
439
40
3/2011
Core melt
from cooling loss
Fukushima Daiichi 2
BWR
760
37
3/2011
Core melt
from cooling loss
Fukushima Daiichi 3
BWR
760
35
3/2011
Core melt
from cooling loss
Fukushima Daiichi 4
BWR
760
32
3/2011
Damage from
hydrogen explosion
Slovakia
Bohunice A1
Prot GCHWR
93
4
1977
Core damage
from fuelling error
Spain
Vandellos 1
GCR
480
18
mid 1990
Turbine fire
Switzerland
St Lucens
Exp GCHWR
8
3
1966
Core melt
Ukraine
Chornobyl 4
RBMK LWGR
925
2
4/1986
Fire and meltdown
USA
Three Mile Island 2
PWR
880
1
3/1979
Partial core melt

Reactors closed prematurely by political decision

Country
Reactor
Type
MWe net each
Years operating each
Shut down
Armenia
Metsamor 1
VVER-440/V270
376
13
1989
Bulgaria
Kozloduy 1-2
VVER-440/V230
408
27, 28
12/2009
Kozloduy 3-4
VVER-440/V230
408
24, 26
12/2006
France
Super Phenix
FNR
1200
12
1999
Germany
Greisfwald
VVER-440/V230
408
10, 12, 15, 16
1990
Muelheim Kaerlich
PWR
1219
2
1988
Rheinsberg
VVER-70/210
62
24
1990
Italy
Caorso
BWR
860
12
1986
Latina
GCR
153
24
1987
Trino
PWR
260
25
1987
Lithuania
Ignalina 1
RBMK LWGR
1185
21
2005
Ignalina 2
RBMK LWGR
1185
22
2009
Slovakia
Bohunice 1
VVER-440/V230
408
28
12/2006
Bohunice 2
VVER-440/V230
408
28
12/2008
Sweden
Barseback 1
BWR
600
24
11/1999
Barseback 2
BWR
600
28
5/2005
Ukraine
Chornobyl 1
RBMK LWGR
740
19
12/1997
Chornobyl 2
RBMK LWGR
925
12
1991
Chornobyl 3
RBMK LWGR
925
19
12/2000
USA
Shoreham
BWR
820
3
1989

Process of installation decommissioning is divided into the following stages:

Final shutdown – the stage of the process of installation decommissioning when it is brought to the state that includes the possibility to use the installation for the purposes for which it was constructed.

Mothballing – a stage of the process of installation decommissioning when it is brought to the state that corresponds to the safe storage of ionizing radiation sources during the certain period of time.

Hold-up – stage of the process of installation decommissioning during which it is in the quiescent mode that corresponds to the safe storage of ionizing radiation sources that are in it.

Dismantling – stage of the process of facility installation decommissioning when ionizing radiation sources that are in this installation, are removed from the facility or are located at its territory in radwaste storages.

The decommissioning activity is subjected to government regulation and is performed on the basis of certain permissions. The stage of operation termination precedes the stage of the decommissioning. Activity at the stage of operation termination is performed within the installation operation license, although the implementation of this stage requires separate permission of regulatory body. To gain such permission operating organization has to present following documents:

  • Installation operation termination program;
  • Report on safety analysis;
  • Changes in technical regulation of facility operation.

Pursuant to the requirements of national standards of Ukraine it is necessary to elaborate the concept of nuclear facility decommissioning at the stage of its designing. The initial concept of installation decommissioning has to be presented by the operating organization during the process of documents submission in order to obtain the constructing license. The concept of installation decommissioning has to be reconsidered by taking into account the experience of operation conduction and acquisition of new knowledge in outlined issue.

Decommission of installation is performed according to the decommissioning design, approved by regulatory authority, which includes radiation protection programme, radioactive waste (RAW) management programme, quality assurance programme, action plan in case of radiation accident and facility physical protection action plan.

License for installation decommissioning presupposes obtaining of certain permit to implement each stage of facility decommissioning.

Hygiene passport of installation has to be processed by authorities of State Sanitary Control for each stage of installation decommissioning. Hygiene passport has to contain the main sanitary, radiation and radiation dose monitoring characteristics of the installation, which is in the process of decommissioning, that allow to determine the level of radiation safety for personnel, population and environment.

Operating organization presents a report on information about the conducted work on the certain stage to the regulatory authority upon completion of the installation operation termination stage and each stage of installation decommissioning. In the report there has to be included information about radiation and other dangerous impacts on the personnel, population and environment and evidences that facility is brought into the state planned by the design.

According to the IAEA recommendations there are three options of the NPP decommissioning: Safe Enclosure of NPP, Entombment, and Immediate Dismantling.

The option “Safe Enclosure” presupposes a state in which reactor installation and other radioactive systems and equipment are mothballed, isolated from outside environment and maintained in safe state with the following decontamination to the level that allows its unlimited use in the future. During the realization of this option it is possible to perform preparatory works, dismantle, remove the non-polluting and low level equipment with its further disposal and reprocessing, conversion of premises, buildings and constructions, consequent reprocessing of low level RAW, partially decontaminate etc.

During the process of “Entombment” the most dangerous radioactive items, including reactors, primary coolant equipment and others, are enclosed, for example, in concrete, and are cooled till in the result of radionuclide decay the radiation of it will achieve an acceptable level. According to this option it is used the effect of activity self-destruction in the result of radioactive decay. In addition it is possible to carry out works of uncomplete decontamination of premises, dismantling and disposal of equipment that is beyond the leak tight zone, and other types of activity that do not lead to violation of the indicated barriers integrity.

Option “Immediate Dismantling” presupposes the achievement of two possible stages of final state of the reactor installation. The exemption of the site presupposes the dismantling of equipment, buildings and constructions that are not intended for further use, reprocessing and removal of all RAW from the site of reactor installation and bringing the site to the state that is appropriate to the requirements of nuclear power, for instance, for new unit building or RAW storage facility. This state of the site is called as “brown site”.

Turbine shop at Greifswald NPP (Germany) before NPP decommissioning

Turbine shop at Greifswald NPP (Germany) after equipment dismantling

The state of the site as “green site” presupposes the dismantling of reactor facility buildings, reprocessing, packing and removal of the radioactive and nonradioactive waste, recultivation of the exempted territory for its unlimited further use.

Decommissioning of the certain installation is determined by national peculiarities and depends upon technical and economic, political and social and other aspects.

Costs for NPP decommissioning depends upon many factors (in particular such as type and state of the nuclear power facility, problems connected with processing and storage of residual materials, limit norms of the radiation protection, methodology of obtaining the license, costs for personnel, work schedule), including such items as capacity of the unit, its operating life, and time before the final shutdown.

According to rough estimates total costs for one nuclear power unit decommissioning and dismantling can amount from 20% to 30% of costs necessary for new unit building. National peculiarities, including volume of necessary works and method of RAW management, have a significant impact on costs. Total costs depend upon the quantity of RAW, methods of their reprocessing etc.

Costs for NPP decommissioning

NPP, country
Type of reactor, capacity,
MW
Costs,
$ million
Remarks
Big Rock Point, USA
BWR, 70
25,0
Reactor vessel is removed after the offloading of spent nuclear fuel. Total mass of RAW was 290 t. Spent nuclear fuel storage with area 43,3 hectares remained at the site. Area of NPP was 182,2 hectares.
Fort Saint Vrain, USA
HTGR, 330
173,9
Variant of immediate dismantling. It was converted into gas-turbine station.
Tokaimura,
Japan
GCR, 166
772,5
Dismantling began in 2001 and it will have been accomplished in 2017. In the process of dismantling it will be created 177000 t of RAW, including 18000 t of highly radioactive ones.
Stade,
Germany
PWR,672
668,4
The first NPP that is decommissioned after the adoption of the law on nuclear phase out. Fuel will be sent to France for reprocessing. 150 people of personnel out of 300 have remained at dismantling works.
Biblis-A,
Germany
PWR,1225
141,2
Costs for total unit dismantling
Loviisa-1,
Finland
VVER, 440
166,5
Costs for total unit dismantling

The experience of Ukraine

Performance of Chornobyl NPP units decommissioning works is an urgent task for nuclear power of Ukraine.

Chornobyl NPP units №1, 2, 3 are at the operation termination stage. The activity at these units is regulated by State Nuclear Regulatory Inspectorate license terms of Series EO № 000040 of March 22, 2002 for a right to perform the decommissioning of Chornobyl NPP nuclear facilities.

Since January 01, 2010 Law of Ukraine on “State Program of Chornobyl NPP Decommissioning and Shelter Transformation into Ecologically Safe System” (SDP) came into force.

In the period till 2013 expected results of SDP implementation among others are to be:

  • completion of operation termination of Chornobyl NPP units № 1, 2, 3 and the beginning of works of their final shutdown and mothballing;
  • creation of effective system for radioactive waste management at Chornobyl NPP;
  • completion of construction and commissioning of new storage facility for spent nuclear fuel;
  • completion of construction and commissioning of New Safe Confinement over the Shelter.

Within the frames of this State Program it has to be provided works connected to the elaboration of design of final shutdown and mothballing of the units № 1, 2, 3 at Chornobyl NPP, design of cooling pond decommissioning and design documentation on new facilities for RAW management, which are necessary for Chornobyl NPP decommission.

Radioactive waste that were accumulated during the Chornobyl NPP operation, accident elimination in 1986, and those that are created during the process of decommissioning of units № 1, 2, 3 and shelter transformation into ecologically safe system, are stored in the existing storage of RAW at the site of Chornobyl NPP: in storage facility of solid RAW, storage facility of liquid RAW, storage facility of liquid and solid RAW, or they are transmitted for entombment in the storage facilities of Radioactive Waste Disposal Sites “Buriakivka”.

System of liquid RAW (LRW) storage is composed of storage facilities that are connected with special transfer tubes for LRW:

  • storage facility for liquid RAW, designed for 26000 cubic meters, is composed of 5 receiving containers with 5000 cubic meters volume and 2 receiving containers with 500 cubic meters volume, which are made of corrosion resistant steel;
  • storage facility for liquid and solid RAW that functions only in the part of LRW storage designed for 1200 cubic meters that is composed of 12 receiving containers with 1000 cubic meters volume that are made of corrosion resistant steel;
  • temporary storage warehouse of waste radioactive oil designed for 144 cubic meters, which is composed of two tanks with volume of 72 cubic meters.

There are low and medium level liquid RAW in these storage facilities:

  • vat residue;
  • pulp of spent ion exchange resins;
  • perlite pulp.

Solid RAW of Chornobyl NPP are temporary kept in the storage facility of solid RAW of the first, second and third groups of activity. In 2003 the storage facility was closed to RAW reception because of the beginning of building of industrial complex of solid RAW management within which it was built facility for solid RAW removal from this storage facility (Lot 1). Total volume of accumulated RAW in the storage facility that are objected to the removal and further reprocessing is 1096 cubic meters of the first group RAW, 926,5 cubic meters of the second group ones and 506,93 cubic meters of the third group ones.

Low and medium level solid RAW produced in the process of units decommissioning and during the performance of the activity of Shelter transformation into ecologically safe system, are transmitted for disposal at Radioactive Waste Disposal Sites “Buriakivka”.

High level waste is collected into special containers (KTZV-0.2) and are placed into storage facility for high level solid waste, which is located in the premises of the former storage of fresh fuel at the site of Chornobyl NPP.

Creation of the infrastructure objects for RAW management at Chornobyl NPP

In the process of decommissioning of Chornobyl NPP, facilities for RAW management are built, that is plant for liquid radioactive waste reprocessing and industrial complex for solid radioactive waste management (ICSRM). These facilities have to provide the existing storage facilities exemption of accumulated RAW at Chornobyl NPP, reprocessing of RAW to the necessary state for disposal of RAW package at near-surface storage facility and temporary storage of long-lived and high level RAW that are objected to disposal in geologic storage facility.

According to “Integrated Programme on Radioactive Waste Management on the Stage of Chornobyl NPP Decommissioning and Shelter Transformation into Ecologically Safe System” it is planned a range of additional building of facilities for RAW management, including a plant for containers and RAW packages production, the building of which it is being completed; storage site, fragmentation and decontamination of dismantled equipment and other RAW; facility for initial reprocessing of liquid RAW in order to provide the possibility of liquid RAW reprocessing of “Shelter” facility at the plant of liquid radioactive waste reprocessing; complex for contaminated metal reprocessing etc.

Plant for liquid radioactive waste reprocessing

Financing of design implementation is carried out by using the donor country funds, which are accumulated on the Nuclear Safety Account in EBRD.

Works on design completion of the plant for liquid radioactive waste reprocessing were resumed in 2007 pursuant to “Strategy for Completion of the Plant for Liquid Radioactive Waste Reprocessing” that was approved by Assembly of Donors of Nuclear Safety Account in EBRD. The completion of the design is carrying out by Chornobyl NPP along with national enterprises.

Building and the main equipment of plant for liquid radioactive waste reprocessing were constructed before 2006. However during the further analysis of the design, which was held in 2009 by OJSC Kyiv Institute “Energy project” (KIEP), it was found a set of disadvantages of the design, to improve which it is necessary to make certain changes and modifications in the design. It was determined the necessity to make 22 modifications in the technical approach about making changes in the design of the plant for liquid radioactive waste reprocessing that was elaborated by Chornobyl NPP authority and approved by State Nuclear Regulatory Inspectorate. In particular, modifications connected to the issue of radiation safety, are related to the radiation monitoring system, screening, decontamination, ventilation, automated control etc. Equipment for removal of liquid RAW from existing storage facilities and their transmission to the plant for liquid radioactive waste reprocessing was admitted as ineffective one; and it was agreed appliance of the existing conveyance system for liquid RAW with the use of compressed air at Chornobyl NPP.

During the whole period since 2006, operational service of systems and equipment has been carrying out by efforts of Chornobyl NPP authority to maintain equipment and building of the plant for liquid radioactive waste reprocessing in working order till the object has been in the state of unfinished building.

Industrial Complex for Solid Radioactive Waste Management (ICSRM) includes:

Lot 1 – Facility for removal of solid radioactive waste aimed to remove solid RAW from existing solid RAW storage facility at Chornobyl NPP and transmit RAW for reprocessing to the Lot 2.

Lot 2 – Plant for solid RAW reprocessing aimed to sort all-type solid RAW and reprocess (fragment, incinerate, compact and cement) low and medium-level short-lived solid RAW removed from the Lot 1 and waste removed after the Chornobyl NPP decommissioning, and to transform Shelter into ecologically safe system. At Lot 2 it is involved the packing of long-lived and high-level RAW that will appear during the process of sorting, and conveyance of these packages for the storage at temporary storage facility, which is Lot 0.

Lot 0 – Temporary storage facility for low and medium-level long-lived radioactive waste and high-level radioactive waste. Temporary storage facility is aimed for interim (during 30 years) storage of long-lived and high-level RAW that will be created during the process of sorting at Lot 2 and during carrying out of preparatory works of New Safe Containment (New Shelter) building. This storage facility is created by means of reconstruction and re-equipment of premises located at upper sections of liquid and solid RAW storage facilities at Chornobyl NPP that has not been in operation till now.

Lot 3 – SESFSRW – Specially equipped near-surface storage facility for solid RAW (conditioned at plants for reprocessing of liquid and solid RAW), build on the site of “Vector” complex.

Financing of the design is carrying out by European Commission within the framework of TACIS programme and by means of investment through the government budget of Ukraine.

Building of all objects of ICSRM is completed, thus works on their commissioning are being carried out.

On May 13, 2010 the Regulation Body issued a separate written authorization № 000040/3 for commissioning of Lot 1, 2 within the framework of the first stage of commissioning implementation (tests with radioactive waste located in the hermeneutical packages with foregone characteristics).

On December 10, 2010 the Regulation Body issued a separate authorization № 00004/4 for Temporary storage facility, which is Lot 0.

Authorization gives the right to carry out the operation works at Lot 0, which are connected with receiving and storage of the packages with RAW to the complete loading of storage sections. In future, but not later than in 10 years, Chornobyl NPP has to make revaluation of storage facility safety by the results of which term of RAW packages storage in the storage facility after its complete loading will be defined.

One of key issues of safety of temporary storage facility operation is to ensure reliability of containers for correspondent RAW types (165 and 200 liter drums) including conditions of storage and term of storage facility operation. Pursuant to the agreed technical specifications of State Nuclear Regulatory Inspectorate Chornobyl NPP authority plans to produce drums for RAW storage at a plant for production of RAW containers and packages.

Lot 3 (SESFSRW) with the capacity of 50250 cubic meters is aimed to bury conditioned RAW of Chornobyl NPP: which are concrete containers from Lot 2 and 200 liter drums with cemented RAW from liquid radioactive waste reprocessing plant.

On July 2, 2009 license EO № 000894 on commissioning of 2 % of SESFSRW was issued to the State Specialized Enterprise (SSE) “Tekhnocenter” for 5 years. In 2010 operating organization SSE “Tekhnocenter” proceed to carry out the special license terms, which should be implemented to the beginning of RAW receiving for disposal, particularly:

– measures of implementation of “Action Programme on Revealing and Elimination of Water Inflow under the Storage Facility of SESFSRW”

– calculations and evaluation of seismic stability of acceptable value of SESFSRW constructions subsidence and deformation, and correspondent analysis of ensuring the carrying out of functions provided by the design with constructions and systems located under the storage facility.

Sources:

  1. Decommissioning of nuclear power installations” / А.Nosovskiy,V.Vasilchenko, A.Klyuchnikov, O.Yashchenko; Edited by A.Nosovskiy. – K.: Tekhnika, 2005. –P.27-39.
  2. Nuclear and Radiation Safety in Ukraine Annual Report 2010.
  3. О.Э.Муратов, М.Н.Тихонов. Снятие АЭС с эксплуатации: проблемы и пути решения // Агенство ПроАтом.
  4. Decommissioning Nuclear Facilities // World Nuclear Association.