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Armenian Nuclear Power Plant Decommissioning

#A-1295


Radiological Characterization and Database Creation in Support of ANPP Decommissioning Planning

Tech Area / Field

  • ENV-MRA/Modelling and Risk Assessment/Environment
  • FIR-DEC/Decommissioning/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

Status
8 Project completed

Registration date
27.05.2005

Completion date
12.07.2010

Senior Project Manager
Kulikov G G

Leading Institute
Yerevan State University, Armenia, Yerevan

Supporting institutes

  • Armenian NPP, Armenia, Metsamor

Collaborators

  • Georgia Institute of Technology / The Nuclear & Radiological Engineering & Health Physics Program of the George W. Woodruff School of Mechanical Engineering, USA, GA, Atlanta\nStanford University / Department of Economics, USA, CA, Stanford\nUniversity of Notre Dame / Department of Physics, USA, IN, Notre Dame\nForschungszentrum Karlsruhe in der Helmholts-Gemeinschaft, Germany, Karlsruhe\nNuclear Safety Solutions Limited, Canada, ON, Toronto\nUniversity of Wisconsin-Madison / College of Engineering, Nuclear and Engineering Physics, USA, WI, Madison\nKorea Atomic Energy Research Institute, Korea, Yusung Taejon\nUniversity of Florida / College of Engineering/Department of Nuclear and Radiological Engineering, USA, FL, Caipesville\nUniversity of Lund / Department of Radiation Physics, Sweden, Lund

Project summary

The number of existing nuclear power plants in the world exceeds 500. The total capacity of the operated NPPs is about 400 GWt. Besides, over a hundred research reactors operate in most of the developed countries.

Armenian NPP consists of two WWER 440, model 270 units (the seismically upgraded version of V-230 model). Currently the nuclear share in Armenian energy sector is about 40%. Unit 1 was put into operation in 1976, Unit 2 – in 1980, respectively. After an earthquake in northern Armenia in December 1988, both units were shut down in 1989 for safety reasons. Unit 2 was restarted in November 1995. Unit 1 remains in long-term shutdown mode. Design lifetime of Unit 2 expires in 2016.

The decommissioning is the final stage of the facility operation and is defined as administrative and technical actions taken after permanent facility shutdown aimed at removal of some or all regulatory controls from a nuclear facility.

In compliance with the established practice in the area of nuclear regulation, the decommissioning starts after removal of spent nuclear fuel from the facility. Thus, the decommissioning of a nuclear facility is a complex optimization task with a purpose of minimization of the radiological, environmental and economical damage, and the decisions to be taken, together with the selection of the approaches and technologies shall be based on multiattribute analysis, including the consideration of the nuclear facility specific features. Optimization is achieved with use of ALARA principle, appropriate selection of the dates for start and sequence of the specific activities, implementation of up-to-date technologies, scientific, methodological and informational support, and implementation of quality assurance program as well. The selection of the most suitable strategy is essential for all decommissioning process.

Radiological characterization is one of the key elements in the overall process of the preparatory activities for the planning of NPP decommissioning. The data obtained during radiological characterization enables to develop and define concretely the decommissioning strategy, thus solving the main objective of the decommissioning: to perform these activities in safe and cost-effective manner. It is extremely important for the decommissioning planning to evaluate the actual volume and the activity inventory of the radioactive material, accumulated during the facility operation, their nuclide composition and physical/chemical properties. Radiological characterization provides a reliable information database, which allows to predict the radiological conditions and to take decisions on such important activities as decontamination, choosing the appropriate methods/periods for dismantling of systems/components, demolition of the structures, management of the decommissioning waste and, consequently, to estimate the decommissioning cost.

The objects of the radiological characterization are the rooms, equipment, components and systems, which during the NPP operation directly contact with he sources of radioactive contamination or are irradiated by neutrons, as well as the systems designed for storing, disposing of or processing of the waste, such as: radioactive process equipment and systems, building structures and structures designed for radiological protection, materials and equipment to be disposed off.

Radiological characteristics to be monitored are as follows:

  • -dose rates, density of - and -particles and spatial distribution of -dose rates;
  • surface and in-depth distribution of the activity in the materials and structures of the radiological protection;
  • surface contamination and activity of deposits on internal surface of equipment/components;
  • nuclide composition of radioactive sources on equipment and in the plant areas/rooms.

One of the main tasks of the proposed Project is implementation of these type investigations. The results obtained will facilitate the purposeful selection (at the phase of reactor facility design and construction) of the least activated constituents and raw materials for steel and reinforced concrete. Advanced computer codes will be used for the calculation of induced activity in biological shielding and structures of the reactor facility.

During the NPP operation the radiation protection service at ANPP performs the required radiological and technological monitoring in compliance with the established Technical Specifications, procedures, regulatory and legislative documents having a multilevel hierarchic structure. The scope of this information is sufficient to assure safe operations, however, as it was mentioned above, much more information is needed for the activity planning during NPP decommissioning.

In the area of ANPP location, within a radius of 20 km, live about 300.000 people; the average density of population is about 235 men/km2. Population density of the whole Ararat valley is 360 men/km2.

The abovementioned high density of population, the importance of Ararat valley for the economics of Armenia are the reasons for undoubted importance of complete and reliable radiation monitoring in ANPP area during normal operation conditions and, in particular, during the decommissioning.

It is envisaged, within the proposed Project, to carry out the comprehensive radiological characterization with creation of the computerized information database in support of the ANPP decommissioning activities.

As a result of the project implementation together with the comprehensive monitoring of the rooms of the ANPP controlled area the following information will be available:

  • -maps and level on the surface contamination of the ANPP rooms and equipment;
  • radionuclide composition of surface contamination of the rooms, equipment and deposits built-up on the internal surfaces of the primary circuit equipment and piping,
  • results of induced activity calculations for structures and the shielding of the reactor facility;
  • data on in-depth penetration of the radioactive contamination into building structures of the controlled area rooms (concrete, plastic, painting);
  • spatial distribution of surface activity based on air kerma in the rooms.

Collected information will serve the technical basis for
  • optimizing activities on the planning of further radiological characterizations (as it is well known that the radiological characterization during decommissioning is the multistage process and each step builds on information gathered from earlier activities);
  • decision making about the systems, which may need in decontamination and/or fixing of contamination;
  • planning the dose loads for the plant personnel performing the decommissioning activities and; developing radiation protection programme in support of decommissioning,
  • evaluating the volumes/activity and the categories of the radioactive waste produced during the ANPP decommissioning for the development of the waste management strategy and the proper sizing of the storage/disposal facilities;
  • defining the scope of the radiation monitoring of environment during the ANPP decommissioning;
  • selecting the most suitable strategy for the ANPP decommissioning.

We believe that the results of our studies will be useful for other NPPs with WWER reactors.


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