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Cesium Trap for BN-350 Reactor


Develop, Install, and Operate a Cesium Trap, Based on the U.S. Technologies, to Reduce Cesium Levels in the BN-350 Primary Sodium and Enhance Plant Fire Protection Capabilities to Support Cesium Trap Operation

Tech Area / Field

  • FIR-DEC/Decommissioning/Fission Reactors

8 Project completed

Registration date

Completion date

Senior Project Manager
Tocheny L V

Leading Institute
Nuclear Technology Safety Center, Kazakstan, Almaty

Supporting institutes

  • National Nuclear Center of the Republic of Kazakstan / Institute of Atomic Energy (1), Kazakstan, Kurchatov\nMAEC-Kazatomprom, Kazakstan, Aktau


  • Nuvia Ltd., UK, Dors, Winfrith Newburgh\nBattelle Energy Alliance LLC (BEA) / Idaho National Laboratory, USA, ID, Idaho Falls

Project summary


Kazakhstan operates one nuclear power reactor at its plant in Aktau. The Soviet-designed BN-350 is a sodium-cooled, fast-breeder reactor that began operating in 1972. It was a key source of electricity and heat for Aktau, a city on the banks of the Caspian Sea in sparsely populated western Kazakhstan. The reactor also bred high purity weapons grade plutonium in its blanket --- whose elements were subsequently stored in the plant’s spent fuel pool. The disposition of these spent fuel elements is the subject of a separate bi-lateral project between the U.S. and Kazakhstan.

Kazakhstan formally announced on April 22, 1999, that it intended to decommission the reactor. Kazakhstan also requested U.S. assistance in planning the decommissioning and assistance in the development of certain safety upgrades, e.g., fire protection enhancement and lowering the cesium levels in the plant’s primary sodium coolant. The fire protection situation at the plant is such that there is immediate threat to personnel at the plant.

At an IAEA sponsored Decontamination and Decommissioning (D&D) workshop conducted in May 1999 in Almaty, Kazakhstan, government officials announced that it was their intention to place the plant in a ‘SAFESTORE’ configuration within a 5 year time frame and maintain that configuration for about 50 years. Specific technical objectives were announced for nuclear, radiological, and industrial safety including removing the fuel from the site, draining and deactivating the primary sodium, and removing or stabilizing radioactive and hazardous contamination and waste. Lowering the cesium concentration in the primary sodium coolant will be a key step in the path to draining and deactivating the primary sodium. The current 137Cs level in the BN-350 primary sodium has been stated to be~250 kBq/ g (~6.75 µCi/g). At this level, the contact dose rates from containers containing BN-350 primary sodium could be expected to be in the low R per hour range just from the 137Cs. Calculations provided by the IPPE Institute in Obninsk, Russia at an IAEA conference on BN-350 decommissioning confirm this.

Hazards and costs involved with the SAFESTORE of the BN-350 reactor (and potentially risks to the public through upsets and accidents) will be significantly increased by this level of cesium in the BN-350 primary sodium. It would thus be highly desirable to decrease the amount of cesium prior to commencing active work involving the BN-350 primary sodium. Previous and on-going collaborative between U.S. and Kazakhstan personnel at the BN-50 studied the options available to accomplish this, recommended an option, and developed a concept to implement that option. This option is based on the experience gained by U.S. personnel at the Experimental Breeder Reactor -II (EBR-II), located at Argonne National Laboratory-West, (ANL-W). In addition, a lack of Kazakh codes and standards related to the design of nuclear components requires the experience of U.S. personnel in supporting the design effort.

This proposal seeks to implement that option in the BN-350 as a Technical Demonstration of this technology. This will be useful not only for the BN-350 but will provide meaningful data for the decommissioning of other sodium cooled reactors throughout the world.


The technical objective of this proposal is to implement the design concepts previously developed and install and operate a cesium trap at the BN-350 in order to lower the existing cesium concentration to the lowest practical level. Concomitant with this, appropriate fire protection enhancements will be made. Cesium Levels achieved at the EBR II (about 1.0 x 10-2 µCi/g) have been shown to be adequate. The objective is further to document the results of the work so that others decommissioning sodium cooled reactors may benefit form the experience gained.


National Nuclear Center (NNC) and BN-350 personnel in cooperation with a design team from ANL-W will design the Cesium Trap in accordance with western codes and standards. An ANL fire protection engineer who has already performed a preliminary survey will also confirm his conclusions with plant fire protection personnel to decide what fire protection enhancements will be required. The methods by which this will be accomplished will be documented in Project Work Plans --- approved by BN-350 (MAEC), NTSC, KAEC, and U.S. personnel. The Kazakhstan Nuclear Technology Safety Center (henceforth known as the Center) will act as a coordinating agency for all participants plus provide contract administration internal to Kazakhstan. In this capacity, the Center will interface with the BN-350 and NNC personnel accomplishing the work (or other Kazakhstan agencies as appropriate) on contractual matters including coordinating agreements on scopes of work, administrative review of deliverables, and payment for personnel and materials. In addition, subcontracts performed to fabricate the traps, as well as the procurement of equipment, will be managed by the Center. Through review and approval processes of the project work plans, an infrastructure supporting the review and approval of technical documents, including the safety review of such documents, will be established within the Kazakhstan government.


The strategy for development of the plan involves a series of tasks following standard engineering practices as follows:

Task 1 – Project Work Plan

This task is to prepare and approve a Project Work Plan (PWP) document that identifies the design process, quality assurance, safety codes, and review and approval requirements as specifically related to the cesium trap design, installation, and operation. An additional PWP will deal with fire protection. Once approved, this document will establish the codes and standards required to support the fabrication, installation, and testing of the cesium trap. All quality control requirements will be derived from this document, including welding certification.

Task 2 - Final Design

This task encompasses the engineering and administrative duties required for the final design for the cesium trap and system, as well as fire protection upgrades, in accordance with the approved PWP. The task includes engineering design effort, preparation of analyses, preparation of drawings and sketches, preparation of fabrication, installation, and operation procedures, and the assembly of all design documents into a Final Design Package suitable for review and approval.

Task 3 – Final Safety Evaluation

This task is to prepare a Final Safety Evaluation document, based on the Preliminary Safety Evaluation and the Final Design Package, and assembles the evaluation into a document suitable for review and approval. The document will include the fire protection enhancements as appropriate.

Task 4 – Final Design Reviews and Approvals

This task is to perform the Final Design Reviews in accordance with the requirements of the approved PWP.

Task 5 – Fabrication

This task is for the procurement of fire protection and cesium trap materials and the fabrication of the cesium traps and system equipment in accordance with the approved Final Design Package.

Task 6 – Installation and Checkout

This task includes the installation of the initial cesium trap and all supporting equipment, performance of an operational checkout of the system in accordance with the approved Final Design Package, and documentation of all as-built changes for configuration control.

Task 7 – Operational Readiness Review

This task is for the performance of an independent review of the operational checkout results and the as-built installation documentation to assure the cesium trap and fire protection system are ready for safe operation.

Task 8 – Operation

This task includes the cesium trapping of the primary system sodium and documents the results achieved.

Task 9 – Contract Administration

This task involves work by the Kazakhstan Nuclear Technology Safety Center to support and manage the designated work with BN-350 and NNC, to act as a liaison for Argonne, and to interface with other involved organizations as required to support the cesium trap and fire protection upgrade efforts.


The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.


ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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