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Characterization of Samples with Spontaneously Fissioning Isotopes

#2585


Development of the Method for Characterization of the Samples, Containing Spontaneously Fissioning Radionuclides, by Measuring Fission Products Gamma-Radiation (for the System of NM Control and Accountability of the Federal State Unitarian Enterprise "PA"

Tech Area / Field

  • FIR-INS/Nuclear Instrumentation/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

Status
8 Project completed

Registration date
08.08.2002

Completion date
18.04.2011

Senior Project Manager
Genisaretskaya S V

Leading Institute
MIFI, Russia, Moscow

Supporting institutes

  • All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow\nNPO Mayak, Russia, Chelyabinsk reg., Oziorsk

Collaborators

  • Radiation and Nuclear Safety Authority, Finland, Helsinki\nUniversity of British Columbia / TRIUMF, Canada, BC, Vancouver\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe

Project summary

Traditionally, systems of nuclear materials (NM) control and accounting apply two combinations of methodologies: neutron coincidence counting in combination with gamma-spectrometry or calorimetry in combination with gamma-spectrometry that increases duration, laboriousness and cost of assays.

The present project is devoted to developing the complex method for determination of mass and isotopic composition of fissionable materials by gamma-spectrometric techniques for further application in systems for NM Control and Accounting at enterprises for nuclear fuel reprocessing and fabrication (at the Federal State Unitary Enterprise «Production Association Mayak», etc.).

The main problem to be resolved by the methodology to be developed is a control over plutonium produced in reprocessing of spent fuel assemblies from nuclear reactors of VVER-type, BN-type and from transport reactors. Till now, several tens of tons of reactor-grade plutonium are accumulated and stored in special containers (about 1.5 kg plutonium in each container).

The methodology to be developed must be able to determine mass and isotopic composition of NM sample from results of one gamma-spectrometric measurement. This allows us to carry out only one experiment with one device instead of two experiments with application of two measuring devices. As a result, assay time, laboriousness and cost of assay can be reduced significantly (cost of a neutron coincidence counter and a calorimeter is of the same order of magnitude that a sum requested for the project performance and larger by a factor of 3-5 than cost of a gamma-spectrometer).

The proposed methodology is based on the following circumstance. Spontaneous fission of NM is accompanied by generation of radioactive fission products which emit gamma-radiation in beta-decays. The measurements will be carried out in two energy ranges. Measurement of gamma-radiation emitted by spontaneous fission products (high-energy range) can give an information about the number of spontaneous fissions in NM sample and, as a consequence, about content of even-even plutonium isotopes in the sample, i.e. information traditionally obtained from calorimetric measurements or from neutron coincidence counting. Analysis of the same gamma-radiation spectrum in typical range of plutonium isotopes (low-energy range) with application of the computer code FRAM will allow us to determine isotopic composition of the sample.

Development of the proposed methodology will allow us to realize basic advantages of non-destructive methods: short time of measurements, low labor expenses for assays, low occupational radiation doses.

To assess a possibility for proper interpretation of experimental data on gamma-radiation emitted by fission products, experiments will be carried out with plutonium samples of different isotopic compositions, mass and geometry. Correction factors to take into account a non-identity of the sample under assay and the reference sample, and neutron multiplication in the sample will be calculated by Monte Carlo method with application of appropriate software tools.

The developed methodology will be tested at the RT-1 plant of the FSUE «PA Mayak» by the specialists from MEPhI and VNIINM during their special missions to the plant. Several tens of plutonium samples will be assayed with application of the complex gamma-spectrometric methodology and traditional methodologies (neutron coincidence counting, gravimetry and mass-spectrometry). Comparison of the results obtained by different methodologies will allow us to make the well-grounded conclusions on correctness, main characteristics and potential applicability areas of the proposed method.

To expand potential applicability areas of complex gamma-spectrometric method (in the first turn, for analysis of the samples with low plutonium content), active version of the methodology will be developed that includes short-term irradiation of the samples under assay with neutrons emitted by radioactive sources and further measurements of radiation emitted by fission products. In active assays, the measurements will be carried out within the same energy ranges that those used in passive assays.

Besides, the project includes an applicability assessment of active version for complex control of uranium samples. Feasibility for successful resolving the problems involved into the project performance is confirmed with preliminary studies. The results obtained in these studies are published in the following papers:

1. Bushuev A.V., Zubarev V.N., et al. Gamma-Spectrometric Control of Large Plutonium Samples. - Atomnaya Energiya, Vol. 90, #6, June 2001, pp. 487-490.

2. Bushuev A.V., Bosko A.L., Zubarev V.N., et. al. Development of the Method for Characterization of Samples Containing Spontaneously Fissioning Nuclides Using Fission Products Gamma-Spectrometry. - Journal of Nuclear Materials Management, 2002, Vol. XXXI, #1, pp. 59 62.

3. Bushuev A.V., Zubarev V.N., Proshin I.M. A Possibility of Activation Gamma-Spectrometric Measurements for Determination of Nuclear Materials Mass in the Samples. - Atomnaya Energiya, Vol. 94, #4, 2002, pp. 286 290.

4. Bushuev A.V., Kozhin A.F., Zubarev V.N., et al. Activation Gamma-Spectrometric Methodology for Mass Determination of Nuclear Material Samples. - Atomnaya Energiya, Vol. 94, #4, 2003, pp. 299 304.

Participation of the specialists from MEPhI, the FSUE Bochvar R&D Institute of Inorganic Materials (VNIINM), the FSUE “PA Mayak” is planned in the project performance including 25 specialists from defence area.

The specialists from Institute of Transuranium Elements (Karlsruhe, Germany) and from Los Alamos National Laboratory (LANL, USA) have agreed to act as the Foreign Collaborators of the project.

Regular contacts with the Foreign Collaborators will promote successful fulfillment of the project. These contacts pursue the following aims:


- discussion and coordination of plans for investigations; information exchange about the measuring methodologies and devices, exchange with publications and reference data;
- joint consideration and analysis of the results obtained at different stages of the studies;
- discussion and elaboration of additional requirements to experimental instrumentation and software tools;
- arrangement of joint symposia and workshops.


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