Monitoring of plutonium contaminated solid waste streams. A technical guide to design and analysis of monitoring systems Report

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Commission of the European Communities NUCLEAR SCIENCE AND TECHNOLOGY Monitoring of plutonium contaminated solid waste streams A technical guide to design and analysis of monitoring systems Report EUR 10026 EN Commission of the European Communities NUCLEAR SCIENCE AND TECHNOLOGY Monitoring of plutonium contaminated solid waste streams A technical guide to design and analysis of monitoring systems G. Birkhoff Commission of the European Communities Joint Research Centre Ispra Establishment 1-21020 Ispra (VA) Ofrefcrøfflll-Seneral for Science, Research and Development Joint Research Centre 1986 EUR 10026 EN Published by the COMMISSION OF THE EUROPEAN COMMUNITIES Directorate-General Information Market and Innovation Bâtiment Jean Monnet LUXEMBOURG LEGAL NOTICE Neither the Commission of the European Communities nor any person acting on behalf of the Commission is responsible for the use which might be made of the following information Cataloguing data can be found at the end of this publication Luxembourg, Office for Official Publications of the European Communities, 1986 ISBN 92-825-5842-8 Catalogue number: I © ECSC-EEC-EAEC, Brussels · Luxembourg, 1986 Printed in Belgium Preface The primary objective of this technical guide is to launch a coherent methodology in the domain of Monitoring Plutonium Contaminated Solid Waste Streams from the nuclear fuel cycle.

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Commission of the European Communities
NUCLEAR SCIENCE AND TECHNOLOGY
Monitoring of plutonium contaminated
solid waste streams
A technical guide to design and analysis
of monitoring systems
Report
EUR 10026 EN Commission of the European Communities
NUCLEAR SCIENCE AND TECHNOLOGY
Monitoring of plutonium contaminated
solid waste streams
A technical guide to design and analysis
of monitoring systems
G. Birkhoff
Commission of the European Communities
Joint Research Centre
Ispra Establishment
1-21020 Ispra (VA)
Ofrefcrøfflll-Seneral for Science, Research and Development
Joint Research Centre
1986 EUR 10026 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Information Market and Innovation
Bâtiment Jean Monnet
LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on behalf of the
Commission is responsible for the use which might be made of the following information
Cataloguing data can be found at the end of this publication
Luxembourg, Office for Official Publications of the European Communities, 1986
ISBN 92-825-5842-8 Catalogue number: I
© ECSC-EEC-EAEC, Brussels · Luxembourg, 1986
Printed in Belgium Preface
The primary objective of this technical guide is to launch a coherent methodology in the
domain of Monitoring Plutonium Contaminated Solid Waste Streams from the nuclear fuel
cycle. This is a rather ambitious undertaking, because of the complexity of the scientific and
practical aspects involved in this matter. The way we try to promote a methodology is marked
by the technical possibilities and hence the limitations in measuring the plutonium contents
in contaminated solids.
Primary monitoring objectives are the nuclear safety and radiological protection in all stages
of treatment, storage and final disposal of Plutonium Contaminated Materials (PCM). These
objectives can be approached on the basis of the determination of the plutonium contents
in PCM items and streams with appropriate accuracies and detection sensitivities.
Since publication of our first version of the present technical guide there were certain
reaction from Pu-plant operational sides as well as from research and development.
The methodology itself was investigated more deeply by theoretical studies on capabilities
and limitations of radiometric assay of PCM and by integral experiments on the PCM
monitoring system of an FBR fuel reprocessing facility. Both the reactions of plant operators
as well as the progress in the methodology of PCM-monitoring have been adopted in the
present guide.
The first chapter on the planning of monitoring systems starts from the objectives and
technical and managerial constraints and presents a conceptual PCM monitoring scheme.
Chapter 2 is devoted to the principles and the theory of the radiometric assay of PCM,
which forms the scientific basis ot the procedures for the determination of the Pu-contents
in PCM items and streams.
Chapters 3, 4 and 5 are dedicated to the design and the analysis of monitors based on
the measurement of radiations emitted by Pu isotopes either spontaneously or after irradiation
by neutrons from an external source. Emphasis is given to the mathematical modelling of
instruments and methods and to the data bases for the design of instruments and interpretation
of measurements. Reference monitors are described for the considered radiometric assay
by passive gamma, passive neutron and active neutron-techniques.
The present guide is the outcome of a longstanding collaboration between the Joint
Research Centre, the TECHNION-Haifa and the University Claude Bernard-Lyon-I. The names
and addresses of the contributors are listed below.
Chapter 1 was conceived firstly by G. Birkhoff and A. Notea, but the present version of it
has been strongly revised.
G. Birkhoff, L. Bondar, A. Notea and Y. Segal developed the fundamentals of the radiometric
assay of Chapter 2.
Passive gamma assay of Chapter 3 was worked out by G. Birkhoff, J.L. Barou, J. Depraz
and A. Notea.
The theory of the passive neutron assay and the reference monitor of Chapter 4 were
developed by G. Birkhoff, L. Bondar, J. Depraz and C. Souga.
Active neutron assay is still in the development state. Chapter 5 presents the views of this
topic from the author G. Birkhoff.
The achievement of the principal objective of this guide, namely the introduction of a
coherent methodology in monitoring of plutonium in solid waste streams, will depend on
the coordination of research and development in this field. This guide is intended to help
in finding the orientation of such a work.
G. Birkhoff
September 1983
III Contributors
Prof. A. Notea
TECHNION-Haifa, Department of Nuclear Engineering, Israel
Prof. Y. Segal ,t of Nuclear, Israel
Prof. J. Depraz
Université Claude Bernard Lyon I, Institut de Physique Nucléaire, France
J.L. Barou
Université Claude Bernard Lyon I, Institut de Physique Nucléaire, France
C. Souga
Université Claude Bernard Lyon I, Institut de Physique Nucléaire, France
L. Bondar
CEC, Joint Research Centre, Ispra Establishment, Italy
IV Contents
Chapter 1 : Planning of Monitoring Systems
1.1 Introduction 1
1.2 Definitions 5
1.3 Waste Management 8
1.3.1e arising 10
1.3.2 Radiological hazard4
1.3.3 Criticality hazard7
1.3.4 Segregation and packaging
1.3.5 Monitoring objectives8
1.4 Waste Monitoring 21
1.4.1g techniques
1.4.1.1 Passive gamma technique2 2e neutrone
1.4.1.3 Activen technique '.9
1.4.1.4 Calorimetry 30
1.4.2 Radiation interactions and their importance in waste
measurements
1.5 Conceptual Monitoring Scheme5
1.5.1 Measurement uncertainty6
1.5.2 Detection limit7
1.5.3 Liquid PCM monitoring
1.5.4 Gaseous PCM monitoring8
1.5.5 Solid PCMg
1.5.5.1 Characterization of solid PCM streams 42 Theoretical assessment of measurement
uncertainty 42
1.5.5.3 Calibration and interpretation of solid PCM
measurements3
1.5.5.3.1 Methodology2 Practical application6
1.5.5.3.3 Physical standards 51
1.6 Examples of Monitoring Solid PCM-Streams 5
1.6.1 Stream of untreated PCM
1.6.2m of PCM treated prior to storage5
1.6.3 Streams of segregated PCM
1.6.4s of classified and segregated PCM9
1.6.5s ofd and highly segregated PCM 62
References 6
Chapter 2 : Principles and Theory of Radiometric Assay
2.1 Definition of the Problem 71
2.2 Theory of Radiation Leakage6
2.2.1 Homogeneous absorbing sphere8
2.2.2.1 Source density distribution 82
2.2.2 Heterogeneous absorbing sphere2.2.3 Radiation scattering 88
2.2.4 Source self-attenuation 90
2.2.5 Absorbing cylinders and other bodies
2.2.6 The equivalent sphere model4
2.2.7 Discussion7
2.3 Measurements9
2.3.1 Measurement of radiation leakage
2.3.1.1 Discrimination of background radiation 102 Anisotropy of radiation leakage
2.3.1.3 Variation of energy spectrum1
2.3.2 Reference monitors 10
2.3.3 Measurements for estimation of absorption parameters 102
2.3.4s forn of source density distribution 104
2.3.5 Interpretation5
2.3.5.1 Historical data8
2.3.5.1.1 Isotopie composition2 Radiation removal cross section
2.3.5.2 Experimental data9
2.3.5.2.1 Bulk quantities and radiation removal parameter 111 2 Radiation transmission andl cross section2
2.3.5.2.3 Surface-escape probability 113 4n current at the surface and source
density distribution4
2.3.5.2.5 X-ray transmission pattern
2.3.5.3 Statistical data6
2.3.5.3.1 Frequency distribution of matrix composition and first
guess of radiation escape probability
2.3.5.3.2y distribution of radiation leakage rate and
instrumental requirements
2.3.5.3.3 Frequency distribution of radiation escape probability 117
2.4 Conclusions 118
2.5 Some Remarks on Standardization 120
References 122
Appendix 2.1 Radiation escape from a purely absorbing
homogeneous sphase3
Chapter 3 : Passive Gamma Assay
3.1 Fundamentals9
3.1.1 Gamma emission processes 131
3.1.2a ray energy spectra
3.1.3 Selection of gamma energy lines
3.1.4 Leakage of uncollided gamma rays8
3.1.5 Detection of gamma rays 140
3.1.5.1 Scintillation detectors (Nal)2 Semiconductors (Ge)
3.1.6 Instrumentation
3.1.6.1 Characteristics of gamma spectrometers2 2 High resolution spectrometry (Ge)3
3.1.6.3 Lowny (Nal)4 4 Collimator and filter5
3.1.7 Counting statistics8
3.1.8g geometry 151
3.1.8.1 Point detector geometry2
VI 3.1.8.2 Ring detector geometry 152 3 Cylindrical shell detector geometry
3.1.8.4 4ir-detector geometry
3.1.9 Mathematical models5
3.1.9.1l sample6 2 Point source
3.1.9.3 Physical source7 4 Uniformly distributed source in a
homogeneous medium9
3.1.9.5 The equivalent sphere model 160 6 Point detector geometry1
3.1.9.7 Scanning at cylinder wall3 8g atr top (or bottom)
3.1.9.9 4?r-scanning ,. 17
3.1.9.10 Segmented scanning4
3.1.9.10.1 Passive gamma measurements2 Gamma transmissions5
3.1.9.10.3 Homogeneous sample6 4 Segmentwise homogeneous sample7
3.2 Reference Monitor 180
3.2.1 High resolution gamma spectrometry and
π-scanning1
3.2.2 Gamma transmission measurements2
3.2.3 Interpretation^ model4
3.2.3.1 The escape probability (Pe)5
3.2.3.2 Escape probability ratios (Pe/PeiJ3 Self attenuation ratios (Peo/PeJ6
3.2.3.4 The correlation between attenuation ratio of gamma line
pairs and escape probability of the higher energy
line gamma rays 18
3.2.4 Interpretational procedure 198
3.2.4.1 Procedure for experimental data 202 2 Sources of errors
3.2.4.3 Numerical examples5
References 209
Appendix 3.1 - Gamma lines energies and intensities for
nuclides 235U, 237U, 238U, zsepu, 239pUi 24opu, 24iPu and 24iAm . 211
Appendix 3.II - Linear attenuation coefficients of various
materials as functions of energy 220
Chapter 4 : Passive Neutron Assay
4.1 Fundamentals 227
4.1.1 Neutron emission processes 231
4.1.2 Detection of neutrons
4.1.2.1 Organic scintillators2 2 Thermalizing neutron detector assemblies
4.3.1 Discrimination between spontaneous fission
and (a, n) process :23
4.1.3.1 Time correlated signals
4.1.4 Neutron energy spectrum
4.1.5 Instrumentation 235
4.1.5.1 Fast measurement systems
VII 5.2 Slow measurement systems 235 4.1
5.3 Gross neutron counting9 4.1
4.1 5.4 Coincident neutron counting
4.1 5.5 Background requirements 240
5.5.1 d sources4.1
5.5.2 Measures for background suppression4.1
6 Neutron interactions with materials4.1
4.1 6.1 Elastic scattering · 241
4.1 6.2 Inelasticg of fast neutrons3
6.3 4.1 Radiative capture
6.4 Induced fission4.1
7 Theoretical methods for calculating 4.1
fast neutron penetration through matter 244
4.1 Phenomenology and assessment studies5
4.1 8.1 Neutron reaction and leakage rates
of bare samples 246
4.1 8.1.1 Polyethylene8
4.1 8.1.2 Carbon (C)
4.1 8.1.3 Iron (Fe)
4.1 8.2 Counting of neutron leakage9
4.1 8.2.1 Estimated normalized fast neutron
count rates for PE, C and Fe samples 250
4.1 8.2.2 Counting by thermalizing neutron
detectors 254
4.1 8.2.2.1 Counting efficiency for fission neutrons
4.1 2 Variation of counting efficiency due
to spectrum degradation6
4.1 8.2.2.3 Fission neutron count rates for PE-,
C-, and Fe-samples relative to point source 257
4.1 8.3 Sample-detector interaction effects
(the Albedo Effect)
4.1 8.4 The neutron escape probability 27
4.1 The fast neutron escapey8.4.1
4.1 Epithermal neutron escape probability 280 8.4.2
4.1 The effectiveney8.5
4.1 Effective fission neutron escape probability 8.5.1
curves for PE-, C-, and Fe-samples7
4.1 8.5.1.1 The "Cross-Over" of effective escape
probabilities 28
8.6 4.1 Neutron thermalization 295
4.1 8.6.1 Absorption probability of thermal neutrons6
4.1 9 Some proposals
4.1 9.1 Neutron leakage spectrum unfolding by
variation of the PE-filter thickness
4.1.9.2 Measurements at "Cross-Over" points of the
effective escape probabilities9
4.2 The Reference Monitor 303
4.2.1 The computerized system4
4.2.1.1 Simulation of pulse distributions by
Monte Carlo technique
4.2.1.1 The randomizer and pulse to time converter 306
4.2.1.3 The autocorrelation method7
4.2.1.3.1 Then function 311
4.2.2 The interpretational model5
4.2.2.1 The volume averaged detection probability (e) 318 2 The fast neutron removal9
4.2.2.2.1 The experimental determination of the Albedo Effect 322
4.2.2.3 Guess of 240Pu mass 324
VIII