NUVIA - decommissioning Ing. Tomáš...

Nuclear Technology and Innovation

Ing. Tomáš Grísa NUVIA a.s.

NUVIA - decommissioning Free Release Measurement Facility

Nuclear Technology and Innovation 2

NUVIA Czech / Radioactive Waste Measurement


NUVIA Czech / Radioactive Waste Measurement

• Development, production, supply, implementation and technical support of

measuring systems for:

• Ionizing radiation monitoring and control, Radioactive waste classification and assay

• Radiological characterization of the nuclear equipment, components and buildings

before decommissioning

• Characterization of all radwaste from Dukovany and Temelin NPPs (the

only Czech company authorized by State Office for Nuclear Safety and

Czech Metrology Institute for provision of free release measurement of

RW)

• Measuring systems and spectrometric SW for RW characterization and

FRM (incl. preparation for decommissioning)

• FRM - gamma spectrometry measurement of potentially radioactive materials before

their release into the environment (incl. nonstandard forms)


EMRP Projects


EMRP Projects

• EMRP JRP ENV09 – Metrology for Radioactive Waste Management

(Metro RMW)

• 1. 10. 2011 – 30. 9. 2014

• 7 work packages

• Experimental facility built in NRI Řež

• EMRP JRP ENV54 – Metrology for Decommissioning Nuclear Facilities

(MetroDecom)

• 1. 10. 2014 – 30. 8. 2017

• 7 work packages

• Implementation of free Release measurement facility on decommissioning site (JRC

Ispra)


Clearance levels


Clearance levels in Czech Republic

• Mass and surface activity divided into 4 groups:

• It is impossible to measure each kg of material separately. Assumptions

enabling averaging of activity must be accepted!


Clearance levels in Czech Republic


Free Release Measurement Facility „SuperMUM“


FRMF „SuperMUM“

• New generation of FRMF – „SuperMUM“

• Measuring of waste in boxes (2 types) and 220l drums + universal holder

• Installation in ISPRA (2016)

• 4 HPGe detectors

• 4 plastics detectors & SCA4 (NUVIA) – experimental setup for

segregation facility

• 3 neutron detectors – experimental setup of JRC Ispra

• GAMWIN SW for gamma spectrum analysis

• Low background natural shielding bricks


FRMF „SuperMUM“ – 3D overview


FRMF „SuperMUM“ – Installation in Ispra

Loading conveyor

Unloading conveyor

Safety sensors

Measuring chamber

Cabinet with Electronics


Principle of measurement

• Material is loaded in the box

• The box is put on the loading conveyor

• Operator enters required data

• Material is weighted

• The box is moved into the chamber

• Spectra are acquired at 3 positions

• The box is moved to the unloading conveyor

• Spectra are analyzed

• Results are displayed and saved


Measurement chamber

Lead collimator

Box with material

IDM module


IDM – Interchangeable Detector Module

• HPGe detector (85 mm diameter × 30 mm deep) – 50% rel. eff.

• Mechanical Stirling cooler

• MCA – Digital Signal Processing (DSP)

• Integrated High Voltage supply

• USB connection

• Identical efficiency

Lead shielding

collimator

Detector top MCNP

model


FRMF „SuperMUM“ – Neutron detectors

Neutron detectors

• JRC experimental setup

• Passive neutron counting

• He3 detectors


FRMF „SuperMUM“ – Plastic scintillators

Plastic scintillators

• Implemented to FRMF as an

experimental setup

• Proof of concept for segregation

facility (fast scan of material)

• Material is measured for total

gamma counts

• 4 x 5l plastic scintillators – high

absolute efficiency


Free Release Measurement Facility - Shielding


NuRAD – Special shielding bricks



1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 0.5 1 1.5 2 2.5

Bac

kgro

un

d c

ou

nt

rate

[cp

s]

Energy [MeV]

Background without shielding Background with shielding


Free Release Measurement Facility - Software and

algorithms


Software components

• Measurement and analysis module –

measurement, communication with HW (MCA,

PLC etc.), spectra acquisition and analysis

• Operator module with GUI – control and

visualization, interface for users

• Database – data storage

• Application server – interface for other parts of

system and external systems, web based

application

Web Client Application server

Database

Measuring and

communication

module for FRMF

Client module for

FRMF

Gamma

spectrometric

system

MCA PLC


Software – Client application


Algorithms

I. Input parameters (entered by user)

• Measurement geometry (1, 2 or 3 positions)

• Measurement time

• Material type (steel, aluminum, plastic …)

• Box type

• Filling of box in percent (level)

• Note, description or batch ID

II. Weighing

• Reading gross weight on input conveyor

• Calculating net weight and density of material


Algorithms

III. Spectra acquisition

• HV check

• Detector temperature check

• 4 detectors x 3 positions = 12 spectra files

• All spectra are saved

IV. Searching for hot-spots

• Each spectrum is divided into regions

• Hypothesis test, that CPS (corrected for different efficiency of each spectra due to different geometry –

different segment of the box) in given region are same in all spectra files

• If the hypothesis is rejected, material is said not to be homogeneous

• Results displayed for operator


Algorithms

V. Sum spectrum

• Done only for homogeneous

material (for lower detection limit)

• If hot-spot is found all spectra are

analyzed individually

• Precise energy calibration (identical

FWHM for single and sum spectra)

Single spectrum

Sum spectrum of 12 individual spectra


Algorithms

VI. Efficiency calibration (sum or individual spectrum)

• Eff. file used for actual material, density, filling, container type and geometry (1-3 positions)

• All efficiencies (calibrations) calculated by CMI

• Model verified by comparison with measurement of reference materials


Algorithms

VII. Analysis of spectrum

• Limited nuclide library, based on ROI analysis (expected

nuclides)

• Wide nuclide library, based on peak search

• Activity/MDA calculated

• Raw reports generated

• Results are combined together (greater value selected)

VIII. Scale factors

• Read from customer DB

• Hard-to measure nuclides are calculated and added to

results

IX. Release coefficient calculation

• Comparison with limits

X. Reporting and displaying results to user

XI. Saving to DB

• All data and files are saved to DB using WS (Web Services)


Software – Web based application


Free Release Measurement Facility – Reference materials


Reference materials

• Phantoms (steel & plastic balls)

• Reference materials (gravel, clay, steel tubes)

Steel balls each 100 Bq of Cs-137

Plastic ball

Gravel


Reference materials


Monte Carlo calculations

• Monte Carlo calculations in cooperation with CMI (HPGe detectors and plastic

scintillators)

• Optimization of number and dimensions of detectors

35 Nuclear Technology and Innovation

Ing. Tomáš Grísa

+420 724 901 015

[email protected]

www.nuvia.cz

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