11. Overview of ISTec activities - grs.de 11.pdf · 159 [ Annual Report 2008 ] In 2008, again, the...

159 [ Annual Report 2008 ]

In 2008, again, the objectives and main emphases of our activities

were geared to being able to operate competitively as a commer-

cial enterprise in the free market in the future. In addition to the turnovers

and orders in the nuclear sector of the diagnosis and safety technology

segments, the non-nuclear activities in the areas of traffic engineering, pet-

rochemistry and wind energy in particular contributed to achieving this goal.

Dr. Wolfgang Wurtinger

11. Overview of ISTec activities

Activities of the Institute for Sa-fety Technology (ISTec) GmbH

Monitoring of wind power stations. The Condi-tion-Monitoring System (WKA-COMOS) offered by ISTec for the monitoring of wind power stations has been in use in approx. 30 plants of the Fuhr-länder Company. The company eviag AG which will manufacture the FL 2500 by Fuhrländer in li-cence from 2009 on also equips its plants with the WKA-COMOS. Furthermore, service contracts could be concluded for the diagnosis technology-related servicing of Fuhrländer plants in three wind farms.

Air-borne sound monitoring system for gas storage facilities. The monitoring technology based on air-borne sound (ta-COMOS) developed by ISTec for the leakage monitoring of petrochem-ical plants has meanwhile been employed in three gas storage facilities. A fourth gas storage facility in Bierwang, Bavaria, for which Siemens will sup-ply the plant technology, will be equipped with the ta-COMOS technology by Siemens as subcontrac-tor in 2009.

ISTec


Traffic safety diagnosis for ICEs. In the traffic-related sector, the focus is on the activities relating to the further development of the on-board diag-nosis technique for monitoring the bogies of ICE-3. In addition to that, the power cars of the ICE-1 were equipped with the on-board diagnosis tech-nique to ensure by measurement an expansion of the maintenance intervals for the replacement of wheelset bearings. The technical servicing of the ICE-2 (Tz 213) equipped with the on-board diag-nosis technique, which had been resumed in 2007, was continued in 2008 as well. All activities were carried out by order of the Deutsche Bahn AG.

Water law provisions for repositories. In the field of repository safety, the activities commis-sioned by the Federal Office for Radiation Protec-tion (Bundesamt für Strahlenschutz – BfS) on the implementation of the water law-related incidental provisions of the plan approval decision for the Konrad repository took centre stage. Furthermore, an increasing workload originated from orders by the Helmholtzgesellschaft, activities which were started in 2007 in the context of the decommis-sioning of the test repository ASSE.

IT development work. In the IT sector, the de-velopment work on the programme RAMMSIS which was developed in a consortium with GNS could be successfully concluded. It serves the tracking, control and documentation of radioac-tive remnants and waste occurring during the decommissioning of nuclear-powered submarines run by the Russian North Sea Fleet.

As far as research activities are concerned, the main focus was on the projects already begun in 2007 on the development of a suitable degree of complexity for control and instrumentation soft-ware and of methods for the derivation of reliabil-ity parameters. The activities relating to the devel-

opment of methods for the early fault recognition of sensors and measuring channels were conclud-ed in 2008.

Out of the range of ISTec’s activities, two topics shall be discussed in detail in the following. On the one hand, in the field of instrumentation and con-trol, the »Early fault recognition of safety-relevant instrumentation through feature-based condition monitoring« and, on the other hand, in the field of waste management the »Activities relating to the implementation of the qualified permission issued under water law as stipulated in the plan approval decision for the Konrad repository«. Early fault recognition of safe-ty-relevant instrumentation through feature-based condi-tion monitoring

Autoregressive Models (AR). The signal valida-tion or analysis comprises the safe recognition of deterministic proportions. In addition to the Fou-rier analysis, numerous tests to determine a cor-rect autoregressive (AR) model were carried out. All AR models are based on the assumption of a stochastic (stationary/non-stationary) signal.

So far, it has not been tried to solve the prob-lem of analysis and synthesis – as known from the Fourier transformation – by means of an AR model which is based on deterministic functions as sine and cosine.

Autoregressive harmonic analysis (AR-HA). Within the scope of a project funded by the Fed-eral Ministry of Economics and Technology (Bun-desministerium für Wirtschaft und Technologie – BMWi), a new method, the autoregressive har-monic analysis (AR-HA), was introduced. It is based on the assumption that every piecewise con-

11 Overview of ISTec activities


tinuous function can be represented as a sum of harmonic functions (sine/cosine) and a stochastic residual.

The method is based on the invariants K of the harmonic functions:

with being the discrete, equidistantly recorded signal values. From this it follows that only four measured values suffice to yield a complete de-scription of a harmonic function.

Within the scope of the project it was demon-strated that it is possible to find an exact AR model which consists of a superposition of M harmonic functions which can be determined from the 2M+3 previous values. This results in:

In a first step, the 2M + 3 coefficients are de-termined. These contain sums of products of the M invariants from equation (1). The M coef-ficients contain only frequency information. In a second step, the amplitudes and phases are determined.

Model order determination by means of a new discriminant function. It was demonstrated that the order of the AR model cannot be found by means of the analysis of the model residual. This is due to the dependence of the model residual from equation (2) on the number of data points. The Akaike criterion and comparable criteria are inapplicable; this also applies to the analysed de-

terministic case. Therefore, a new discriminant function was introduced. With this discriminant function, the model order can be determined. It is based on the predictive residual (in contrast to the model residual of equation (2)) and the coef-ficient variance of a given model. The capability of this function to determine the exact model order is shown in Fig. 78.

As soon as the correct model order is known, also the amplitudes of the harmonic functions of equation (2) can be determined.

Example of application. The application of the method will be explained by means of the exam-ple shown in Fig. 79-81. The superposition of several harmonic components with some being present only shortly and starting at different points in time is represented over 7 seconds in Fig. 79. The frequency analysis with a Fast Fourier transform (FFT) is shown in Fig. 80. The model order deter-mined with AR-HA is represented in Fig. 81.

In case of an analysis with the discrete Fourier transform (DFT), the entire time sequence (here approx. 7 seconds) is included in the calculation

MODEL ORDER

Fig. 78Curve of the discriminant over the model order per measured value. 100 measured values were represented. The signal con-tains 9 harmonic portions



(see Fig. 80). The temporarily existing components are determined by means of smaller amplitudes. Between the actually existing frequencies, there are additional frequency lines.

With the AR-HA the correct model orders are determined via samples of the length of 2M + 3 (here approx. 42 ms with 9 components). The cor-rect amplitudes can be determined in ranges with a known model order. No »intermediate frequen-cies« occur.

First-time automated determination of the model order of an AR model. The AR-HA meth-od was applied to a signal which consists of har-monic components, equation (2). Within the scope of this project, the automated determination of the model order of an AR model was indicated for the first time, i.e. the synthesis and analysis for har-monic signals was also solved in the time domain. For this case, also an analytical formula of the co-efficients of the AR model was indicated.

In contrast to DFT which requires a set of or-thogonal harmonic functions with equidistant frequencies, the AR-HA functions are not subject

to any restrictions. The required sample length is considerably shorter than in case of DFT. The tracking of a frequency shift to be observed has thus become markedly easier and better.

High sensitivity. A sensitivity analysis conduct-ed within the scope of the project showed that the amplitudes of frequencies above Nyquist frequen-cy can be determined with a high degree of accura-cy, even when they are damped by an anti-aliasing filter. That way, signal components which in other models are treated as noise become available for monitoring tasks. Implementation of the qualified permission issued under water law as stipulated in the plan ap-proval decision for the Konrad repository

Qualified permission issued under water law. Within the scope of the licensing procedure for the Konrad mine as repository for radioactive waste with negligible heat generation, the licensing au-thority required an analysis of the possible pollu-tion of the groundwater with substances listed in

SIGNAL SYNTHESIS

Fig. 79SIGNAL SYNTHESIS over the time with model orders between 8 and 10

FREQUENCY ANALYSIS

Fig. 80Frequency analysis with FFT of the signal from Fig. 79. The upper ordinate limit is 1

AR-HA METHOD

Fig. 81TIME RESPONSE of the model or-der determined with AR-HA Fig. 79



the Lists I and II of the annex to the Groundwater Ordinance (Grundwasserverordnung – GrwV) /1/. Both the analysis and the basic data underlying the analysis constitute the basis of the »qualified per-mission issued under water law for the final stor-age of radioactive waste in the Konrad repository« in Annex 4 /2/ to the plan approval decision Kon-rad (PFB) /3/ in which the radioactive and non-ra-dioactive inventory permissible for final disposal is stipulated:

For 10 radionuclides and the entire alpha and entire beta/gamma emitters, the maximum emplaceable activities at the end of the op-erating phase of the Konrad repository are indicated.

For 94 non-radioactive, groundwater-relevant substances (elements and compounds), the respectively maximum emplaceable masses are specified.

Incidental provisions of the qualified permis-sion issued under water law. To ensure that the permissible masses of the groundwater-relevant substances are not exceeded, the incidental provi-sions of the qualified permission issued under wa-ter law stipulate the following requirements (cit.):

1. The operator has to monitor the composition of the waste destined for final disposal. The radio-nuclides actually emplaced which are listed under I.1 and the non-radioactive hazardous substances (I.2, I.3, I.4) are to be continuously recorded and balanced according to their type and quantity. Hazardous substances which may cause adverse changes pursuant to § 137 NWG /28/ and which are not covered by the permission must not be ad-mitted for final disposal. For the existing condi-tioned waste (so-called old waste), the components of the waste packages are to be estimated. The results of the estimation are to be recorded in the waste data sheets belonging to the packages.

2. The Bezirksregierung Braunschweig (Regional Authority, Braunschweig) being the water author-ity in charge has to be informed of the beginning of the disposal operations four weeks beforehand. The annual data on the actual emplacement has to be submitted to the Bezirksregierung Braunschweig in form of an Annual Report until 31 March of the following year. In doing so, for the emplaced ra-dioactive inventory, the nuclide-specific activity and mass, and for the non-radioactive hazardous substances, the mass of each individual substance have to be indicated.

The operator of the repository, the Federal Office for Radiation Protection (Bundesamt für Strahlen-schutz – BfS), records and balances the substances the masses of which in the repository are to be lim-ited pursuant to the Annex 4 of the PFB Konrad. Basis for the recording and balancing is the mate-rial description of the waste package by the waste generator which was already verified within the scope of the material product control carried out by the BfS. The concept for the material descrip-tion of waste and for the balancing of the danger-ous waste components will be described in the following Basic concept for the material description and balancing

Qualification and Quantification of waste constituents. The determination of the composi-tion or the constituents of hazardous waste is of vital importance for the declaration and balanc-ing. It follows the logic represented in Fig. »BaSIC

ConCEPT«.

The waste to be described, the hazardous compo-nents of which have to be recorded and balanced, is composed of the actual waste material, the mate-rial the container is made of, a fixation, if appli-




cable, and/or shielding materials, where necessary. Knowing its components, this waste is transferred to a level of substances or materials. Here, the con-tainer name »Konrad Container Typ IV«, for ex-ample, is being allocated to the group of »steel« or »alloy« which classifies it in more detail. The level of the substances and materials is itself based on the specifications on the amounts or masses of the hazardous constituents to be declared. Thus, Container Type IV with the intermediate infor-mation steel becomes a quantitative description of the proportion of iron, nickel and similar steel admixtures whereby the hazardous proportions, here, e.g. nickel, have to be recorded and balanced. This information can then be printed as a report in hardcopy form or displayed as dataset in a da-tabase for the purpose of balancing, declaration or documentation.

Description of hazardous materials by may of material and container lists. To meet the require-ments of the incidental provisions 1 and 2 of the qualified permission issued under water law, a multi-stage procedure for the description, verifica-tion, recording and balancing of the non-radioac-tive, hazardous constituents of a waste package will be introduced. Within the scope of this procedure, the material composition of the radioactive waste will be described at first. In doing so, the so-called material list and the container list which represent an overview of the material information on the waste components, waste flows and container ma-terials, which could be made available during the work on the project, serve as basis for the genera-tion of the required descriptions. The material list contains in a structured form, among other things,

Basic concept Qualification and quantification of waste constituents

Waste container

Descriptionby the waste originator

Registration and accountingby the operator

Components

WasteContainerFixationShielding

Documentationin print and in a database

Steel

Hg cI

…

…

Materials

Substances relevant with regard to legal water rights

Identification of substances relevant with regard to legal water rights

concrete


a clear material name, specifications of the ma-terials, risk-relevant properties, thresholds to de-scribe the composition and to record and balance the hazardous material constituents as well as the proportions of the hazardous material constitu-ents in the considered material. The container list comprises specifications about mass, volume and material composition of the used waste container. Description of the material composition

Description threshold. To describe the material composition, the waste generator identifies a ma-terial and its share in the gross mass of the waste package or, if applicable, of a batch or a waste flow. In the next step, he determines the appropriate material for this waste package component in the material list and compares the mass fraction in the waste package with the indicated description threshold. The description threshold is usually 1 % for new waste and 5 % for old waste. For substanc-es which bear an increased risk of adverse changes to the groundwater, the description thresholds are partially even below the mentioned values of 1 % and 5 %, respectively. If the mass fraction of a sub-stance in the waste package exceeds the descrip-tion threshold, the substance and the mass thereof have to be indicated in the material description of the waste package. If the waste package contains substances which are not included in the material list, an application for the inclusion of these sub-stances in the material list has to be filed with BfS. The used waste and inner containers have to be in-dicated with the code stated in the container list and the quantity. For waste containers and inner containers which are not included in the container list, an application for inclusion in the container list must be filed with BfS. The resulting material description is submitted, together with the other waste documentation, to the BfS and will be re-viewed within the scope of a product control.

Reference value for material description. As a rule, the reference value for the material descrip-tion of waste packages is the gross weight of the package. This procedure is not a dilution, but is based on the requirements for radioactive waste. High active waste, for example, requires a radia-tion shield or a thermal shielding which may also contain substances hazardous to water, e.g. lead. In addition, gaps inside of the waste must be avoided, i.e. the waste must be potted. In doing so, also con-taminated potting compounds can be used which, however, have to be considered for both the radio-logical and the material characterisation of a waste package. These substances are appropriately taken into account when fulfilling the incidental provi-sions as well as during the determination of the so-called »slip« (mass of a substance which can, due to the fact that it falls below the declaration threshold, be emplaced into the repository without balancing). Recording and monitoring of non-radioactive hazardous sub-stances

Declaration threshold. As operator of the re-pository, the BfS reviews the material composition of the registered waste packages described by the waste generator. The non-radioactive hazardous substances in the description by the waste gen-erators are identified, recorded and balanced. To that end, the declaration threshold will be used. The declaration threshold is a percentage of the mass from which it is expected that a constituent of the material can have an adverse impact on the groundwater (cf. cut-off value in Directive (EU) 1272/2008 /4/).

Substances which exceed their individual dec-laration threshold are identified as harmful sub-stances. For those, the components which have to be balanced and annually reported to the author-



ity in charge are determined by means of the ma-terial list. The waste generator provides a material description of the radioactive waste to be disposed. In doing so, all components of the waste package such as waste, container, fixation and shielding, have to be considered. The accuracy of the descrip-tion (description threshold) for the respective sub-stance results from the material list.

Data review. As operator, the BfS reviews in a first step all substances stated by the waste gen-erator in respect of their percentage by mass of the waste package. If the percentage by mass of one of the stated substances exceeds the declaration threshold stated in the material list, the substance has to be recorded and balanced. It is classified analogously to the legal provisions on the disposal of conventional waste on the basis of declaration thresholds. Pursuant to the incidental provision 2 of the Annex 4 PFB, the BfS presents the recorded and balanced data annually. Derivation of the declaration threshold

Due to global pollution, some of the substances listed in the incidental provisions issued under water law nowadays occur ubiquitously. This re-sults in these substances occurring in radioac-tive waste in the form of pollution, too, but in concentrations which cannot be detected with a justifiable effort. In this regard, the following specifications are stipulated in Annex 4 of the plan approval decision (PFB) Konrad: »During quantity determination and balancing, the substances small amounts of which may be contained in the package or batch as trace impu-rity are not taken into account. To be considered as trace impurities are both substances pursuant to I.1 to I.4 and other substances the quantities of which can not be quantified. The trace impurities

must not exceed the amount up to which adverse changes in the near-surface groundwater can defi-nitely be ruled out.«

Conformity with AVV. The requirement is im-plemented by means of a specified declaration threshold which indicates the concentration from which a non-radioactive hazardous substance in the waste package has to be recorded and bal-anced. When specifying the declaration thresh-old, again, it is aimed for conformity with the legal provisions on the disposal of conventional waste. As no limit concentrations are specified in the Groundwater Ordinance /1/ underlying the incidental provisions issued under water law, the question arises from which concentration on a substance has to be considered as harmful sub-stance or up to which concentration it has to be considered as pollution. In other European and German legal and administrative regulations, this is specified by the stipulated concentration limits. Pursuant to the European Dangerous Substances Directive /5/ impurities have to be taken into ac-count as far as concentration limits are exceeded. Since the Ordinance on the European list of waste (Abfallverzeichnisverordnung – AVV /6/) of 10 De-cember 2001 came into force, concentration limits have been used for the assessment of dangerous-ness in the German waste legislation as well.

Hazardous waste according to AVV. In respect of the characteristics of hazardous waste proper-ties, the AVV refers in § 3 (2) to the Dangerous Substances Directive /5/ und thus establishes a connection between the properties of hazardous waste and hazardous substances and preparations. The AVV system for the classification of hazard-ous waste is thus based on the classification of substances and preparations according to the law on hazardous substances and uses the character-istics of hazardous substances and R-phrases (risk-



phrases to harmonise the marking of hazardous substances and mixtures) stated there.

Handling of limits. All limits of the regulations are adopted, even though they exceed 1 % as in even case of values above 1 %, the protection goal of the above-mentioned incidental provisions to rule out an adverse alteration of the near-surface groundwater can definitely be achieved.

For substances which do not show hazardous characteristics, it is examined whether a self-clas-sification in a water pollution hazard class accord-ing to the administrative regulation on water pol-lutants (Verwaltungsvorschrift wassergefährdende Stoffe – VwVwS /7/) exists. If this is the case, the water pollution hazard class will be allocated, along the lines of the three graded classifications of water pollution hazardousness in the respective R-phrases, to a concentration which will then be adopted as declaration threshold. Current state of the implemen-tation of the requirements pur-suant to water law

Currently, the concept developed by ISTec by or-der of the BfS is being discussed with the licens-ing authority and its expert. The basic concept of describing and balancing hazardous non-radioac-tive constituents of radioactive waste has been ap-proved already. The discussion focuses on the de-tails of the derivation of thresholds and the proof that an adverse change of the groundwater can be ruled out for the substances individually listed in the PFB Konrad.



Fig. 78Curve of the discriminant over the model order per measured value. 100 measured values were represented. The signal contains 9 harmonic portions.

Fig. 78

MODEL ORDER

14 Annex – Figures Chapter 11

Master file


Fig. 79 (from 79-81)Application example of the AR-HA method

79 SIGnaL SynThESIS over the time with model orders between 8 and 10

Fig. 79

CALCULATION RESULT

Temporary Components (Amp=1)

Time [s]

Am

plit

ude


Master file



80 FREquEnCy anaLySIS with FFT of the signal from FIG. 79. The upper ordinate limit is 1

Fig. 80

CALCULATION RESULT

Frequency [Hz]

Am

plit

ude

100 120 140 160 180 200


Master file



81 TIME RESPonSE of the model order determined with aR-ha

Fig. 81

AR-HA METHOD


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