Radiation Protection Dosimetry (2014), Vol. 160, No. 4, pp. 259 –263 Advance Access publication 12 February 2014

doi:10.1093/rpd/ncu010

REMOTE MONITORING OF NUCLEAR POWER PLANTS IN BADEN-WUERTTEMBERG U. Neff1,*, U. Mu¨ller1, C. Mandel1, P. Coutinho1, R. Aures1, C. Grimm2, M. Hagmann2, T. Wilbois3 and Y. Ren3 1 State Institute for Environment, Measurements and Nature Conservation, Baden-Wuerttemberg (LUBW), Karlsruhe, Germany 2 Ministry of the Environment, Climate Protection and the Energy Sector, Baden-Wuerttemberg (UM), Stuttgart, Germany 3 T-Systems GEI GmbH, Ulm, Germany

As part of its responsibilities as nuclear supervisory authority, the Ministry of the Environment, Climate Protection and the Energy Sector Baden-Wuerttemberg (UM) operates a computer-based system for remote monitoring of nuclear power plants (NPPs) (KFUe, Kernreaktor-Fernu¨berwachung). In addition to the Baden-Wuerttemberg NPPs located at Philippsburg, Neckarwestheim and the disused Obrigheim, those in foreign locations close to the border area, i.e. Fessenheim in France, and Leibstadt and Beznau in Switzerland, are monitored. The KFUe system provides several methods to evaluate and present the measured data as well as to ensure compliance of threshold limits and safety objectives. For the UM, it serves as an instrument of the nuclear supervision. In case of a radioactive release, the authorities responsible for civil protection can use dispersion calculations in order to identify potentially affected areas and to initiate protective measures for the population. Beyond the data collected at the plant sites, various international radiation and meteorological measuring networks are integrated in the KFUe. The State Institute for Environment, Measurements and Nature Protection (LUBW), the technical operator of the KFUe, runs its own special monitoring network for ambient gamma dose rate and nuclide specific activity concentration measurements in the vicinity of each NPP. This article gives an overview of the solution to combine data of different sources on a single screen: dose rate networks, dose rate traces measured by car, airborne gamma spectra of helicopters, mobile dose rate probes, grid data of weather forecasts, dispersion calculations, etc.

INTRODUCTION The KFUe collects data from various types of measuring networks and mobile devices (Figure 1). The task of the communication server is to manage the data exchange with measuring stations and the other measuring networks. Its second task is to convert data formats into an own internal KFUe format used in the central database. The flexible structure of the database allows handling the heterogeneous data structures, including non-uniform time series. Beyond the data of the nuclear power plants (NPPs) and the own measuring networks, a bilateral and cooperative data exchange is practised with numerous partners: German states Hesse, Bavaria and Rhineland-Palatinate; the Federal Office for Radiation Protection (BfS); the German Weather Service (DWD), the fire departments with their ABC-explorer vehicles; France (EDF, IRSN), Switzerland (ENSI, NAZ), etc. Altogether, 5000 measurement time series are recorded with various time resolutions, such as 1 s or 10 min. THE KFUe CLIENT SOFTWARE As shown in the screenshots on the right side of Figure 1, the KFUe provides several methods and views to analyse and present the data as well as to ensure compliance of alarm limits and safety objectives. For this purpose, a special software—the KFUe

client—has been developed (Figures 2 –4). This tool provides the necessary database queries to present the results in charts, tables or maps. With respect to emergency protection, the major task is to provide an overview of the radiological situation. In addition, it also serves for system administration tasks. The remainder of this paper illustrates some examples of typical evaluation procedures of the KFUe client application. Stationary measurements The LUBW dose rate-measuring network consists of 111 radio probes in the vicinity of the NPPs. Of them, 24 are equipped with two redundant GM tubes with a measuring range of 20 nSv h21 to 10 mSv h21. These probes are engaged in the monitoring area of Fessenheim and Leibstadt. The other 87 probes have two different GM tubes for high- and low-dose rates (10 nSv h21 to 10 Sv h21). The integration time is fixed to 10 min. Every 3 y, each probe is sent to the manufacturer for a complete revision and calibration. The net dose rates are calculated according the algorithm of Czarnecki et al. (1). Mobile measurements Each of the 44 fire departments in BadenWuerttemberg owns an ABC-explorer vehicle

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*Corresponding author: [email protected]

U. NEFF ET AL.

Figure 2. Aerogamma spectrometry exercise in April 2011: a trace of dose rate measured by the helicopter team of the BfS. The chart in the upper corner shows the data as a time series varying from 30 to 110 nSv h21. For a detailed description, see Hohmann et al.(3).

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Figure 1. Basic system architecture of the KFUe. For a more detailed description of the KFUe system and its dispersion calculation, see Wilbois et al.(2).

REMOTE MONITORING OF NUCLEAR POWER PLANTS

equipped with a natural background rejection (NBR) detector. The NBR system uses a plastic scintillator and a proportional counter for higher dose rates. This device produces four-time series of dose rate and is able to discriminate between natural and artificial (low and medium energy) dose rate accompanied by the high-dose rate of the proportional counter. The measurement has a time resolution of 1 s, and each value contains global positioning system (GPS) coordinates. During an exercise, the teams are guided to different incident measuring points in order to perform manual dose rate measurements. On their route, the NBR automatically produces a highresolution dose rate trace. After the ABC explorers have completed their missions, the measured data are uploaded to the KFUe Internet portal and transferred to the central database. The KFUe client software allows the combination of the measurements of different mobile devices like cars and helicopters to get a common view with a harmonised legend on the map. In Figure 4, a combination of 35 missions measured by 19 different teams is displayed. In case of a

radioactive release, the combination of the NBR traces can give a helpful overview of the dose rate and the ground shine in the monitoring area. Whereas the data transfer of the fire brigades is done offline, the NBR systems of the BfS, the Kerntechnische Hilfsdienst GmbH and the LUBW have the possibility to transmit the data continuously and on-line to their headquarters. A useful technique for environmental monitoring is a gamma spectrometric scan by helicopter or plane, called aerogamma spectrometry. After validation of the spectra, surface and specific activities of the ground as well as dose rates are available and can be presented. Similar to car-borne measurements, high-resolution data with GPS information can be visualised. Due to the high spatial resolution, in some cases, an interpolation of the data can be ventured. Therefore, the KFUe client provides various features to visualise the distribution, interpolation and quantification of the data. In order to ensure the necessary performance, the implemented algorithm follows the Delaunay triangulation(4). In addition, a

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Figure 3. Stationary dose rate probes of the KFUe (upper corner right) and the BfS (striped symbols) combined with grid data of precipitation and wind field (arrows), delivered by the DWD in the vicinity of the NPP Neckarwestheim. The chart in the upper corner shows the increase in the 10-min values of a stationary dose rate probe (black dots) from 120 to 180 nSv h21. The evidence for a radon washout is given by the correlation between the does rate and the radar precipitation time series (grey squares) showing a value of 0.8 mm h21.

U. NEFF ET AL.

couple of parameters are available to optimise the representation of the data (e.g. by defining scales in space and time in order to generate mean values). To detect hidden peak values, the traces can also be shown in a chart as indicated in Figure 2. Each point of the chart can be centred on the map by mouse selection.

Quasi-stationary measurements The LUBW operates a couple of quasi-stationary dose rate probes equipped with GPS modules and the same detectors such as the stationary probes. They are located at local fire departments in the monitoring area of the NPP in Fessenheim, France. In case of a radioactive release, they can be installed by the fire brigades to intensify the dose rate network. The GPS module is triggered by a movement sensor. If the probe is moved to another location, the GPS module is activated and the new coordinates are sent to the central database within the next data delivery. Because of the uncertainty of the GPS, the database contains an algorithm to check whether the measurement point is new or already known. The history of locations in the database can be edited manually.

When the location of the station has changed, the corresponding icon of the probe moves on the map according to the new location.

Meteorological data The DWD provides two kinds of grid data for the KFUe: radar precipitation measurements and numerical weather forecasts for the most important parameters such as precipitation, temperature, wind, etc. At the moment, two prognostic models are integrated that differ by their spatial resolution, i.e. the COSMO-EU, which contains a forecast of 72 h and a grid resolution of 4` 7 km2, and the COSMO-DE, providing a forecast of 24 h and a resolution of 2` 2 km2. Whereas the forecasts are based on usual geographical coordinates, the radar measurements refer to polar stereographic projection. The mesh size there is 4` 4 km2. For the measuring network administrator, a combined view of the radar measurements and stationary dose rate probes helps to explain increased dose rate values due to rain events. As illustrated in Figure 3, a time series of the selected observable referring to the current spatial position can be obtained by a simple drag-and-drop operation. Here, web services

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Figure 4. Exercise Philippsburg 2010. Combination of simulated dose rates: results of the dispersion calculation (dose rate plume of ground shine), stationary dose rate probes (coloured dots) and car-borne traces (coloured thick lines).

REMOTE MONITORING OF NUCLEAR POWER PLANTS

are implemented to transfer the requested data asynchronously. Simulation mode

REFERENCES 1. Czarnecki, J., Baggenstos, M., Schuler, J. and Vo¨lkle, H. Bestimmung der Nettodosis mit Hilfe der TLDUmgebungsdosimetrie. Loseblattsammlung FS-78-15AKU, Blatt 3.4.1 (1988). 2. Wilbois, T., Ren, Y., Neff, U., Scheuermann, W., Grimm, C. and Hagmann, M. Remote monitoring of nuclear power plants in Baden-Wuerttemberg—from measurement to emergency protection. Radioprotection 48(5), 95–102 (2013). 3. Hohmann, C., Krol, I., Strobl, C. and Thomas, M. StrahlenschutzPraxis, Heft 3/2011. ISSN 0947-434 X, pp. 29 (2011). 4. Delaunay, B. N. Sur la sphe`re vide. Bull. Acad. Sci. USSR 7(6), 793– 800 (1934). 5. Wilbois, T. et al. SIM-NOT—Einsatz von Simulationen im radiologischen Notfallschutz. FþE-Vorhaben KEWA— Kooperative Entwicklung wirtschaftlicher Anwendungen fu¨r Umwelt und Verkehr in neuen Verwaltungsstrukturen, Phase IV, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 7500, pp. 71–80 (2009).

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As shown in Figure 4, the KFUe also provides a separate simulation environment to support regular exercises, in which the interaction of the system and organisations involved is trained(5). When the system is switched to simulation mode, the imported data can be adapted to a fictive level according the scenario of the exercise. The dose rate traces of the ABC explorers, e.g. which showed the normal background level during the upload of the data (blue lines), are now following the simulated ground shine level, when the vehicles have crossed the contaminated area, which is defined by using spatial and time-dependent distribution functions based on dispersion calculations, which defined the scenario (yellow and red lines). The transformation is performed during runtime and the data are stored in the simulation database only. The time series of the stationary dose rate probes (dots) is transformed in the same way as the mobile measurements. It is displayed following the same colour scale as the other dose rate devices. In case of a real incident, this combined view of dose

rate would enable a validation of the calculated diagnostic dispersion calculation by comparing them with the real measured values of the stationary dose rate probes.

Remote monitoring of nuclear power plants in Baden-Wuerttemberg.

As part of its responsibilities as nuclear supervisory authority, the Ministry of the Environment, Climate Protection and the Energy Sector Baden-Wuer...
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