Within the framework of the Strahlenschutzvorsorgegesetz (StrVG - Act on
the Precautionary Protection of the Population against Radiation), the BSH
routinely monitors radioactivity in the North Sea and Baltic Sea including
the coastal waters. Its function is that of a control station for the Federal
monitoring network operated within the "Integrated Measuring
and Information System for Environmental Radioactivity
Monitoring" (IMIS) of
The
Federal Environment Ministry (BMU). Radioactivity monitoring
covers the following three areas:
-
direct monitoring of accident-related high radioactivity concentrations in
sea water by means of the radioactivity monitoring network
-
determination of specific radionuclides in sea water, suspended particulate
matter and sediment based on extensive sampling and analyses (including trace
analysis) within routine monitoring programmes, and
-
drift forecasts after incidents.
Within the radioactivity monitoring network, which consists of seven offshore
stations, six coastal stations, and three mobile ship stations, the total
gamma radiation is measured directly in sea water using NaI detectors. The
limit of detection of the monitoring measurements is about 1 Bq/l (related
to K40 gamma), depending on conditions at the monitoring station. The data
are transmitted hourly, via satellite or telephone modem, from the fixed
monitoring stations to the BSH's monitoring network computer at Hamburg or
Rostock.
The offshore stationsare operated in connection with the oceanographic monitoring network
of the BSH. They are installed on unmanned equipment carriers (light-vessel
replacement systems, buoy, lighthouse, measuring pile).
The coastal stations are installed on coastal facilities (harbour pier, gauge
station, promenade pier, sea water sampling station). In case of an alarm,
samples are taken by the personnel on duty.
Because of variable water depths at the coastal
stations the measuring instruments used include pressure
sensors enabling the influence of cosmic radiation, which varies in dependence
on the thickness of the water layer above the measuring instrument, to be
compensated in the evaluation of results. Besides, the stations have been
fitted with a novel monitoring instrument developed and tested by the BSH
which, in addition to the total gamma radiation measurements carried out
so far, is capable of determining the activity of individual nuclides by
means of gamma-ray spectroscopy. Even small increases in artificial radioactivity
within the variable spectrum of natural gamma radiation can be detected in
this way, which considerably improves the detection sensitivity of the
instrumentation.
Also three vessels of
the BSH, as mobile stations, have been equipped with radioactivity monitoring
instruments. In case of incidents the ships can detect and measure hot spots
of elevated radioactivity or sources of radioactivity in the sea.
The control station computers at the BSH collect the data from the monitoring
network stations and evaluate them automatically. An in-house alarm is triggered
if the data meet certain pre-set alarm criteria. In case elevated radioactivity
levels are confirmed by analyses of the sample that has triggered the alarm,
an urgent message is sent to the responsible IMIS office at
the Federal Office for Radiation
Protection (BfS)(-->"The Ministry" --> "Federal Office
for Radiation Protection").
All monitoring data received are routinely checked and evaluated for IMIS.
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