Health assistant's evening routine

It is late afternoon over Risø, and the shadows from the silver poplars have grown long. However, the security team at DD is staying put, even though the lights are being switched off one by one in the offices. There are always people on the Risø site, around the clock, all year round, where DD's guards go around checking the buildings and taking samples, among other things.

H Health assistant Jens Heidelbach takes out a log sheet and reviews the comments left by the outgoing guard. In addition to the usual tasks, there is a message in the log sheet that he must measure a concrete cutter. It has been used in the reactor hall and nothing can leave the area without being checked for radioactivity. Not even humans.

Jens takes a handful of small, numbered paper bags and an overview and sets out on the evening round. This evening, among other things, he will be laying behind the DR3 reactor and checking the area by the cabin where sandblasted demolition waste will be carried out. Along the way, he bows and dries vigorously on the floor in the places designated by the inventory. Exactly the same places are dried and control measured every Thursday. Exactly the same every Tuesday. The round is part of the DD quality assurance provided by the nuclear regulatory authorities:

Continuous measurements of radiation levels, surface pollution and air pollution shall be carried out at nuclear installations and levels shall be established to trigger predetermined action plans.

This means that every night health assistants walk around DD 's area, rubbing samples of the floor in several places and checking them for radioactivity. About 8,000 samples a year. After each round, the samples are put in a drawer in the multi counter at the laboratory. It measures alpha and beta activity, and all results are checked and stored.

The air is controlled
With him out on the round, Jens has a long glass flask. It is a freezing trap that can detect radioactive contamination from the air. The freezer trap picks up the humidity with any substances that may get stuck in it. Jens pulls up a frozen freezer trap and puts the new one in. He also changes the air filter through which the dry ventilation air from the DR3 reactor is sent. The procedure is subject to Operational Limits and Conditions . Every day, wiping samples and controlled air filters are taken.

Inside the DR3 reactor itself, Jens checks the computer screen on a so-called iCAM that measures the dust in the air. The acronym stands for Continuous Air Monitor, and the instrument constantly sucks air through a filter. The measurements are stable and show nothing abnormal. Today's work on milling concrete from the reactor's façade can be seen on the filter. The underside is white, as when the filter was inserted. The upper side is dark grayish brown. The work has been dirty, but there has been no unexpected radioactivity on filtered.

The filters are measured
Jens reviews the various instruments in the reactor hall, but no one shows any impacts or levels above the expected background level. Then he enters the lab and puts the wiping samples in the drawer for the multi counter with tweezers. It takes about ten minutes to get the results out of the samples. The dry air filter from the ventilation takes some longer. 10,000 seconds or just under three hours, the filter must be in a box of lead stones while measured with a gamma spectrometer. The instrument's sensitive meter or detector is of germanium, which is cooled down with liquid nitrogen. The container is empty, so Jens grabs a glove and fills up. Liquid nitrogen is minus 196 degrees celcius and provides immediate frostbite if it gets on the skin.

Control of tools and laundry
While the samples and air filter are put over for measurement, slowly wipe the freezer trap onto the table. The liquid must be poured into a bottle, which is sent for analysis by DTU Nutech, located in the neighboring building. DTU Nutech is Denmark's research centre for radioactive substances, and DD in several areas. Jamie goes out to perform the other control tasks. The concrete cutter stands on a pallet in the AH hall, and Jens carefully strokes over it with a handheld measuring instrument, a so-called plastic scintillation counter, but he finds no trace of radioactivity. Then the cutter gets a label telling it to leave the area. Two green garbage bags and six red laundry bags are also checked and labelled ok.

The evening falls and it's time for dinner. DD The health assistant guard spends the night in the area and hands over the guard to the replacement the next morning.



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