Whole report - STUK

STUK-YTO-TR 175
mechanical components of the detector head are
also presented in Figure 5. The opening between
the prongs is nominally 149 mm whereas the
thickness of the assembly with a fuel channel is
nominally 139 mm.
The rear end of the collimator housing is enclosed
by a blind flange. The detector head forms a
closed watertight package, which is connected by
a flange joint to a 350 mm long vertical amplifier
housing, which contains the PDT210A module in a
lead shield. All joints are sealed with o-rings to
make the joints watertight. All flanges are fixed
with acid resisting stainless steel screws. The
polyethylene prongs are fixed with screws using a
fixing steel ring to provide an even compression to
the flange of the polyethylene prong.
An 8 m long vertical pipe consisting of four 2 m
long sections holds the detector head during the
measurements and brings the dry cables from the
pond up to the floor level. The pipe sections are
connected to each other by screw joints sealed
with o-rings. An extra 1 m long section is provided
to adjust the height of the vertical pipe at 1 metre
intervals (7, 8 or 9 metres).
The vertical pipe is fixed in the periscope
console in the edge of the pond (Figure 4 and
Figure 5). In order to keep the measurement
system in a fixed position, there is a direction rail
in the periscope console and a collar is attached to
the uppermost pipe section. The collar is wide
enough that the measurement system cannot drop
into the pond. The guide plate of the collar prevents
the measurement system from rotating in
the guide rail. In addition to this, a safety chain
connected to the pond railing holds the pipe in
order to ensure that the measurement system
cannot be dropped into the pond should the pipe
become unfastened from the periscope console.
The height and angle of the fixing in the console is
adjustable. The accurate fixing point can be defined
with the help of the scale of the uppermost
pipe section.
Figure 4. Fastening of the vertical pipe in the periscope
console.
Figure 5. Fastening of the vertical pipe in the periscope
console and the main mechanical components
of the detector head. The safety chain is not presented
in this picture.
8