atw Vol. 63 (2018) | Issue 3 ı March
One of the most important feature of
this design is the small core, very
similar to the core of the AVR. The
results of the MCA tests with heat
rise by decay heat (Figure 20) can
be put into consideration. So, we
are able to increase the primary
maximum helium heat temperature to
the highest possible temperatures,
possibly to 1,100 °C, limited only
by the maximum allowable metallic
tube temperature of the He/He heat
exchanger inside the PCPV.
Design of important components
for a new 600 MW el /
1.500 MW th Pebble Bed
Reactor and potential risks
The Pre-stressed concrete
pressure vessel. (PCPV)
The reactor vessel is, for safety reasons,
the most important component
of every nuclear power station. The
calculation for larger cores for pebble
bed reactors showed that the diameter
of the core is too great for construction
using steel pressure vessels and
therefore cannot be manufactured
using metallic materials. It was
decided to look for other construction
materials for a large HTR pebble bed
design with high volume and high
Two solutions had been taken into
consideration, a pre-stressed cast iron
vessel and a pre-stressed concrete
pressure vessel. The PCPV had been
chosen due to its excellent safety
advantages versus the cast iron vessel.
Several safety conditions could not be
reached with a pre-stressed cast iron
vessel and the construction would
have some fundamental problems.
This HTR design was a completely
new construction without any prior
experience and the operational
helium gas pressure was calculated
at 40 bar. It was decided to perform
experiments with a 1:20 scale model.
The model was pressurized with
warm water. Very small cracks began
to form at a pressure between 90-120
bar. The main crack was reached at
After the pressure dropped to 40
bar, the vessel was nearly gastight
again. After the pressure drop the
cables pulled the concrete together
. These results were deemed very
important since this test proved that
oxygen could not enter into the vessel
in event of a crash. Throughout the
testing, all necessary factors were
measured and used as a baseline for
new calculation programs to calculate
the PCPV for the THTR-300.
| | Fig. 21.
Arrangement of stressing cables of the
| | Fig. 22.
Top of the steam generator of THTR-300.
| | Fig. 23.
Installation of the thermal shield.
Development, design and
erection of the THTR-300
pre-stressed concrete pressure
Figure 21 shows the cross section of
the reactor . Located Inside are
the core, graphite and carbon brick
structures, thermal shield, six steam
generators, blowers, shut down rods,
measuring devices, and isolation with
liner and liner cooling system further
the penetrations for the steam generators,
the holes in the concrete are
reinforced by steel layers with steel
tops (Figure 22). There are 135 penetrations
in total, the largest of which
are for extracting the steam generators
at 2.25 m. All of the penetrations
are surrounded by cables and have
| | Fig. 24.
PCPV during manufacturing.
| | Fig. 25.
Model of bottom of THTR-300 core.
| | Fig. 26.
Results of pressure test of the THTR-PCPV.
encountered no design problems. The
construction phase is demonstrated in
Figures 23, 24 and 25.
The results of the pressure test
Figure 26 shows the accuracy between
the measured and calculated
factors. The pressure tests were performed
using nitrogen and helium to
ensure accurate measuring. The design
pressure was 39.2 bar and the
highest possible pressure in case of an
accident was calculated at 46.1 bar.
The test reached the calculated and
highest possible pressure (as required
RESEARCH AND INNOVATION 173
Research and Innovation
The Technology of TVHTR-Nuclear- Power Stations With Pebble Fuel Elements ı Urban Cleve