Regulatory oversight of nuclear safety in Finland. Annual ... - STUK

4.1 Loviisa NPP
STUK carried out an inspection of operation activities,
which primarily focussed on the activities
of the power company’s operating and maintenance
organisations and its quality assurance unit.
Following the observations made in the course
of oversight and inspections, STUK required the
Loviisa power plant to develop further the flow of
information between Fingrid, the company responsible
for the monitoring and maintenance of the
national electric grid, and the Loviisa power plant.
Furthermore, the power plant must complete the
instructions for kick-off meetings and implement
the related induction training.
STUK composed a dedicated team for overseeing
the annual maintenance outages. The team
consisted of experts in different fields of technology
as well as of resident inspectors from the department
of nuclear reactor regulation. Following the
oversight, it was found that the annual maintenance
activities of the power plant had, in the
main, been well organised and that the power
company had clear objectives for developing them
further. The oversight team made observations
of varying degrees of importance, mainly related
to the activities of the Loviisa NPP organisation
and to irregularities in certain documents. STUK
paid attention to the cleaning methods and equipment
in work locations where employees could
be exposed to significant amounts of radiation.
Following the observations, STUK required the
power company to improve further the cleaning
methods in use.
STUK used a total of 234 man-days on on-site
oversight during the annual maintenance outages;
these days were made up of equipment and system
inspections and oversight work in different areas
of expertise. In addition, two resident inspectors
worked regularly on site.
4.1.3 Ensuring plant safety functions
Because the plant’s safety functions are secured
with multiple parallel systems and equipment and
in some cases also with systems and equipment
that have different operating principles, the individual
failures observed in the plant’s equipment
have not prevented the activation of safety functions
in any situations.
In 2010, the power company made modifications
to the operation of the pressure emergency
water tanks of the low-pressure emergency cooling
STUK-B 147
system on the basis of updated safety analyses (see
the 2010 Annual Report). The problem has been
the potentially poor leak tightness of the tank’s
original Russian-made isolation balls as there
was a risk that they would release nitrogen into
the cooling circuit when the system was required
to operate. In 2011, the power company commissioned
the Lappeenranta University of Technology
to conduct a series of tests on new isolation balls
from another manufacturer, where the results
were compared with analyses and tests carried out
in 2010 on the old balls. The results indicated that
the new isolation balls of a different structure had
clearly better leak-tightness than the original ones
in a situation where the system is required to operate.
Fortum intends to replace old balls with new
ones starting from the 2012 annual maintenance.
STUK will assess the power company’s modification
proposal in early 2012.
4.1.4 Integrity of structures and equipment
STUK monitored the integrity of structures and
equipment on the basis of the periodic inspection
programmes and repairs and modifications carried
out. No significant deviations were observed in the
monitoring and inspections of the primary circuit
or other equipment and structures important to
safety.
Fortum carried out periodic inspections of pressure
equipment and pipeline condition inspections
as part of the plant units’ ageing management
programs in connection with annual maintenance
outages and during operation. No observations
restricting the use of pressure equipment were
reported following the inspections. However, STUK
observed that some periodic inspections of pressure
equipment had not been carried out by the
due dates, and they had to be carried out later
than planned. Following the observation, STUK
required the Loviisa power plant to develop its
inspections monitoring system and its inspection
activities so that the set deadlines are kept.
In 2011, STUK carried out a special inspection
related to ageing management where the
sufficiency of spare parts and the functionality of
spare parts management at the plant units were
assessed. The inspection found that the licensee is
aware of the challenges related to the availability
of spare parts and has initiated in 2011 a task to
determine spare parts needs. STUK will continue
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