atw - International Journal for Nuclear Power | 02.2022

atw Vol. 67 (2022) | Ausgabe 2 ı März
systems, DHR1 and DHR2, both composed of Isolation
Condenser systems (IC) connected to Steam
Generators (SG) secondary side (i.e. one IC for each
SG) [3]. The use of passive systems for decay heat
removal systems gives large grace times available
for the operator intervention, if needed [9]. There is
no need for core catcher due to the fact that the
scenario of core melt is practically eliminated by
design. Also, there is no risk of re-criticality in case
of core damage due to the floating of the fuel
elements in the lead coolant [3]. There are large
safety margins in terms of core voiding by a very
improbable vaporization of the lead. On the other
hand, lead is a low moderating medium and has low
absorption cross-section leading to a hard neutron
fast spectrum.
The lead-cooled fast reactors concepts have taken
into account the corrosive nature of lead oxide and
its tendency to form deposits in the form of slag
accumulations (formed by the interaction of the
coolant with moist air and their accumulation on
metal surfaces in reactor core), which have been
minimized by use of coolant chemistry control
systems [3], [9]. The extremely corrosive character
of molten lead on structural materials is controlled
by managing the oxygen level in the primary circuit.
The formation of lead oxide deposits is inhibited by
reducing the oxide with the help of hydrogen. To
avoid contamination of the lead with oxygen from
the air, the free space above the coolant is filled
with inert gas [3].
In addition to noble gases, lead is considered to
have a high capacity to retain fission products. It
has been observed that iodine and cesium tend to
form stable compounds with lead up to a temperature
of 600 ° C. Thus, following an event that would
lead to a massive failure of the fuel clad, the noble
gases would be released into the cover gas, while
the fuel and other fission products would be
retained in the coolant, either by solubilization or
forming lead compounds. Volatile fission products
could be released also into the cover gas. Because
due to the low-pressure pool configuration of the
reactor vessel, coolant loss events are highly unlikely
and self-limiting (due to solidification of lead
as its temperature decreases), radioactivity release
accident scenarios are almost exclusively related to
cover gas leaks [3].
Regulatory frame
The Romanian authorization practice for nuclear
installations is based on the provisions of Law no.
111/1996 and of the regulations issued by
Romanian Regulatory Authority in Nuclear -
National Commission for Nuclear Activities Control
(CNCAN) [2]. As required by law and regulations,
the primary responsibility for the safety of a nuclear
power plant rests with the licensee. It is also stipulated
that for each of the stages of the life of a
nuclear installation a license is required. For a
nuclear power plant, the authorization steps include
obtaining a license for the design, siting, construction,
commissioning, operation and decommissioning
[2].
Regarding the authorization of a nuclear installation,
three main topics should be followed, topics
related to obtaining the authorization for location,
obtaining the construction and operating license,
and obtaining the environmental permit.
When ALFRED implementation in Romania was
decided, the existing Romanian regulation framework
hadn’t been explicitly applied to advanced
reactor systems, and demonstrator-type reactors.
There are no regulatory policy statements specifically
developed for Gen.IV reactors, and particularly
for ALFRED design [4].
Up to now, only commercial reactors, with prior
validated designs, have been approved for construction,
and therefore the acceptance of a proposed
design by CNCAN has only occurred upon issuance
of the construction license. The norms about reactor
licensing [2] are stipulating the typical route of
submittal, by the applicant, of Safety Analysis
Reports (first Preliminary one, then Final) [4].
FALCON Efforts
An international Consortium Fostering ALFRED
Construction (FALCON), having as members the
well-known organizations Ansaldo Nucleare
(Italy), ENEA (Italy) and RATEN ICN (Romania)
has been established in 2013, with the aim to implement
ALFRED as the prototype of a viable LFR technology,
in the Small Modular Reactor (SMR)
segment, by 2035-2040 [1], [17]. Based on its
member activities, FALCON represents a central
point for gathering European organizations who
aim to implement ALFRED as cornerstone of the
LFR technology.
As a member of the FALCON Consortium, RATEN
ICN is responsible for the licensing activities of the
ALFRED project in Romania, and is consequently
the main promoter of these activities in relation to
CNCAN. CNCAN was officially notified in 2017 of
the intention to authorize the lead-cooled demonstration
reactor, and the notification was the starting
point for multiple meetings and discussions
between CNCAN and FALCON members.
Facing the foreseen licensing of ALFRED, both
parties, CNCAN and FALCON Consortium,
convened about the benefit of adding a preparatory
phase to the authorization process (in anticipation
OPERATION AND NEW BUILD 43
Operation and New Build
Setting-up the Pre-Licensing Phase for Alfred ı Mirela Nitoi