atw 2015-01

atw Vol. 60 (2015) | Issue 1 ı January
Completeness Assessment of General
Safety Requirements for Sodium-Cooled
Fast Reactor Nuclear Design Utilizing
Objective Provision Tree
Namduk Suh, Moohoon Bae, Yongwon Choi, Bongsuk Kang and Huichang Yang
1. Introduction The Korea Atomic Energy Research Institute (KAERI) is developing a Prototype Gen-IV Sodiumcooled
Fast Reactor (PGSFR) of 150 MWe size with a plan to apply the construction permit by 2020. The Korea Institute
of Nuclear Safety (KINS) is performing a regulatory research to prepare the licensing of this future reactor, developing
regulatory requirements and safety analyses methodologies.
The development of regulatory requirements
is needed because in a
prescriptive regulatory framework adopted
by the countries like United
States or Korea, licensing review of
nuclear power plant is performed
evaluating whether the design satisfies
the prescriptive design criteria or
regulatory requirements previously
established. For this, U.S. Nuclear Regulatory
Commission (NRC) has the
well established General Design Criteria
(GDC) [1] for Light Water Reactor
(LWR) that served for many decades
in assuring the safety of the nuclear
power plant. The GDC is top level
regulatory requirements enforced by
law. The corresponding regulatory requirements
for LWR are stipulated in
the Korean “Regulations on Technical
Standards for Nuclear Reactor Facilities”
which has the same level of binding
force and similar contents with
those of GDC. Thus, preparing the licensing
of PGSFR requires first of all a
development of GDC like General
Safety Requirements (GSR) for SFR.
The approach we use in developing
the GSR for SFR is 1) to evaluate the
applicability of the current LWR GSR
to SFR and 2) to reflect the other
safety requirements for SFR, developed
by Gen-IV International
Forum (GIF) or American Nuclear Society
(ANS). Following this approach
we have developed a draft version of
SFR GSR with 59 articles. The next
step is to assess the draft versions for
its completeness and the normal approach
is to depend on the engineering
judgement of experts. The NRC’s
GDC is developed also based on the
accumulated experiences of LWR licensing
and operation, but unfortunately
the similar experiences are not
available for SFR. To assure that the
developed GSR includes all the necessary
requirements and guarantee the
safety of SFR from Defence-in-Depth
(DID) point of view, we have decided
to utilize the Objective Provision Tree
(OPT) methodology developed by International
Atomic Energy Agency
(IAEA) [2]. We found that this methodology
provides a systematic and integral
approach in complementing the
GSR developed referencing the current
requirements of similar kind.
The OPT is a methodology to ensure
and document the provision of
essential “lines of protection” for successful
prevention, control or mitigation
of phenomena that could potentially
damage the nuclear system.
[2,3] The OPT is normally developed
by designer to confirm whether the
design fulfills the DID concept, but we
have developed the OPT to apply it in
assessing whether there is missing
safety requirements in our GSR under
development from DID concept. In the
following section, we first describe the
strategy of GSR development for SFR
and the next section presents the development
of OPT. Then, the completeness
assessment on the requirements
of nuclear design utilizing the
“reactivity control” safety function is
presented in the following section.
Through out this paper, we will use a
terminology GSR for common understanding,
instead of GDC or Technical
Standards which are used in the regulation
of United States and Republic of
Korea, respectively.
2. Development of general
safety requirements
for SFR
This section describes the position of
general safety requirements in the
framework of Korean atomic law system
and then how we have developed
the draft version of the SFR GSR. The
current Korean legal framework for
nuclear safety regulation has 4 levels.
The nuclear safety act positions at the
highest level and then follows, sequentially,
enforcement decree of the
nuclear safety act, enforcement regulation
of the nuclear safety act, regulations
on technical standards for nuclear
reactor facilities. Basic concept
and role of act and decrees are the
following:
1) Nuclear safety act stipulates the basic
principles concerning nuclear
safety
2) Enforcement decree of the nuclear
safety act stipulates the particulars
entrusted by the act
3) Enforcement regulation of the nuclear
safety act stipulates the particulars
entrusted by the Act and/or
Decree and necessary for their enforcement
(including detailed procedures
and format of documents)
4) Regulations on Technical Standards
for Nuclear Reactor Facilities
stipulate conceptual technical
standards as entrusted by the Act
and/or Decree. It contains also the
details on technical standards, procedures
or format as entrusted by
the Act, Decree and/or Regulations
Thus, the GSR which corresponds
to LWR GDC of U.S. NRC is the regulations
on Technical Standards in
Korean atomic legal framework. This
GSR for SFR is developed referencing
the LWR GSR, so the first step is to
evaluate the applicability of the LWR
GSR to SFR. Performing the evaluation
we could classify the requirements
of LWR GSR into 3 groups, i.e.,
1) LWR requirements which are not
applicable to SFR, thus need to be excluded,
2) requirements applicable to
SFR as it is, 3) requirements needed to
be revised/amended. In addition to
this, taking into account the SFR specific
features, there are requirements
to be newly added. The overall
strategy and process are depicted in
Figure 1.
In revising/amending the current
LWR requirements and to identify
ENERGY POLICY, ECONOMY AND LAW 27
Energy Policy, Economy and Law
Assessment of General Safety Requirements for SFR ı Namduk Suh, Moohoon Bae, Yongwon Choi, Bongsuk Kang and Huichang Yang