Design of Electrical Power Systems for Nuclear Power Plants (DS430)
Reviewer:
Date: 17.10.2013
COMMENTS BY REVIEWER
WNA
RESOLUTION
Com
ment
No.
Para/Line
No.
Proposed new text
Reason
Acce
pted
Accepted, but modified as
follows
1
Fig
1,3,4
Add the following note, in a
similar manner to that of figure
2
“This figure is only an
example for illustration
purpose of the described
relationship”
Otherwise, the figures may be
interpreted as a requirement to
separate safety from non safety
in the single line diagram
2
1.7, 1.10
There should be no requirements
in a safety guide, only
recommendations.
x
1.7 Accepted.
1.10 wording will be
modified to … the
recommended design
requirements…
3
5.42
1.7. It might not be practicable
to apply all the requirements
recommendations of this Safety
Guide to nuclear power plants
that are already in operation or
under construction. For the
“5.42. When it is impractical to
provide adequate physical
separation and isolation from
electrical faults between a safety
The current text reads as if
physical separation is the usual
practice. This is in fact only
reflecting a particular national
x
This clause is related to
electrical separation
5.42. When it is impractical
to provide adequate
Rejec
ted
Reason for modification/rejection
Current wording:
1.12. Figures 1, 2 and 3 show
examples of the electrical power
systems of nuclear power plants
to illustrate the scope of this
Safety Guide and terminology
used. Further explanation is
provided in the list of definitions.
Fig 1. This figure provides only
an example.
Fig 2. This figure provides only
an example.
Fig 3. Schematic representation of
the different parts of the electrical
power supplies for a nuclear
power plant, as discussed in this
Safety Guide, with their
boundaries. (Typical for one
train.)
See “Design and construction
rules for electrical equipment of
nuclear islands” RCC-E (AFCEN,
December 2012), Volume D
circuit and a circuit of a lower
class function, is not provided
the lower class circuit
(associated circuit) should be:
(a) Analysed or tested to
demonstrate that the association
does not unacceptably degrade
the safety class circuits with
which it is associated,
(b) Identified as part of the
safety division with which it is
associated, and
(c) Physically separated from
other components in the same
manner as the circuits of the
safety division with which it is
associated. […]”
4
5.117
“5.117. The approach for
cable separation should be
justified.
If needed to fulfill safety
functions, Physical separation
by use of appropriate methods
(e.g. distance or physical
barrier) should be provided, as
practice. In Europe, it is not the
case. The proposed modification
reflects this matter of fact and
his therefore more consensual
and not excluding practices in
place on 1/3 of NPPs
worldwide, at least.
Same as it is recommended in
5.129 for example, the approach
should be justified.
The objective is that the safety
functions are fulfilled. It is up to
the designer to justify what is
the most appropriate method
that will allow fulfilling the
physical separation and
isolation from electrical
faults between a safety
circuit and a circuit of a
lower class function, the
lower class circuit
(associated circuit) should
be:
(a) Analysed or tested to
demonstrate that the
association does not
unacceptably degrade the
safety class circuits with
which it is associated,
(b) Identified as part of the
safety division with which
it is associated, and
(c) Electrically Physically
separated from other
components in the same
manner as the circuits of
the safety division with
which it is associated.
x
5.117. Physical separation
by use of appropriate
methods (e.g. distance or a
physical barrier) should be
provided between:
a. Cables classified as
safety and cables
without safety
7500 Electrical Separation
D 7530 Separation of
equipment with different
classifications in the same
safety train
With regard to the electrical
supply, separation is achieved
by selective protection (C
2300), which prevents
an electrical fault on a non-C1
classified outgoing feeder from
causing a loss of supply to a
piece of
equipment with a higher
classification.
However, under certain
conditions specific to each
project, it is acceptable for nonC1 classified equipment
not to be separated
electrically from equipment
with a higher classification. In
this case, the non-C1
equipment is considered to
be associated with the higher
classification equipment and
is subject to the same
separation rules.
See “Design and construction
rules for electrical equipment of
nuclear islands” RCC-E (AFCEN,
December 2012), Volume D 7300
Physical separation:
D 7310 Separation between
different safety trains
The cables in, or associated
relevant, between:
safety function. The guide can
neither impose design solutions
a. Cables classified as
nor specific national practices.
safety
and
cables Otherwise, this would suggest
without
safety that other practices which are
classification; […]
recognized as best practices by
experienced regulatory bodies
are not acceptable.
It may be that a combination of
a) and / or b) and / or c) might
be sufficient to fulfil the safety
functions and not necessarily a +
b + c. This is why 5.117 cannot
be left as currently written.
classification;
b. Cables belonging to
different safety divisions;
c. Cables of different
voltage classes.
5.118. Separation by safety
classification is intended to
avoid damage to safety
classified cables as a result
of failures in systems or
cables without safety
classification. Separation
between cables of different
safety divisions is intended
to prevent a single hazard
from affecting more than
one redundant item in a
safety system. Separation
by voltage classes is
intended to prevent the
electromagnetic
interference expected in
higher energy circuits from
unacceptably affecting
lower energy circuits.
This is already contained in
revised version before the
NUSSC meeting. The
objective is to distinguish
between safety cables and
cables without safety
classification. We have
deleted “lover safety
classifications”.
with, a safety train shall not be
installed on the same cable tray
as the cables in,
or associated with, another
safety train.
Furthermore, the minimum
distance between the two cable
trays shall be 10 cm.
This protects the cables in one
train from damage caused by a
short circuit in a cable, or the
overheating of a
power cable, in the other train
(with the exception of a fire30
that may be caused by these
faults).
D 7320 Separation between
different safety classifications
(in the same
train)
In this case, no physical
separation is required.
D 7330 Separation between
safety-classified and nonclassified cables
Non-classified cables can be
routed along cable trays in a
safety train. They are then
considered to be
associated with this safety train
and are subject to the
requirements in D 7310.
5
6.23
Delete “6.23. It is preferable if
A charged auxiliary transformer
with few operational load which
at least one off-site power circuit failure do not endanger the
safety power supply and do not
is directly connected to each
lead to unwell transient on the
core ease the monitoring of the
division of the safety power
grid connection.
Additionally the note on figure 2
systems without intervening
precise that this is an example.
connections to non-safety buses.
See Figs 1, 2, and 3 for
examples.”
x