14.7 - Fault and Protection Schedule - EDF Hinkley Point

PRE-CONSTRUCTION SAFETY REPORT
CHAPTER 14: DESIGN BASIS ANALYSIS
SUB-CHAPTER : 14.7
PAGE : 15 / 48
Document ID.No.
UKEPR-0002-149 Issue 02
3.6. PERMISSIVE SIGNALS
3.6.1. Definitions
Permissives are introduced to authorise the activation or deactivation of certain protection
signals, according to the current operating status of the plant unit. Consequently, certain manual
or automatic actions, related to the permissive, are authorised or not.
As these deactivations are detrimental to safety when the reactor is at power, they are
authorised only in certain conditions, called permissives.
Each permissive is associated with a key. The permissive corresponds to the condition to be
satisfied, and the key launches the actions authorised by the permissive. There are two types of
permissives, depending on whether the key triggers automatic or manual actions. A given
permissive can be of the manual type with respect to activation, and be automatic with respect
to deactivation, or vice versa.
Permissives are identified by the letter P followed by a suffix. Permissives related to PS
protection functions are for example: P12, P14, P15... Keys are identified by the word KEY
(upper cases) followed by the same suffix as the associated permissive (e.g. KEY12 for P12).
3.6.2. Principles
It must be possible to perform the actions associated with the permissives in normal operating
conditions and in post-accident phases. Therefore, validation of permissives and KEY actuation
by the operator is possible from both the PICS (Process Information and Control System) and
the SICS (Safety Information and Control System). The PICS and SICS are the systems which
allow the display of information from the different I&C automation systems in the main control
room.
3.6.3. Permissive list
Examination of permissive requirements with respect to P/S related protection functions has led
to definition of the following list (non exhaustive):
NAME
P12
P13
P14
P15
P16
P17
P18
P19
USE
Inhibition of signals for return to cold shutdown
Inhibition of signals for draining or filling of SGs during cold shutdown
Authorisation to connect LHSI in RHR mode
Activation of loop level protection
Authorisation to switch RIS [SIS] cold to hot leg injection
Activation of cold overpressure protection
Authorisation to open transfer blowdown lines between SG
Authorisation to perform secondary depressurisation