ML17285A005
| ML17285A005 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 10/11/2017 |
| From: | Leblond P Nuclear Energy Institute |
| To: | Office of Nuclear Reactor Regulation |
| Holonich J | |
| References | |
| Download: ML17285A005 (10) | |
Text
BACK-UP BIN SLIDES Peter LeBlond NEI 96-07 Appendix D Team Nuclear Energy Institute October 11, 2017
An informal Binning System will be introduced to assist in organizing the most common digital-related permutations
- Slide 20 is generalized to describe this approach
- Following this generalization, we can describe four commonly encountered situations.
o Each of these Bins will have a nominally expected outcome Standardized Approach Can Be Graphically Expressed
Identify the DBF(s) involved and classify its relationship with the identified functions below using NEI 96-07, definition 3.3.
(If no DBF apparently exists, specialized evaluations may be required.)
Graphical Summary of Approach Describe the activity Identify any functions involved Identify all Safety Analyses that credit directly or indirectly the DBF identified below.
(If no Safety Analysis apparently exists, specialized evaluations may be required.)
Is the DBF preserved?
Was a FMEA needed to assess the propagation of effects?
Do all assumptions remain valid?
Does the Safety Analysis remain valid?
Determine if SCCF:
Is classed as create a possibility.
Induces effects across trains FMEA is needed?
Slide 20
- Inspection of the graphic on the previous slide results in the recognition that repetitive Evaluation patterns are likely o
In every instance, an individual assessment must be made
- Four expected patterns, or Bins will be described Repetitive Patterns of Evaluation
Repetitive Patterns of Evaluation Four Bins Bin #1 Non-Safety Related Safety Related w/o Single Failure Criteria (SFC)
Requirement Bin #2 Safety Related w/
SFC req.
o NOT immediately required o
NO short-term auto actions Bin #3 Safety Related w/
SFC req.
o SCCF likelihood sufficiently low Bin #4 Safety Related w/
SFC req.
o SCCF likelihood NOT sufficiently low
Description - Involves functions that are either:
o Non-Safety Related o
Safety-Related but not associated with any single failure criteria Discussion Points:
o Typically would be incapable of having a different result (Criterion 2 would control.)
o Safety Analyses already assume mis-behaviour of NSR SSCs o
Care must be taken to ensure all Safety Analyses remain valid (e.g., functions combined, etc.)
Examples:
o Turbine or FW controls o
AFW turbine controls o
MCR Chillers with no rack cooling functions Repetitive Patterns of Evaluation Cont. - Bin #1
Description - Involves Safety-Related functions required to comply with single failure criteria that:
o Are not immediately required to respond to an event o
Typically are not associated with very short-term automatic actions Discussion Points:
o A new FMEA would likely be required o
Compliance with current procedures results in detection and a restorative response Examples:
o Digital EDG jacket water surge tank controls o
MCR Chillers with rack cooling functions o
Radiation Monitors that actuate CREFS Repetitive Patterns of Evaluation Cont. - Bin #2
Description - Involves Safety-Related functions required to comply with single failure criteria and an engineering evaluation determined the likelihood of SCCF is sufficiently low:
o May immediately respond to an event o
Can be associated with very short-term automatic action Discussion Points:
o Does not create a possibility of a SCCF o
Relies on results from engineering evaluations Examples:
o EDG voltage regulator digital upgrade with no analog back-up o
Replacement of transmitters with digital devices that control safeguard actuation Repetitive Patterns of Evaluation Cont. - Bin #3
Description - Involves Safety-Related functions required to comply with single failure criteria and an engineering evaluation determined the likelihood of SCCF is not sufficiently low:
o May immediately respond to an event (typical) o Can be associated with a very short-term automatic action o
System application is complex Discussion Points:
o Does create a possibility of a SCCF o
No potential for FMEA application o
LAR required Examples:
o Reactor Protection System upgrade Repetitive Patterns of Evaluation Cont. - Bin #4