**Attachment 6**

**Guidance for the Identification of Targets and**

**Their Ignition and Damage Criteria**

The identification of nearest ignition and damage targets will most
often involve the identification of cables as both ignition and damage
targets. Often the same cable will represent both targets. For cables,
the ignition and damage criteria will be assumed to be the same. Heat
flux and temperature criteria for damage and/or ignition are identified
below:

+----------------------+-----------------------+-----------------------+
| **Table A6.1 -       |                       |                       |
| Screening Criteria   |                       |                       |
| for the Assessment** |                       |                       |
|                      |                       |                       |
| **of the Ignition    |                       |                       |
| and Damage Potential |                       |                       |
| of Electrical        |                       |                       |
| Cables**             |                       |                       |
+----------------------+-----------------------+-----------------------+
| **Cable Type**       | **Radiant Heating     | **Temperature         |
|                      | Criteria**            | Criteria**            |
+----------------------+-----------------------+-----------------------+
| Thermoplastic        | 6 kW/m^2^ (0.5        | 205ºC (400ºF)         |
|                      | BTU/ft^2^s)           |                       |
+----------------------+-----------------------+-----------------------+
| Thermoset            | 11 kW/m^2^ (1.0       | 330ºC (625ºF)         |
|                      | BTU/ft^2^s)           |                       |
+----------------------+-----------------------+-----------------------+

Additional rules for application in the target identification task are:

[Cables in conduit]{.underline} will be considered potential damage
targets, but not ignition targets. Cables in conduit will not contribute
to fire growth and spread. The conduit will be given no credit for
delaying the onset of thermal damage.

[Cables coated by a fire-retardant coating]{.underline} will be
considered as both thermal damage and fire spread targets. For the
purposes of the Phase 2 analysis, no credit will be given to the coating
for delaying or preventing the onset of damage and/or ignition.

In identifying damage targets, do not include components directly within
or associated with the fire ignition source itself. The fire ignition
source will inherently be assumed to be damaged given any fire involving
itself as the source so further evaluation of the components as damage
targets is unnecessary.

> Example: for an electrical panel fire, all equipment and components
> within the panel will be assumed to fail. Per the counting guidance, a
> panel will be defined as a distinct vertical section in this context.
>
> Example: Given a self-ignited cable fire, all cables in the initiating
> raceway will be assumed to fail immediately on fire ignition (time
> zero).

[Mixed Cable Insulation/Jacket Type Configurations]{.underline}

There are cables that are formulated with a thermoset insulation and a
thermoplastic jacket, and potentially, *vise-versa*. Armored cables may
have a bare metal armor exposed, or may have either a thermoset or
thermoplastic covering over the metallic armor. For such cases, some
special consideration is needed.

In the SDP process, the analysis does not distinguish between ignition
and damage behaviors. Ignition of a cable is taken as an indication of
imminent failure. In the assessment of whether to treat a cable as a
thermoset or thermoplastic, the weakest link will dominate. For example,
a cable with a thermoset insulation and a thermoplastic jacket will be
treated using the failure criteria of a thermoplastic cable to reflect
the reduced resistance to ignition of the jacket material. A cable with
a thermoplastic insulation and a thermoset jacket will also be treated
as a thermoplastic due to the likelihood of melting of the insulation
material.

The following table provides a decision matrix for the selection of
which failure/ignition property set to apply to a given cable.

  -------------------------- ---------------------- ----------------------
  **Table A6.2 - Cable                              
  Properties Selection                              
  Decision Matrix**                                 

  **Cable Construction /                            **Ignition/Damage
  Configuration**                                   Parameter Set to be
                                                    Used**

  **Insulation Type**        **Jacket/Covering      
                             Type**                 

  TS                         TS                     TS

  TS                         TP                     TP

  TP                         TS                     TP

  TP                         TP                     TP

  Armored - TS               TS, or No Cover        TS

  Armored - TS               TP Cover               TP

  Armored - TP               TS, TP, or No Cover    TP
  -------------------------- ---------------------- ----------------------

TS = Thermoset TP = Thermoplastic

[Targets other than electrical cables]{.underline} may also be
vulnerable to fire damage. Large, strictly mechanic components (e.g.,
pipes, check valves, structural supports, tanks, etc.) are not
considered vulnerable to fire damage for the purposes of SDP Phase 2
analyses. Should an issue related to potential fire-induced failures of
such elements (e.g., fire-induced collapse of a structure or structural
supports) be deemed relevant, the analyst should consult NRC HQ staff
for guidance.

For the majority of plant components, electrical cables servicing the
equipment (power, control, and/or instrument cables) will be the most
vulnerable aspect of the component. Hence, failure of the cables will
represent the predominant failure mode for the component. In these
cases, the failure criteria for the component will be based on failure
of the cables servicing the component as already described. This
approach applies to any electrical or electro-mechanical component with
a thermal mass that exceeds that of a short segment of cable. Such
components would include motors, pumps, fans, most valves, transformers,
electro-mechanical relays, switchgear, breakers, mechanical switches,
hand switches on a control board, etc.

The only case where damage criteria other than those applied to cables
should be considered is solid state devices and printed circuit based
components (e.g., circuit cards, electronic relays, computers,
electronic signal conditioning equipment, digital instrumentation and
control circuits, electronic displays, etc.). Electronic devices are
generally vulnerable to failure at temperatures much lower than those
that may cause cable failures. If a scenario should arise involving
solid state control components as a potentially risk-important thermal
damage target, the failure criteria to be applied in screening are 0.25
BTU/ft^2^s and 150ºF, unless information is available to indicate the
components are qualified for continuous operation at a higher
temperature. The criteria for ignition of the components will assume
properties similar to thermoplastic cables (0.5 BTU/ft^2^s and 400ºF).

For cables, damage and ignition thresholds are treated as equal. Unlike
cables, for the electronic components, failure of the component [will
not]{.underline} be taken as indication of the ignition of the
component. For electronic components, the ignition temperatures far
exceed the damage temperatures. If electronic components are important
as secondary combustibles (i.e., as a specific path for fire spread to
another critical target), *the ignition criteria established for
thermoplastic cables (as described previously) should be used* to
characterize the ignition behavior of solid state devices and printed
circuit cards.

Intentionally Blank