**Attachment 7**

**Guidance for Fire Growth and**

**Damage Time Analysis**

*[General Caution Regarding Complex Fire Growth Scenarios]{.underline}*

*The fire modeling tools provided to support the Phase 2 fire growth and
damage time analysis are relatively simple correlation-based modeling
approximations. These tools cannot handle all fire growth conditions
accurately. When a scenario presents complicated fire growth conditions,
this scenario is a potential candidate for a Phase 3 assessment.*

**[Fire Growth and Damage Time Analysis - FDS1 Scenarios]{.underline}**

The time to damage for FDS1 scenarios is based on the effects of heating
in the fire plume and/or direct radiant heating. Fire spread to
secondary combustibles may also be a concern.

[Plume heating]{.underline}

For fire plume exposures, the plume temperature at the target location
is estimated. The plume temperature correlation gives a single value
result based on the height above the fire source and fire intensity
(HRR). Another factor that must be input is the convective fraction of
the heat release.

[Plume temperature analysis correlation]{.underline}

The plume temperature correlation used in the SDP is described in detail
in Chapter 9 of NUREG-1805. The **Plume_Temperature_Calculations.xls**
spreadsheet is used to calculate centerline temperature of a buoyant
fire plume.

Inputs required for use of this correlation are also described in detail
in NUREG-1805, and are summarized as follows:

-   Heat release rate of the fire (kW)

-   Distance from the origin to the target within the plume (ft)

-   Surface area of the combustible fuel (ft^2^) \[Use 6.0 ft^2^ as a
    standard value.\]

-   A value of 0.7 is used for the convective fraction

For certain specific physical configurations, the HRR utilized in the
fire plume correlation must be adjusted. In particular, close proximity
of the fire ignition source to a wall or corner amplifies the effects of
the plume as follows:

-   For a fire in an open area (away from walls or corners) the nominal
    fire heat release rate (HRR) is used,

-   For the same fire next to a wall, multiply the nominal HRR by two,

-   For the same fire in a corner, multiply the nominal HRR by four.

Given an exposure temperature, the time to damage for thermoset and
thermoplastic cables, respectively, is estimated in the following
tables:

+-----------------------+-----------------------+-----------------------+
| **Table A7.1 -        |                       |                       |
| Failure               |                       |                       |
| Time-Temperature      |                       |                       |
| Relationship for      |                       |                       |
| Thermoset Cables**    |                       |                       |
+-----------------------+-----------------------+-----------------------+
| **Exposure            |                       | **Time to Failure**   |
| Temperature**         |                       |                       |
|                       |                       | **(minutes)**         |
+-----------------------+-----------------------+-----------------------+
| **°C**                | **°F**                |                       |
+-----------------------+-----------------------+-----------------------+
| 330 ≤ T \< 335        | 625 ≤ T \< 634        | 28                    |
+-----------------------+-----------------------+-----------------------+
| 335 ≤ T \< 340        | 634 ≤ T \< 642        | 24                    |
+-----------------------+-----------------------+-----------------------+
| 340 ≤ T \< 345        | 642 ≤ T \< 651        | 20                    |
+-----------------------+-----------------------+-----------------------+
| 345 ≤ T \< 350        | 651 ≤ T \< 660        | 16                    |
+-----------------------+-----------------------+-----------------------+
| 350 ≤ T \< 360        | 660 ≤ T \< 680        | 13                    |
+-----------------------+-----------------------+-----------------------+
| 360 ≤ T \< 370        | 680 ≤ T \< 700        | 10                    |
+-----------------------+-----------------------+-----------------------+
| 370 ≤ T \< 380        | 700 ≤ T \< 716        | 9                     |
+-----------------------+-----------------------+-----------------------+
| 380 ≤ T \< 390        | 716 ≤ T \< 735        | 8                     |
+-----------------------+-----------------------+-----------------------+
| 390 ≤ T \< 400        | 735 ≤ T \< 752        | 7                     |
+-----------------------+-----------------------+-----------------------+
| 400 ≤ T \< 410        | 752 ≤ T \< 770        | 6                     |
+-----------------------+-----------------------+-----------------------+
| 410 ≤ T \< 430        | 770 ≤ T \< 805        | 5                     |
+-----------------------+-----------------------+-----------------------+
| 430 ≤ T \< 450        | 805 ≤ T \< 840        | 4                     |
+-----------------------+-----------------------+-----------------------+
| 450 ≤ T \< 470        | 840 ≤ T \< 880        | 3                     |
+-----------------------+-----------------------+-----------------------+
| 470 ≤ T \< 490        | 880 ≤ T \< 915        | 2                     |
+-----------------------+-----------------------+-----------------------+
| T ≥ 490               | T ≥ 915               | 1                     |
+-----------------------+-----------------------+-----------------------+

+-----------------------+-----------------------+-----------------------+
| **Table A7.2 -        |                       |                       |
| Failure               |                       |                       |
| Time-Temperature      |                       |                       |
| Relationship for      |                       |                       |
| Thermoplastic         |                       |                       |
| Cables**              |                       |                       |
+-----------------------+-----------------------+-----------------------+
| **Exposure            |                       | **Time to Failure**   |
| Temperature**         |                       |                       |
|                       |                       | **(minutes)**         |
+-----------------------+-----------------------+-----------------------+
| **°C**                | **°F**                |                       |
+-----------------------+-----------------------+-----------------------+
| 205 ≤ T \< 220        | 400 ≤ T \< 425        | 30                    |
+-----------------------+-----------------------+-----------------------+
| 220 ≤ T \< 230        | 425 ≤ T \< 450        | 25                    |
+-----------------------+-----------------------+-----------------------+
| 240 ≤ T \< 245        | 450 ≤ T \< 475        | 20                    |
+-----------------------+-----------------------+-----------------------+
| 245 ≤ T \< 260        | 475 ≤ T \< 500        | 15                    |
+-----------------------+-----------------------+-----------------------+
| 260 ≤ T \< 275        | 500 ≤ T \< 525        | 10                    |
+-----------------------+-----------------------+-----------------------+
| 275 ≤ T \< 290        | 525 ≤ T \< 550        | 8                     |
+-----------------------+-----------------------+-----------------------+
| 290 ≤ T \< 300        | 550 ≤ T \< 575        | 7                     |
+-----------------------+-----------------------+-----------------------+
| 300 ≤ T \< 315        | 575 ≤ T \< 600        | 6                     |
+-----------------------+-----------------------+-----------------------+
| 315 ≤ T \< 330        | 600 ≤ T \< 625        | 5                     |
+-----------------------+-----------------------+-----------------------+
| 330 ≤ T \< 345        | 625 ≤ T \< 650        | 4                     |
+-----------------------+-----------------------+-----------------------+
| 345 ≤ T \< 355        | 650 ≤ T \< 675        | 3                     |
+-----------------------+-----------------------+-----------------------+
| 355 ≤ T \< 370        | 675 ≤ T \< 700        | 2                     |
+-----------------------+-----------------------+-----------------------+
| T ≥ 370               | T ≥ 700               | 1                     |
+-----------------------+-----------------------+-----------------------+

[Radiant heating]{.underline}

The approach for radiant heating is similar to that for plume heating.
An exposure heat flux is calculated using the appropriate fire modeling
correlation from NUREG-1805 fire modeling tool set, and the damage time
is assessed base on the intensity of the exposure. The inspector must
establish the line of sight distance from the fire to the target. A
second factor required is the fraction of the total fire heat output
that is released as thermal radiation.

-   For evaluating damage due to radiant heat, assume 30% of heat
    released by fire is radiant energy (radiant fraction = 0.3).

[Radiant heating correlation]{.underline}

The correlation for estimating fire radiant heating effects is described
in detail in Chapter 5 of NUREG-1805. Only the Wind Free Condition
correlation is applied in the Phase 2 SDP process. The following
spreadsheet from NUREG-1805 applies:

-   Wind Free Condition (i.e., indoor fires):
    **Heat_Flux_Calculations_Wind_Free.xls** (Click on Point Source) or
    **Heat_Flux_Calculations_Wind_Free_Given_HRR.xls**

Inputs required for use of this correlation are also described in detail
in Section 5.6 of NUREG-1805, and are summarized as follows:

-   Fuel type (material)

-   Fuel spill area or dike area (ft^2^)

-   Distance between fire and target (ft)

-   Vertical distance of target from ground level (ft) \[For Solid Flame
    2 calculation\]

Once the exposure heat flux has been estimated, the time to damage due
to exposure heat flux for thermoset and thermoplastic cables,
respectively, is estimated in the following tables:

  ------------------ -------------------- -------------------------------
  **Table A7.3 -                          
  Estimated Damage                        
  Time for Radiant                        
  Heating                                 
  Exposures -                             
  Thermoset Cables**                      

  **Exposure Heat                         **Damage Time (minutes)**
  Flux**                                  

  **BTU/ft^2^s**     **kW/m^2^**          

  \<1.0              \<11                 No Damage

  1.0                11                   19

  1.2                14                   12

  1.4                16                   6

  1.6                18                   1

  1.75 or greater    20 or greater        1
  ------------------ -------------------- -------------------------------

  ------------------ -------------------- -------------------------------
  **Table A7.4 -                          
  Estimated Damage                        
  Time for Radiant                        
  Heating                                 
  Exposures -                             
  Thermoplastic                           
  Cables**                                

  **Exposure Heat                         **Damage Time (minutes)**
  Flux**                                  

  **BTU/ft^2^s**     **kW/m^2^**          

  \<0.5              \<6                  No Damage

  .5                 6                    19

  .7                 8                    10

  0.9                10                   6

  1.0                11                   4

  1.25               14                   2

  1.4 or greater     16 or greater        1
  ------------------ -------------------- -------------------------------

**[Fire Growth and Damage Time Analysis - FDS2 Scenarios]{.underline}
5.2.6.2Task 2.6.2: Fire Growth and Damage Time Analysis ‑ FDS2
Scenarios**

The analysis of time to damage for FDS2 fire scenarios will be
determined by one or more of the following factors:

-   The time required for fire to grow to a sufficient size and
    intensity so as to create a damaging hot gas layer (HGL) exposure
    condition,

-   The time required for the fire to spread to a critical location
    damaging exposed fire damage targets, or

-   The time required to cause damage to components or cables protected
    either by a moderately degraded fire barrier system or by a
    non-degraded fire barrier system with a fire endurance rating of
    less than two hours.

[Fire creates a damaging HGL - exposed (unprotected) cables]{.underline}

*HGL Exposure Without Fire Spread:*

If the fire ignition source itself is sufficient to create a damaging
HGL, the damage time is taken as the sum of two values; namely, the time
required to create/reach a damaging HGL and the time to damage
associated with the calculated temperature of the HGL. For this case, it
is assumed that the [minimum]{.underline} time required to create a
damaging HGL is 10 minutes. To calculate damage time:

-   Using the FDT HGL spreadsheet, check HGL temperature at 10 minutes.

-   If the temperature at 10 minutes equals or exceeds the damage
    threshold:

    -   Record the calculated HGL temperature at 10 minutes,

    -   Use the cable temperature - damage time lookup table (A7.1 or
        A7.2) to get damage time at the calculated HGL temperature (full
        value is used),

    -   Total damage time is 10 minutes plus the damage time from the
        cable temperature - damage time lookup table

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-   If HGL temperature reaches damage threshold in greater than 10
    minutes:

    -   Determine the time required to achieve the damaging HGL using
        the FDT spreadsheet,

    -   Total damage time is the time to reach damage threshold plus the
        damage time from the lookup table at the threshold temperature
        (i.e., either 28 or 30 minutes depending on cable type).

*HGL Exposure With Fire Spread:*

In some scenarios, fire damage will occur to exposed (unprotected)
cables due to a HGL exposure, but only after the fire spreads beyond the
fire ignition source. The fire ignition source itself may not be of
sufficient intensity to create a damaging HGL, but if the fire spreads
to secondary combustible, then a damaging HGL could be created.

In such situations the secondary combustible is likely to be cables.
Common examples include a hot work fire that ignites a cable tray, a
self-ignited cable tray fire, a transient fire that ignites one or more
cable trays, or an electrical equipment fire that ignites one or more
cable trays.

The Fire Dynamics Tool Hot Gas Layer correlation is applied.

-   Increase (or decrease) the fire HRR in increments of 50 kW until the
    HGL temperature predicted at [10 minutes]{.underline} is above the
    appropriate cable damage threshold (i.e., thermoplastic or
    thermoset). Use the **Time to HGL From Fire Spread_Locked.xls**
    cable fire spread - hot gas layer spreadsheet to determine the time
    to achieve a HGL from fire spread, or perform the following
    calculation:

    -   Subtract from the resulting fire intensity, the fire intensity
        of the postulated fire ignition source.

    -   The remainder of the fire frequency must be accounted for by
        fire spread, presumably into overhead cable trays (the "fire
        spread HRR"):

        -   Assume a that a cable tray will burn at an intensity of 400
            kW/m^2^

        -   Divide the fire spread HRR (in kW) by 400 to determine the
            square meters of cable tray required to create a fire of
            this intensity. (1m^2^ = 10.76ft^2^)

        -   Determine if there are sufficient cable trays available to
            support a fire of this size.

        -   *If the available cable trays are not sufficient to support
            the required fire intensity (there are not enough exposed
            trays), then this FDS2 HGL fire scenario is determined to be
            implausible, and should be discarded. Consider possible FDS2
            scenarios that involve direct spread of fire to the
            necessary target set (see discussion below).*

        -   If the trays present are sufficient, apply the fire spread
            rules for cable tray fires and estimate the time required
            for the fire to spread to this size (e.g., following the
            rules for horizontal and vertical fire spread, and for
            spread to adjacent cable stacks).

-   This time is taken as the FDS2 HGL scenario fire damage time.

[Fire spreads to the location of an exposed fire damage
target]{.underline}

In some scenarios, the mechanism for fire damage may be the spread of
fire from a fire ignition source to the location of a critical target.
In this case, it is likely that fire spread through one or more cable
trays will be the concern. A typical case might involve a fire ignition
source that ignites cables directly overhead, and the subsequent spreads
of fire through the tray(s) to the location of a cable "pinch point"
where the routing of a target cables converge with the fire spread path.

In such cases, the fire damage time is determined by the time required
to spread fire to the target cable location. Once fire spreads to the
target, no additional failure time delay is assumed (due to pre-heating
of the cable during the period of fire spread).

The rules for the analysis of cable tray fires to estimate the required
fire spread time are provided in Attachment 3.

[Fire causes failure of protected cables]{.underline}

In this scenario, a prolonged fire is postulated to cause the failure of
one or more protected cables or components (e.g., cables encased in a
localized fire barrier that is not highly degraded). Due to the low
likelihood of fires lasting two hours or greater, fire scenarios should
not be postulated as leading to the failure of cables protected by a
fire barrier wrap with an effective fire barrier endurance rating of two
hours or more. The barrier would typically be a one-hour barrier (one,
two, and three hour barriers are the most common). Recall that FDS2
scenario can involve either of the following two cases:

-   [A moderately degraded fire barrier that is given some credit for
    fire protection]{.underline}: For a moderately degraded barrier, the
    fire endurance rating is reduced to reflect the degradation. The
    fire barrier system would typically be protecting required or
    associated circuit cables where the Appendix R Section III.G.2
    protection strategy involved a three-hour fire barrier wrap, or a
    one-hour wrap plus detection and suppression.

-   [A non-degraded raceway fire barrier system protecting important
    safe shutdown system with a rating of less than two
    hours]{.underline}: In this case, the barrier may be associated with
    an exemption or exception to the separation requirements of Appendix
    R Section III.G.2, or that analysis may involve a finding against
    other aspects of the III.G.2 requirements (e.g., the fire detection
    and/or suppression systems).

For scenarios involving failure of protected cables, three specific
sub-cases will be considered:

-   Protected cables located directly above the fire (in the fire plume)
    and within the zone of influence for the fire source.

-   Protected cables located outside the zone of influence for the fire
    source where the fire ignition source itself is sufficient to create
    a damaging HGL exposure (no fire spread is needed).

-   Protected cables located outside the zone of influence for the fire
    source where fire spread must occur in order to create a damaging
    HGL exposure.

Each of the specific sub-cases require calculation of the fire endurance
rating of the fire barrier after any penalties for degradation have been
applied. Recall:

-   A non-degraded fire barrier is credited for its full nominal fire
    endurance rating.

-   Moderate A degradation reduces the fire barrier endurance to 65% of
    the nominal rating.

-   Moderate B degradation reduces the fire barrier endurance to 35% of
    the nominal rating.

*Fire Plume Zone of Influence Exposures:*

If the protected cables are located directly above the fire source and
within the zone of influence for the fire source, the damage time is
based on the sum of two time values; namely, the fire endurance time of
the fire barrier system (after applying any degradation penalties) plus
one-half the time to damage normally associated with the fire exposure
temperature at the location of the protected raceway. To calculate
damage time:

-   Establish the fire endurance rating of the raceway (including
    degradation).

-   Use the FDT fire plume spreadsheet to calculate the plume
    temperature at the location of the protected raceway given the only
    the heat release rate of the original fire source (i.e., no fire
    spread is assumed).

    -   If the calculated plume temperature is less than the cable
        damage threshold, use one of the damage time analysis approaches
        that assume the cable is outside the fire source's zone of
        influence.

    -   If the calculated plume temperature equals or exceeds the damage
        threshold, record the calculated exposure temperature and
        continue with this analysis.

        -   Using the cable damage time table (either A7.1 or A7.2) get
            the nominal damage time at the calculated exposure
            temperature. Divide this value by two.

        -   Add the fire endurance rating plus one-half the damage time
            at the calculated exposure temperature.

One cautionary statement is added for this case: If the predicted plume
exposure temperature is very high (e.g., ≥1500°F), this may indicate
that the protected raceway is engulfed in flames from the ignition
source. In such cases, some additional consideration of barrier
performance may be needed. The standard time-temperature exposure test
used to certify such fire barriers does not consider direct flame
impingement. Direct flame impingement may erode a fire barriers
performance substantially. In such cases, it is recommended that
additional guidance be sought from the fire protection staff at NRC
headquarters.

*HGL Exposure Without Fire Spread:*

If the fire ignition source itself is sufficient to create a damaging
HGL, the damage time is taken as the sum of three values; namely, the
time required to create/reach a damaging HGL, the fire endurance time of
the fire barrier system (after applying any degradation penalties) and
the time to damage associated with the calculated temperature of the
HGL. For this case, it is assumed that the [minimum]{.underline} time
required to create a damaging HGL is 10 minutes. To calculate damage
time:

-   Establish the fire endurance rating of the fire barrier (including
    degradation).

-   Using the FDT HGL spreadsheet, check HGL temperature at 10 minutes.

-   If the temperature at 10 minutes equals or exceeds the damage
    threshold:

    -   Record the calculated HGL temperature at 10 minutes,

    -   Use the cable temperature - damage time lookup table (A7.1 or
        A7.2) to get damage time at the calculated HGL temperature (full
        value is used),

    -   Total damage time is 10 minutes [plus]{.underline} fire barrier
        endurance rating time [plus]{.underline} time from cable damage
        time lookup table

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-   If HGL temperature reaches damage threshold in greater than 10
    minutes:

    -   Determine the time required to achieve the damaging HGL using
        the FDT spreadsheet,

-   Total damage time is time to reach damage threshold
    [plus]{.underline} barrier fire endurance time [plus]{.underline}
    damage time from lookup table at the threshold temperature (i.e.,
    either 28 or 30 minutes depending on cable type).

*HGL Exposure With Fire Spread:*

For this subcase, the fire ignition source alone is not sufficient to
create a damaging hot gas layer. This case considers the potential (and
timing) for fire spread to create a damaging hot gas layer. For this
case, the damage time is taken as the sum of three time values; namely,
the time required to create/reach a damaging HGL, the fire endurance
time of the fire barrier system (after applying any degradation
penalties) and the time to damage associated with the calculated
temperature of the HGL. To calculate damage time:

-   Establish the fire endurance rating of the raceway (including
    degradation).

-   Use the FDT HGL tool to determine the HRR needed to get a damaging
    HGL in the room of interest (the required HRR):

    -   Using FDT, input room parameters (dimensions, ventilation)

    -   Adjust the fire HRR assumed in the spreadsheet until the HGL
        temperature at 10 minutes equals the cable damage threshold
        temperature (i.e., 625°F or 400°F depending on cable type).

    -   Record the required HRR value (refine value to no better than
        50kW resolution).

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-   Estimate the time to ignition of the first cable tray above the fire
    ignition source (i.e., in the same manner cable damage/ignition is
    calculated for FDS1 scenarios).

-   Use the cable fire spread - hot gas layer spreadsheet to calculate
    and record the time required for fire spread to create a fire of the
    required HRR.

    -   Inputs are the required HRR, the HRR of the fire ignition source
        itself, the time to ignition of the first tray, number of trays
        in the vertical stack, and average or typical cable tray (or
        cable bundle) width.

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-   Total fire damage time is: fire spread time to reach required heat
    release rate plus the fire endurance rating of the fire wrap plus
    one-half the damage time at a threshold exposure condition (i.e,
    one-half of either 28 or 30 minutes depending on cable type).

*Examples:*

> Example 1: A particular cable tray containing thermoplastic cables is
> wrapped with a fire barrier system that has a nominal 1 hour fire
> endurance rating. The barrier system is degraded, and the degradation
> rating was "Moderate B." Given the degradation, the 1 hour fire
> barrier fire endurance rating is reduced to 21 minutes (35% of the
> nominal performance rating). It was determined that the fire plume for
> a given fire ignition source creates a potentially damaging fire
> exposure condition with an exposure temperature of 245ºC (475ºF). The
> damage time at this exposure temperature taken from the Failure
> Time-Temperature Relationship for Thermoplastic Cables Table above is
> 15 minutes. Hence the net damage time for the protected cables is
> (21+15/2) = 28 minutes. *(Note: The time to damage is rounded down to
> the nearest minute.)*
>
> Example 2: A particular cable tray containing thermoplastic cables is
> wrapped with a fire barrier system that has a 20 minute fire endurance
> rating. The barrier system is not degraded, but failure of the
> protected cables could impact post-fire safe shutdown. It was
> determined that the fire plume for a given fire ignition source
> creates a potentially damaging fire exposure condition with an
> exposure temperature of 245ºC (475ºF). The damage time at this
> exposure temperature taken from the Failure Time-Temperature
> Relationship for Thermoplastic Cables Table above is 15 minutes. Hence
> the net damage time for the protected cables is
> (20+15/2) = 27 minutes. *(Note: The time to damage is rounded down to
> the nearest minute.)*
>
> Example 3: The licensee separation compliance strategy utilized a
> one-hour fire barrier wrap plus automatic detection and suppression.
> The fire suppression system was found to be highly degraded, and will
> not be credited in the analysis. The fire barrier is not degraded and
> will be given full credit in the analysis. One identified FDS2
> scenario involves failure of the cables within the wrapped raceway. It
> was determined that a fire involving a particular fire ignition source
> can create a damaging plume exposure condition. The minimum time to
> fire damage for this FDS2 scenario is one hour. The damage time may be
> longer depending on the calculated hot gas layer temperature. If, for
> example, the hot gas layer calculated at ten minutes equaled 245ºC
> (475ºF), and the cables are thermoplastic, then the total damage time
> would be 10 minutes + 60 minutes + 15 minutes = 85 minutes.

**[Fire Growth and Damage Time Analysis - FDS3 Scenarios]{.underline}
5.2.6.3Task 2.6.4: Fire Growth and Damage Time Analysis ‑ FDS3
Scenarios**

Given the screening criteria used in Tasks 1.3.2 and 2.2.2, FDS3 fire
scenarios will only be analyzed under very specific and limited
conditions. FDS3 scenarios are relevant under one of the following three
cases:

-   Any high degradation fire confinement finding,

-   A moderate degradation fire confinement finding that did not meet
    the finding screening criteria of Task 1.3.2, or

-   A finding other than fire confinement that did not meet the FDS3
    screening criteria of Task 2.2.2.

These three cases are each treated somewhat uniquely.

[High Degradation Fire Confinement Finding]{.underline}

For a high degradation fire confinement finding, a fire barrier
separating two fire areas is assumed to provide no fire protection
benefit. In this case, the only FDS fire scenario(s) being considered
will be the FDS3 scenario(s).

In this case, treat the two fire areas normally separated by the
degraded fire barrier as a single expanded fire area.

Define a set of FDS3 fire scenarios using the rules normally applied in
to define FDS2 fire scenarios (see Step 2.5). Fire ignition sources in
both fire areas are counted and considered to estimate fire frequency
and in developing fire scenarios. All defined scenarios
[must]{.underline} involve damage to targets located in both fire areas.

The newly defined FDS3 scenarios are evaluated using the same tools
applied to FDS2 fire scenarios (see FDS2 scenario analysis guidance).
All fire ignition sources existing in [both]{.underline} fire areas are
included in the fire analysis.

Include credit for any fixed fire detection or suppression systems
installed in either fire area using the general guidance already
provided. For any given fire scenario credit no more than one fixed fire
suppression system (i.e., credit only that fire suppression system that
provides protection for the postulated fire ignition source).

[Moderate Degradation Fire Confinement Finding]{.underline}

For a moderate degradation fire confinement finding the degraded fire
barrier is given some credit for confining fires to the room of fire
origin. In this case, the only fire scenario(s) being considered will be
the FDS3 fire scenario(s).

The fire endurance rating of the inter-compartment fire barrier is
reduced to reflect the degradation (to either 65% or 35% of the nominal
fire endurance rating for Moderate A and Moderate B respectively).

Based on the screening rules used in Task 1.3.2, the fire areas being
analyzed will also display the following characteristics (or else the
finding would have screened to green in Phase 1):

-   The fire endurance rating of the degraded fire barrier is limited
    and implies further conditions:

    -   At most, the fire endurance rating is less than 2 hours.

    -   If the fire endurance rating of the degraded barrier is 20
        minutes or more, then there are in-situ fire ignition sources or
        fire spread paths that can lead to direct flame impingement onto
        the degraded barrier. In this case, focus on these fire sources
        and fire growth scenarios.

    -   If the fire endurance rating is less than 20 minutes, there are
        still potentially damaging fire ignition source present or the
        finding would have screened out in Step 2.4 (no challenging fire
        scenarios).

-   Fixed fire suppression capability in the exposing fire area is
    limited, non-existent, or non-functional so fixed fire suppression
    in the exposing fire area will not credited:

    -   A limited coverage system that does not cover all in situ
        combustible may exist. In this case, consider only the fire
        ignition sources not provided with suppression coverage and do
        not credit fixed suppression.

    -   The fire area may have no fixed fire suppression capability, or

    -   The installed fixed fire suppression system is highly degraded.

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-   The exposed fire area [does]{.underline} contain fire damage targets
    that are unique from those in the exposing fire area and:

    -   Damage targets are exposed (un-protected), or

    -   Damage targets are protected by passive fire barriers with an
        effective fire endurance rating of less than 20 minutes (this
        also covers the credit given a moderately degraded raceway fire
        barrier).

Select/define no more than two fire ignition source / fire growth
scenarios to represent all fires for the FDS3 fire scenario. If
possible:

-   One scenario is chosen that will create a damaging HGL, and/or

-   One scenario is chosen that will lead to fire spread up to, and
    direct flame impingement on, the degraded fire barrier.

If no fire scenario can be developed that satisfies one or both of these
conditions, the FDS3 fire scenarios are deemed to be incredible, and the
finding screens to green.

Fire growth and damage times are estimated using the FDS2 analysis tools
and rules. Determine the time required to:

-   Create a damaging HGL in the exposing fire area, and/or

-   To spread fire to the point where flames will directly impinge on
    the fire barrier (e.g., fire spread along a cable tray).

Choose the one fire scenario that conservatively bounds these two cases
in terms of the fire growth and damage times. The corresponding time is
taken as the fire growth time.

Assume the fire barrier will successfully confine any fire to the
exposing fire area for a period equal to the degraded fire endurance
rating. Add the effective fire endurance rating of the degraded fire
barrier to the fire growth time.

Add to this time the fire endurance rating for any raceway fire barriers
protecting the targets in the exposed fire area.

The result is the total fire damage time:

(fire damage time) = (fire growth time)+(effective fire endurance rating
for the inter-compartment fire barrier)+(effective fire endurance rating
for raceway fire barriers in the exposed area if available).

Continue to step 2.7 using the following assumptions:

-   Use the "All Events" manual suppression curve estimate fire
    non-suppression probability regardless of the fire ignition source.

-   Fixed fire suppression capability may be available in the exposed
    fire area and may be credited as follows:

    -   If a non-degraded water-based automatic fire suppression system
        installed in the exposed fire area, and the system provides
        coverage in the area immediately adjacent to the degraded fire
        barrier, it will be credited for fire suppression prior to
        damage using the nominal reliability of 98% (0.02 failure
        probability) without explicit consideration of actuation timing.

    -   If a moderately degraded water-based automatic fire suppression
        system is installed in the exposed fire area, and the system
        provides coverage in the area immediately adjacent to the
        degraded fire barrier, it will be credited for fire suppression
        prior to damage at a reduced reliability of 90% (0.1 failure
        probability) without explicit consideration of actuation timing.

    -   No other fixed fire suppression capability in the exposed fire
        area will be credited.

[Findings Other than Fire Confinement]{.underline}

For a finding other than fire confinement, the FDS3 fire scenario(s)
will not be the only fire scenarios being analyzed. One or more FDS1 and
FDS2 fire scenarios should already have been developed.

FDS3 scenarios do not need to be considered for this case if the
analysis:

-   Was unable to identify any credible FDS2 damage scenarios, and

-   Did not identify any FDS1 scenarios the could lead to direct flame
    impingement on the degraded fire barrier.

If these conditions are met, proceed to Step 2.7. The FDS3 fire
scenarios will not be considered credible and need not be further
analyzed.

Based on the screening rules used in Task 2.2.2, the exposing and
exposed fire areas will also display the following characteristics (or
else the finding would have screened to green in

Phase 1):

-   The fire endurance rating of the inter-area fire barrier will be
    less than two hours, but the barrier should note be degraded and
    will be given full credit for containing fires to the exposing fire
    area for a time equal to the fire endurance rating.

-   There will be no non-degraded fixed fire suppression capability in
    either the exposing or the exposed fire area. Fixed fire suppression
    systems will not be analyzed.

    -   No credit is given to a highly degraded water based system
        given.

    -   A degraded gaseous system either (moderate or high) may be
        present but will not be credited in the FDS3 scenarios. Fixed
        fire suppression capability may be available in the exposed fire
        area.

        -   The exposed fire area [does]{.underline} contain exposed
            (un-protected) fire damage targets that are unique from
            those in the exposing fire area.

One fire scenario will be selected to represent the FDS3 fire scenarios.
The representative scenario will be chosen from the following cases:

-   Any FDS2 fire scenario associated development of a HGL.

-   Any FDS1 or FDS2 fire scenario that could result in direct flame
    impingement on the degraded fire barrier. If necessary, extend the
    fire spread time analysis to encompass fire spread up to the fire
    barrier (e.g., along a cable tray) if this was not already done for
    the selected scenario already.

From the available scenarios meeting these criteria, select the scenario
with the shortest FDS fire growth and damage time. This will be used as
the representative fire growth time for the FDS3 scenarios.

Assume the inter-compartment fire barrier will successfully confine any
fire to the exposing fire area for a period equal to the degraded fire
endurance rating. Add the effective fire endurance rating of the
inter-compartment fire barrier to the fire growth time.

Add to this time the fire endurance rating for any raceway fire barriers
protecting the targets in the exposed fire area.

The result is the total fire damage time:

(fire damage time) = (fire growth time)+(effective fire endurance rating
for the inter-compartment fire barrier)+(effective fire endurance rating
for raceway fire barriers in the exposed area if available).

Continue to step 2.7. For FDS3 scenarios, use the manual suppression
curve for the "All Events" category to estimate fire non-suppression
probability regardless of the fire ignition source.