**NRC INSPECTION MANUAL**APOB

INSPECTION MANUAL CHAPTER 0609 APPENDIX G, ATTACHMENT 3

PHASE 2 SIGNIFICANCE DETERMINATION PROCESS TEMPLATE

FOR BWR DURING SHUTDOWN

Effective Date:  03/01/2020

0609, App F		Issue Date: 02/28/05

TABLE OF CONTENTS0609G Att 03-01	PURPOSE	101.01	ENTRY CONDITIONS FOR SDP-RELATED INSPECTION FINDING	101.02	MANAGEMENT DIRECTIVE 8.3 ENTRY	101.03	APPLICABILITY	10609G Att 03-02	LIMITS AND PRECAUTIONS	10609G Att 03-03	ABBREVIATIONS AND DEFINITIONS	30609G Att 03-04	PROCEDURE FOR SIGNIFICANCE DETERMINATION	5Step 4.1 - Transition from SDP Phase 1		5Step 4.2 - Determine if the finding is a precursor to an initiating event (a loss of the DHR function) or a condition finding	5Step 4.3 – Process for Assessing Precursor Findings	5Step 4.4 – Process for Assessing SDP Condition Findings	7Step 4.5 – Process for Assessing Events Under MD 8.3	10

List of Tables

Table 1 – Initiating Even Likelihoods (IELs) for LOOP Precursors	13

Table 2 – Initiating Event Likelihood (IELs) for Loss of Inventory (LOI) Precursors	14

Table 3 – Initiating Event Likelhoods (IELs) for LORHR Precursors	15

Table 4 – Initiating Even Likelihoods (IELs) for Condition Findings – BWRs	16

Table 5 - Mitigation Capability Credits for Installed Equipment	17

Table 6 - Credit for Temporary Equipment	18

Table 7 - Counting Rule Worksheet	19

List of Figures

Figure 1 – Determination of Applicable POSs and Time Windows – BWRs	12

Figure 2 – Event Tree for Loss of Inventory – BWR POS – 1	37

Figure 3 – Event Tree for Loss of Inventory – BWR POS – 2	38

Figure 4 – Event Tree for Loss of Inventory BWR POS - 3	39

Figure 5 -  Event Tree for Loss of Offsite Power- BWR POS - 1	40

Figure 6 – Event Tree for Loss of Offsite Power – BWR POS 2	41

Figure 7 – Event Tree for Loss of RHR – BWR POS -1	42

Figure 8 – Event Tree for Loss of RHR – BWR POS 2	43

List of Worksheets

Worksheet 1 – BWR Loss of Inventory in POS 1 (Head on)

Worksheet 2 – BWR Loss of Inventory in POS 2 (Head off or RCS Vented)

Worksheet 3 – BWR Loss of Inventory in POS 3 (Cavity Flooded) 

Worksheet 4 – BWR Loss of Operating Train of RHR in POS 1 (Head On)

Worksheet 5 – BWR Loss of Operating Train of RHR in POS 2 (Head Off or RCS Vented)

Worksheet 6 – BWR Loss of Offsite Power in POS 1 (Head On)

Worksheet 7 – BWR Loss of Offsite Power in POS 2 (Head Off or RCS Vented)

Issue Date:  01/08/20	i	0609 App G Att 3 

# 0609G Att 3-01	PURPOSE

The shutdown Significance Determination Process (SDP) consists of three phases:  Phase 1, Definition and Initial Screening of Findings; Phase 2, Initial Risk Significance Approximation and Basis; and Phase 3, Risk Significance Finalization and Justification. Inspection Manual Chapter (IMC) 0609 Appendix G, Attachment 1, Shutdown Operations Significance Determination Process Phase 1 and Initial Screening and Characterization of Findings is used by inspectors to conduct the phase 1 screening analysis. This template is used by SRAs or headquarters risk analysts to perform phase 2 analyses for certain BWR shutdown findings discussed below. 

# 01.01 ENTRY CONDITIONS FOR SDP-RELATED INSPECTION FINDING

This template provides a simplified, risk-informed framework to estimate the increase in core damage frequency (CDF) during shutdown operations due to findings that are identified as requiring quantitative assessment from the Phase 1 screening in IMC 0609 Appendix G, Attachment 1.

# 01.02	MANAGEMENT DIRECTIVE 8.3 ENTRY

Procedures are given in Section 4 for using this template to perform quantitative assessment of shutdown events to satisfy Management Directive (MD) 8.3.   

# 01.03	APPLICABILITY

The process in this template is designed to provide SRAs and analysts with a simple, scrutable probabilistic risk framework for use in identifying potentially risk-significant shutdown issues within the Initiating Events, Mitigation Systems, and Barrier Integrity cornerstones. The results from this SDP tool are intended to facilitate communication on the basis of risk significance between the NRC and licensees. 

# 0609G Att 3-02	LIMITS AND PRECAUTIONS

02.01	LIMITS

This template is a simplified tool that generates order-of-magnitude assessment of the risk significance of inspection findings during shutdown. If appropriate, a more detailed risk assessment may be performed in a SDP Phase 3 evaluation, especially if the analyst feels that the risk is not being properly assessed in the Phase 2 evaluation. Program guidance in IMC 0609, Attachment 5, “Inspection Finding Review Board” and IMC 0609, Attachment 1, “Significance and Enforcement Review Panel Process,” should be followed to determine if a planning SERP is required before committing resources to a detailed risk evaluation in a Phase 3 analysis.    

02.02	PRECAUTIONS

· The SRA or analyst should consider each evaluated Core Damage sequence using the event trees included at the end of this procedure to ensure that the scenario makes sense for the deficiency.  The variability of plant configurations at shutdown and timing issues may result in findings which do not directly map on the event trees.  Contact a risk analyst in NRR/APOB for assistance if needed. 

Issue Date:  01/08/20	20	0609 App G Att 3 

· The SRA or analyst must understand: (1) the differences between precursor and condition findings, (2) the definitions of the plant operational states (POSs), and (3) the definitions of the shutdown initiating events. These terms are defined in IMC 0609, Appendix G.  

· The availability of standby reactor coolant system (RCS) injection along with operator error drives shutdown risk.  As long as standby injection is available, in most cases, standby injection buys time for other operator recovery actions such as: leak path termination and residual heat removal (RHR) recovery.  If there are factors that could render the standby RCS injection unavailable such as: gas intrusion or support system unavailability, then these factors (assumptions) become risk significant and should be assessed carefully.   

· Findings that involve freeze seals that are installed in systems connected to the RCS where failure could lead to a loss of inventory are not covered by these worksheets and go directly to Headquarters for Phase 3 analysis.

· Findings that involve containment closure are assessed using IMC 0609 Appendix H “Containment Integrity Significance Determination Process”.

· It has been identified that it’s possible for operator dominated sequences to have HEP values that are below levels recommended in the Risk Assessment of Operational Events (RASP) manuals Volumes 1 and 4 when following this procedure. Analysts should be cognizant of this potential and pay closer attention to operator action dominated sequences. If an analyst feels that this procedure is not adequately capturing the risk, they may depart from this procedure and perform a Phase 3 detailed risk assessment.

Issue Date:  01/08/20	20	0609 App G Att 3 

# 0609G Att 2-03	ABBREVIATIONS AND DEFINITIONS

03.01	ABBREVIATIONS

CD			Core Damage

High Decay Heat	Decay heat of early time window

Low Decay Heat	Decay heat of late time window

CCW			Component Cooling Water

DHR			Decay Heat Removal

ECCS			Emergency Core Cooling System

IEL			Initiating Event Likelihood

INDIC			Indication

IMC			Inspection Manual Chapter

LOI			Loss of Reactor Inventory Initiating Event

LER			Licensee Event Report

LOOP			Loss of Offsite Power

LORHR		Loss of RHR Initiating Event

OP			Operator

POS			Plant Operational State

PRA			Probabilistic Risk Assessment

RCS			Reactor Coolant System

RHR			Residual Heat Removal

ROP			Reactor Oversight Process

SDP			Significance Determination Process

SG			Steam Generator

SG PORV		Steam Generator Power Operated Relief Valve

SRW			Site Raw Water

SSW			Standby Service Water

TBB			Time to Boiling

TW			Time Window

TW-E			Early Time Window, before refueling operation

TW-L			Late Time Window, after refueling operation

03.02	DEFINITIONS

For a complete list of definitions refer to IMC 0609, Appendix G.

Available - A piece of equipment is considered available if:  (1) it can be put into service within half the time that is needed before the equipment will be used to perform its function, (2) procedures or standing orders exist for using the equipment to meets its intended function, (3) all necessary supporting systems (such as AC power, cooling water, and DC control power) can be put into service within half the time that is needed before the equipment will be used to perform its function, and (4) operators have been trained for using the equipment for the given situation.  

Shutdown Operations - Shutdown Operation exists during refueling outages, forced outages, and maintenance outages starting when the plant has met the entry conditions for RHR/DHR and cooling has been initiated, and ending when the plant is heating up and RHR/DHR has been secured. 

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Types of Shutdown Findings

Precursor Finding - Inspection Findings that: (1) cause an event (e.g., a loss of the operating train of RHR/DHR), or (2) increase the likelihood of an event. 

Condition findings - Inspection findings that only involve a degradation of the licensee’s capability to mitigate an event if an event were to occur. Findings only affecting the standby train of RHR/DHR are condition findings.  

Shutdown Initiating Events

Loss of RHR (LORHR) - Includes losses of RHR/DHR resulting from failures of the RHR/DHR system (such as RHR/DHR pump failure) or failures of the RHR/DHR support systems other than offsite power.

Loss of Offsite Power (LOOP) - Includes losses of offsite power which cause a loss of RHR.

Loss of Reactor Inventory (LOI) - Includes losses of RCS inventory that lead to a loss of RHR/DHR function due to automatic isolation of RHR/DHR on low level or loss of RHR/DHR pump suction. 

Plant Operational States (POSs)

POS 1 - This POS starts when the RHR/DHR system is put into service. The vessel head is on and the RCS is closed such that an extended loss of the DHR function without operator intervention could result in a RCS re-pressurization above the shutoff head for the RHR pumps.

POS 2 - This POS represents the shutdown condition when (1) the vessel head is removed, and reactor pressure vessel water level is less than the minimum level required for movement of irradiated fuel assemblies within the reactor pressure vessel as defined by Technical Specifications OR (2) the vessel head is on; however, a sufficient RCS vent path exists for decay heat removal.  

POS 3 - This POS represents the shutdown condition when the reactor pressure vessel water level is equal or greater than the minimum level required for movement of irradiated fuel assemblies within the reactor pressure vessel as define by Technical Specifications.  This POS occurs during Mode 5 (refueling).

Time Windows

Early Time Window (TW-E) - This time widow represents the time before POS 3 is entered.  The decay heat is relatively high.  The reactor is either in POS 1 or 2.  

Late Time Window (TW-L) - This time window represents the time after POS group 3.  The decay heat is relatively low.  

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# 0609G Att 3-04	PROCEDURE FOR SIGNIFICANCE DETERMINATION

Step 4.1 – Transition from SDP Phase 1

Use the Information Gathered in the Phase 1 process to identify the set of equipment that the licensee planned to meet the following safety functions:  Standby RCS injection, and RCS pressure control if applicable.  

Step 4.2 – Determine if the finding is a precursor to an initiating event (a loss of the DHR function) or a condition finding.

NOTE:	Precursor findings: (1) cause an event (e.g., a loss / interruption of the operating train of RHR/DHR), or (2) increase the likelihood of an event. Condition findings only involve a degradation of the licensee’s capability to mitigate an event if an event were to occur.  Findings only affecting the standby train of RHR are condition findings.  The template treats precursor and condition findings differently. 

Go To Step 4.3 for Precursor Findings 

OR

Go To Step 4.4 for Condition Findings

NOTE:	If this tool is being used to assess a shutdown event under Management Directive 8.3, Go to Step 4.5.

# Step 4.3 – Process for Assessing Precursor Findings

Step 4.3.1 – Identify each time window (TW) and plant operation state (POS) where the finding could have occurred.

Figure 1 defines the POSs and TWs for a BWR plant. It also shows the relationship between the POSs and the modes defined in the Technical Specifications (TSs).

Step 4.3.2 – Determine the IEL.

The initiating event likelihood (IEL) is the conditional likelihood of having a loss of the RHR function given the occurrence of the findings.

· IF a finding increases the likelihood of a loss of offsite power (LOOP) or actually caused a LOOP, THEN LOOP is the applicable initiating event.  Use Table 1 to determine the IEL.  Go to Step 4.3.3.

· IF a finding increases the likelihood of a loss of reactor inventory (LOI) or actually caused a LOI, THEN LOI is the applicable initiating event.  Use Table 3 to determine the IEL. Go to Step 4.3.3.

· IF a finding increases the likelihood of a loss of the operating train of RHR (LORHR) or actually caused a LORHR (except for LOOP and LOI), THEN LORHR is the applicable initiating event.  Use Table 3 to determine the IEL. Go to Step 4.3.3.

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· IF a finding involves the RHR support systems (except for LOOP and LOI), THEN LORHR is the applicable initiating event.  Use Table 4 to determine the IEL. Go to Step 4.3.3.

Step 4.3.3 – Use the SDP worksheet.

Choose the SDP worksheet that contains the POS and initiating event that were determined to be applicable in steps 4.3.1 and 4.3.2. The SDP worksheets are included at the end of this procedure.

Step 4.3.4 – Enter the time to RCS boiling.

Enter the time to RCS boiling and an approximate time to core uncover/core damage in the first line of the worksheet.

Tools exist for determining these times, including an electronic Core Uncovery Calculator located on the RASP Tool Box web page, or by using licensee values if available.

Step 4.3.5 – Fill-in the IEL determined in step 4.3.2 in each row of the lower section of the applicable worksheet.

Determine the credit for each top event function.

A.	Verify that the licensee has the important instrumentation referenced for the top event function.  

NOTE: 	If the licensee does not have the referenced instrumentation available or the referenced instrumentation is not reflective of RCS conditions, then the default operator credit MUST by decreased by two. 

B.  	To obtain the Equipment Credit, credit each available system that is (1) capable of maintaining the top event function and (2) is not impacted by the finding. Use the event tree associated with the worksheet to help understand the successes and failures associated with each accident sequence.  Use the guidance in Tables 5 and 6 to determine equipment credits.  Document key assumptions.  

C.	To obtain the Operator Credit, use the default operator credit unless any of the following four conditions are applicable:

1. If the referenced instrumentation is missing or misleading, then decrease the operator credit by two.

2. The default time is incorrect and significantly reduced.  If the diagnosis time is less than 20 minutes OR the time to perform the action is approximately the time required, then decrease the operator credit by one.

3. If the action is complicated by missing or inaccessible equipment, steam or high radiation, or loop seals for venting pumps, then decrease the operator credit by two.

4. If the procedures are incomplete for the shutdown plant configuration, then decrease the operator credit by one.

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NOTE:	If the default operator credit is changed and results in a negative operator credit, then the operator credit is zero.

D.	Determine the Credit for Function for each Top Event Function needed.  Select the lower of Equipment Credit and Operator Credit and enter the value in this column.

Step 4.3.7 – Quantification of Core Damage Scenarios

Quantify each accident scenario by adding the credits for IEL + Mitigation Credit.   Enter the sum in the Result column.

NOTE:	 For phase 2 analyses, the recovery credit is not used.****

Step 4.3.8 – Identify the frequency of finding occurrence

Select between Condition A or B.

A. If the finding occurred during an outage (forced outage, refueling outage, etc.), the preliminary color of the finding is determined by using Table 7 – Counting Rule Worksheet. The resulting ICCDP associated with the finding is interpreted as the addition to the licensee’s total CDF contribution over the previous year (previous 12 months).  Therefore, the resulting ICCDP becomes the increase in delta CDF.

B.	If the deficiency needs a random event to reveal the deficiency (e.g. at Palisades, the digging of a sign revealed underground protective cabling common to both offsite power sources outside the protected area), then the frequency of the random event (1/32 calendar years of operation) is multiplied by: 

The Frequency that the licensee enters an outage (1 outage per 18 months) * (12 months/ calendar year) *(Number of Days of POS 1 operation/ outage) * (1 calendar year/365 days) *(CCDP of POS 1 operation)

Added to:

The Frequency that the licensee enters an outage (1 outage per 18 months) * (12 months/ calendar year) *(Number of Days of POS 2 operation/ outage) * (1 calendar year/365 days) *(CCDP of POS 2 operation).

# Step 4.4 – Process for Assessing SDP Condition Findings

NOTE:  Only the core damage scenarios impacted by the finding are quantified.

Step 4.4.1 – Select the applicable initiating events.

Select the applicable initiating events (LOOP, LORHR, and/or LOI) by identifying the equipment or safety functions affected and determine the initiating event scenarios that must be evaluated (i.e., the affected function plays some role in mitigating the initiating event scenario).

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Step 4.4.2 – Determine the exposure times.

Determine the exposure times for the degraded condition in the mitigating system.  A separate exposure time must be determined for each POS for findings that span one or more POS.  Using Table 4, determine an IEL for each applicable initiating event in each applicable POS. Figure 1 defines the POSs and TWs for a BWR plant. It also shows the relationship between the POSs and the modes defined in the TSs.

Step 4.4.3 – Choose the SDP Worksheet(s)

Choose the SDP worksheet(s) that contain the POSs and initiating events that were determined to be applicable in Steps 4.4.1 and 4.4.2.   Perform the following steps on the Worksheet for each applicable POS and initiating event.  The SDP worksheets are included at the end of this procedure.

Step 4.4.4 – Enter the time to RCS boiling

Enter the time to RCS boiling and an approximate time to core uncovery/core damage in the first line of the worksheet.

Tools exist to estimate these times, including an electronic Core Uncovery Calculator located on the RASP Tool Box web page, or by using the licensee values if available.

Step 4.4.5 –Fill-in the IEL determined in step 4.4.2 in each row of the lower section of the worksheet.

Step 4.4.6 – Determine the revised credit for each top event function impacted by the finding.

A.	Verify that the licensee has the important instrumentation referenced for the top event function.  

NOTE:	If the licensee does not have the referenced instrumentation available or the referenced instrumentation is not reflective of RCS conditions, then the default operator credit must be decreased by two.  

B.  	To obtain the Equipment Credit, credit each available system that is (1) capable of maintaining the top event function and (2) is not impacted by the finding. Use the event tree associated with the worksheet to help understand the successes and failures associated with each accident sequence.  Use the guidance in Tables 5 and 6 to determine equipment credits.  Document key assumptions.  

NOTE:	Each top event has an equipment credit and an operator credit, only the equipment credit change or the operator credit change is propagated through the worksheets.  See the following example:

Example:  If the licensee has a finding that changes the MINJ equipment credit from 5 to 3, then the revised credit for the MINJ&SRV becomes 3, regardless of the SRV credit or the operator credit.

Issue Date:  01/08/20	20	0609 App G Att 3 

C.	Determine the revised Operator Credit. Use the default operator credit listed in the worksheet unless any of the following four conditions are applicable.

1. If the referenced instrumentation is missing or misleading, then decrease the operator credit by two.

2. The default time is incorrect and significantly reduced.  If the diagnoses time is less than 20 minutes OR the time to perform the action is approximately the time required, then decrease the operator credit by one.

3. If the action is complicated by missing or inaccessible equipment, steam or high radiation, or loop seals for venting pumps, then decrease the operator credit by two.

4. If the procedures are not complete for the shutdown plant configuration, then the operator credit is decreased by one.

Caution:  It has been identified that it’s possible for operator dominated sequences to have HEP values that are below levels recommended in the Risk Assessment of Operational Events (RASP) manuals Volumes 1 and 4 when following this procedure. Analysts should be cognizant of this potential and pay closer attention to operator action dominated sequences. If an analyst feels that this procedure is not adequately capturing the risk, they may depart from this procedure and perform a Phase 3 detailed risk assessment.

NOTE:	If the default operator credit is changed and results in a negative operator credit, then the operator credit is zero.

Example: If the licensee has a finding that changes the operator credit from a 5 to a 3 due to a loss of instrumentation, then the revised credit for the MINJ&SRV becomes 3, regardless of the equipment MINJ&SRV equipment credit.  

D. 	Determine the Credit for Function for each Top Event Function needed.****Select the lower of Equipment Credit and Operator Credit and enter the value in the Credit for Function column.

Step 4.4.7 – Quantification of Core Damage Scenarios.

Quantify each accident scenario that is impacted by the finding adding the credits for IEL + Mitigation Credit.   Enter the sum in the Result column.

NOTE:	 For phase 2 analyses, the recovery credit is not used.****

Step 4.4.8 – Go to the next applicable worksheet and begin at step 4.4.1, or if all worksheets are completed, continue to step 4.4.9.

Step 4.4.9 – Estimating the risk significance of the inspection finding

The preliminary color of the finding is determined by using Table 7 – Counting Rule Worksheet. Using the quantified values obtained from steps 4.4.7 and 4.4.8, complete the Counting Rule Worksheet. The result is the Risk Significance (Green, White, Yellow or Red) of the inspection finding based on the internal initiating events that lead to core damage.

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# Step 4.5 – Process for Assessing Events Under Management Directive 8.3

Step 4.5.1 – Identify the TW and POS where the shutdown event occurred.

Step 4.5.2 – Identify the appropriate shutdown initiating event.

Use an IEL = 0 if the event caused a loss or interruption of the RHR

function. 

OR

Determine the IEL.  Evaluate each question in order. Only one of the following will apply:

· IF a finding increases the likelihood of a loss of offsite power (LOOP) or actually caused a LOOP, THEN LOOP is the applicable initiating event.  Use Table 1 to determine the IEL.  Go to Step 4.5.3.

· IF a finding increases the likelihood of a loss of reactor inventory (LOI) or actually caused a LOI, THEN LOI is the applicable initiating event.  Use Table 2 to determine the IEL. Go to Step 4.5.3.

· IF a finding increases the likelihood of a loss of the operating train of RHR (LORHR) or actually caused a LORHR (except for LOOP and LOI), THEN LORHR is the applicable initiating event.  Use Table 3 to determine the IEL.  Go to Step 4.5.3.

· IF a finding involves the RHR support systems (except for LOOP and LOI), THEN LORHR is the applicable initiating event.  Use Table 3 to determine the IEL.  Go to Step 4.5.3.

Step 4.5.3 – Use the SDP worksheet that contains the POS and initiating event that were determined to be applicable in Step 4.5.1 and 4.5.2.

Step 4.5.4 – Enter the time to RCS boiling.

Enter the time to RCS boiling and an approximate time to core uncover/core damage in the first line of the worksheet.

Tools exist for determining these times, including an electronic Core Uncovery Calculator located on the RASP Tool Box web page, or by using licensee values if available.

Step 4.5.5 – Fill-in the IEL determined in step 4.5.2 in each row of the lower section of the worksheet.

Step 4.5.6 – Determine the revised Credit for Function for each top event function impacted by the finding for the as found condition during the event.

A.	Verify the licensee has the important instrumentation referenced for the top event function.  

NOTE:  If the licensee does not have the referenced instrumentation available or the referenced instrumentation is not reflective of RCS conditions, then the default operator credit MUST be reduced by two. 

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B.  	To obtain the Equipment Credit, credit each available system that is (1) capable of maintaining the top event function and (2) is not impacted by the finding. Use the event tree associated with the worksheet to help understand the successes and failures associated with each accident sequence.  Use guidance in Tables 5 and 6 to determine equipment credits.  Document key assumptions.  

C.	To obtain the Operator Credit, use the default operator credit unless any of the following four conditions are applicable:

1. If the referenced instrumentation is missing or misleading, then decrease the operator credit by two.

2. The default time is incorrect and significantly reduced.  If the diagnoses time is less than 20 minutes OR the time to perform the action is approximately the time required, then decrease the operator credit by one.

3. If the action is complicated by missing or inaccessible equipment, steam or high radiation, or loop seals for venting pumps, then decrease the operator credit by two.

4. If the procedures are not directed for the shutdown configuration that the plant is in, then the operator credit is decreased by one.

NOTE:	If the default operator credit is changed and results in a negative operator credit, then the operator credit is zero.

D.	Determine the Credit for Function for each Top Event Function needed.****Select the lower of Equipment Credit and Operator Credit and enter the value in the Credit for Function column.

Step 4.5.7 – Quantification of Core Damage Scenarios

Quantify each accident scenario by adding the credits for IEL + Mitigation Credit.   Enter the sum in the Result column.

NOTE:	 For phase 2 analyses, the recovery credit is not used. 

Step 4.5.8 – Go to the next applicable worksheet and begin at step 4.5.1, or if all worksheets are completed, continue to step 4.5.9.

Step 4.5.9 – Estimating the Risk Significance of the Inspection Finding

The preliminary color of the finding is determined by using Table 7 – Counting Rule Worksheet. Using the quantified values obtained from steps 4.4.7 and 4.4.8, complete the Counting Rule Worksheet. The result is the Risk Significance (Green, White, Yellow or Red) of the inspection finding based on the internal initiating events that lead to core damage.

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Figure 1 – Determination of Applicable POSs and Time Windows – BWRs

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Table 1 – Initiating Even Likelihoods (IELs) for LOOP Precursors

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Table 2 – Initiating Event Likelihood (IELs) for Loss of Inventory (LOI) Precursors

Table 3 – Initiating Event Likelihoods (IELs) for LORHR Precursors

Note: For findings affecting Loss of the Operating Train of RHR and RHR Supports System Including SSW, AC and DC components

Table 4 – Initiating Even Likelihoods (IELs) for Condition Findings – BWRs

1. 	The likelihood ratings are presented in terms of 0, 1, 2, etc. A rating of 0 is comparable to a frequency of 1 per year, a rating of 1 is comparable to a frequency of 1E-1 per year, and similarly, a rating of 2 is comparable to a frequency of 1E-2 per year.

Table 5 - Mitigation Capability Credits for Installed Equipment

Table 6 - Credit for Temporary Equipment

0609, App G, Att 2	G2-28	Issue Date: 02/28/05

Worksheet 1. SDP for a BWR Plant - Loss of Inventory in POS 1 (Head on)

	DRAFT

Issue Date:  XX/XX/2012	Att 1-1	0609, App F

Issue Date:  01/08/20	20	0609 App G Att 3 

Notes:

1. Different non-ECCS sources may apply for different plants.  Examples include: firewater and high-pressure service water. 

2. Failure of ECCS and alternate injection sources is assumed to fail the ability of the operator to recover RHR and is assumed to fail         suppression pool cooling and makeup.

3. Failure to isolate the leak reduces the ability to recover RHR. 

4. Non-ECCS systems are not assumed to be able to keep core covered if leak path is not isolated.

5. If a leak is isolated by the operator, it is assumed that ECCS will not automatically be activated.

6. Actions to steam the core at high or low pressure to prevent core damage are treated as recovery actions

Worksheet 2 SDP for a BWR Plant - Loss Inventory Control in POS 2 (Head off or RCS vented)

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Notes:

1. Different non-ECCS sources may apply for different plants.  Examples include: firewater and high-pressure service water.  

2. Failure of ECCS and alternate injection sources is assumed to fail the ability of the operator to recover RHR

3. Failure to isolate the leak reduces the ability to recover RHR. 

4. Non-ECCS systems are not assumed to be able to keep core covered if leak path is not isolated.

5. If a leak is isolated by the operator, it is assumed that ECCS will not automatically be activated.

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Worksheet 3 SDP for a BWR Plant - Loss of Inventory in POS 3 (Cavity Flooded)

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Notes:

1. Different non-ECCS sources may apply for different plants.  Examples include: firewater and high-pressure service water.  

2. Failure to isolate the leak reduces the ability to recover RHR. 

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3. Non-ECCS systems are not assumed to be able to keep core covered if leak path is not isolated.

Worksheet 4 SDP for a BWR Plant - Loss of Operating Train of RHR (LORHR) in POS 1 (Head On)

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Notes:

1. Failure to recover RHR before RHR shutoff head is reached is assumed to fail short term injection using LPCI.

2. Actions to prevent core damage by steaming the core at high or low pressure are treated as recovery actions. 

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Worksheet 5. SDP Worksheet for a BWR Plant   — Loss of Operating Train of RHR in POS 2 (Head Off or RCS Vented)

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Worksheet 6. SDP Worksheet for a BWR Plant - Loss of Offsite Power in POS 1 (Head On)

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Notes:

1. Different non-ECCS sources may apply for different plants.  Examples include: firewater and high-pressure service water.

2. In sequence 1, LOOP followed by successful start of an EDG or EAC source, analyze the Loss of RHR sequences.  The IEL for the Loss of RHR analysis should the LOOP IEL.  The analysis must consider the complexities of recovering RHR with specific deficiencies of the electrical system.  

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Worksheet 7. SDP Worksheet for a BWR Plant - Loss of Offsite Power in POS 2 (Head Off or RCS Vented)

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Notes:

1. Different non-ECCS sources may apply for different plants.  Examples include: firewater and high-pressure service water.

2. In sequence 1, LOOP followed by successful start of an EDG or EAC source, analyze the Loss of RHR sequences. The IEL for the Loss of RHR analysis should the LOOP IEL. The analysis must consider the complexities of recovering RHR with specific deficiencies of the electrical system.  

Issue Date:  01/08/20	36	0609 App G Att 3

Figure 2 – Event Tree for Loss of Inventory – BWR POS – 1

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Figure 3 – Event Tree for Loss of Inventory – BWR POS – 2

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Figure 4 – Event Tree for Loss of Inventory BWR POS - 3

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Figure 5 -  Event Tree for Loss of Offsite Power- BWR POS - 1

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Figure 6 – Event Tree for Loss of Offsite Power – BWR POS 2

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Figure 7 – Event Tree for Loss of RHR – BWR POS -1

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Figure 8 – Event Tree for Loss of RHR – BWR POS 2

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ATTACHMENT 1

Revision History for IMC 0609, Appendix G, Attachment 3

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Issue Date:  01/08/20	Att1-2 	0609 App G Att 3

Issue Date:  01/08/20	Att1-3 	0609 App G Att 3

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