DCL-10-066, License Amendment Request 10-03, Damping Values for the Seismic Design and Analysis of the Reactor Vessel Integrated Head Assembly

License Amendment Request 10-03, Damping Values for the Seismic Design and Analysis of the Reactor Vessel Integrated Head Assembly

ML101660039
Person / Time
Site:	Diablo Canyon
Issue date:	06/14/2010
From:	Becker J Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-10-066
Download: ML101660039 (42)

Text

Pacific Gas and Electric Company James R. Becker Diablo Canyon Power Plant Site Vice President Mail Code 104/5/601

p. O. Box 56 Avila Beach, CA 93424 805.545.3462 June 14, 2010 Internal: 691.3462 Fax: 805.545.6445 PG&E Letter DCL-1 0-066 10 CFR 50.90 10 CFR 50.59(c)(2)(viii) u.s. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Diablo Canyon Units 1 and 2 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 License Amendment Request 10-03, "Damping Values for the Seismic Design and Analysis of the Reactor Vessel Integrated Head Assembly"

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.90, Pacific Gas and Electric (PG&E) hereby requests an amendment to Facility Operating License Nos. DPR-80 and DPR-82, for Diablo Canyon Power Plant (DCPP) Units 1 and 2, respectively, to allow revision of the licensing basis, as described in the Final Safety Analysis Report Update (FSARU),

to include damping values for the seismic design and analysis of the integrated head assembly (IHA) that are consistent with the recommendations of Regulatory Guide (RG) 1.61, "Damping Values for Seismic Design of Nuclear Power Plants,"

Revision 1. The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis safe-shutdown earthquake (SSE) damping values applicable to steel structures of different connection types is also applied to determine the IHA design-basis operating-basis earthquake (OBE) damping values .

The IHA is analyzed for the following DCPP design-basis seismic events: the Design Earthquake (DE), Double Design Earthquake (DDE), and the Hosgri Earthquake (HE). The DE and DDE correspond to the OBE and SSE as described in Appendix A to 10 CFR 100, respectively. The HE is also considered by the NRC to be the SSE. These relationships are discussed in FSARU, Section 3.7, and in NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No.7, Section 2.5.2 dated May 26, 1978. includes a description of the proposed changes, the supporting technical analyses, and the no significant hazards consideration determination. includes additional information regarding the determination of the proposed damping values.

A member of the STARS (Strat e gic Te aming and Resource Sharing) Alliance Callaway. Comanche Peak. Di ablo Canyon. Palo Verde . San Onofre. South Te x as Project . Wolf Creek

Document Control Desk PG&E Letter DCL-10-066 June 14, 2010 Page 2 PG&E has determined that this license amendment request (LAR) does not involve a significant hazard consideration as determined per 10 CFR 50.92. Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment needs to be prepared in connection with the issuance of this amendment.

PG&E requests approval of this LAR by September 30, 2010, and that the license amendments be made effective upon NRC issuance, to be implemented within 30 days. The Unit 2 IHA was installed with the replacement reactor vessel closure head during the Unit 2 Fifteenth Refueling Outage in Fall 2009.

The proposed amendments have been reviewed by the Plant Staff Review Committee and approved by the Station Director. Pursuant to 10 CFR 50.91, a copy of this proposed amendment is being sent to the California Department of Public Health.

PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter.

This letter includes no revisions to existing regulatory commitments.

If you have any questions or require additional information, please contact Tom Baldwin at (805) 545-4720.

I state under penalty of perjury that the foregoing is true and correct.

Executed on June 14, 2010.

~

James R. Becker Site Vice President tcg5 SAPN50276288 Enclosures cc: Diablo Distribution cc/enc: Gary W. Butner, California Department of Public Health Elmo E. Collins, NRC Region IV Michael S. Peck, NRC, Senior Resident Inspector Alan B. Wang, NRC Project Manager, Office of NRR A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway. Comanche Peak. Diablo Canyon. Palo Verde. San Onofre. South Te x as Project. Wolf Creek

Enclosure 1 PG&E Letter DCL-10-066 Evaluation of the Proposed Change

Subject:

License Amendment Request 10-03, "Damping Values for the Seismic Design and Analysis of the Reactor Vessel Integrated Head Assembly"

1.

SUMMARY

DESCRIPTION

2. DETAILED DESCRIPTION

3. TECHNICAL EVALUATION

4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration 4.4 Conclusions

5. ENVIRONMENTAL CONSIDERATION

6. REFERENCES

Enclosure 1 PG&E Letter DCL-10-066

1.

SUMMARY

DESCRIPTION This evaluation supports a request to amend Facility Operating License Nos.

DPR-80 and DPR-82 for Diablo Canyon Power Plant (DCPP), Units 1 and 2, respectively, to revise the licensing basis, as described in the Final Safety Analysis Report Update (FSARU), to include damping values for the seismic design and analysis of the integrated head assembly (IHA) that are consistent with the recommendations of Regulatory Guide (RG) 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1. The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis safe-shutdown earthquake (SSE) damping values applicable to steel structures of different connection types is also applied to determine the IHA design-basis operating-basis earthquake (OBE) damping values.

The IHA is analyzed for the following DCPP design-basis seismic events: the Design Earthquake (DE), Double Design Earthquake (DOE), and the Hosgri Earthquake (HE). The DE and DOE correspond to the OBE and SSE, as described in Appendix A to 10 CFR 100, respectively. The HE is also considered by the NRC to be the SSE. These relationships are discussed in FSARU, Section 3.7, and in NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No.7, dated May 26,1978, Section 2.5.2.

2. DETAILED DESCRIPTION Proposed Amendment The proposed change would revise FSARU Section 3.7.1.3, "Critical Damping Values," to include the following damping values (percent of critical damping) for the IHA for the DE, DOE, and HE, respectively:

Type of Structure Percent of Critical Damping DE DOE HE Integrated Head Assembly 6.85(g) 6.85(g)

The following footnote would also be added to the damping values for the DE, DOE and HE:

(g)Damping values for the IHA are based on the recommendations in RG 1.61, Revision 1, Tables 1 and 2, using a weighted average for "Welded Steel or Bolted Steel with Friction Connections" and "Bolted Steel with Bearing Connections. "

1

Enclosure 1 PG&E Letter DCL-1 0-066 The proposed change would also add RG 1.61, Revision 1 to FSARU Section 3.7.7 as a reference.

Purpose for Proposed Amendment RG 1.61, "Damping Values for Seismic Design of Nuclear Power Plants,"

Revision 1 provides acceptable damping values to be used in the elastic dynamic seismic analysis and design of structures, systems, and components (SSCs),

where energy dissipation is approximated by viscous damping unless otherwise specified.

The purpose of this proposed change is to obtain NRC approval for the use of damping values consistent with the recommendations of RG 1.61, Revision 1, for the seismic design and analysis of the IHA for the DE, DDE, and HE. The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis SSE (DDE and HE) damping values applicable to steel structures of different connection types, is also applied to determine the IHA design-basis OBE (DE) damping values.

RG 1.61, Revision 1, is not specifically described in the DCPP FSARU.

Therefore, PG&E determined that the proposed change requires prior NRC approval as a departure from a methodology in accordance with 10 CFR 50.59(c)(2)(viii).

Risk-Informed Licensing Change The requested change in the LAR is not a risk-informed licensing change.

3 TECHNICAL EVALUATION

System Description

The IHA (Figure 1) is primarily a bolted steel structure (with some welded connections) consisting of various components designed to provide cooling for the control rod drive mechanisms (CRDMs), radiation shielding for workers performing activities near the replacement reactor vessel closure head (RRVCH),

seismic support for the CRDMs and other IHA components, and to facilitate lifting of the IHA and the RRVCH during refueling outages. The IHA is a new structure that does not have an existing equivalent. However, the IHA incorporates the functions of the former CRDM seismic support structure, the CRDM ventilation cooling system, and the head lift rig. The IHA consists of the following major components:

• Integral ductwork supplying exhaust fans for the CRDM air cooling system (NOTE: The ductwork forms part of the IHA structure and is not traditional round or rectangular sheet steel ducts such as described on Table 5 of 2

Enclosure 1 PG&E Letter DCL-1 0-066 RG 1.61, Revision 1. Therefore, RG 1.61, Revision 1 damping values corresponding to steel structures are applied to those portions of the IHA that provide an air duct function.)

• Seismic support structure for the CRDMs and other IHA components

• Integral missile shield for postulated CRDM assembly missiles

• Lift rig for IHAlRRVCH lifting and movement

• Access ports for RRVCH nozzle inspection

• Radiation shielding above the RRVCH in the IHA lower shroud region

• Access ports for core exit thermocouple (CET) cable connections and other components

• Supports for CET cable trays

• Walkway for personnel access to IHA electrical cables and other components

• Cable bridges to route IHA electrical and instrumentation cables to bulkheads on the refuel floor The above components are assembled together to form primarily a bolted steel structure that is bolted and pinned to the reactor vessel closure head. The IHA and RRVCH are lifted and moved as a single unit during refueling outages.

The seismic support structure assembly is an integral part of the IHA shroud assembly near the refueling floor elevation that provides lateral structural support for the IHA and CRDMs. Figure 2 shows the major components included in the seismic support structure assembly (some items that are attached to the support structure are excluded for clarity). The seismic support structure assembly includes eight seismic tie-rod restraints to transfer loads from the IHA and CRDMs to the cavity walls. Each tie-rod is pinned at both ends to connect the IHA to the reactor cavity concrete wall just below the refueling floor elevation.

The inner section of the IHA seismic support structure interfaces with the CRDM digital rod position indication (DRPI) plates and the filler plates through gaps between the outer row of plates and the inner section of the seismic support structure to maintain the original design concept to transfer loads from the CRDM, through the DRPI plates, to the seismic support structure by impact through the gaps. The outer section of the seismic support structure interfaces with the containment walls through seismic tie-rods to form a continuous load path in the horizontal direction to tr-ansfer loads from the CRDMs to the containment walls. For the rest of the IHA components, one load path is through the IHA support columns and through the seismic tie-rods into the containment wall. The other load path is through the IHA support columns and lift rods into the RRVCH.

3

Enclosure 1 PG&E Letter DCL-1 0-066 Proposed Damping Values The IHA seismic analyses were performed using 4.9 percent damping for the DE, 6.85 percent damping for the DOE, and 6.85 percent damping for the HE.

These values correspond to the damping values contained in RG 1.61, Revision 1, for structures using a weighted average of the damping values corresponding to bolted bearing connections and welded connections. The damping values in RG 1.61, Revision 0, were previously considered acceptable for use in the re-evaluation of Design Class I structures for the HE during the licensing of DCPP, as discussed in NUREG-0675, Supplement No.7, Section 3.8.5.3.

Section 3.8.5.3 states:

Allowing the use of higher damping values in this reevaluation is realistic and should not be regarded as an arbitrary lowering of the margins of safety. The values given in the Regulatory Guide have been acceptable for several years and are thus acceptable for this reevaluation."

RG 1.61, Revision 1 updated the NRC guidance in RG 1.61, Revision 0, to incorporate the latest data and information, and reduce unnecessary conservatism in specification of damping values for seismic design and analysis of SSCs in nuclear power plants.

The various components of the IHA are generally connected with bolted bearing connections. However, the IHA includes a small number of welded connections.

RG 1.61, Revision 0, does not provide damping value guidance for structures that include different types of connections. Therefore, the note on Table 1 of RG 1.61, Revision 1, was used that states: "For steel structures with a combination of different connection types, use the lowest specified damping value, or as an alternative, use a "weighted" average damping value based on the number of each type present in the structure." Since the IHA contains mostly bolted bearing connections, using the damping value associated with all connections being welded would be overly conservative. Therefore, the damping values associated with the weighted average of connection types were determined. The IHA connections that transfer a significant level of seismic inertia load were identified and categorized as either welded or bolted. Of 185 total significant load carrying connections, 9 connections are welded and the remaining 176 are bolted bearing connections. All pin connections are also conservatively treated as bolted bearing connections. These values were used to determine a weighted average 6.85 percent damping value for DOE and HE and a 4.9 percent damping value for DE. A discussion of the determination of the damping values is provided in Enclosure 2.

RG 1.61, Revision 1, Table 2 for OBE (DE) damping values does not contain the same note as found in Table 1 for SSE (DOE and HE) that describes how to 4

Enclosure 1 PG&E Letter DCL-1 0-066 address steel structures with different types of connections. However, use of the note for the determination of the DE damping value is consistent with the use of the note for the determination of the DDE and HE damping values, and a weighted average damping value more realistically represents the IHA structure.

All analysis results meet the acceptance criteria as described below.

IHA Seismic Analysis A finite element structural analysis model was created for the IHA as depicted in Figure 3. Shell elements were used to modellHA plate components and beam elements were used to modellHA linear members such as columns and beams.

The model included mass elements to represent the mass of components that were not explicitly included in the model such as the exhaust fans and pipe supports. The analysis model accounted for the tie-rod tension-only capability by adjusting the tie-rod stiffness for each of the three directions of seismic excitation such that modeled stiffness represents the stiffness associated with only the "active" tie-rods that resist applied loads in tension.

Seismic loads applied to the various components of the IHA were determined using the response spectrum analysis method. Response spectra inputs to the IHA seismic analyses were developed by enveloping the containment interior structure response spectra at the seismic support structure tie-rod elevation and the RRVCH spectra. Modal responses (displacements, accelerations, shears, moments, etc.) were combined by the square root of the sum of the squares (SRSS) method consistent with the DCPP current licensing basis (FSARU 3.7.2.1.3).

Due to the enveloping of the containment interior structure and RRVCH response spectra, the response spectra analysis method sometimes provided overly-conservative analysis results. To reduce unnecessary conservatism, selected seismic analyses were also performed using the time-history modal superposition method (FSARU 3.7.2.1.2). The time-history of response in each mode is determined from the acceleration time-history input by integration of the equations of motion. RRVCH time-history inputs are applied where the IHA connects to the RRVCH and Containment interior structure time-history inputs are applied where the IHA tie-rods connect to the building structure. The modal responses are combined by algebraic sum to produce an accurate summation at each time step (FSARU 3.7.2.1.2).

Modal mass participation exceeded 90 percent in each of the three directions of seismic loading (North-South, East-West, and vertical). For the DE and DDE seismic analyses, the responses due to the absolute summation of the responses due to the North-South and vertical seismic analyses were compared to those due to the absolute summation of the East-West and vertical seismic 5

Enclosure 1 PG&E Letter DCL-1 0-066 analyses and the maximum values of stress, load and displacement were used in the IHA evaluation. For the HE analysis, the responses due to the North-South, East-West and vertical seismic analyses were combined by the square root of the sum of the squares method to determine the stresses, loads and displacement for use in the IHA evaluation. The seismic analyses loads, stresses and displacements were combined with those due to other applicable loads such as deadweight and pressure to determine the total loads, stresses and displacements for the various components of the IHA.

The resulting IHA loads and stresses for DE, DOE, and HE were evaluated for acceptance using the ASME Boiler and Pressure Vessel Code,Section III, Division 1 - Subsection NF, "Component Supports," 2001 Edition through 2003 Addenda. All loads and stresses met acceptance limits. The complete IHA analysis includes hundreds of stress and load comparisons to allowable limits.

The following table summarizes the IHA analysis results for the safety-related IHA connections and selected safety-related components with the largest stress ratios. The stress ratio is the calculated load or stress divided by the allowable value. Stress ratios equal to 1.0 represent an acceptable load or stress value with the required margin per applicable code, and stress ratios below 1.0 represent additional margin beyond that required by the applicable code. Tables 1 through 4 provide the member stress summaries for the controlling load combination. Table 5 provides a summary of the evaluation of connections between Design Class I (Seismic Class I) components.

Summary A finite element structural analysis model was created for the IHA using critical damping values consistent with RG 1.61, Revision 1. The Table 1 note, allowing use of a "weighted average" for SSE damping values applicable to steel structures of different connection types, is also applied to the determination of OBE damping values. The IHA was evaluated for the following seismic events:

DE, DOE, and HE. The DE corresponds to the OBE. The DOE and HE correspond to the SSE. The resulting IHA loads and stresses were evaluated for acceptance using the ASME Boiler and Pressure Vessel Code,Section III, Division 1 - Subsection NF, "Component Supports", 2001 Edition through 2003 Addenda. All loads and stresses met acceptance limits.

4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria Regulatory Guide (RG) 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1.

6

Enclosure 1 PG&E Letter DCL-10-066 RG 1.61, Revision 1, specifies the damping values that the NRC staff currently considers acceptable for complying with the agency's regulations and guidance for seismic analysis. Revision 1 updated the NRC guidance for use in reviewing elastic modal (dynamic) seismic analysis of Seismic Category I SSCs. This revision incorporates the latest data and information, and reduces unnecessary conservatism in specification of damping values for seismic design and analysis of SSCs in nuclear power plants.

Section 0, "Implementation," of Revision 1 states that "NRC staff will use the methods described in this guide to evaluate (1) submittals in connection with applications for construction permits, standard plant design certifications, operating licenses, early site permits, and combined licenses; and (2) submittals from operating reactor licensees who voluntarily propose to initiate system modifications if there is a clear nexus between the proposed modifications and the subject for which guidance is provided herein."

The proposed damping values for the seismic design and analysis of the IHA (4.9 for the DE, and 6.85 for the DOE and HE) are consistent with the recommendations of RG 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1. The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis SSE damping values applicable to steel structures of different connection types is also applied to determine the design-basis OBE damping values. RG 1.61, Revision 1, Table 2 for OBE (DE) damping values does not contain the same note as found in Table 1. However use of the note for the determination of the DE damping value is consistent with the use of the note for the determination of the DOE and HE damping values, and a weighted average more realistically represents the IHA structure.

4.2 Precedent RG 1.61, Revision 1, is referenced in the Vogtle Electric Generating Plant, Units 3 and 4, Combined Operating License Application, Part 2, FSAR, Revision 0, dated March 23, 2008, and in NUREG-1923, "Safety Evaluation Report for an Early Site Permit (ESP) at the Vogtle Electric Generating Plant (VEGP) ESP Site," dated July 2009.

4.3 No Significant Hazards Consideration The proposed change would revise the licensing basis as documented in the Final Safety Analysis Report Update (FSARU) to specify critical damping values consistent with Regulatory Guide (RG) 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1, dated 7

Enclosure 1 PG&E Letter DCL-1 0-066 March 2007, for the seismic design and analysis of an integrated head assembly (lHA). The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis safe-shutdown earthquake (SSE) damping values applicable to steel structures of different connection types, is also applied to determine the IHA design-basis operating-basis earthquake (OBE) damping values. For the Diablo Canyon Power Plant, the Design Earthquake (DE) and the Double Design Earthquake (DOE) correspond to the OBE and SSE as described in Appendix A to 10 CFR 100, respectively. The Hosgri Earthquake (HE) is also considered by the NRC to be the SSE.

The IHA, installed with a replacement reactor vessel closure head (RRVCH), is primarily a bolted steel structure (with bolted bearing connections and some welded connections) consisting of various components designed to provide cooling for the control rod drive mechanisms (CRDMs), radiation shielding for workers performing activities near the RRVCH, seismic support for the CRDMs and other components, and to facilitate lifting the RRVCH and IHA during refueling outages. The IHA is a new structure that does not have an existing equivalent. However, the IHA incorporates the functions of the former CRDM seismic support structure, the CRDM ventilation cooling system, and the head lift rig.

PG&E has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:

1. Does the change involve a significant increase in the probability or consequences of an accident previously evaluated?

The proposed change would allow use of critical damping values consistent with the recommendations of RG 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1, dated March 2007, for the seismic design and analysis of the IHA. The RG 1.61, Revision 1, Table 1 note allowing use of a "weighted average" for design-basis SSE damping values applicable to steel structures of different connection types, is also applied to determine the IHA design-basis OBE damping values. RG 1.61, Revision 1, Table 2 for OBE damping values does not contain the same note as found in Table 1. However use of the note for the determination of the DE damping value is consistent with the use of the note for the determination of the DOE and HE damping values, and a weighted average more realistically represents the IHA structure.

8

Enclosure 1 PG&E Letter DCL-1 0-066 RG 1.61, Revision 1, specifies the damping values that the NRC staff currently considers acceptable for complying with the agency's regulations and guidance for seismic analysis. Revision 1 incorporates the latest data and information, and reduces unnecessary conservatism in specification of damping values for seismic design and analysis of SSCs.

The proposed change does not change the design functions of the IHA or its response to design-basis events, nor does it affect the capability of related SSCs to perform their design or safety functions. The use of the proposed damping values in the seismic design and analysis of the IHA is related to the ability of the IHA to function in response to design-basis seismic events, and is unrelated to the probability of occurrence of those events, or other previously evaluated accidents. Therefore the proposed change will not have any impact on the probability of an accident previously evaluated.

The proposed damping values are an element of the seismic analyses performed to confirm the ability of the IHA to function under postulated seismic events while maintaining resulting stresses within ASME Section III allowable values. Therefore, the use of damping values consistent with the recommendations of RG 1.61, Revision 1 does not result in an increase in the consequences of accidents previously evaluated.

Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the change create the possibility of a new or different kind of accident from any accident previously evaluated?

The proposed change does not involve changes to any plant SSCs, nor does it involve changes to any plant operating practice or procedure. The damping values are an element of the seismic analyses performed to confirm the ability of the IHA to function under postulated seismic events while maintaining resulting stresses within ASME Section III allowable values. Therefore, no credible new failure mechanisms, malfunctions, or accident initiators not considered in the design and licensing bases are created that would create the possibility of a new or different kind of accident.

Therefore the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

9

Enclosure 1 PG&E Letter DCL-1 0-066

3. Does the change involve a significant reduction in a margin of safety?

The design basis of the plant requires structures to be capable of withstanding normal and accident loads including those from a design basis earthquake. The proposed change would allow the use of damping values in the IHA seismic analyses that are in general more realistic and, thus, more accurate than the damping values recommended in RG 1.61, Revision 0, used in the analysis for the HE, or the plant specific damping values used in the original analysis for the DE and DOE. The NRC stated, in NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No.7, that allowing use of the higher damping values in RG 1.61, Revision 0 for the HE re-evaluation, versus the lower values used in the original analysis, is realistic and should not be regarded as an arbitrary lowering of the margins of safety. The damping values in RG 1.61, Revision 0, were based on limited data, expert opinion, and other information available in 1973. NRC and industry research since 1973 show that the damping values provided in the original version of RG 1.61 may not reflect realistic damping values for SSCs. RG 1.61, Revision 1, therefore, provides damping values based on the updated research results that predict and estimate damping values for seismic design of SSCs in nuclear power plants, and similarly should not be regarded as an arbitrary lowering of the margins of safety.

As discussed above, damping values are an element of the seismic analyses performed to confirm the ability of the IHA to function during design-basis seismic events while maintaining resulting stresses within ASME Section III allowable values. The proposed change ot allow use of damping values consistent with the recommendations of RG 1.61, Revision 1, versus the damping values in the current licensing basis could result in lower calculated stresses. The analysis done for the IHA using the proposed damping values showed the ASME Section III allowable values are met. Sufficient safety margins are maintained when Codes and standards or alternatives approved for use by the NRC are met.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above evaluation, PG&E concludes that the change proposed by this license amendment request (LAR) satisfies the no significant hazards consideration standards of 10 CFR 50.92( c), and accordingly a no significant hazards finding is justified.

10

Enclosure 1 PG&E Letter DCL-1 0-066 4.4 Conclusions In conclusion, based on the considerations discussed above: (1) There is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5. ENVIRONMENTAL CONSIDERATION PG&E has evaluated the proposed amendment and has determined that the proposed amendment does not involve: (1) a significant hazards consideration, (2) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (3) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

6 REFERENCES

1. Regulatory Guide 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 1, March 2007

2. Regulatory Guide 1.61, "Damping Values for Seismic Design of Nuclear Power Plants," Revision 0, October 1973

3. NUREG-0675, "Safety Evaluation Report Related to the Operation of Diablo Canyon Nuclear Power Plant, Units 1 and 2," Supplement No.7, dated May 26, 1978

4. Vogtle Electric Generating Plant, Units 3 and 4, Combined Operating License Application, Part 2, FSAR, Revision 0, March 23, 2008

5. NUREG-1923, "Safety Evaluation Report for an Early Site Permit (ESP) at the Vogtle Electric Generating Plant (VEGP) ESP Site," July 2009

6. Final Safety Analysis Report Update, Revision 19 11

Enclosure 1 PG&E Letter DCL-1 0-066 Table 1 Member Stress Summary for Controlling Load Combination Design Class I / Seismic Category I Linear Components Component Description Controlling Load Stress Combination Ratio Support Columns DL + P +/- srss(DDE+LOCA) 0.85 Lift-Rods DL + P +/- srss(DDE+MI) 0.96 Bottom Ring Beam DL + P +/- srss(DDE+LOCA) 0.54 Seismic Support Beam DL + P + T +/- DE 0.26 Seismic Ring Beam DL + P +/- srss(DDE+LOCA) 0.51 Seismic Reinforced Beam DL + P +/- DE 0.28 Duct Support in Mid/Upper Shroud DL + P +/- srss(DDE+LOCA) 0.30 Angle connecting Duct Sections DL + P +/- DE 0.73 Cable Support Ring Beam DL + P +/- HE 0.37 Cable Bridge Longitudinal Tube in Foldable DL + P +/- srss(DDE+LOCA) 0.92 Section Cable Bridge Lateral Tube in Foldable DL + P +/- srss(DDE+LOCA) 0.76 Section Cable Bridge Vertical Tube and Wing Frame DL + P +/- srss(DDE+LOCA) 0.48 in Foldable Sect.

Bridge Lifting Mech. Horizontal Support Tube DL + P +/- srss(DDE+LOCA) 0.66 Bridge Lift-Mechanism Tube DL + P +/- srss(DDE+LOCA) 0.38 12

Enclosure 1 PG&E Letter DCL-1 0-066 Component Description Controlling Load Stress Combination Ratio Cable Bridge Support Tube under Missile DL + P +/- srss(DDE+LOCA) 0.54 Shield CET Vertical Trays DL + P +/- srss(DDE+LOCA) 0.15 CET Vertical Tray Support Bracket DL + P +/- HE 0.40 Seismic Bar (Tie-Rod Lug) DL + P +/- srss(DDE+LOCA) 0.17 Seismic Tie-Rod Bracket DL + P +/- srss(DDE+LOCA) 0.49 Seismic Tie-Rod Tube DL + P +/- HE 0.84 Pipe Rod Connecting Cable Bridge & DL + P +/- srss(DDE+LOCA) 0.66 Lift-Mechanism Support Tube under Walkway at Bridge DL + P +/- srss(DDE+LOCA) 0.67 Seismic Tie-Rods DL + P +/- srss(DDE+LOCA) 0.53 13

Enclosure 1 PG&E Letter DCL-1 0-066 Table 2 Member Stress Summary for Controlling Load Combination Design Class I / Seismic Category I Plate Components Component Description Controlling Load Stress Combination Ratio Missile Shield DL + P +/- DE 0.38 Seismic Support Plate on Seismic Ring Beam DL + P +/- DE 0.37 Stiffener Plate on Bottom Ring Beam DL + P +/- DE 0.52 CRDM DRPI Plates DL + P +/- srss(DDE+LOCA) 0.34 Support Bracket connecting Monorail & DL + P + ML 0.81 Walkway to Column Walkway Plate away from Bridges DL + P +/- srss(DDE+LOCA) 0.22 Walkway Plate Edge Stiffener DL + P +/- DE 0.36 Walkway Plate under Bridges DL + P + ML 0.35 Cable Bridge Vertical Supp Plates in DL + P +/- DE 0.95 Stationary Section Cable Bridge Support Cross Plates in DL + P +/- DE 0.61 Stationary Section Cable Bridge Support Plates in Foldable DL + P +/- DE 0.68 Section 14

Enclosure 1 PG&E Letter DCL-1 0-066 Table 3 Member Stress Summary for Controlling Load Combination Design Class II/Seismic Category 1111 Linear Components Component Description Controlling Load Stress Combination Ratio Angle Beams at Boundary of each Assembly DL + P +/- DDE 0.75 Tripod Rods DL + P +/- DDE 0.23 Monorail DL + P + ML 0.88 Baffle Support Beam DL + P +/- DDE 0.35 Stiffener at CET Doors & Windows in Duct DL + P + T 0.36 Fan Support Top Horizontal Tee Ring DL + P +/- DDE 0.52 Fan Support Vertical Tube DL + P +/- DOE 0.80 Stiffener at Base of Duct DL + P +/- HE 0.61 Baffle Cover Support Angle DL + P +/- HE 0.17 Plenum Center Column DL + P +/- DDE 0.31 Angle Frame for Plenum DL + P + ML 0.35 Angle Attached to Duct at Top DL + P +/- DDE 0.45 Angle Stiffener for Ducts DL + P +/- DDE 0.35 Cable Bundle Supports DL + P +/- DDE 0.32 Plenum Angle attached to MS DL + P +/- DDE 0.30 Vertical Angle Stiffener to Duct DL + P +/- DDE 0.17 Vertical Angle Stiffener to Duct DL + P +/- HE 0.43 15

Enclosure 1 PG&E Letter DCL-1 0-066 Component Description Controlling Load Stress Combination Ratio Baffle Support Link DL + P +/- HE 0.31 Fan Support Bottom Ring DL + P +/- DDE 0.39 Monorail End Supp Bracket DL + P + ML 0.22 16

Enclosure 1 PG&E Letter DCL-1 0-066 Table 4 Member Stress Summary for Controlling Load Combination Design Class II/Seismic Category 1111 Plate Components Component Description Controlling Load Stress Combination Ratio Baffle DL + P +/- HE 0.35 Stiffener Plate at top of Baffle DL + P +/- DDE 0.29 Radiation Shield Doors DL + P +/- HE 0.17 Lower Assy Shroud Panels DL + P +/- DDE 0.27 Mid Assy Shroud Panels DL + P +/- HE 0.16 Lower Assy Duct DL + P +/- DDE 0.43 Baffle Cover DL + P +/- HE 0.51 Mid Assy Duct DL + P +/- DDE 0.29 Upper B Assy Shroud Panels DL + P +/- HE 0.20 Upper B Assy Duct DL + P +/- DDE 0.40 Upper A Assy Shroud Panels DL + P +/- HE 0.33 Upper A Assy Duct DL + P +/- DDE 0.48 CET Access Doors in Lower Assy Duct DL + P +/- DDE 0.09 Plenum Cover Plates DL + P + ML 0.29 Plenum Top Panels DL + P +/- DDE 0.11 Plenum Side Panels DL + P +/- DDE 0.50 17

Enclosure 1 PG&E Letter DCL-1 0-066 Table 5 Summary of Evaluation of Connections between Design Class I (Seismic Category I) Components Max.

Connection Controlling Load Stress Number Connection Description / Controlling Combination Ratio Component SCN-01 Connection of Seismic Tie-Rods:

Tie Rod Lug Mounting Bolts DL +P+T +/-DE 0.58 SCN-02 Connection of Lift-Rod Clevis to RRVCH Lug:

DL+P+T+/-

Pin srss(DDE+MI) 0.21 SCN-03 Connection of Bottom Ring Beam to Intermediate Pads:

Bolts DL +P+T +/-DE 0.53 SCN-04 Connection of Bottom Ring Beam to Clevis of Lift-Rod: DL+P+T+/-

Bolt Bearing / Edge Distance srss(DDE+LOCA) 0.48 SCN-05 Connection of Stiffener Plate and Bottom Ring Beam: DL+P+/-

Weld srss(DDE+LOCA) 0.79 SCN-06 Connection of Columns to Bottom Ring Beam:

DL+P+T+/

Base Plate srss(DDE+LOCA) 0.86 SCN-07 Lower Splice Connection of Columns: DL+P+T+/-

Bolt Bearing / Edge Distance srss(DDE+LOCA) 0.68 SCN-08 Mid Splice Connection of Columns:

Bolt Bearing / Edge Distance DL +P+T +/-HE 0.60 SCN-09 Upper Splice Connection of Columns: DL+P+T+/-

Bolt Bearing / Edge Distance srss(DDE +LOCA) 0.73 SCN-10 Connection of Bridge Support Tubes Under Walkway to Seismic Ring:

CJP Weld - no evaluation n/a n/a SCN-11 Connection of Tangential Tie-Rod Tubes to Outer Bridge Support Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.88 18

Enclosure 1 PG&E Letter DCL-1 0-066 Max.

Connection Controlling Load Stress Number Connection Description I Controlling Combination Ratio Component SCN-12 Connection of Tangential Tie-Rod Tubes to Inner Bridge Support Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.86 SCN-13 Connection of Bridge Support Tubes Under Walkway to Walkway:

Weld DL +P+ T +/-DE 0.89 SCN-14 Connection of Seismic Ring Beam to Columns: DL+P+T+/-

Weld srss(DDE+LOCA) 0.76 SCN-15 U-Bolt Connection of Lift-Rods to Ring Angles:

DL+P+T+/-

U-bolt Bolt Bearing / Edge Distance srss(DDE+LOCA) 0.26 SCN-16a Connection of Walkway to Support Brackets, 90 &

270 Deg. Loc Bolts DL +P+T +/-DE 0.33 SCN-16b Connection of Walkway to Support Brackets, 30, 150,210,330 Deg. Loc:

Bolts DL +P+T +/-DE 0.85 SCN-17 Connection of Walkway Support Brackets to Columns: DL+P+T+/-

Bolt Bearing / Edge Distance srss(DDE+LOCA) 0.49 SCN-18 Connection of Cable Bridge Support to Walkway:

Bolts DL+P+T+/-DE 0.97 SCN-19 Connection of Bridge Support Vertical Cross Plate to Vertical Side Plates: DL+P+T+/-

Weld srss(DDE+LOCA) 0.72 SCN-20 Connection of Bridge Support Top Horizontal Cross Plate to Side Plates: DL+P+T+/-

Weld srss(DDE+LOCA) 0.78 SCN-21 Connection of Bridge Support Bottom Horizontal Cross Plate to Side Plates: DL+P+T+/-

Weld srss(DDE+LOCA) 0.88 SCN-22 Connection of Bridge Support Horizontal Cross Plate to Vertical Cross Plate: DL+P+T+/-

Weld srss(DDE+LOCA) 0.19 19

Enclosure 1 PG&E Letter DCL-1 0-066 Max.

Connection Controlling Load Stress Number Connection Description I Controlling Combination Ratio Component SCN-23 Connection of Bridges to Stationary Supports (Pivot):

Shaft DL +P+T +/-DE 0.97 SCN-24 Connection of Bridge Lateral Tubes to Longitudinal Tubes:

Weld DL+P+T+/-HE 0.92 SCN-25a Connection of Bridge Vertical Tubes to Longitudinal Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.78 SCN-25b Connection of Bridge Vertical Tubes to Longitudinal Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.88 SCN-26 Connection of Bridge Wing Frame Lateral &

Diagonal Tubes to Main Frame: DL+P+T+/-

Weld srss(DDE+LOCA) 0.68 SCN-27 Connection of Bridge Wing Frame Long. &

Diagonal Tubes to Lateral Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.27 SCN-28 Connection of Bridge Wing Frame Vertical Tubes to Lateral Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) i 0.30 SCN-29 Connection of Cable Bridge Link Pipes:

Lug Plate (axial + bending) DL+P+T+/-DE 0.86 SCN-30a Connection of Bridge Lifting Mechanism Support Tubes to Tube Rings: DL+P+T+/-

Weld srss(DDE+LOCA) 0.86 SCN-30b Connection of Bridge Lifting Mechanism to Support Tubes: DL+P+T+/-

Weld srss(DDE+LOCA) 0.82 SCN-31 Connection of Cable Support Tube Rings to Columns:

Bolt Bearing / Edge Distance DL+P+/-HE 0.64 SCN-32 Connection of Upper A Top Tube Ring to Columns:

Bolts DL +P+T +/-DE 0.46 20

Enclosure 1 PG&E Letter DCL-1 0-066 Max.

Connection Controlling Load Stress Number Connection Description I Controlling Combination Ratio Component SCN-33 Connection of Adjusting Disks to Seismic Reinforced Beam: DL+P+T+/-

Bearing Between Disc and Screw srss(DDE+LOCA) 0.45 SCN-34 Connection of Missile Shield Alignment Pins to Top of Columns: DL+P+T+/-

Weld srss(DDE+LOCA) 0.68 SCN-35 Connection of Missile Shield to Lift-Rods:

Leveling Nut (thread engagement verified) n/a n/a SCN-36 Connection of Seismic Plates to Seismic Ring Beam & Inner Beam: DL+P+T+/-

Weld srss(DDE+LOCA) 0.40 SCN-37 Connection of CET Vertical Trays to Support Brackets:

Weld DL +P+ T +/-HE 0.10 SCN-38 Connection of CET Vertical Trays Support Brackets to Duct Support Brackets:

Base Plate DL +P+T +/-HE 0.95 SCN-39 Connection of Mid & Upper B Duct to Support Brackets: DL+P+T+/-

Weld of Support Bracket to Base Plate srss(DDE+LOCA) 0.62 SCN-40 Connection of Mid & Upper B Duct Support Brackets to Columns: DL+P+T+/-

Weld of Support Bracket to Base Plate srss(DDE+LOCA) 0.68 21

Enclosure 1 PG&E Letter DCL-1 0-066 Figure 1: Replacement Reactor Vessel Closure Head with Integrated Head Assembly 22

Enclosure 1 PG&E Letter DCL-1 0-066 Center line of ORPI plates Pin connection Pin connection Between seismic tie-rods and Between seismic tie-rods and IHA seismic support brackets seismic wall support brackets Figure 2: Seismic Support Structure Assembly 23

Enclosure 1 PG&E Letter DCL-1 0-066 Figure 3: IHA Structural Analysis Model 24

Enclosure 2 PG&E Letter DCL-1 0-066 Damping Values for Use in the Integrated Head Assembly Seismic Response Analysis at Diablo Canyon Power Plant (DCPP) Units 1 and 2

Document No. 06042TR-04 Rev. 4 DAMPING VALUES FOR USE IN THE INTEGRATED HEAD ASSEMBLY SEISMIC RESPONSE ANALYSIS AT DIABLO CANYON POWER PLANT (DCPP) UNITS 1 AND 2 A WHITE PAPER PRESENTED TO PACIFIC GAS AND ELECTRIC COMPANY ADVENT ENGINEERING SERVICES, INC.

AREVA NP Inc.

A EVA ,nAREVAandSiomer.scompany 12647 ALCOSTA BLVD., SUITE 440 38-9039840-004 SAN RAMON, CALIFORNIA, USA 94583 June,2010

Document No. 06042TR-04 Rev. 4 Revision Summary Rev.

No. Description Affected Pages 0 Initial Issue All 1 Signatures were missing in Rev. O. They were Cover page, Page 2, added in Rev. 1; List of References was added; A 3,6 damping value was corrected.

2 Modifications to the Table 1 list of major All connections in the IHA to reflect the IHA's final design. Incorporation of the computation of a "weighted" damping value for the IHA, based on a new Table 2. Incorporation of drawings of the connections identified in Table 2.

3 Revised to incorporate the results from the IHA All, except response spectrum analysis using USM method. Attachment A.

"ADVENT Proprietary" was removed from the Content changes are header, and the proprietary statement was removed indicated by revision (sheet 2 of the previous revision). Editorial changes bars.

were made.

4 Incorporated AREVA and PG&E comments. All, except Clarified Note 1 to Table 2 regarding the total Attachment A.

number of connections identified at the bottom of Content changes are Table 2. indicated by revision bars.

ADVENT Engineering Services, Inc. Sheet 2 of 14

Document No. 06042TR-04 Rev. 4 DAMPING VALUES FOR USE IN THE INTEGRATED HEAD ASSEMBLY SEISMIC RESPONSE ANALYSIS INTRODUCTION This white paper identifies the damping The ADVENT/AREVA team is designing an requirements for response spectrum analyses of Integrated Head Assembly (IHA) as a replacement steel structures such as IHA, per the guidance of structure for the existing reactor vessel head Regulatory Guide 1.61, Revision 1. Based on the service structure at Diablo Canyon Units 1 and 2. presence of critical connections in the IHA that are An isometric view of the IHA is provided in the primary source of dissipating seismic energy, Figure 1 and its plan view in Figure 2. The this white paper presents the computation of concept of integrating all the removable upper "weighted" damping values for the IHA, based on reactor vessel head components into one the recommendations of the NRC Regulatory removable structure is the object of this design. Guide 1.61, Revision 1.

However, functionality of each head component is maintained in the integrated head assembly. REGULATORY GUIDE 1.61 REVISION 1 I REQUIREMENTS FOR DAMPING The IHA is a steel structure that provides required support for the CRDM cooling components, CRDM For bolted steel with bearing connections, seismic components, CRDM missile shield Regulatory Guide 1.61, Revision 1 provides 5.0%

structure, CRDM cooling fans, reactor vessel head and 7.0% damping values for the OBE and SSE lift rig structure, and for the head area cable earthquakes respectively (for DCPP, the Design routing. The IHA is a four-story high Earthquake (DE) is equivalent to an OBE; the (approximately 43 feet tall) steel structure and has Double Design Earthquake (DDE) is equivalent to more than 10,000 parts assembled together by an SSE; the Hosgri Earthquake (HE) is an bolted and welded connections. The number of additional SSE equivalent earthquake). Section bolted connections is significantly larger than the 3.7.1.3 of the Diablo Canyon FSARU, where number of welded connections in the IHA. In critical damping values are discussed, is addition, all bolted connections in the IHA are applicable to Design Class I systems, structures, bearing connections with specified snug-tight and components (Safety Related and Seismic requirements. The IHA has no friction type bolted Category I) and Design Class II turbine building connections. The bolted and welded connections and intake structure. Since the integrated head that are potentially critical for the transfer of loads I assembly is an assembly of Design Class I and the dissipation of energy during a seismic components, as well as Design Class 1111 event are listed in Table 1. The types of components (Non Safety Related and Seismic connection listed in Table 1 occur at numerous Category 11/1), and is considered a support of the locations within the IHA. reactor coolant loop components (CRDM support),

ADVENT Engineering Services, Inc. Sheet 3 of 14

Document No. 06042TR-04 Rev. 4 it is considered that this section of the FSARU is value for the connections in the combination be applicable to the IHA. used or a "weighted average" damping value, based on the number of each type of connection Bolted connections which transmit load are present in the structure, be computed.

categorized in the Regulatory Guide as either "friction-type" or "bearing-type". The "friction-type" Table 1 lists different types of major connections in connection depends upon high clamping force to the IHA and identifies whether they are welded prevent slip of the connected parts under connections or bolted connections. Welded anticipated service conditions. This clamping force connections of components of assemblies listed in is developed by pre-torquing the bolt to a tension Table 7-78 and 7-79 of 06042TR-03, that are typically equal to 70% of its ultimate strength, and connected via bolts or pins to other major special surface preparation may be specified on components of the IHA were excluded from the bearing members so as to achieve high friction Table 1, since the bolts/pins provide the major force. This connection behaves more like a welded source of damping. Energy dissipation through a connection under the anticipated service loads. pin connection is addressed as it is for a bearing The "bearing-type" connection depends upon type bolted connection; a pin connection has a contact of the fastener shank against the sides of similar value of damping as does a bearing type their holes to transfer the load from one connected bolted connection, based on the clearances part to another. With relatively easy slip between provided in the pin-to-hole dimensions.

the joined members, the energy dissipation capacity of a "bearing-type" connection is much DISCUSSION ON TYPES OF CONNECTION higher than that of the "friction-type" connection.

The integrated head assembly does not have any The NRC issued Regulatory Guide 1.61, Revision friction type connections. All bolted connections in 1 in March 2007. Regulatory Guide 1.61, Revision I the IHA are bearing type specified as being snug-1 differentiates between a welded steel or bolted tight. However, the IHA includes a small number of steel with friction connections and a bolted steel welded connections.

with bearing connection based on the differences in their energy absorbing capabilities. Per Table 2 lists those of the IHA connections listed in Regulatory Guide 1.61, Revision 1, the damping Table 1 which transfer a significant level of inertia values for welded steel or bolted steel with friction load during a seismic event. The table includes a connections are 3.0% for the Operating Basis description of each connection, referenced Earthquake (OBE) and 4.0% for the Safe drawing(s) that depict the connection, the type of Shutdown Earthquake (SSE). The damping values each connection and the quantity of each for bolted steel with bearing connections are 5.0% connection type. The table identifies only 9 welded for the OBE and 7.0% for the SSE. connections. Certain of the welded connections listed in Table 1 are not included in Table 2 and Regulatory Guide 1.61, Revision 1 requires that for are, therefore, not included in the calculation of the steel structures with a combination of different IHA's "weighted" damping value. These welds connections, either the lowest specified damping include:

ADVENT Engineering Services, Inc. Sheet 4 of 14

Document No. 06042TR-04 Rev. 4

• Connection 4: Bottom Ring Beam

• Connection 34: Support Column Stiffener to Bottom Ring Beam Alignment Pins to Support Columns The bottom ring beam stiffeners are The support column alignment pin welded to the bottom ring beam with a assemblies are CJP welded to the two sided weld (%" fillet & %" bevel support columns. Since the weld is a weld). The ring beam, along with the CJP weld, these assemblies are stiffeners, is considered to be one considered to be an integral part of the composite member and hence, it is columns.

concluded that this welded connection need not be considered as a component

• Connection 39: Air Plenum Base Angle connection for the calculation of the to Air Plenum weighted average. The air plenum base angle is welded to the air plenum to form a flange at the

• Connection 17: Connecting Plate to the bottom of the air plenum to enable it to Upper/Lower Shroud Segments be bolted to the missile shield. The The connecting plates are welded to the bolted connection between this angle upper/lower shroud segments to provide and the missile shield is the critical surfaces where the shroud panels can connection in transferring loads from be welded or bolted. As discussed for the air plenum to the missile shield.

Connection 19 below, there is little load Hence, it is concluded that this welded transferred through these plates and, connection need not be considered in hence, it is concluded that this the calculation of the weighted average.

connection is not significant in dissipating energy. Attachment A contains drawings that depict and identify the connections, as numbered in Table 2.

• Connection 19: Shroud Panels to Columns Further, the integrated head assembly is a The IHA seismic analysis results show vertically standing structure bolted to three support that the stresses are low (maximum stress lugs on the replacement reactor vessel head ratio less than 0.50). In addition, the (RRVCH) and pinned to three lift lugs on the shroud panels are only 0.12 inches thick. reactor vessel head. In addition to these six This low stress ratio in the thin shroud attachment points on the RRVCH, there are eight panels indicates that there is little load seismic tie rods pinned to the IHA seismic ring transfer from support columns to the beam at the refuel floor elevation. On the cavity shroud panels through the welded wall side, these tie rods are pinned to wall lugs that connection and, hence, it is concluded are an integral part of plates that are bolted to the that this connection is not significant in containment wall. All eight seismic tie rod dissipating energy. connections on both ends of the tie rods are pin connections (See Figures 1 and 2).

ADVENT Engineering Services, Inc. Sheet 5 of 14

Document No. 06042TR-04 Rev. 4 "WEIGHTED" DAMPING VALUES FOR IHA RESPONSE SPECTRUM ANALYSIS As shown in Table 2, there are a total of 185 connections in the IHA which transfer a significant level of inertia load. Among these connections, there are a total of 9 welded connections and 176 bearing - bolted / pinned connections. Based on these quantities, the "weighted average" is calculated as below ForOBE:

(3% x 9 + 5% x 176) / (9+176) = 4.90%

For SSE:

(4% x 9 + 7% x 176) / (9+176) =6.85%

The calculated weighted average damping value of 4.90% for the OBE (DE) is used in the IHA seismic analysis. The calculated weighted average damping value of 6.85% for the SSE (DDE and Hosgri) is used in the IHA seismic analysis.

REFERENCES

1. Pacific Gas and Electric Company (PG&E),

Diablo Canyon Power Plant Units 1 and 2 FSAR Update.

2. Nuclear Regulatory Commission, Regulatory Guide 1.61, Revision 1, March, 2007, Damping Values for Seismic Design of Nuclear Power Plants.

ADVENT Engineering Services, Inc. Sheet 6 of 14

Document No. 06042TR-04 Rev. 4 Figure 1: Integrated Head Assembly - Isometric View ADVENT Engineering Services, Inc. Sheet 7 of 14

Document No. 06042TR-04 Rev. 4 Figure 2: Integrated Head Assembly - Plan (Top) View ADVENT Engineering Services, Inc. Sheet 8 of 14

Document No. 06042TR-04 Rev. 4 Table 1: A List of Major Connections in the IHA Bolted-Connection Description Welded Bearing or Connection Pin Connection Design Class I and Seismic Category I Components (Safety Related) 1 Seismic Tie Rods to Seismic Ring Beam/ Tie Rods Brackets .j (Pin) 2 Lift Rod Clevis to RRVCH Lift Lug (Pin) .j 3 Bottom Ring Beam to Lift Rod Clevis .j 4 Bottom Ring Beam Stiffener to Bottom Ring Beam .j 5 Support Columns to Bottom Ring Beam .j(1) .j (1) 6 Support Column Splice Connections .j 7 Seismic Tie Rod Bracket Mounting Plate to Seismic Ring .j BeamlTie Rods Brackets 8 Seismic Ring Beam to Support Columns .j 9 Lift Rod Clevis to Lift Rod .j 10 Lift Rod Leveling Nut to Lift Rod .j 11 Seismic Tie Rod Clevis to Cavity Wall Lug (Pin) .j 12 Lift Rod Lift Nut to Lift Rod .j 13 U-Bolt Connection between Lift Rod & Shroud Angles .j 14 CRDM Seismic (DRPI)Plates to Seismic Reinforced Ring .j 15 Seismic Wall Brackets to Wall

.j(2) 16 Bottom Ring Beam to IHA Support Lugs on the RRVCH .j Design Class" and Seismic Category 1111 Components (Non Safety Related) 17 Connecting Plate to the Upper/Lower Shroud Segments .j 18 Upper Section A Removable Shroud Panels to Columns .j ADVENT Engineering Services, Inc. Sheet 9 of 14

Document No. 06042TR-04 Rev. 4 Bolted-Connection Description Welded Bearing or Connection Pin Connection 19 Shroud Panels to Columns -J 20 Shroud Subassembly Angles to Support Columns -J 21 Angles to Angles between Shroud Subassemblies -J 22 Baffle to Baffle -J 23 Baffle Support to Support Columns -J 24 Radiation Shield Door Support Angle to Support Column -J 25 Radiation Shield Doors to Support Columns (Hinge) -J 26 Air Ducts to Support Columns -J 27 Air Duct Sub Assembly to Sub Assembly -J 28 Messenger Wire Support Ring Tube to Support Columns -J 29 Monorail Support Bracket to Support Columns -J 30 Monorail to Monorail Support Bracket -J 31 Monorail Support Bracket to Walkway -J 32 Cable Bridge to Walkway -J 33 Cable Bridge Stationary Section to Foldable Section -J 34 Support Column Alignment Pins to Support Columns -J 35 Tripod Leg Upper Clevis to Tripod Lift Eye (Pin) -J 36 Lift Block to Missile Shield -J 37 Tripod Leg Lower Clevis to Lift Block -J 38 Air Plenum Base Angle to Missile Shield -J 39 Air Plenum Base Angle to Air Plenum -J 40 Cooling Fan to Cooling Fan Support -J ADVENT Engineering Services, Inc. Sheet 10 of 14

Document No. 06042TR-04 Rev. 4 Bolted-Connection Description Welded Bearing or Connection Pin Connection 41 Cooling Fan Support to Missile Shield ,j 42 Missile Shield to Support Column (Pin) ,j 43 Radiation Shield Door Latches ,j 44 Cable Bridge Link Assembly to Cable Bridge (Pin) ,j 45 RVLlS and RVHVS Support to Support Column ,j 46 RRVCH Insulation Support To Bottom Ring Beam ,j Notes:

(1) Connection 5 of each support column to the bottom ring beam is a hybrid connection, which transfers load through a combination of the weld between the bottom ring beam vertical stiffener plates and the column and through the bolted connection between the column base plate and the bottom flange of the bottom ring beam.

(2) The seismic wall brackets are beyond the scope of the IHA; they are analyzed and evaluated by AREVA.

ADVENT Engineering Services, Inc. Sheet 11 of 14

Document No. 06042TR-04 Rev. 4 Table 2: List of Connections which Transfer a Significant Level of Inertia Load During a Seismic Event Connection Connection Reference Type of QTY No. Description Drawings Connection(3) 1 Seismic Tie Rods to Seismic 06042-M-172, Pinned 8 Ring Beam / Tie Rods Sheet 1 Brackets (Pin) 2 Lift Rod Clevis to RRVCH Lift 06042-M-201, Pinned 3 Lug (Pin) Sheet 1 3 Bottom Ring Beam to Lift Rod 06042-M-051, Bolted 6 Clevis Sheet 2 5 Support Columns to Bottom 06042-M-053, Bolted & 3 (4)

Ring Beam Sheet 1 &

Welded 3(4) 06042-M-052, Sheet 1 6 Support Column Splice 06042-M-005, Bolted 36 Connections Sheet 2 7 Seismic Tie Rod Bracket 06042-M-171, Bolted 8 Mounting Plate to Seismic Sheet 1 Ring Beam / Tie Rods Brackets 8 Seismic Ring Beam to 06042-M-151, Welded 6 Support Columns Sheet 1 9 Lift Rod Clevis to Lift Rod 06042-M-201, Bolted 3 Sheet 1 10 Lift Rod Leveling Nut to Lift 06042-M-201, Bolted 3(1)

Rod Sheet 1 11 Seismic Tie Rod Clevis to 06042-M-172, Pinned 8 Cavity Wall Lug (Pin) Sheet 1 12 Lift Rod Lift Nut to Lift Rod 06042-M-201, Bolted 3 (1)

Sheet 1 15 Seismic Wall Brackets to Wall 06042-M-175, Bolted 4 (2)

Sheet 1 16 Bottom Ring Beam to IHA 06042-M-051, Bolted 3 Support Lugs on the RRVCH Sheet 2 ADVENT Engineering Services, Inc. Sheet 12 of 14

Document No. 06042TR-04 Rev. 4 Connection Connection Reference Type of QTY No. Description Drawings Connection(3) 21 Angles to Angles between 06042-M-005, Bolted 3 Shroud Subassemblies Sheet 1 22 Baffle to Baffle 06042-M-061, Bolted 2 Sheet 1 23 Baffle Support to Support 06042-M-062, Bolted 24 Columns Sheets 1 & 2 25 Radiation Shield Doors to 06042-M-055, Pinned 24(5)

Support Columns (Hinge) Sheet 1 &

06042-M-056, Sheet 1 43 Radiation Shield Door Latches 06042-M-058, Bolted Sheets 1 & 2 32 Cable Bridge to Walkway 06042-M-250, Bolted 4 Sheet 1 33 Cable Bridge Stationary 06042-M-251, Pinned 4 Section to Foldable Section Sheets 1 & 2 35 Tripod Leg Upper Clevis to 06042-M-203, Pinned 3 Tripod Lift Eye (Pin) Sheet 1 36 Lift Block to Missile Shield 06042-M-203, Bolted 3 Sheet 1 37 Tripod Leg Lower Clevis to Lift 06042-M-203, Pinned 3 Block Sheet 1 38 Air Plenum Base Angle to 06042-M-005, Bolted 1 Missile Shield Sheet 1 40 Cooling Fan to Cooling Fan 06042-M-330, Bolted 3 Support Sheet 1 41 Cooling Fan Support to 06042-M-302, Bolted 3 Missile Shield Sheet 1 42 Missile Shield to Support 06042-M-180, Pinned 6 Column (Pin) Sheet 1, 06042-M-182, Sheets1 - 4 &

06042-M-206, Sheet 1 ADVENT Engineering Services, Inc. Sheet 13 of 14

Document No. 06042TR-04 Rev. 4 Connection Connection Reference Type of QTY No. Description Drawings Connection(3) 44 Cable Bridge Link Assembly 06042-M-251, Pinned 8 to Cable Bridge (Pin) Sheets 1 & 2 Total 185 (1)

Notes:

(1) The missile shield is restrained in the vertical direction; by the lift nuts against upward motion (Connection 12), and by the leveling nuts against downward motion (Connection 10). Only either the lift nuts or the leveling nuts are addressed in the determination of effective connections in the load path from the IHA missile shield component to the RVCH in the vertical direction. Therefore, the total number of connections of 185 considers a total of 3 for Connections 10 and 12.

(2) The seismic wall brackets are beyond the scope of the IHA; they are analyzed and evaluated by AREVA.

(3) All bolted connections are bearing connections.

(4) Connection 5 of each support column to the bottom ring beam is a hybrid connection, which transfers load through a combination of the weld between the bottom ring beam vertical stiffener plates and the column and through the bolted connection between the column base plate and the bottom flange of the bottom ring beam. This connection transmits most components of load and moment through the bolted connection, e.g. radial load, moment about the tangential axis, and moment about the vertical axis. Due to the contribution of dead load in minimizing tension loading in the column, relatively little vertical load is transferred through either the weld or the bolted connection. Owing to the nature of this connection, each of the components of the connection have been "weighted" by halving their number (while there are six such connections, only 3 welds and 3 bolted connections have been considered).

(5) For Connection No. 25, Radiation Shield Doors to Support Columns, the net effect of the two hinges and the latches (Connection No.43) is conservatively considered to be only one connection per door (24 doors).

ADVENT Engineering Services, Inc. Sheet 14 of 14