ML20072M857

Rev 0 to Plan Mod 94-0077, Unit 2 Core Shroud Mod

ML20072M857
Person / Time
Site:	Brunswick
Issue date:	03/29/1994
From:	Moore D CAROLINA POWER & LIGHT CO.
To:
Shared Package
ML20072M829	List: BSEP-94-0335, Forwards Response to GL 94-03, IGSCC of Core Shrouds in BWRs & Engineering Evaluation Rept 94-0077,Rev 0, Evaluation of Unit 2 Core Shroud Indications & Operablility Assessment ML20072M846 ML20072M857
References
94-0077, 94-77, NUDOCS 9409020210
Download: ML20072M857 (60)

Text

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ATTACHMENT 2 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS. 50-325 & 50-324 OPERATING LICENSE NOS. DPR 71 & DPR-62 RESPONSE TO NRC GENERIC LETTER 94-03, INTERGRANULAR STRESS CORROSION CRACKING OF CORE SHROUDS IN BOILING WATER REACTORS PLANT MODIFICATION 94-007 UNIT 2 CORE SHROUD MODIFICATION MARCH 1994 l

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PM 94-007 Rev. O Page C]_

REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 1 of 10 f SAFETY REVIEW COVER SHEET ,

DOCUMENT NO. PM 94-007 REV. NO. O >

DESCRIPTION OF TITLE: Unit 2 Core Shroud Modification ,

1. Assigned Responsibilities:

Safety Analysis Preparer Rooer Steckel Lead let Safety heviewer: Rocer Steckel 2nd Safety Reviewers Esgs Ebs7z

2. Safety Analysis Preparer: Complete PART I, SAFETY ANALYSIS Safety Analysis Preparer y ~

Date b l2 !D

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3. Lead 1st Safety Reviewers Complete Part II, Item Classification, t

4. Lead let safety Reviewer: III may be completed. If either question 1 or 2 is "yes," then Part IV is not required.

5. Lead let safety Reviewer: Determine which DISCIPLINES are required for review of this item (including own) and mark the appropriate blocks below.

DISCIPLINES Recuired: (Print Name) Sionature/Date (Sten 7)

O [ ] Nuclear Plant Operations

[X) Nuclear Engineering Steve Ganthner

-; .s A7 T h [ l 2 3 .ffu b r 7// f

[X; Mechanical

[ ] Electrical Rooer Steckel 'fd F 6'

Mll//d [ '

[ ] Instrumentation & Control , /

[X) Structural John McIntyre #f//kdktM O 9-/2-%

[X) Metallurgy dgffe 5# -St: : '- illiere t%/n @/M/ (M4 .N.r-M

[ ] Chemistry / Radiochemistry

[ ] Health Physics

[ ] Administrative Controls  ;

6. A QUALIFIED SAFETY REVIEWER will be assigned for each DISCIPLINE marked in step 5 and his/her name printed in the space provided. Each person shall perform a SAFETY REVIEW and provide input into the Safety Review Package, wed:h/H '

7. The Lead 1st Safety Reviewer will assure that a Part III or Part IV is completed (see step 4 above) and a Part VI if required (see 9 ,M'of Part II)

Each person listed in step 5 shall sign and date next to his/her name in step 5, indicating completion of a SAFETY REVIEW.

8. 2nd Safety Reviewers Perform a SAFETY REVIEW in accordance with Section 8.0 2nd Safety Reviewer / Date 7 9M DISCIPLINE: Mechanical Yes Eq_

9. PNSC review required? If "yes" attach Part V and mark reason [ ] [X) below:

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[ ] Potential UNREVIEWED SAFETY QUESTION

[ ] Question 9 of Part IV answered "Yes"

[ ] Other (specify):

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.' PM 94-007 Rev. No. O Page C4 hEVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 2 of 10 PART I SAFETY ANALYSIS (See instructions in Section 8.4.1)

(Attach additional sheets as necessary)

DOCUMENT NO. PM 94-007 REV. NO. O DESCRIPTION OF CHANGE:

NOTE: The attached General Electric Safety Evaluation (Attachment 1, 9 pages) forms a part of this analysis.

The purpose of this plant modification (PM) is to install mechanical clamps on the U2 core shroud at the H2 and H3 welds. The clamps are designed to provide structural integrity across the H2/H3/ top guide support ring interface and thereby eliminate reliance on the H2 and H3 welds.

Twelve (12) clamps will be installed symmetrically around the shroud. The clamps will be secured to the exterior of the shroud by bolting. Holes will be machined (EDM process) in the shroud to accommodate the bolting; with two (2) bolts above the H2 weld in the upoer shroud section and two (2) bolts below the H3 weld in the middle shroud section. The bolting will be tack welded (nut keepers to bolts) after assembly to assure the parts are captured.

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\ ANALYSIS:

This analysis and the attached General Electric (GE) Safety Analysis demonstrate that the installation of the mechanical clamps on the core shroud will result in the core shroud maintaining its design basis safety related requirements. The analysis demonstrates that the changes made by the modification will not introduce new effects or factors which would prevent any other equipment or system from meeting their design basis functions. The analysis also shows that installation processes will not create a safety concern.

DESIGN BASIS FUNCTIONS The reactor internals perform the following safety related design basis functions as specified in the UFSAR:

1. Provide a floodable volume in which the core can be adequately cooled in the event of a breach in the nuclear system process barrier external to the reactor vessel.

2. Limit deflections and deformation to assure that the control rods and the core standby cooling systems can perform their safety functions during abnormal operational transients and accidents.

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3. Assure that the safety design bases (1) and (2) above are satisfied I so that the safe shutdown of the plant and removal of decay heat are I O not impaired.

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REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A '

k CP&L SAFETY REVIEW PACKAGE Page 3 of 10 PART I: SAFETY ANALYSIS i (CONT'D.) I ANALYSIS (Cont'd.):

The location of the H2 and H3 welds at the top guide support ring is above the design basis floodable volume. Failure of the core shroud at the H2 or H3 {

welds could not prevent the core shroud from performing its design basis function relative to floodable volume. Complete failure of the H2 or H3 weld

• could result in shifting of the upper shroud section and top guide assembly. t This movement could affect the shroud's support of the core spray lines and top guide assembly. Therefore, the design must limit shifting of the upper shroud section and top guide assembly to assure that the core spray lines remain functional, and the control rods can insert.

The design specification, GE 24A5118, paragraph 4.3.4.1, requires that the  !

clamps be bolted to the shroud below the H3 weld and attached to the shroud '

above the H2 weld in a manner which will prevent relative movement across both the H2 and H3 welds during all normal and upset conditions (operating basis .

(

earthquake, plus upset pressure differential, plus deadweight). Some movement i could occur for loads greater than the limiting upset condition. This  ;

movement is limited by the fabrication clearances between the bolts and the  :

bolt holes in the shroud and clamp, and does not affect the ability of the top guide to maintain core geometry, or the Core Spray piping and spargers to  ;

provide coolant during emergency conditions.  :

For all conditions required by the UFSAR (Normal, Upset, Emergency, and Faulted) the design specification (paragraph 4.3.5) requires the clamps and '

the adjacent base material be sufficient to " satisfy the structural criteria" ,

of the UFSAR. Analysis shall be performed to demonstrate that the clamps and -

adjacent base material meet those requirements. The clamps are safety related components and the design, fabrication, and installation will be controlled by an approved GE QA Program. The design of the assemblies (i.e., locking devices / tack welding of the bolting) precludes mechanical disengagement.

Structural analysis indicates that sufficient margins exist to limit deflections to values less than that allowed by the UFSAR.

3 OTHER IMPACTS f

The modification ensures the core shroud maintains its structural integrity, j but the modification introduces other factors which could affect the system.  ;

The design requires electro-discharge-machining (EDM) of holes in the core shroud, above and below the H2 and H3 welds respectively, to accept the clamp  ;

bolts. The EDM process produces a thin, glaze-like melt on the surface of the bolt hole. Teste performed on EDM surfaces have demonstrated that it is highly resistant to Intergranular Stress Corrosion Cracking (IGSCC) i initiation. The EDM process has been used for many years in BWR environments, including core shrouds, without incident. In addition,' the area surrounding l

the holes will be in compression, due to the bolt preloads, which will further inhibit ICSCC initiation. Thus, IGSCC crack initiation in the holes is not a Concern.

The materials for the clamp, bolts and nuts, and other parts of the modification have been specifically selected to be resistant to IGSCC. The stainless steel O materials have carbon controlled to < 0.02 wt %. The nuts and bolts are XM-19 alloy with carbon controlled to 0.04 wt % max.

This material has shown excellent resistance to IGSCC for many years in BWR reactor environments.

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• PM 94-007 Rev. No. O Page C6

, REVISION 3 10CFR50.59 PROGRAM MANUAL iN ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 4 of 10 PART I SAFETY ANALYSIS (CONT'D.)

ANALYSIS (Cont'd.):

Thermal expansion has been considered in the stress analysis. Evaluation of the galvanic corrosion potential for the belted clamp design has been performed, and it has been concluded that the clamp / shroud / bolting materials (316L/304/XM-19) are compatible from a galvanic corrosion design perspective.

Radiation effects have been considered, and allowances made for radiation induced relaxation in the bolted connection. Thus, the materials are suitable for the modification.

The holes will allow some leakage flow from inside the shroud to the annulus area between the shroud and the Reactor Pressure Vessel (RPV) wall. GE design specification 24A5118 (paragraph 4.6) requires that the design control the normal operating condition leakage through the repair clamp holes to prevent cavitation of the jet pumps. Analysis has been performed to evaluate the effects of the leakage on steam separation and on the jet pumps. This analysis determined that the leakage path through the bolt holes will have no significant adverse consequences.

c The clamps will place some restriction in the annulus between the shroud and g w) the RPV wall. Analyses have been performed to demonstrate that the clamps will not significantly affect the annulus flow, or prevent required maintenance and inspection activities.

The design of the clamps will result in the parts being " captured" and thereby eliminates the possibility of pieces becoming dislodged during all analyzed conditions. The installation of the clamps on the core shroud will be accomplished with the reactor defueled. Controls exist within the installation process to account for tools and parts used in or over the vessel.

EER 93-0536 analyzed the Unit 2 core shroud, and found that its condition is acceptable for continued operation through the current fuel cycle, which the EER assumed would end on 3/16/94. The EER will be revised to bound continued operation as reflected in the current outage schedule. This revision will also include some additional margin beyond the shutdown date. The shroud will .

be inspected during the modification installation to ensure the assumptions made by the EER are justified. The additional margin will provide assurance of shroud structural integrity throughout the outage, since the cracks only grow when the reactor is critical. Clamp installation will be completed prior to fuel reload and fuel may be loaded prior to modification operability.

The modified core shroud will meet its design basis safety related functions as defined in the UFSAR.

REFERENCES:

UFSAR sections: 1.5.6, 3.2.1, 3.2.1.2, 3.7.1.1.1, 3.7.1.1.2, f' - '

3.9.1.1, 3.9.1.1.1, 3.9.1.1.2, 3.9.1.1.3, 3.9.1.1.4, 3.9.2.4, 3.9.2.5.1, 3.9.2.5.2, 3.9.5.1, 3.9.5.1.1, 3.9.5.3, 4.5.2, 9.1.3, Chapter 15, Table 3.9.2-5 ; Tech Specs: 3.4.1.2, 3.4.8 Design Basis Document B94-007 P' ".' E : L' .r! -1 r . c: C, j'

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REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 5 of _10_

PART II: ITEM CLASSIFICATION DOCUMENT NO. PM 94-007 REV. NO. O Yes No

1. Does this item represents

a. A change to the facility as described in the SAFETY [ } (X)

ANALYSIS REPORT?

b. A change to the procedures as described in the [ ] (X]

SAFETY ANALYSIS REPORT 7

c. A test or experiment not described in the SAFETY [ } (X]

ANALYSIS REPORT 7

2. Does this item involve a change to the individual plant [ ] [X]

Operating License or to its Technical Specifications?

3. Does this item require a revision to the FSAR7 4.

(X] [ ]

Does this item involve a change to the Offsite [ ] [X)

Dose Calculation Manual?

5. Does this item constitute a change to the Process control Program?

() (X]

6. Does this item involve a major change to a Radwaste Treatment [ ] [X)  ;

System?

7. Does this item involve a change to the I

[ ] [X}

g Technical Specification Equipment List?

8. Does this item impact the NPDES Permit (all 3 sites) or [ ] (X) constitute an "unreviewed environmental question" (SHNPP Environmental Plan Section 3.1) or a "significant environmental impact" (BSEP)?

9. Does this item involve a change to a previously accepted:

a. Quality Assurance Program ( ] [X]

b. Security Plan (including Training, [ ] (X)

Qualification, and Contingency Plans)?

c. Emergency Plan?

[ ] [X)

d. Independent Spent Fuel Storage Installation license? [ ] (X} '

(If yes, refer to Sectica 8.4.2, " Question 9," for special considerations. Complete Part VI in accordance with Section 8.4.6)

SEE SECTION 8.4.2 FOR INSTRUCTIONS FOR EACH "YES" ANSWER.

REFERENCES. List FSAR and Technical Specification references used to answer questions 1-9 above. Identify specific reference sections used for any "Yes" answer.

See Safety Evaluation references.

• The FSAR does not describe the core shroud to the detailed level that the H2

& H3 welds are identified. Text will be added to the FSAR to describe the addition of the clamos for clarity.

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., PM 94-007 Rev. No. O Page C8 REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 6 of 10 PART III: UNREVIEWED SAFETY QUESTION DETERMINATION SCREEN DOCUMENT NO. PM 94-007 REV. NO. 0 LEE NO

1. Is this change fully addressed by another completed [ ] [X]

UNREVIEWED SAFETY QUESTION determination? (See Section 7.2.1, 7.2.2.5, and 7.9.1.1)

REFERENCE DOCUMENT: REV.

YES NO

2. For procedures, is the change a non-intent change which only [ ] [X]

(check all that apply): (See Section 7.2.2.3) N/A

[ ] Correct typographical errors which do not alter the meaning or intent of the procedure; or,

[ ] Add or revise steps for clarification (provided they are consistent with the original purpose or applicability of the procedure); or,

( [ ] Change the title of an organizational position; or,

[ ] Change names, addresses, or telephone numbers of persons; or,

[ ] Change the designation of an item of equipment where the equipment is the same as the original equipment or is an authorized replacement; or,

[ ] Change a specified tool or instrument to an equivalent substitute; or,

[ ] Change the format of a procedure without altering tho meaning, intent, or content; or

[ ] Deletes a part or all of a procedure, the deleted portions of which are wholly covered by approved plant procedures?

If the answer to either Question 1 or Question 2 in PART III is "Yes," then PART IV need not be completed.

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- ,s REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 7 of _10_

PART IV: UNREVIEWED SAFETY QUESTION DETERMINATION DOCUMENT NO. PM 94-007 REV. NO. O Using the SAFETY ANALYSIS developed for the change, test or experiment, as well as other required references (LICENSING BASIS DOCUKENTATION, Design Drawings, Design Basis Documents, codes, etc.), the preparer of the SAFETY EVALUATION must directly answer each of the following seven questions and make a determination of whether an UNREVIEWED SAFETY QUESTION exists.

A WRITTEN BASIS IS REQUIRED FOR EACH ANSWER Yes Ho

1. May the proposed activity increase the [ ] [X) probability of occurrence of an accident evaluated previously in the SAFETY ANALYSIS REPORT 7 See attached.

2. May the proposed activity increase the consequences of an [ ] [X)

,s accident evaluated previously in the SAFETY ANALYSIS REPORT 7 g

v

) See attached.

3. May the proposed activity increase the probability of [ ] [X) occurrence of a malfunction of equipment important to safety evaluated previously in the SAFETY ANALYSIS REPORT 7 See attached.

4. May the proposed activity increase the consequence [ ] [X) of a malfunction of equipment important to safety evaluated previously in the SAFETY ANALYSIS REPORT 7 See attached.

5. May the proposed activity create the possibility [ ] [X) of an accident of a different type than any evaluated previously in the SAFETY ANALYSIS REPORT 7 See attached.

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REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 8 of 10 PART IV (Continued)

DOCUMENT NO. PM 94-007 REV. NO. O I Yes No

6. May the proposed activity create the possibility of a () [X) malfunction of equipment important to safety of a different type than any evaluated previously in the SAFETY ANALYSIS REPORT 7 See attached.

7. Does the proposed activity reduce the margin of safety as [ ] [X) defined in the basis of any Technical Specification?

See attached.

8. Based on the answers to questions 1 - 7, does this item [ ] [X) result in an UNREVIEWED SAFETY QUESTION 7 If the answer to ,

any of the questions 1-7 is "Yes", then the item is l

[ ) considered to constitute an UNREVIEWED SAFETY QUESTION.

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9. Is PNSC review required for any of the following reasons? [ ] [X)

If, in answering questions 1 or 3 "No", it was determined that the probability increase was small relative to the uncertainties; or, in answering question 2 or 4 "No", it was determined that the doses increased, but that the dose was still less than the NRC ACCEPTANCE LIMIT; or in answering question 7 "No", a parameter would be closer to the NRC ACCEPTANCE LIMIT, but the end result was still within the NRC ACCEPTANCE LIMIT; then PNSC review is required.

REFERENCES:

See Safety Evaluation references.

This Unreviewed Safety Question Determination is for the following DISCIPLINE (s): (Additional Part IV forms may bo included as appropriate.)

[ ] Nuclear Plant Operations [X) Structural

[X) Nuclear Engineering [X) Metallurgy

[X) Mechanical [ ] Chemistry / Radiochemistry

[ ] Electrical [ ] Health Physics

[ ] Instrumentation & Control [ ] A&ninistrative Controls O

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Page C11 j REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page 9 of 10 PART IV (Continued)

DOCUMENT NO. PM 94-007 REV. NO. 0

1. May the proposed activity increase the probability of occurrence of an accident evaluated previously in the SAFETY ANALYSIS LtPORT?

No. The design, materials, and installation requirements for the modification meet the original design basis function for the core shroud. l The modification ensures the shroud will meet its design function of maintaining the core geometry and providing a floodable volume. The ,

modification therefore does not increase the probability of an accident. 'F

2. May the proposed activity increase the consequences of an accident evaluated previously in the SAFETY ANALYSIS REPORT?

No. The core shroud provides a passive structural function. The  :

modification ensures the structural integrity of the core shroud at the  :

area of the H2 and H3 welds. This ensures that the core internal geometric alignment will be maintained, and that the Core Spray piping and spargers will perform their safety function. Insignificant effects on Peak Cladding Temperature (PCT) for the design basis LOCA result from the clamp leakage '

f flow paths, with no impact on the release from the analyzed accident.

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Therefore, the modification will not increase the consequences of any accident.

3. May the proposed activity increase the probability of occurrence of a- ,

malfunction of equipment important to safety evaluated previously in the SAFETY ANALYSIS REPORT?

No. Installation of the clamps in the area of the H2 and H3 welds ensures the structural integrity of the upper shroud. As long as structural integrity is maintained, the shroud will continue to provide its safety  ;

function. The leakage effects on jet pump operation have been evaluated and shown to be acceptable. Therefore, the probability of a malfunction of equipment important to safety remains unchanged.

4. May the proposed activity increase the consequence of a malfunction of equipment important to safety evaluated previously in the SAFETY ANALYSIS REPORT?

I No. The core shroud functions to maintain a floodable volume above two-thirds core height and to maintain core alignment to ensure control rod insertion. The design, materials, and installation requirements of the -

modification meet the original design basis function for the core shroud.

Therefore, the modification has no effect on the consequences of any equipment malfunction.

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." PM 94-007 Rev. No. O Page C12 REVISION 3 10CFR50.59 PROGRAM MANUAL ATTACHMENT A CP&L SAFETY REVIEW PACKAGE Page .,1Q_ of ,,,1Q_

PART IV (Continued) ,

DOCUMENT NO. PM 04-007 REV. NO. 0

5. May the proposed activity create the possibility of an accident of a dif ferent type than any evaluated previously in the SAFETY ANALYSIS REPORT 7 No. The modification ensures that the core shroud will maintain its design requirements under postulated conditions in the UFSAR. The leakage flow at the bolt holes will have negligible effect on system operation, thus a there is no different accident that can be postulated as occurring as a result of the modification.

6. May the proposed activity create the possibility of a malfunction of equipment important to safety of a different type than any evaluated previously in the SAFETY ANALYSIS REPORT?

No. The modification ensures that the core shroud will maintain its design '

requirements, so the possibility of any malfunction of the core shroud is-unchanged. The design of the clamps precludes parts coming loose. This ensures that the function of other components will not be affected.

7. Does the proposed activity reduce the margin of safety as defined in the basic ~of any Technical Specification?

No. The modified core shroud provides the structural integrity to meet the design basis, including specified safety factors. This assures the ability to insert the control rods, and maintain a floodable volume. The clamps will be inspected to ensure they continue to meet their design requirements, therefore no reduction in a safety margin of any kind would result from the modification. The analysis performed on leakage flow determined that the effects would be negligible. In addition, there is no basis of any Tech. Spec. which would be specifically impacted by the core shroud modification. >

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, i Plant Mod. No. 99-oo , BNP-SE002 j ev. O  ;

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SAFETY EVALUATION FOR .

t INSTALLATION OF CLAMPS ON THE BRUNSWICK UNIT 2 CORESHROUD p

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SAFETY EVALUATION FOR INSTALLATION OF CLAMPS

1.0 DESCRIPTION

OF CHANGE i l

Welds H2 and H3 of the core shroud will be structurally replaced by clamps. -

Figure I shows the location of the clamps. The clamps will be attached to the j shroud above weld H2 with two bolts and will be attached to the shroud below I weld H3 with two bolts. The clamps will perform all of the functions ofwelds H2  ;

and H3. The clamps.are designed to the same criteria as the original shroud.  ;

i The core shroud is a safety-related component. It provides horizontal support for i the fuel assemblies, control rods and incore instrumentation. It provides vertical support for the peripheral fuel assemblies. It provides a floodable volume inside  ;

the reactor pressure vessel. It supports the core spray spargers and core spray lines.

The H2 and H3 welds are located near the top of the shroud above the required floodable volume. The H2 and H3 welds provide horizontal support for the top of the fuel assemblies, control rods and incore instrumentation. They do not provide venical support for peripheral fuel assemblies. They do support the core spray spargers and core spray lines. Therefore, the H2 and H3 welds are safety-related.

The clamps have been designed to the same stmetural criteria specified for the original shroud in the Bmnswick UFSAR. The Design Specification for the repair is 24A5118 (Reference 6.1). The clamps were designed assuming that both welds - '

H2 and H3 were cracked 360 degrees through-wall. No credit was taken for any part of either weld. The design considered the effect ofirradiation on the clamps and the bolts. The bolts have adequate fast neutron fluence margin to accommodate the scheduled power uprate assuming an average 85% capacity factor to the end of the plant license. The fluence values that were used were based on historic core loadings and fuel designs.

There are 12 clamps located on 30 degree centers around the shroud circumference. Each clamp has four (4) shoulder bolts. The nut on each of the i i

bolts is captured with a keeper that is tack welded to the bolt. Thus, the possibility ofloose pans does not exist. .Two of the bolts are above H2 and two are below H3. The load path for forces and moments generated above weld H2 will be from the upper shroud to the upper pair of clamp bolts, to the~ clamp body, to the lower '

pair of clamp bolts and finally back into the shroud below weld H3. The bolts are prestressed with stud tensioners. The prestress is large enough to prevent any motion during normal operation and during the limiting upset event. During emergency and faulted events, slippage ofless than 0.32 inch could occur before the shoulder on the clamp bolts would prevent additional motion. The maximum 1

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slippage of 0.32 inch could occur during a design basis eanhquake (DBE). The slippage could open a leakage path through the shroud at the H3 weld. The leakage path would be detected and repaired during the reactor internals inspections which would occur following the DBE. The slippage will not affect the ability of the core spray lines and spargers to perform their function. The stresses in the clamp bolts during all UFS AR load combinations are within the allowable values. The stress analysis for the repair is documented in GE-NE-771-15-0294 (Reference 6.2).

The effect of the clamps on the core shroud has been evaluated. The stresses in the shroud with the clamps meet all of the UFSAR requirements for normal, upset, emergency and faulted conditions including LOCA and the design basis earthquake (DBE). In addition, the secondary stresses satisfy ASME Code allowable values during limiting upset event, which includes the operating basis earthquake (OBE). ,

The shroud displacements are acceptable during all events. The UFSAR (see Paragraph 3.9.5.3) allows secondary stresses to exceed ASME Code values provided displacements are acceptable. The stiffness and mass of the clamps is such that the dynamic response of the shroud, during both normal operation and seismic events, will not be significantly changed by the replacement of welds H2 and H3 with the clamps.

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The clamp bolts and associated holes through the core shroud permit a small fraction of the core flow to bypass the steam separators. The holes are above the floodable volume which terminates at 2/3 core height and there is no safety consequence to this small leakage with respect to maintaining the floodable volume.

The total leakage flow at rated power and 75 to 105% rated core flow is predicted to be about 0.2% of the core flow. The leakage flow includes steam flow, which effectively increases the total carryunder in the downcomer by about 0.02%,

compared with a design value of 0.25%. At rated core flow, the separator test data show that the actual carryunder is less than the design value, and that the design value is still met when the shroud bolt hole leakage is taken into account.

At rated power and 75% rated core flow, the bolt hole leakage increases the carryunder above the design value and the core inlet enthalpy is increased by about 0.1 Btu /lb, compared with the no-leakage condition.

The impacts ofincreased carryunder onjet pump cavitation margin, fuel thermal margin, emergency core cooling system (ECCS) performance and fuel cycle length have been evaluated. The impact onjet pump cavitation margin is determined from the increase in enthalpy of the fluid entrained by thejet pumps.

The results show that jet pump cavitation margin decreases slightly but remains adequate.

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The transient code used to calculate fuel thermal margin includes carryunder as one of the inputs. The effect ofincreased carryunder due to shroud bolt hole leakage has been assessed and it has been concluded that the operating limit .

minimum critical power ratio is not impacted. The sequence of events and peak l pressures remain essentially unchanged for the transients with the leakage paths.

ECCS performance impact was assessed based on ECCS sensitivity results.

Shroud leakage causes the initial core inlet euthalpy to increase slightly, with a corresponding decrease in the core inlet subcooling. Sensitivity results show that this effect would decrease the peak cladding temperature (PCT) for the design basis event slightly. Another effect of the shroud leakage is to slightly decrease the time to core uncovery. This effect would increase the PCT for the design basis event slightly. When both effects are combined, there is essentially no impact on the PCT and the licensing basis PCT for the normal condition with no leakage is applicable. The sequence of events remains essentially unchanged for the loss-of-coolant accidents (LOCAs) and main steam line breaks (MSLBs) with the leakage paths.

The increased carryunder due to shroud bolt-hole leakage results in an increase in the core inlet enthalpy by about 0.1 Btu /lb, compared with the no-leakage condition. This impact has a minor effect (=0.3 days) on fuel cycle length and is considered negligible. Further, at end-of-cycle (EOC) conditions, the core flow rate is expected to be equal to or above rated core flow where design carryunder is met. Hence, there is no impact at EOC and fuel cycle time is not impacted when compared with the design condition.

The leakage flow, during normal operation, has a temperature approximately 30 degrees F higher than the clamps. There will not be any fatigue of the clamps due to impingement of the leakage flow, because of the small temperature difference.

The clamps will not significantly affect the flow within the downcomer and will not adversely affect the performance of any reactor internal. The water inventory in the downcomer with the clamps exceeds the volume used in existing analyses which are based on minimum RPV diameter.

The clamps are not located in a region identified by the UFSAR to have significant thermal shock due to ECCS injection.

Cracking of welds H2 and H3 will not propagate into the clamp. The clamp design is based on the assumed complete severance of welds H2 and H3. Therefore, there is no requirement to perform additional examination on welds H2 and H3 after clamp installation. The 12 clamps also restrain the 6 segments of the top guide support plate. There is no combination of weld failures that could prevent the top guide support plate from performing its support function. The structural analysis .

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v structural analysis of the clamps did not rely on the strength of any of these welds.

Therefore, there is no requirement to perform additional examination on the top guide suppon plate ring segment welds.

The clamp materials are 316L with 0.02 % maximum carbon and XM19 with 0.04

% carbon. These materials have high resistance to IGSCC and have thermal expansion coeflicients similar to the existing shroud. The clamps have a design life equal to the remaining Plant life. The shroud holes will be machined with electrical

discharge machining (EDM). The qualification testing of the EDM holes has shown, with optical metallography, that the shroud holes will be acceptable.

2.0 REASON FOR THE CHANGE ,

Cracks were detected during in-vessel visual inspection (IVVI) of the core shroud ,

at Brunswick Unit 1. This Safety Evaluation discusses potential cracks near welds H2 and H3 and the repair of those cracks for Brunswick Unit 2. Figure 1 shows the location of welds H2 and H3.

The cracks in Brunswick Unit I were repaired in the same manner as is discussed herein for Unit 2. The Brunswick Unit 1 Safety Evaluation is documented in Reference 6.3.  !

3.0 DESIGN AND LICENSING DOCUMENTATION REVIEW The Brunswick Unit 2 Updated FSAR was reviewed. The results of the review are as follows. The numbers in ( ) are the paragraph numbers from which the l information was extracted.

(3.2.1) Stmetures and equipment are classified as Seismic Class Iif they are essential for safe shutdown or if their failure could result in the release of radiation ,

with dose consequences potentially exceeding the guidelines of 10CFR100.

(3.2.1.2) The core shroud is classified as Seismic Class I.

(3.9.2.5.2) and (Table 3.9.2-5) Define the pressure drop across the shroud during normal operation and LOCA.

(3.9.5.1) The core shroud is a reactor vessel internal. The core shroud up to the level of thejet pump nozzles is a pan of the floodable inner volume of the reactor vessel.~

. 1 (3.9.5.1.1) Gives a brief description of the shroud.

(3.9.5.2.1) The following load combinations and safety factors were used.

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1. The OBE plus normal loads plus upset loads should be evaluated with a safety factor of 2.25.

2. The DBE plus normal loads should be evaluated with a safety factor of l 1.50. R l

3. The load combination of DBE plus LOCA plus normal loads should be l evaluated with a safety factor of 1.125. )

4. The load combination of LOCA plus normal loads should be evaluated with a safety factor of 1.50.

(3.9.5.3) The design of the reactor vessel internals was in accordance with applicable portions of the ASME B & PV Code,Section III,1965 Edition through Summer 1967 Addenda.

Note: There are no applicable portions of Section III for the core shroud.

Where applicable Codes and Standards did not exist, the reactor vessel internals were designed to the criteria in UFSAR Section 3.9.5.2 and to the limits in UFSAR Tables 3.9.5-1 through 3.9.5-4. The safety design basis that is relevant to D the core shroud welds H2 and H3 was that deflection and deformation were limited such that the control rods can perform their safety function during abnormal operational transients and accidents.

(3.7.1.1.2) The DBE ground horizontal acceleration is 0.16g. The vertical DBE ground acceleration is equal to two thirds of the horizontal acceleration. OBE ground acceleration is one half of the DBE accelerations.

GE documentation was reviewed to determine the applicable forces, moments, and pressures on the core shroud during each of the required load combinations. The seismic forces and moments for OBE and DBE were obtained from Reference 6.4 and 6.5. The pressure differences across the upper shroud for all operating conditions were obtained from Reference 6.6 and from the UFSAR.

The GE Design Specification for the Clamps is 24A5118.

4.0 ANSWERS TO TIIE APPLICABILITY DETERMINATION CRITERIA Does the procedure, design change, modification, test or experiment, to which this evaluation is applicable, represent:

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4.1 Yes No _X_ A change to the facility (plant) as described in the SAR?

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Plant Mod. No. W- 0 i BNP-SE002 Field Rev. No. o Rev.O Page No. C 19 Of 4.2 Yes No _X_ A change to a procedure or analysis as described in the SAR?

4.3 Yes No _X_ A change to a test or experiment as described in the SAR?

4.4 Yes No _X_ A new structure, system, component, procedure, test or experiment, which could impact the safety of operations or affect nuclear safety in a way not previously evaluated in the SAR?

4.5 Yes __ No _X_ A change to the existing situation, but is not covered by Questions 4.1 - 4.4, which could impact the safety of operations or affect nuclear safety in a way not previously evaluated in the SAR?

4.6 Yes No _X_ A change that is already bounded by a valid and approved 10CFR 50.59 safety evaluation?

4.7 Yes No _X_ A change to the Technical Specifications?

t All of the above answers are no because the clamps are designed to the same criteria as the original core shroud. >

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S 5.1 Yes No _X_ Will an USAR update be required? ("Yes", if 4.1, 4.2 or 4.3 is "Yes", or may be "Yes", if only 4.4 or 4.5 is "Yes" But always "No" for a temporary change.)

5.2 Yes No _X_ Is a safety evaluation (USQD) required? ("Yes",

if 4.1,4.2,4.3,4.4 or 4.5 is "Yes" and 4.6 is "No" But always "No", if 4.6 or 4.7 is "Yes".)

5.3 Yes No _X_ Will a Tech Spec change be required? ("Yes", if 4.'i is "Yes".)

6.0 REFERENCE 6.1 GE Design Specification for Clamps,24A5118 Rev.1.

6.2. GE Stress Analysis for Clamps, GE-NE-771-15-0294 Rev 0.

A ,

Q 6.3. Safety Evaluation for Installation of Clamps on the Brunswick Unit 1 Core Shroud, BNP-SE001, Rev 0.

6.4. GE-NE-523-159 Rev. O, Brunswick Unit 1 Seismic Analysis for Shroud Repair.

6.5. Letter to Jim Charnley from P.B. Shah, " Brunswick Unit 2 - Seismic Loads for Shroud Repair," Feb. 10,1994.

6.6 GE Reactor Internal Pressure Differences for Brunswick I and 2 Power Uprate, DRF A00-04082.

Prepared by: '

Date: 3 f 9V V

Verified by: Aedez- Date: 3 /f/N Approved by: - Date: 3- 9 ~ YY o

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Item ' . Quan; PO Number NIRF/R - Part Nof Q Statusi

Description L'

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12 (LATER) NED N/A 3 RACKET ASSEMBLY - CONSISTING OF: GE SPEC Q Q l - BR ACKET PER GE DRAWING ll2D5181 24A5118 g SEE NOTE 4 - BOLTS, GE DWG 148C6308 EA 4 - NUTS, GE DWG 148C6309 4 - WASHERS, GE DWG 148C6310 4 - KEEPERE. OE DRAWING 148C6311 1 NOTE: MATERIAL WILL BE SUPPLIED UNDER GE CONTRACT (LATER). CP&L PO (LATER) IS FOR RECIEFT INSPECTION

PURPOSES ONLY.

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INSTALLATION DRAWINGS  :

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NOTE: All installation will be accomplished by General Electric (GE) in accordance with GE drawings which shall be reviewed / approved by NED. No Plant Modification Sketches are applicable. -

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SECTION E  ;

INSTALLATION INSTRUCTIONS PAGE NO.

1.0 PURPOSE . . . . . . . . ....... . . . . ............. 3 2.0 BEFERENCES . . . . . . . ......... . . . . . . . . . . . . . . . . 3 3.0 RESPONSIBILITIES . . . . . ............ . . . . . . . . . .. 3 4.0 GENERAL REOUIREMENTS . . . ................... . . .. .4 5.0 PREREOUISITES . . . . . . ..... .................. 5 6.0 PRECAUTIONS AND LIMITATIONS ............ . . . . . . .... 6

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7.0 PROCEDURAL STEPS . . . . . ............. . . . ....... 8 i

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O E3 1.0 PURPOSE The purpose of this procedure is to provide the controls for implementing the modification to the core shroud at the H2 and H3 welds. The actual modification activities will be performed by the contractor (General Electric) in accordance with the Contractor's QA/QC program, the Quality Implementation Plan and the Project Implementation Plan.

2.0 REFERENCES

2.1 Contractors procedures and drawings as accepted by CP&L.

2.2 AI-106, Cleanliness Control for Reactor Refueling Floor 2.3 AI-ll2, Control of Material in the Spent Fuel Pools 3.0 RESPONSIBILITIES 3.1 NED NED shall. coordinate all design engineering for the modification.

NED shall also provide engineering support during modification O . installation to resolve installation problems affecting the design and provide field revisions as necessary.

3.2 PMS Unit Ensuring all work is accomplished in accordance with the plant modification procedures. Also, coordinating work sequence with other groups (i.e., Contractor, Operations, Plant Services).

Obtaining and releasing necessary clearances as required.

Project turnover and plant modification operability.

Review and approval of documentation associated with plant modification.

Providing temporary power, service air, work platforms, etc.

3.3 MSS /NDE Unit Review and acceptance of NDE records.

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(/) Installation Package Rev. No. O Installation Instructions Page No. E4 3.4 EERC Perform all Health Physics functions as required to support work performed in accordance with plant modification.

3.5 OPERATIONS Be cognizant of the operational support required for the implementation of this plant modification.

Responsible for administration of LCO's and Clearances, and '

manipulation of plant valves and equipment as required.

3.6 INSTALLATION CONTRACTOR (GE)

Responsible for all work associated with installation of the clamps including fitup, tackwelding and all NDE inspections in accordance with their procedures, QA Manual, and the terms and conditions of the contract.

4.0 GENERAL REOUIREMENTS O

Q 4.1 All work performed shall be in accordance with the installation instructions as set forth in this planc modification package and the Contractnr's work packages and procedures, as applicable and as accepted by CP&L. The contractor's procedures, travelers, and instructions used to accomplish the work will be incorporated into this plant modification via the turnover package.

4.2 NED review and acceptance of Design Documents as required by the r installation portion of this PM, and documented by signoff therein, shall be per the Project Implementation Plan. Review and acceptance shall be performed prior to signoff.

4.3 All work performed per this plant modification in radiation l environments shall be coordinated with other work in the same area in order to minimize delays and reduce exposure.

4.4 Personnel who will be performing work in high radiation areas or in the RPV shall be trained on mockups or by other suitable means. l 4.5 Maintain cleanliness per AI-106.

4.6 Observe all radiological precautions as directed by Health Physics and E&PC 4100.

4.7 NPMP Form 16 - Field Deviation Request Form may be used in the performance of this installation instruction.

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Mod. No.94-007 Installation Package Rev. No. O {

Installation Instructions Page No. ES-t 5.0 GENERAL PREREOUISITES 5.1 An RWP has been established for the work. .

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PMS Project Manager or Designee Date 5.2 Temporary shielding has been installed as required by the HP/ALARA groups in order to reduce exposure, and personnel have been instructed to minimize stay time in the radiation area, and to observe all ALARA rules.

PMS Project Manager or Designee Date 5.3 The Unit 2 Shift Supervisor has been notified of the scope and expected duration of the work required by this modification.

r PMS Project Manager or Designee Date 5.4 obtain necessary clearances and plant conditions to support in vessel modifications.

PMS Project Manager or Designee Date 5.5 Verify that the Contractor has read and is familiar with the requirements of this Plant Modification. Special note should be made of the ALARA considerations (Section 6.1)

PMS Project Manager or Designee Date 5.6 A tool control log per AI-106 has been established.

PMS Project Manager or Designee Date

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O E6 6.0 PRECAUTIONS AND LIMITATIONS 6.1 All work performed in radiation areas shall be in accordance with o E&RC requirements and consistent with BNP ALARA Program and as follows:

6.1.1 Any plugs or EDM Swarf containers must be moved underwater to the Spent Fuel Pool and placed in an equipment disposal can per AI-ll2 Attachment A and BNP ,

Nuclear Engineer Department instructions.

6.1.2 An under water vacuum suction must be in place to collect particle debris created by the EDM cutting process.

i 6.1.3 Under water vacuum filter assembly should be located on the Equipment Pool ledge at the north end or other suitable location approved by Health Physics to reinimize personnel exposure.

6.1.4 Health Physics perscannel will monitor dose rates on vacuum filters and in the general area above the vacuum assembly during EDM cutting.

6.1.5 Health Physics personnel must approve any changes in '

location of the underwater vacuum filter assembly.

e 6.1.6 Maximum filter dose rates, if required, must be determined by Radwaste Shipping in advance of EDM l cutting.

6.1.7 Adjustment / handling of EDM and associated equipment i used in the shroud cutting process should be done j underwater (work tank on 117' elevation) or in a containment unless waived by Health Physics personnel.

6.1.8 All EDM cutting equipment and associated- tools, including underwater cameras, must be washed with  ;

demineralized water during removal from the ~ reactor cavity and must be surveyed by Health Physics technicians prior to transfer to work areas on the refuel floor. Leave equipment in the water as long as possible to avoid exposure to personnel.

6.1.9 Health Physics technicians on the refuel floor must be consulted prior to work on any equipment or component removed from the Reactor Vessel, the Reactor cavity, the Spent Fuel Pool or the Equipment Pool.

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{ Installation Package Mod. No.94-007 Rev. No. O Installation Instructions Page No. E7 6.1.10 Attemt to design EDM fixture and tooling that elimates t crud u aps or can be readily flushed.

6.1.11 Redesign the swarf collection system used in the U/1 i Shroud repair to improve the capture efficiency and reduce the number of filters.

6.1.12 Attempt to locate the EDM controls and tool work areas in the lowest dose rate field that is feasible.

6.1.13 Schedule loading of filters and other highly radioactive equipment into shipping containers -to I coincide with the fewest number of required personnel on the Refuel Floor.

6.1.14 Positive steps shall be taken to prevent entry of foreign materials into the reactor pressure vessel.

Materials or tools dropped into the RPV must be retrieved. Tool control shall be in accordance with AI-106.

6.2 The volume of radwaste generated (swarf and filters) as a result of the EDM cutting process may be significant. The swarf and filters should be stored underwater and their disposal coordinated with the Radwaste shipping group.

6.3 The CP&L Refueling Floor Manager or his designee is responsible for overall control of activities on the refueling floor. He shall be informed of any unexpected occurrences or conditions that occur during the performance of this PM.

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Mod. No.94-007 Installation Package Rev. No. O Installation Instructions Page No. E8 7.0 PROCEDURAL STEPS l

This subsection provides the guidelines necessary to control and document the installation of the core shroud modification. The actual installation will be accomplished by the contractor using CP&L approved contractor procedures and drawings.

7.1 All General Prerequisites have been signed off.

i PMS Project Manager or Designee Date 7.2 EDN HOLE CUTTING 7.2.1 PREREQUISITES FOR EDM HOLE CUTTING ACTIVITIES  ;

7.2.1.1 Contractor's design documents applicable to EDM cutting have been received by CP&L and have been reviewed and accepted as documented by the completion of an Owners Review per NED procedure No. 310. The Design Documents are listed in the Project Implementation Plan.

• NED Lead Engineer or Designee Date 7.2.1.2 Preliminary activities (i.e., procedures, travelers, mockup training, etc.) that are required to be performed by the Contractor prior to EDM cutting have been completed, and have been reviewed and accepted by CP&L as required by the Project Implementation Plan.

PMS Project Manager or Designee Date l

NED Lead Engineer or Designee Date j

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7.2.1.3 Temporary services (i.e., electrical power,  !

service air, etc.) have been installed and are readily accessible at the required work site to  !

support EDM cutting, f

5 PMS Project Manager or Designee Date 7.2.1.4 The three (3) rows of double blade guides closest to the core shroud have been removed.

PMS Project Manager or Designee Date 7.2.1.5 Covers have been installed on the jet pumps (20 total).

PMS Project Manager or Designee Date i

7.2.1.6 Fuel support casting covers have been installed

• in the three rows closest to the core shroud (92 total plus 12 peripheral).

PMS Project Manager or Designee Date 7.2.1.7 The area of the shroud wall to be modified has '

been inspected for interferences (i.e.,

interference encountered during the- U1 modification at the 195* azimuth) . t I

PMS Project Manager or Designee Date t 7.2.1.8 The swarf collection and filter system is  !

installed and functional.  ?

PMS Project Manager or Designee Date 6

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/ Mod. No.94-007 Q]' Installation Package Installation Instructions Rev. No. O Page No. E10 7.2.1.9 Obtain Unit 2 Shift Supervisor's approval to proceed with EDM cutting.

Unit 2 Shift Supervisor Date 7.2.2 PMS Project Manager shall notify the Contractor that the prerequisitas have been met and work may proceed for EDM cutting only.

PMS Project Manager or Designee Date 7.3 CLAMP INSTALLATION 7.3.1 PREREQUISITES FOR CLAMP INSTALLATION ACTIVITIES 7.3.1.1 Contractor's design documents applicable to clamp installation have been received by CP&L and have p/ been reviewed and accepted as documented by the y completion of an owners Review per NED procedure No. 310. The Design Documents are listed in the Project Implementation Plan.

NED Lead Engineer or Designee Date 7.3.1.2 Preliminary activities (i.e., procedures, travelers, mockup training, etc.) that are required to be performed by the contractor prior to clamp installation have been completed, and have been reviewed and accepted by CP&L as required by the Project Implementation Plan.

PMS Project Manager or Designee Date NED Lead Engineer or Designee Date 7.3.1.3 Temporary services (i.e., electrical power, service air, etc.) have been installed and are readily accessible at the required work site to

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\ Installation Package Rev. No. O Installation Instructions Page No. E11 support clamp installation.

PMS Project Manager or Designee Date t

7.3.1.4 Obtain Unit 2 shift Supervisor's approval to proceed with clamp installation.

Unit 2 shift Supervisor Date 7.3.2 PMS Project Manager shall notify the contractor that the prerequisites have been met and work may proceed for clamp installation. '

PMS Project Manager or Designee Date 7.4 PMS Project Manager shall verify that the installation of the core shroud clamp assemblies has been completed.

PMS Project Manager or Designee Date 7.5 Request clearances be released.

PMS Project Manager or Designee Date 7.6 Temporary services have been removed and work area (s) are restored. I PMS Project Manager or Designee Date 7.7 Notify Shift Supervisor that all work' activities per this plant modification have been completed.

PMS Project Manager or Designee Date O

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7.8 Contractor's final design doctments have been .eceived by CP&L and have bean reviewed and accepted as documented by the completion of an ownert Review per NED procedure No. 310. -

NED Lead Engineer or Designee Date NOTE Vendor documentation is to be included in the turnover package.

7.9 Contractor's completed procedures, inprocess changes and supporting records have been reviewed by CP&L and found acceptable. -

PMS Project Manager or Designee Date NED Lead Engineer or Designee Date i

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O F1 SECTION F O

TESTING REQUIREMENTS l

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This plant modification is a structural modification on which a functional test cannot be performed. By using controlled documents and QA/QC verification of the installation, the installation is acceptable for service.

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O Installation Package Plant Document Revisions Section Title Page Mod. No.94-007 Rev. No.

Page No.

O G1 SECTION G g PLANT DOCUMENTATION REVISIONS O

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Mod. No.94-007 l PLANT DOCUMENT REVISION SHEET Rev. No. O  ;

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DOCUMENT DOCUMENT UPDATE .

• RECORD NUMBER TITLE BEFORE OF OPERA- REVISION BILITY SD-1 Nuclear Boiler System N UFSAR Section 3.9.5.1.1 N AOP-13 Operation during ;Iurricane, Flood Y Conditions, Tornado, or Earthquake 0-PT-90.5 In Vessel Visual Exam N O

For later use in tracking completion of the revision.

NPMP-REV. 4 ,

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l Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. O O

V DESIGN BASIS DOCUMENT l l

DBD B94-007 PROJECT: PM 94-007: Core Shroud Modification '

PLANT: Brunswick Nuclear Plant, Unit 2 CHECK ONE: ,

A design basis document is nonapplicable to this '

project.

Reason:

X The design basis document is attached. t O

Revision Originator /Date Verifier /Date Prin. or Res. Eng./Date ,

Rog Steckel Steve Bertz c N rtheim V

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Reason for change -

Reason >

for change O Design Basis Document B94 007 Rev0 Page 1 l

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Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. O t0

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LIST OF EFFECTIVE PAGES i Page Rev Page Rev Page Rev Page Rev 1 0 5 0 9 0 2 0 6 0 10 0 3 0 7 0 h

4 0 8 0 TABLE OF CONTENTS DBD Section DBD DBD Section DBD Pg. Pg.

1.0 Basic Functions 3 11.0 Hydraulic Requirements 9 2.0 Performance Requirements 4 12.0 operational 9 O, Requirements 3.0 Codes and Standards 4 13.0 Failure Requirements 9 4.0 Design conditions 6 14.0 Test Requirements 9 5.0 Design Loads 7 15.0 Accessibility 10 6.0 Environmental Conditions 7 16.0 Handling / Storage 10 7.0 Classifications 7 17.0 ALARA 10 8.0 Material Requirements 7 18.0 ASME Section XI 10 9.0 Mechanical Requirements 8 10.0 Structural Requirements 8 O Desi0n Basis Document B94-007 Rev0 Pa0e 2

Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. O O

V 1.0 Basic Functions The Core Shroud is a stainless steel cylindrical assembly which provides a partition to separate the upward flow of coolant through the core from the downward recirculation flow. This partition separates the core from the downcomer annulus, thus providing a floodable region in the event of a recirculation line break. The volume enclosed by the core shroud is characterized by three regions, each with a different shroud diameter. The upper shroud has the largest diameter and surrounds the core discharge plenum which is bounded by the shroud head on top and the top fuel guide below. The central portion of the shroud surrounds the fuel and forms the longest section of the sh oud. This section has an intermediate diameter and is bounded at the bottom by the core plate assembly. The lower shroud, surrounding part of the lower plenum, has a tapered diameter and, at the bottom is welded to the reactor vessel shroud support.

The reactor internals, of which the core shroud is a part, have three basic functions:

1. To provide a floodable volume in which the core can be adequately cooled in the event of a breach in the nuclear system process barrier external to the reactor i

j vessel.

Q 2. To limit deflections and deformation to assure that the control rods and the core standby cooling systems can perform their safety functions during abnormal operational transients and accidents.

3. To assure that the safety design bases (1) and (2) above are satisfied so that the safe shutdown of the plant and removal of decay heat are not impaired.

Plant Modification 94-007 will install reinforcing clamps to the core shroud in the area of the top guide support ring to provide structural integrity for the H2 and H3 welds in the event of a through wall 360* crack. This modification has already been performed on the Unit 1 Core Shroud per Plant Modification 93-038.

The function of the reinforcing clamps is to structurally replace the H2 and H3 welds. The welds provide both horizontal and vertical support to the core top guide and shroud head. The core top guide horizontally supports the top of the fuel assemblies and maintains the correct fuel channel spacing to permit control rod insertion. The upper shroud also houses the Core Spray spargers and vertically supports the deadweight and operating loads of the steam separator.

O L.) Design Basis Document B94-007 Rev0 Page 3 l l

Design Package Mod. No._94-007 Design Basis References / Revisions Rev. No. 0 2.0 Performance Requirements This modification is structural in nature and therefore has no .

active per:ormance requirements. l o

3.0 Codes, Standards and Regulatory Requirements The following codes, standards and regulations shall be utilized as applicable to BNP and as committed to the NRC (via the UFSAR) by BNP. The latest edition shall be used unless stated otherwise in the referencing document or below.

3.1 ANSI Standards N18.7 Administrative Controls and Quality Assurance for the Operational Phase of the Nuclear Power Plants - 1976 N45.2.1 Cleaning of Fluid Systems and Associated Components During Construction Phase of Nuclear Power Plants - 1973 O N45.2.2 Packaging, Shipping, Receiving, Storage, and Handling of Items for Nuclear Power Plants -

1972 i

N45.2.11 Quality Assurance Requirements for Design of Nuclear Power Plants - 1974 N52.1 Nuclear Safety Criteria for the Design of Stationary Boiling Water Power Plants i

3.2 Code of Federal Reculations 10CFR20 Standards for Protection Against Radiation l 10CFR50 Domestic Licensing of Production and Utilization Facilities -

Appendix A -

General Design Criteria for i Nuclear Power Plants Appendix B - Quality Assurance Criteria for Nuclear Power Plants 29CFR1910 Occupational Safety and Health Standards Design Basis Document 894-007 Rev0 Page 4 w m-s --

i

-, ._ 1 Design Package Mod. No.94-007 I Design Basis References / Revisions Rev. No. 0 3.3 ASME Boiler and Pressure Vessel Code The core shroud is not classified as an ASME code component; however, material properties and welding qualifications shall be in accordance with the following documents:

Section II, Part D, 1992 Edition Section IX, Welding and Brazing Qualifications,1992 Edition 3.4 DSEP Site Soecifications 248-145 Fluid System Cleanliness 005-011 Seismic Design Criteria 3.5 Specification Waivers None 3.6 General Electric Documents G. E. Design Specification 24A5118, Shroud Repair Clamp G. E. Document P50YP102, Arc Welding of Austenitic Stainless Steel

{

G. E. Document 383HA715, Reactor Components G. E. Document 22A3041, Essential Components >

G. E. Document E50YP13, Sensitization Tests for Austenitic Stainless Steel, Modified ASTM A262 Practice E G. E. Document E50YP20, Determination of Carbide Precipitation in Wrought Austenitic Stainless Steel, -

Modified ASTM A262 Practice A G. E. Document E50YP22A, Liquid Penetrant Examination G. E. Stress Report, GE-NE-771-15-0294 t

G. E. Document 383HA479, Brunswick Nuclear Power Station Seismic Analysis of Reactor Pressure Vessel and Internals G.E. Document NEDO 24225, Reactor Vessel / Shield Wall Annulus Pressurization Following Pipe Break G.E. Document GE-NE-A0003981-1-01, Performance Impact of Shroud Repair Leakage for Brunswick 2 -

O Design Basis Document B94-007 Rev 0 Page 5 -

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Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. 0 0'

3.7 Other Documents ASTM Material Specifications A479 - Type XM-19 A182 - Type F304, F304L, F316, F316L A240 - Type 304, 304L, 316, 316L j A276 - Type 304, 304L, 316, 316L NRC Regulatory Guides per UFSAR commitments, Section 1.8 ENP 16.0, Procedure for Administrative Control of Inservice Inspection Activities BSEP Technical Specifications Sections 2.1.3, B2.1.3, 3/4.1.1, 3/4.4.4, 3/4.4.6, 3/4.9.7, 3/4.11.3.

BSEP Updated Final Safety Analysis Report (UFSAR)

PM 93-038 Unit 1 Core Shroud Modification 4.0 Design Conditions The reinforcing clamps shall be designed to structurally O replace the H2 and H3 welds such that in the event of a d complete failure of those welds, the reinforcing clamps will provide an equivalent structural capacity for the welded connections. This will ensure the structural integrity of the top guide and the shroud head during all analyzed loading combinations. The clamps shall be designed for a life of 21 years, which is equal to the remaining design life of the plant.

All parts of the clamps shall be captured utilizing a method that will last the design life of the clamps; however, the clamps shall be removable.

EDvironmental Conditions These environmental conditions account for a power uprate of approximately 4%, to 2533 MW. e Design Pressure 1250 psig Temperature 550 'F Radiation s 1.0 x 10" neutrons /cm /sec 2

Fluid Chemistry Demineralized Water

/~N NA Design Basis Document B94-007 Rev 0 Page 6

I Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. 0 5.0 Design Loads The design loads and structural criteria are as specified in General Electric Design Specification 24A5118 and General 1 Electric Stress Report GE-NE-771-15-0294.

6.0 Environmental Conditions to be Encountered During Installation The environmental conditions during installation will be in a flooded reactor vessel and cavity with fuel offloaded and water temperature of s 150' F.

7.0 Classification, Boundary and Interface Requirements The core shroud does not fall under any ASME Code classification because the Section of ASME which governs the design of core shroud components (Section III, Subsection NG) did not exist when BNP was licensed. The core shroud is non Code and will be analyzed per the requirements of the UFSAR.

The core shroud modification is classified as Quality Class A (Safety Related) based on the core shroud's function to limit deflections and deformation to assure that the control rods O can insert, and to provide a floodable volume so that the core standby cooling systems can perform their safety functions during abnormal operational transients and accidents.

8.0 Material Requirements The materials to be used for the shroud modification are as '

follows:

Bolt and Nut Material ASTM A479 Type XM-19 with carbon content not to exceed 0.04% '

and annealed at 2000*F 25*F followed by cooling at a rate of at least 200*F per minute. A sensitization test shall be performed as specified in GE Design Specification 24A5118. l Core Shroud Reinforcina Clamo Block Material ASTM A182 Type F304, F304L, F316 or F316L with carbon content not to exceed 0.02%. The material shall be annealed at 1900*F to 2100*F followed by quenching in circulating water to a temperature below 400*F. A sensitization test shall be performed as specified in GE Design Specification 24A5118.

Design Basis Document B94-007 Rev 0 Page 7 t

Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. O O

Other parts other parts, such as retainers and washers shall be made of any of the materials listed for the parts above.

Alternately, ASTM A240 or A276 Type 304, 304L, 316, 316L may -

be used provided the carbon content does not exceed 0.02% and the material is annealed at 1900*F to 2100*F followed by quenching in circulating water to a temperature below 400*F, and a sensitization test is performed as specified in GE Design Specification 24A5118.

Any required weld buildup on the retainers shall be Type 308L per G. E. Document P50YP102.

9.0 Mechanical Requirements The reinforcing clamps have no active mechanical functions.

Thei provide equivalent structural capacity of the core shroud H2 and H3 welds only.

10. Structural Requirements The reinforcing clamps shall be designed to provide structural integrity for a complete circumferential through-wall crack at the H2 and H3 welds for all load conditions identified by the UFSAR.

The reinforcing clamps shall limit the deflection at any point of the shroud adjacent to the H2 and/or H3 welds to less than 2.1" divided by S F,a (2.25 for normal and upset, 1.5 for emergency, and 1.125 for faulted) for all load combinations, in accordance with GE Design Specification 24A5118.

Stress analysis shall be performed by General Electric to evaluate the structural adequacy of the modification, the method of attachment of the clamps, and the operation of the modified system.

[

Design Basis Document B94-007 Rev0 Page 8 h

Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. 0 11.0 Hydraulic Requirements The hydraulic requirements of the reactor vessel should not change as a result of the addition of the reinforcing clamps.

The effect of the clamps on the flow of water inside the reactor pressure vessel shall be minimized.

The design shall minimize the normal operating condition leakage through the shroud clamp holes and any through wall crack at H2 or H3 to prevent cavitation of the jet pumps.

12.0 Operational Requirements The operational requirements of the core shroud shall not change as a result of performing this modification. The reinforcing clamps will maintain the structural integrity of the upper shroud. This will serve to maintain the core geometry via the top guide and maintain the integrity of the Core Spray piping inside the vessel during all transient and accident events.

The reinforcing clamps shall include features which facilitate handling during installation.

O 13.0 Failure Requirements The reinforcing clamps shall be designed to maintain full structural integrity of the core shroud in the vicinity of the H2 and H3 welds without failure during all load conditions including normal loads, upset loads, seismic loads, annulus pressurization loads and pipe rupture loads.

14.0 Test Requirements There is no functional testing requirement for the core shroud '

following the installation of the reinforcing clamps. The modification will be QC verified during installation.

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U Design Basis Document 894-007 Rev0 Page 9 J

+7 Design Package Mod. No.94-007 Design Basis References / Revisions Rev. No. 0 15.0 Accessibility, Maintenance, Repair, and In-Service Inspection Requirements The clamps shall be designed and installed such that removal of the jet pump inlet mixers and the RPV beltline inspection with GERIS 2000 can be performed without removal of the clamps.

There are no maintenance or repair requirements as a result of this modification. The reinforcing clamps will be added to the In-Service Inspection Augmented Program for inspection of the core shroud, 0-PT-90. 5. EER 94-0077 will provide guidance as to the nature and extent of the inspections via an Action Item.

16.0 Handling, Storage and Shipping Requirements Packaging, shipping, receiving, storage and handling of components for this modification shall be per ANSI N45.2.2, Level B.

17.0 ALARA The installation will take place from the refueling platform with the reactor vessel and cavity full of water. The reinforcing clamps shall include features which facilitate handling during installation. Extensive mock-up training will be utilized to minimize the time spent over the reactor vessel.

18.0 ASME Section II Applicability This modification is outside the boundaries of ASME Code Section XI. I l

l O Desian Basis Document B94-007 Rev0 Page 10 1

y, CAROLINA POWER & LIGHT CONPANY FORM 3 NUCLMAR PLANT [X) BNP UNIT NUMBER PROJECT NUMBER MODIFICATION NUMBER NODIFICATION [ } HNP 2 G0250C 94-007 TRAVELER ( ) RNP O ABSTRACT' TITLE: Unit 2 Core Shroud Modification [X) MODIFICATION REASON FOR MOD: Inspection Findinos [ ] EMERGENCY MOD

[ } DOCUMENT CHANGE ONLY SYSTEM NUMBER (S) IOO5 QUALITY CLASSIFICATION: YES NO IMPACT:

[X) A. Q-LIST OR AFFECTS Q-LIST [ ] [X) UNREVIEWED SAFETY QUESTION

[ ] B. REG. GUIDE 1.29 OR 1.97 [ ] [X) TECH SPEC CHANGE

[ } C. RADWASTE-Q [X) [ } FSAR CHANGE i

[ ] D. FIRE PROTECTION-Q [ ] [X) SIGNIFICANT ENVIRONMENTAL IMPACT  !

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[X) DATE

[ ] CNSR (Prior to Implementation) REF:

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CNSR (Review documented on Closecut Sheet - NPM NRC (Prior to Implementation) BEF: gg g O am NPMP - REV. 4 BNP., D00. CONTROC

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CAROLINA PO"ER E LICHT CONPANY FORM 3(CON'T)

NUCLEAR PLANT [X) BNP UNIT NUMBER PROJECT NUMBER MODIFICATION NUMBER NODIFICATION [ } HNP 2 G0250C 94-007  !

p TRAVELER (CON'T) [ ] RNP DESIGN ORGANIZATION INTERNAL APPROVALS Signatures below indicate that the appropriate areas of concern for the listed '

discipline / specialty group have been satisfactorily incorporated into the above document.

Discipline Applicable Not Applicable Sianature/Date AECHANICAL [X) [ ] //, 7/ \ _ 7 "3 .54p q) w ELECTRICAL [ ] [X)

I&C [ ] [X)

CIVIL / STRUCTURAL [X) [ ] (P, du Pr4 7'F2eroa f,k.

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SECTION A CONTENTS CONTROL t

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'- Mod. No.94-007 Installation Package Rev. No. O List of Effective Pages Page No. A2 Pace No. Rev. Pace No. Rev , . P_aae No. Eev, A1 0 D1 0 A2 0 D2 0 A3 0 El 0 B1 0 E2 0 B2 0 E3 0 B3 0 E4 0 E5 0 E6 0 C1 0 E7 0 C2 0 E8 0 C3 0 E9 0 C4 0 E10 0 C5 0 E11 0 C6 0 EIA o C7 0 C8 0 F1 0 C9 0 F2 0 C10 0 C11 0 C12 0 C13 0 G1 0  ;

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Mod. No.94-007 Installation Package Rev. No. O Table of Contents Page No. A3 SECTION DESCRIPTION Pace A CONTENTS CONTROL Al List of Effective Pages A2 Table of Contents A3 B PROJECT.

SUMMARY

B1 Project Summary B2 C INSTALLATION SUPPORT DOCUMENTS C1 Quality Classification Evaluation C2 Safety Review Package C3 Bill of Material C22 D INSTALLATION DRAWINGS D1 Drawing List D2 E INSTALLATION INSTRUCTIONS El Installation Instructions E2 O F TESTING REQUIREMENTS F1 I Testing Requirements F2 G PLANT DOCUMENTATION REVISIONS G1 Plant Document Revision Sheet G2 Y)'%/

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Mod. No.94-007 Installation Package Rev. No. O Project Summary Page No. B1

.O SECTION B PROJECT

SUMMARY

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^ .N Mod. No.94-007 y Installation Package Rev. No. O Project Summary Page No. B2 General Electric (GE) RICSIL No. 54 reported that cracking was found in the core shroud of a BWR/4 located outside the United States. GE provided an interim recommendation (RICSIL No. 054 Revision 1) to perform In Vessel Visual Inspection (IVVI) of the core shroud. During

} IVVI at Brunswick Nuclear Plant (BNP) Unit 1 a near 360 degree circumferential crack near the top guide support ring weld (H3) was found. Further inspections also revealed cracking in the adjacent H2 weld Heat Affected Zone (HAZ). EER 93-0536 provided a detailed evaluation of the conditions found on Unit 1 and provided justification for continued operation of Unit 2 for the remainder of  ;

I the current operating cycle. The H2 and H3 welds join the upper cylindrical shroud section to the slightly smaller diameter middle shroud section via attachment to the outside and inside respectively of the top guide support ring.

From the inspections performed on Unit 1, and the subsequent EER 93-0536, it is likely that similar conditions are present on the Unit 2 shroud. The purpose of this plant modification (PM) is to install mechanical clamps that will ensure structural integrity to the Unit 2 core shroud at the H2 and H3 welds. The clamps are designed to structurally link the upper shroud section, top guide support ring, p and middle shroud section interface, and thereby eliminate the

( reliance on the H2 and H3 welds for structural integrity. This modification has previously been performed on the Unit 1 shroud under PM 93-038.

Twelve (12) clamps will be installed symmetrically around the shroud.

The clamps will be secured to the exterior of the shroud by through bolting. Holes will be machined (Electro-Discharge-Machining (EDM) process) in the shroud to accommodate the bolting; two (2) bolts above the H2 weld in the upper shroud section, and two (2) bolts below the H3 weld in the middle shroud section. The bolting will be tack welded (nut keepers to bolts) after assembly to assure the parts are captured.

The design and location of the clamps will result in negligible maintenance impact on the plant. The clamps are spaced alternate to the jet pump locations thereby allowing for jet pump inlet mixer -

removal without removing or affecting the clamps. The clamps are positioned such that removal of the RPV surveillance specimen capsules will not be impeded.

The clamp assemblies will have washers around the bolts to minimize leakage through the holes in the shrond. The clamps shall be bolted to the shroud below the H3 weld and attached to the shroud above the H2 weld in a manner which will prevent relative movement across both m

the H2 and H3 welds during all normal and upset conditions (operating basis earthquake plus upset pressure plus deadweight). Under design basis accidents and events, a slight shifting of the clamps / upper shroud may occur. This shifting is less than the maximum analyzed

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, Mod. No.94-007

.( Installation Package Rev. No. O Project Summary Page No. B3 movement (approx. 2-1/4") that would affect control rod operation.

GE has been contracted to design, fabricate and install the clamps on  :

the core shroud under the GE Quality Assurance program, the Quality l Implementation Plan and the Project Implementation Plan. The PM I provides the administrative controls for the design and installation of the clamps and the proper documentation of the modification.

The physical scope of work involved in the modification will be as follows:

Prefabrication of clamp assemblies and bolting material.

Machining holes in the core shroud using a Electro-Discharge- >

Machining (EDM) process to accept the bolts.

Installation of the clamp assemblies.

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Mod. No.94-007 Installation Package Rev. No. O Installation Support Documents Page No. C1 O

L SECTION C INSTALLATION SUPPORT DOCUMENTS .

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Mod. No.'94-007 Installation Package Rev. No. O Quality Classification Evaluation Page No. C2 O As defined in the UFSAR (3.9.5.3) the safety design bases of the reactor vessel internals are as follows:

1. Provide a floodable volume in which the core can be adequately cooled in the event of a breach in the nuclear system process barrier external to the reactor vessel.

2. Limit deflections and deformation to assure that the control rods and the core standby cooling systems can perform their safety functions during abnormal operational transients and accidents.

3. Assure that the safety design bases (1) and (2) above are satisfied so that the safe shutdown of the plant and removal of decay heat are not impaired.

The failure of the Core Shroud (fracture and separation at the top guide at welds H2 and H3) would not affect the floodable volume as the crack would be above the jet pump nozzle, however, movement of the upper portion after cracking could prevent full insertion of the control rods.

Therefore, the Core Shroud (and Clamps) are safety-related and are classified as Quality Class A.

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l BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS. 50-325 & 50-324 OPERATING LICENSE NOS. DPR-71 & DPR-62 LIST OF REGULATORY COMMITMENTS The following table identifies those actions committed to by Carolina Power & Light Company in this document. Any other actions discussed in the submittal represent  ;

intended or planned actions by Carolina Power & Light Company. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify the Manager-Regulatory Affairs at the Brunswick Nuclear Plant of any questions regarding this document or any associated regulatory commitments.

^

Committed Commitment date or ,

outage

1. CP&L will provide inspection plans for the B110R1 Unit 1 outage 1/2/95 and the B212R1 Unit 2 outage in accordance with the reporting (U/1) requirements of NRC Generic Letter 94-03 (3 months' prior to '

performing the inspections). 11/2/95' (U/2)

2. CP&L will provide, consistent with the requirements of NRC GL 1/2/95 [

94-03, plans for evaluation and/or repair of the core shroud based (U/1) on the inspection results along with the inspection plan no later than 3 months prior to performing core shroud inspections for 11/2/95 B110R1 and B212R1 refueling outages. (U/2)

3. CP&L will provide the NRC staff the inspection results for Unit 1 B110R1 and Unit 2 within 30 days following completion of the inspections B212R1 associated with B110R1 and B212R1 refueling outages.

4. The Unit 1 B110R1 outage inspection plan will evaluate and NA incorporate, as appropriate, lessons-learned from the Fall 1994 BWR outages.

"Date based on current projected B110R1 Refueling Outage start date of April 1, 1994 and B212R1 Refueling Outage start date of February 2,1996. Dates may be adjusted, as necessary, to be consistent with any changes in the outage schedules.

E2-1 1