ML19332D009

Requests Concurrence W/Revised Commitment to Defer 40 Pipe Support Mods to Facility Cycle 5 Refueling Outage by 891229 to Support Outage Preparation Plans.Evaluation Encl

ML19332D009
Person / Time
Site:	Sequoyah
Issue date:	11/27/1989
From:	Michael Ray TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 8911290294
Download: ML19332D009 (9)

Text

-l y

TENNEIEE VALLEY AUTHORITY

)

CH ATTANOOG A, TENNESSEE 37401 SN 157B Lookout Place NOV t7 888 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk i

Washington, D.C.

20555 i

Gentlemen:

)

In the Matter of

)

Docket Nos. 50-327

' Tennessee Valley Authority

)

50-328 i

i SEQUOYAH NUCLEAR PLANT - RIGOROUSLY ANALYZED PIPING - UNIT.1 CYCLE 4 l

COMMITMENT REVISION

References:

1.

TVA letter to NRC dated August 4, 1988, "Sequoyah Nuclear i

Plant (SQN) Unit 1 - Final Report-for NRC Inspection and Enforcement Bulletin (IEB) 79-14" 2.

TVA letter to NRC dated October 6, 1987, "Sequoyah Nuclear Plant (SQN) - Unit 2 - Pipe Support Modification Restart Criteria Meeting Summary" I

In the referenced letters, we indicated that the postrestart modifications resulting from the rigorous analysis piping program would be installed by the end of the Cycle 4 refueling outage for each unit.

You were also informed in Reference 2 that we were considering the development of an integrated schedule for the prioritization of all outstanding postrestart activities.

He noted l

that, upon development of an integrated schedule, we would meet with you to

. review and discuss the various' schedule items and adjust schedules as appropriate.

Since that time, additional plant improvements and NRC commitments have been identified and we have initiated the integrated

-scheduling process.

As a result of this process, we believe that it would be beneficial to defer work on 40 Unit 1 pipe support modifications inside l

containment until the Unit 1 Cycle 5 refueling outage.

We believe that plant safety is still assured by the interim design criteria used for the pipe supports and that through the integrated schedule process, plant resources will be allocated to the most beneficial projects.

In addition, the radiological dose associated with these 40 modifications will be reduced because of plant simplifications that will be made during the Unit I Cycle 4 outage. Our evaluation of this proposal is included as an enclosure.

This information was discussed with the NRC staff in a meeting in Rockville, Maryland, on November 9, 1989.

TVA requests your concurrence with the revised commitment to defer 40 pipe support' modifications to the Unit 1 Cycle 5 refueling outcge.

In order to support our outage preparation plans, we request that you reply by December 29, 1989.

The Unit 2 commitment and the Unit 1 commitment for outside containment work remain unchanged.

o a8911290294 891127 g

.1PDR_ ALOCK 05000327 P-PDC a

An Equal opportunity Employer

[

t NOV 271989 l

U.S. Nuclear Regulatory Commtsston i

j..'

If you have any questions concerning this, please telephone'N. J. Burzynski at (615) 843-6422.

Very truly yours, 7

TENNESSEE VALLEY AUTHORITY 14 8 6 je Manager, Nucle,ar Licensing and Regulatory Affairs Enclosure cc (Enclosure):

Ms. S. C. Black, Assl> tant Director forProjects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commissior.

Region II 101 Marietta Street, NH, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 i

i e

Enclosure i

Sequoyah Nuclear Plant i

e Rigorously Analyzed Piping Program Unit 1 Cycle 4 Commitment Revision

Background

TVA identified that a large number (approximately 9,000) of pipe support calculations associated with rigorously analyzed Category I piping were not retrievable. The civil calculation review program identified this issue prior to Sequoyah Unit 2 restart. Calculations were regenerated to support the restart of each unit. The calculations were done in accordance with TVA Design Criteria SQN-DC-V-24.2.

Supports not meeting this design criteria were evaluated for restart in accordance with TVA interim Design Criteria CEB-CI-21.89. Supports not meeting the interim criteria were modified to meet the design criteria before restart. At that time. TVA committed to upgrade the remaining supports by the end of the Cycle 4 refueling outage for each unit. This program was reviewed by NRC, and tne acceptance was documented in NUREG-1232. Volume 2, and NUREG-1232 Volume 2 Supplement 1.

Program Status Approximately 930 modifications were identified during the regenerations of the 9,000 calculations. There were 325 modifications required for restart, and the remaining modifications were deferred to the Cycle 4 refueling outages. Since that time, 45 modifications have been eliminated because of plant simplifications being made (i.e., upper head injection (UHI) removal and elimination of the reactor coolant loop bypass lines used for temperature measurement).

To date, all pipe support design calculations have been regenerated and are retrievable. Constructibility walkdowns have been performed, and the design

'4 change packages issued. Material procurement is in progress. The following progress has been made in implementing the pipe support modifications.

1 L

Period Number Completed l

Unit 2 restart (through May 1988) 175 Unit I restart (through November 1988) 192 l~

Unit 2 Cycle 3 (through April 1989) 80 Nonoutage period (May 1989 through October 1989) 84 l

Total 531

3 i

=

1

)

Of the remaining 354 modifications, 217 can only be worked during Mode 5 or f

c refueling outages, and 137 can be worked during nonoutage periods.

i Schedule Development Since the time that the commitments were made for the pipe support calculations. TVA has developed an integrated outage scheduling program. This process considers all factors relevant to scheduling refueling outagest NRC commitments, necessary plant modifications, preferred plant modifications, available resources, available outage periods based on electrical system requirements, and radiological and industrial safety goals. This process is intended to maximize the utilization of available resources.

As a result of this process, TVA has identified some constraints to meeting the pipe support commitment for Unit 1.

In particular, the number of people t

that can work inside containment is limited, and a number of projects are competing for that workspace. The lower containment area is small and compartmentalized in an ice condenser plant (see Final Safety Analysis Report Figures 1.2.3-11 through 1.2.3-13).

In addition to the physical constraints, I

the number of people working in the lower containment must also be limited to properly manage the work to meet the radiological dose (as low as reasonably f

achievable (AI. ARA]) and industrial safety goals.

The key projects that will be worked inside containment include the following:

UHI Removal - This plant simplification is being pursued to improve plant maintainability and to reduce radiation exposure during reactor vessel head disassembly / reassembly during refueling outages.

In addition, TVA is pursuing UHI removal as part of an overall NRC-approved plan to I

resolve a temporary exemption to 10 CFR 50.46 and incorporate best-estimate accident analyd s technology.

Resistance Temperature Device Bypass Elimination - This plant i

simplification is being pursued to eliminate a source of past reactor coolant leaks and to reduce radiation exposure in the lower containment for future steam generator inspection activities. This modification is being pursued in conjunction with the replacement of the reactor protection system and main control room panel human factors modifications to minimize disruptions to control room activities.

Steam Generator Work - This work involves tube inspections, sitdge lancing, and tube plug replacements for Bulletin 89-01. These activities are all part of the overall steam generator preservation program.

Postaccident Monitoring (PAM) Instrumentation - The lower containment work primarily involves conduit and cabling to achieve the required train separation for instrument channels. This work is required to satisfy a license condition to comply with Regulatory Guide 1.97.

I 3

Only the PAM modifications were identified at the time the pipe support i

modification commitawnt was made. The other modificatione were identified since that time, and the scope of the PAM work was recently increased with the decision to make the steam generator wide-range level a Category Al variable, i

adding additional cable and conduit work inside containment.

TVA is also planning to work a number of key safety and reliability improvement modifications outside of containment. Phase 1 of the control room design review (CRDR) modifications and the alternate analysis program are scheduled for completion. These commitments were made prior to the pipe support commitmental however, the implementation schedule for the CRDR modification was accelerated at NRC's request. TVA is also planning to 3

replace the reactor protection set with Westinghouse Electric Corporation Eagle 21 technology to improve plant maintainability and to incorporate feedwater trip reduction technology.

The copper-containing, Stage 3 and 4 feedwater heaters will be replaced with stainless steel heaters as part of the steam generator preservation program.

The second component cooling-water heat exchanger will be replaced to improve reliability and to resolve service water system problems similar to those described in NRC Ceneric Letter 89-13.

The i

boron injection tank requirements will be eliminated to simplify the plant, improve maintainability, and contribute to ALARA dose reduction as described in NRC Generic Letter 85-16.

Proposed Schedule As a result of the integrated scheduling program and detailed evaluation by Nuclear Engineering, Operationa, Modifications, and site management, TVA believes that it is beneficial to defer 40 Unit 1 outage-related pipe support modifications to Unit 1 Cycle 5 (34 known modifications and 6 contingency modifications).

The proposed schedule for the remaining pipe support modifications is as follows:

Period Number to be Worked Nonoutage (November 1989 to March 1990) 137 Unit 1 Cycle 4 (Spring 1990) 81 Unit 2 Cycle 4 (Fall 1990) 102 Unit 1 Cycle 5 (Fall 1991) 34 with an additional 6 for contingency The revised schedule, along with the progress to date, is shown on the attached figure.

The pipe support modifications were evaluated in conjunction with the physical work associated with the other planned modifications to identify the maximum number of pipe support modifications that could be worked. A tabulation of the current number of pipe support modifications on each system for the l

I

ij o

2 i

scheduled outage period is included on the attached-table.

It should be noted l

that the specific list of supports may change as a result of changes in plant I

conditions and emergent physical constraints. However, the total number of deferred modifications inside containment will not exceed 40.

The Unit 2 commitnent remains unchangedt all work will be' completed by the end of the Unit 2 Cycle 4 refueling outage.

The revised schedule for Unit I resolves the constraints for Unit 1 Cycle 4 and schedules the work over two refueling' outages (similar to Unit 2).

A total of 96 percent of the l

modifications will be completed as originally scheduled.

Contingency Plans P

As noted above, all design packages have been issued. Nuclear Engineering has also reviewed the present list of 34 deferred modifications and ranked them based on margin. These modifications can be classified in four categoriest l

increased support member size or bracing, increased support baseplate capacity, adjustments to spring settings and snubber swing angles, and gap adjustments.

TVA will use this information to assist in scheduling additional support modification work if unplanned Mode 5 outages of sufficient duration occur or if unexpected delays occur during the Unit 1 Cycle 4 refueling outage.

It is TVA's intention to work more supports than are currently planned and to take advantage of opportunities that arise. On the other hand, unexpected changes in plant conditions or emergent problems on specific supports may create the need to defer additional modifications. As a result, TVA has included a contingency of 6 additional supports in this deferral request.

Safety Assessment l

The deferred modifications remain in compliance with Interim Design Criteria CEB-CI-21.89 during the interim period.

These design criteria ensure that the pipe supports with deferred modifications have sufficient capacity to resist the faulted loading condition and maintain system functionality. Adequate protection for accident mitigation and the safe shutdown earthquake is i

therefore ensured.

The projected dose for the deferred modifications will be significantly lower J

when the work is done during the Unit 1 Cycle 5 refueling outage. The removal of the reactor coolant bypass lines is estimated to reduce the dose rate in the lower containment in the area of the steam generators and coolant loops by approximately 50 percent.

The revised schedule allows resources to be allocated to the most beneficial safety and reliability improvement modifications without jeopardizing plant safety.

1 l

y

-+

e

Summary TVA has instituted an integrated outage scheduling program to ensure that i

resources are allocated to the most beneficial projects. As a result of this effort TVA believes that it is beneficial to defer up to 40 pipe support modifications inside containment to the Unit 1 Cycle 5 refueling outage.

The reason for this schedule change is the need to relieve physical congestion in the lower containment area and to maximize the utilization of available resources in the completion of several key safety and reliability improvement modifications.

In the interim period, plant safety is ensured by the interim design criteria to which the supports are presently designed. Additional benefits arise from the dose savings that occur with the removal of the reactor coolant loop bypass lines.

e

V,:.

,g -

g

I R

g g

o g

t i

I E

, i t I,

'l i,

k G

N

. l.

EE 4 8

R q t m

~

w Z

o a

O k

d i

H

&f

<s h

l C.) H H 4 li h N

r H [t1

}q W

O5o O g" y

g O

S a.

m 5

g I:

5 I

4

. i Ou v

D e

s LU C

w y 4 W

v O $,

s m

I b

y @'t b

b b

b E

5 8

8 R

8 8

?

8 e

S X

ONINIVH38 500H U3DNVH 30 838HnN l

i E

/

• l 1

t-Fj' e

s. - o CALOJIATICH REGENERATION IHOGRAM CN1Y I RIOCE00 SLY ANAIXZED PIIE SUPKRIS LNIT 1 CITMGE SODPE (Based on 11-16-89 datahana)

UIC4 OUDGE UICS OUIME SYSTD(

INSIDE CUISIIE INSIDE OUISIDE CCNTADGENT CENIADetENT CINTAD41ENT CONTAINMDfr FEEDWATER 1

AUX FEEDWATER 4

2 CVCS 11 6

CDGONENT CDOLING 13 2

1 1

ERCH 18 CONTAD4ENT SPRAY 1

1

}NAC 6

2 i

ICE CONDENSER 1

REACIOR 000IANT 3

2 SAFEIY DUECTION 11 16 SGBD 5

4 3

WASTE DISPDSAL 1

MAIN STEAM 1

'IUrhL 73 8

34 0

1 i

-,,