ML20245B758

Application for Amends to Licenses NPF-71 & NPF-80,revising Operating Procedures to Ensure Adequate Margins to DNB by Maintaining RCS Flow at or Above 400,000 Gpm for 100% Power Operation.Annotated Revs to FSAR Encl.Fee Paid

ML20245B758
Person / Time
Site:	South Texas
Issue date:	04/18/1989
From:	Rosen S HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20245B759	List: ML20245B758 ST-HL-AE-3040, Proposed Revs to FSAR
References
ST-HL-AE-3040, NUDOCS 8904260257
Download: ML20245B758 (10)

Text

- - - - _ _ _ _ _ - - _ - _ _ -

., 4 i

The Light c o mp a ny S uth Texas Project Electric Generating Houston Lighting & Power P. O. Station Box 289 Wadsworth, Texas 77483 l

1 April 18, 1989 ST-HL-AE-3040 File No.: G09.17, G09.18, G21, C26, G02 10CFR50.73 10CFR50.92 U. S. Nuclear Regulatory Commission  !

Attention: Document Control Desk  !

Washington, DC 20555 South Texas Project Electric Generating Station Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Proposed License Amendment concerning the j Effects of the Westinghouse Generic Reactor Coolant System Flow Anomaly Reference 1: Letter ST-HL-AE-2911 from G. E. Vaughn to USNRC Document j' Control Desk dated December 29, 1988 (LER 88-052 Revision 1) 2: Letter ST-HL-AE-3003 from M. A. McBurnett to USNRC Document Control Desk dated March 1, 1989. ,

i 3: Letter ST-HL-AE-3021 from M. A. McBurnett to USNRC Document l Control Desk dated March 30, 1989.

At the beginning of 1987, Westingh o use identified that a thermal-hydraulic flow instability known as the Reactor Coolant System (RCS) flow-anomaly existed in some four loop plants. The flow anomaly, believed to be multiple rotational flows in the lower reactor vessel plenum, causes coolant flow ma1 distributions in the core. The flow maldistribution results in inereased coolant temperatures, local reductions in power, and a reduction in the margin to Departure from Nucleate Boiling (DNB). It is characterized by fluctuations in RCS flow, core exit temperatures, and reactor power, which are aperiodic in nature.

P Confirmation of the presence and magnitude of the anomaly was made CDv2 through an evaluation of STP Unit 1 dats collected at 100 percent power.

E8' Based on a preliminary efaluation, Westinghouse indicated that the available

. generic DNB margin may not fully offset the penalty due to the anomaly.

(Do However, a RCS measured flow greater than the minimum required by Technical y Specification .2.5 (i.e., 395,000 gpm) could provide the additional DNB g

oc margin necessary to offset the effects of the flow anomaly while the detailed evaluation was in process. On this basis, the flow anomaly was determined to f be reportable and the NRC was notified pursuant to 10CFR50.72 on e September 2, 1988, at 1950 hours0.0226 days <br />0.542 hours <br />0.00322 weeks <br />7.41975e-4 months <br />, and a written report was submitted.

@$ ('ef. 1)

I l

ma.a oc /'

af//f0 ,

A Subsidiary of Houston Industries incorporated g 3/ f//{

L4\NRC\ek

_ _ -. _- - - - - - - - =

6 -

1

]

Le . .

ST-HL-AE-3040 lHouston Lighting & Power Company File No.: G09.17, G09.18, South Texas Project Electric Generating Station -G21, G26, G02 10CFR50.73 10CFR50.92 Page 2 o

Immediate corrective actions consisted of revising the operating procedure which addresses the monitoring of RCS flow such that an RCS flow of 400,000 gpm would be maintained for full power operation. Subsequently, Westinghouse completed a detailed evaluation of the flow anomaly which confirmed that-the existing Technical Specification RCS minimum flow of 395,000 gpm is acceptable.

ANALYSIS RESULTS Westinghouse has completed detailed safety evaluations that account for the effects of the RCS. flow anomaly. The analyses have considered the impact of the flow anomaly on the following:

a) DNB, b) fuel and cladding temperatures, c) RCS and secondary side pressure criteria, d) Loss of Coolant Accident (LOCA) criteria, and e) steady state and fluctuating loads on reactor internal and fuel components.

FSAR Chapters 4 and 15 design bases are unchanged with the minor exception discussed below.

Westinghouse analyses show that the RCS flow anomaly will result,in a slight increase in peak clad temperature. The most limiting peak clad temperature . transient. results from the rod ejection at power transient. For this transient, the potential peak clad temperature increase would be less than ten degrees above the FSAR value of 2219 degrees F.

This ten degree or'less increase is a small fraction of the more than 400 degree margin which exists between the FSAR value and the design limit of 2700 degrees F.

CORRECTIVE ACTIONS TAKEN

1. 'As an' interim measure, HL&P revised operating procedures to ensure adequate margins to DNB by maintaining RCS flow at or above 400,000 gpm for 100% power operations.

l

2. HL&P has confirmed that sufficient DNB margin exists to fully offset the penalty due to the flow anomaly. As committed in reference 1, the core DNB criterion has been reevaluated using the WRB-1 correlation which resulted in a reevaluated generic margin of 7.8%

to accommodate DNBR penalties. This represents an increase from the 3.3% provided by the previous correlation. The net result is that additional margin is available to address the flow anomaly, rod bow j, penalty and other DNB penalties that may be encountered. Based on i

i L4\NRC\ek .

L b

e .,

'ST-HL-AE-3040 Houston Light.mg & Power Company File No G09.17, G09.18' South Texas Project Electric Generating Station G21, G26, G02 10CFR50.73 10CFR50.90 Page 3

'1 this evaluation, no changes to the existing FSAR Chapter 15 analyses. "

including core safety limits have been made. .In Reference 2, the NRC was also informed that implementation of the WRB-1 DNB i

-correlation evaluation required revisicn to the safety analysis and design basis discussed in the FSAR. Subsequently,11&P has reviewed the proposed WRB-1 change in accordance with the requirements of 10CFR50.59 and concluded that no unreviewed safety question (USQ) is involved and that there is no resulting significant hazard.  ;

Therefore, the WRB-1 change'does not require NRC approval prior to j implementation;:and accordingly, changes to.the STP FSAR describing the implementation of,WRB-1 have been submitted under a separate-cover - (Ref. 3) .

HL&P does not believe the RCS flow anomaly affects the' staff's conclusions stated in the STP SER (NUREG 0781). However, it meets the criterion of 10CFR50.59 for being a " change" where the consequences of an accident have increased, although slightly, and is therefore considered an unreviewed safety question. Therefore, HL&P will maintain the RCS flow requirement of 400,000 gpm until receiving NRC approval of the HL&P Unit 1 analyses of'the flow anomaly effects. If the flow anomaly is encountered in Unit 2, HL&P' expects it will bt addressed in a manner similar to. Unit 1.

Annotated FSAR pages are also attached, HL&P will incorporate these changes into the STP Updated FSAR.

HL&P has- reviewed the proposed change in accordance with the requirements

.of 10CFR50.59 and 10CFR50.92. The results indicate that an unreviewed safety question (USQ) is involved. HL&P'has reviewed the USQ and concluded there is no.resulting significant hazard.

The South Texas Project Nuclear Safety Review Board has reviewed and approved the attached proposed revision:and concurs with the 10CFR50.59

-determination.

In accordance with 10CFR50.91(b) HL&P is providing the State of Texas with a copy of this proposed amendment, j In accordance with 10CFR170.12(c) an application fee of $150.00 is enclosed. 1 l

L4\NRC\ek

. . . - 1

+

i

., .\

Houston' Lighting & Power Company ST-HL-AE-3040 O

South Texas Project Electric Generating Station , File No.: G09.1 G0 18, 10CFR50.73 10CFR50.90 Page 4

^

-If you should have any' questions on this matter, please contact Mr.

A. W;. Harrison at (512) 972-7298.

S. L. Rosen Vice President Nuclear Engineering and Construction AWH/S'DP/hg Attachments: 1) Significant Hazards consideration RCS Flow Anomaly

-2) Annotated Revisions to FSAR

3) HIAP Check No. 319118 l

~ .

.L4\NRC\ek l

l i .

Houston Lighting & Power Company ,

STHLAE;34 p 0 .17, G09.18' South Texas Proj,ect Electric Generating Station G21, G26, G02 Page 5 cc:

Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 1700 Houston, TX 77001 George Dick, Project Manager U.S. Nuclear ReSulatory Commission INPO Washington, DC 20555 Records Center 1100 circle 75 Parkway Jack E. Bess Atlanta, GA 30339-3064 Senior Resident Inspector / Unit 1 c/o U.S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Be11 port Lane P. O. Box 910 Bellport, NY 11713  !

Bay City, TX 77414 '

D. R. Lacker J. I. Tapia Bureau of Radiation Control Senior Resident Inspector / Unit 2 Texas Department of Health c/o U.S. Nuclear Regulatory 110 W. 89th St.

Commission Austin, Tx. 78756-3189 P. O. Box 910 Bay City, TX 77414 J. R. Newman, Esquire Newman & Holtzinger, P.C. -

1615 L Street, N.W.

Washington, DC 20036 R. L. Range /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 R. John Miner (2 copies)

Chief Operating Officer City of Austin Electric Utility 721 Barton Springs Road Austin, TX 78704 R. J. Costello/M. T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Revised 12/21/88 L4\NRC\ek I 1

Houston Lighting & Power Company South Texas Project Electric Generating Station UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Mutter )

)

Houston Lighting & Power ) Docket Nos. 50-498 Company, et al., ) 50-499

)

South Texas Project )

Units 1 and 2 )

AFFIDAVIT S. L..Rosen, being duly sworn, hereby deposes and says that he is Vice President,. Nuclear Engineering and Construction, of Houston Lighting &

Power Company; that he is duly authorized to sign and file with the Nuclear Regulatory Commission the attached Proposed License Amendment relative to the effects of the Westinghouse Generic Reactor Coolant System Flow Anomaly; is familiar with' the content thereof; and that the matters set forth therein are true and correct to the best of his knowledge and belief.

Y S. L.' Rosen

~

Vice President Nuclear Engineering and Construction STATE OF TEXAS )

)

)

Subscribed and sworn to before me, a Notary Public in and for the State of Texas this /7

• day of //gt , 1989.

e JEAfME SH0CK y

_. ./,81/h /

Nota Pubk State of Tens p AIdb-f My Commission Expres 9-22 92 Noprj Publid it; and for the

$t' ate of Texas My commission expires:

L4\NRC\ek

__ _ _ - - - _ - - - - .1

(L c -

1 ATTACHMENT 1 Significant Hazards Consideration RCS Flow Anomaly I

l i

j L4\NRC\ek

Attschm:nt 1 ST-HL-AE-3040 Page 1 of 2 SIGNIFICANT HAZARDS CONSIDERATION RCS FLOW ANOMALY Does the proposed change:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated:

The RCS Flow Anomaly does not result in plant equipment exceeding their design limits. The RCS Flow Anomaly will not impact the operations of the plant when the changes recommended by this submittal are approved. Therefore, the RCS Flow Anomaly does not increase the probability of occurrence of an accident previously evaluated in the safety analysis report.

Due to the RCS Flow Anomaly, the peak clad temperature fgr the Rod Ejection at Power and Locked Rotor transients increases by 10 F. However, thisincreaseisasmallfractionofthemorethang00Fmarginwhichexists between the FSAR value and the design limit of 2700 F. This margin ensures that fuel failure will not occur. Since fuel failure does not occur, the radiological consequences of these subject transients as documented in the STPEGS FSAR, Tables 15.4-5 and 15.3 4, are not increased. Therefore, the RCS Flow Anomaly does not significantly increase the consequences of an accident previously evaluated.

2) Create the possibility of a new or different kind of accident from any accident previously evaluated:

The RCS Flow Anomaly will not cause changes in the operation of the plant when the changes recommended by this submittal are approved. Therefore, The RCS Flow Anomaly does not introduce the possibility of a new or different kind of accident due to operator actions. The RCS Flow Anomaly only effects the results of existing analysis. Westinghouse has completed a structural evaluation of components that may be impacted by the RCS Flow Anomaly. The results of this analysis sho'w that the design limits for these components are i not exceeded. The components will perform as designed. Therefore, the RCS Flow Anomaly does not create the possibility of a new or different kind of accident due to equipment malfunction or failure.

3) Involve a significant reduction in the margin to safety:

Westinghouse has performed an evaluation which addresses the impact of the RCS Flow Anomaly on LOCA transients, non-IDCA transients, and the structural analysis. The results of the LOCA transient evaluation shows that the results of these analyses are not impacted by the RCS Flow Anomaly.

The results of the non-LOCA transient evaluation show that the RCS Flow Anomaly causes a slight decrease in DNBR. However, there is sufficient generic margin to accommodate this decrease in margin. This evaluation also shows an increase of 10 F in the peak clad temperature for the Rod Ejection at Power and Locked Rotor transients. However, this increase is a small fraction of the more than 400 F margin which exists between the FSAR value and the design limit of 2700 F.

L4\NRC\ek

1 l

Attcchmznt 1

! ST-HL-AE-3040 Page 2 of 2 The results'of the structural analysis evaluation show a slight reduction in the design margin for some Bottom Mounted Instrument (BMI) components.

These components include the secondary support columns and the support 1

column-to-support plate bolts. These components were analyzed to the standards presented in the ASME Boiler and Pressure Vessel Code. Results of the analysis show that the most limiting stresses associated with the RCS Flow '

l Anomaly are less that the stress limits identified in the ASME Boller and i, Pressure Vessel Code.

To summarize, the Westinghouse analyses show a slight reduction in the margin for DNBR, peak clad temperature, and some BMI components. However, sufficient margin exists such that these components will perform as designed.

Therefore, the RCS Flow Anomaly does not involve a significant reduction in the margin to safety. Consequently, HIAP has determined that there is no significant hazards consideration.

L4\NRC\ek

(-_-----

l f;

i.

i, ATTACllMENT 2

.innotated Revisions to FSAR i

L4\NRC\ek i

i f

. _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ - - _ _ _ _ _ _ - _ _ _ - _ - _