ML17212A787

Forwards Response to Generic Ltr 81-14 Re Auxiliary Feedwater Sys Seismic Qualification,Per NRC 810210 Request. Plant & Sys Will Function as Designed & Would Enable Plant to Be Brought to Cold Shutdown Condition Safely

ML17212A787
Person / Time
Site:	Saint Lucie
Issue date:	09/18/1981
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
GL-81-14, L-81-411, NUDOCS 8109240341
Download: ML17212A787 (10)

Text

REGULA QRY INFORMATION DISTRIBUTIUN SYSTEM (RIDS)

ACCESSIOV NBRR8109240341 DOC OATEN': 81/09/18

~ NOTARIZED: NO DOCKKiT' FACIL>>:50-335 St, Lucie Pl antr Unit 1i Florida Power L Light Co, 05000335 AUTH>>s N AMK" AUTHOR AFFILIATION UHRIGR R ~ E ~ Flor ida- Power L Light Co.

REC IP ~ NAblKl RECIPIENT AF F IL>>IATION E>>ISENHUT'r D.G ~ Division of Licensing

SUBJECT:

Forwards response to Generic Ltr 81-14 re auxiliary feedwater sys seismic qualificationiper NRC 810210 request">

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%$ 5 Jllnsti FLORIDA POWER & LIGHT COMPANY September 18, 1981 L-81-411 Office of Nuclear Reactor Regulation Attention: Mr. Darrell G. Eisenhut, Director Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Eisenhut:

Re: St. Lucie Unit 1 Docket No. 50-335 NRC Generic Letter 81-14 Auxiliar Feedwater S stem Seismic (uglification Please find attached our response to Generic Letter 81-14, as requested by your letter dated February 10, 1981.

Very truly yours, Robert E. Uhrig Vice President Advanced Systems and Technology REU/JEM/mbd ~

Attachment cc: Mr. James P. O'Reilly, Region II Harold F. Rei s, Esquire Qooi 5

8i0924034i Bi09i8 PDR ADOCK 05000335 P PDR PEOPLE... SERVING PEOPLE

ATTACHMENT RE: ST. LUCIE UNIT 1 DOCKET NO. 50-335 NRC GENERIC LETTER 81-14 AUXILIARY FEEDMATER SYSTEM SEISMIC UALIFICATION

~Summa r

1) Although the NRC did not: officially recognize t: he APN system as an engineered safety feature unt:il publication of t: he 1975 Standard Review Plans, t:he St Lucie Unit 1 PSAR (docketed Narch 1973) ident:ifies this System as Safety C'ass 3 and Seis-mic Class I.

2) nil mechanical, elect:rical and instrumentation/control components required for the proper operation of the Auxiliary Peedwat:er System are adequately designed to wi'thstand earth-quake induced loads. All essential component:s are located in Seismic Cat:egory 1 structures. The APN system adheres t:o cri-t:eria st:ated in the PSAR and the system design is consistent with ot:her safety grade systems in the plant:.

3) As part of a supplemental review, PPL has established that: all major Class 1H equipment (transformers, switchgear, batteries, inverters, cable tray and control/power pane"s) for the balance of safety system are adequately anchored and support:ed to wit:h-stand t:he SSE event.

4) One generic class of equipment where rigorous analytical proof of seismic adequacy is not available was miscellaneous elec-t:rical equipment supports including those for electrical con-duit: and some electrical boxes. As requested by Generic Letter Ol'14 a field inspection and design evaluation of these items was performed. The results of this review indicate that: the as-built: support system has considerable seismic resistance,sys-and in our best engineering judgement we believe that: t: he

A'InJ.'ACI IHI;N'l'ONTD. I t)80 2 OI 5 AUXILIARY PHHDWATHR SYS'J~ SEISMIC QUALIPICA'J.'ION NRC GENERIC LEVIER v

81-1~

~Summar (Cont'd)

4) tern would remain functional following a Safe Shutdown Earth-quake. This item is discussed further below under Section XXX.

5) The APW system was considered in the responses to NRC XE Bulletins 79-02, 79-04, 79-07, 79-14 and 80-11.

6) The primary source of water and supply paths for St Lucie Unit 1 are seismically qualified and therefore, the require-ment for a qualified secondary water supply path is .not ap-plicable to St Lucie Unit l.

XX Methodolo /Acce tance Criteria The design conditions, design loading combinations and stress limits for major system components are detailed in Chapter 3 of the PSAR. Seismic analysis test reports and engineering eval-uations to substantiate the seismic adequacy of the system are available in our files.

The following is a brief description of the methodologies and criteria used to qualify the AFW system compoments:

A) Pum s and Drives All three AFW pumps (one turbine,. two motor driven) and drivers were qualified .by static analysis methods using acceleration factors of .25g horizontal and .175g vertical for the Operating Basis Earthquake (OBE), and .5g horizontal and .334g vertical for the Safe Shutdown Earthquake (SSE).

The stresses due to the two acceleration directions were added absolutely and acceptance criteria is based on main-taining material stresses within allowables without loss of.

function.

n) ~pi in All above ground piping from the Condensate Storage Tank to the ground was qualified ivy static analysis methods using acceleration factors of .32g horizontal and .24g vertical for the OBE, and .64g horizontal and .48g vertical for the SSE, applied simultaneously. The remainder of the conden-sate piping, the APW system piping, and the Main Steam Sys-tem piping supplying the turbine drives were analyzed by the modal response "spectrum analysis method, based upon 44 damping, with the earthquake directions combined by the SRSS method. The allowable stresses for these systems were based upon B31.7 (1969) requirements.

C) Valves/Actuators All valves and actuators were qualified for 3g horizontal and 2g vertical for SSE, except, for the turbine driven pump steam inlet valve which was designed for 1.5g horizon-

ATTACIIMHNT CONTD.

Page 3 of 5

,AUXILIARY PEEDWATHR SYS SEISMIC QUALIPICATION NRC GENERIC LETTER 81-14 Ne thodolocI /Acce tance Criteria (Coni 'd)

C) tal and .48g vertical. The the large bore valves were qualified by static analysis; small bore valves were qualified by engineering evaluation.

Power Su lies All major electrical equipment tests, has.been seismically qual-ified. This was done through using accelerations ranging from .15g to 4.8g. Cable trays were qualified by analysis, using acceleration factors from the appropri-ate 'response spectra.

E) Px imax Water and Su 1 Path The Condensate Storage Tank was analyzed for. seismic (in-cluding hydrodynamic) and dead load, using acceleration factors of .29g (hor) and .19g (vert) for OBE and .':Gg (hor) and .39g (vert) for SSE. The stresses were combined by Caking the absolute sum of the vertical and one horizon-tal acceleration component, the stresses were compared to 1.33 times the AWWA D-100 allowable stresses for OBE, and 90'4 of. yield stress for SSE. The supply path (piping) is covered under (B) above.

Initiation and t

Control S stem Nosh of the instrumentation devices have been qualified by subjecting them to tests at various input accelerations.

Exceptions to this are as follows:

local gauge 'ot essence ial for sa fe ty sys tom opel a tion ~

The control grade automatic initiation circuitry installed as 'a post-TMI modification will be upgraded to safety'rade and seismic Category 1 during our current outage.

G) Structures Su ortin or IIousin AI":W S stem Com onents All pipe support/restraints were designed to Seismic Cate-goxy I requirements to withstand the piping loads due to (Thermal + Weight. + SSE). Cable tray supports and electri-cal equipment mounting details were qualified by analysis, using loads from the appropriate response spectra. Design load was (Weight + SSE) and resultant stresses were com-bined by taking the absolute sum of the vertical and one horizontal acceleration component. The conduit supports and mounting of certain electrical boxes were not quali-fied by rigorous analysis since the criteria at, the time of installation was to install in accordance with the elec-trical industx'y standards. These items were inspected in the field as discussed below.

ATThCIIMENT CPNTD. Vxjo 4 of 5 AllEILIARY PEHDWAYHR HYS HEXHMXC QUALXPICAYIOM gRC GL'NERXC LETTER 81-14 XXX Field Xns ection/Evaluations 1.0 Auxiliar Peedwater S stem A field inspection was conducted covering all system com-ponents that could not be readily qualified by existing documentation. 'These items consisted of miscellaneous conduit and electrical box supports. The inspection team consisted of personnel highly experienced with electrical equipment and support systems. The inspection verif'ed that in general, the support systems have conservative sup-port spans and were installed in accordance with National Electrical Code Standards using standard commercially a-vailable strut material, clamps, u-bolts, and various steel shapes, in conjunction with ANSX C80.1 rigid steel conduit.

This level of design for m~.scellaneous electrical component supports is consistent with industry practice for plants of the St, Lucie Unit 1 era. These support designs and materials are used universally throughout the nuclear and fossil power plant field as well as other industries and were considered to have adequate seismic resistance at the time. of installa-tion. Industry tests on cable tray/conduit, support assem-based on worst case models indicate that systen.s sup- 'lies ported by commercial grade components similar to those used at St Lucie Unit 1 remain functional after being subjected to tests which simulate earthquake conditions.

Xn addition, when assessing the seismic res).stance of the installed system, certain inherent, conserva'tisms were con-sidered. These include:

X

1) Margins between allowable stresses and ultimate mater-ial strengths.

2) Xnherent ductility of materials.

3) Seismic resistance of non-structural elements in the system.

4) Ability of cable/conductor to suffer considerable de-formation without affecting function.

5) Increased damping values, due to friction between the cable and the inside wall of the conduit.

Also, a substantial data base detailing the effects of actual earthquakes on large industrial facilities (including power plants) exists in the literature. Our review of these reports/

observationsprovide evidence that installations built to commercial standards and local building codes exhibit a high degree of seismic resistance.

2.0 Anchora e/Su ort for all remainin Class lE Electrical E ui mant Based on preliminary findings from the review of the Auxi-

l ATTACHMENT CONTD.

,A'OXILX'Al<Y FEEDWATER SYSTEM SEXSMXC QUALIFICATION NRC GENERIC LETTER 81-14 Page 5 of 5 XXX Field Xns ection/Evaluations 2.0 Anchora e Su ort for all remainin Class 1E Electrical liary Peedwat:er System, PPL decided t:o extend t: he review of electrical equipment support/anchorage to include related all major Class 1E component:s for the balance of safety systems. XE Xnformation Notice 80-21 provided the basis for this supplemental review which includeQswitchgear, the following electrical equipment: transformer, con-trol/power panels, batt:eries, inverters, cable tray, elec-trical boxes and conduit.. Those components whose anchorage/

support could not: be verified by existing documentation were inspected concurrently with the Auxiliary Peedwater conduit System inspect:ions. The components examined included the and electrical box supports in areas that are accessible during plant: operation.

All major elect:rical equipment anchorages and cable tray supports were found to be satisfactory. Miscellaneous elec-trical equipment supports (conduit and boxes) were installed to NEC standards in existence at the time of installation.

As in the case of t:he APW system, the support systems possess a substantial.mrountof inherent seismic resistance and are considered'dequate to withstand the Safe Shutdown Earth-

'quake..'V Conclusion l)esign crit:eria and methods of seismic qualificatio>> for safety related equipment have changed significantly during Major the course sys-of development of commercial nuclear power plant:s.

tem components for the Si. Lucie Unit 1 AFW system were rigorously designed to accept:able crii=eria and guidelines t.hat existed for safei.y relat:ed syst:ems during i.he plant design st:age. Due t:o time, evolving criteria and changes in analysis methods since that the support: systems for some miscellaneous electrical components may not be qualified when strictly compared to curreni= acceptable crit:eria. However, based on our evaluation, we find t:hat: these components possess a reasonable level of inherent: seismic resis- re-tance. We expect that a seismic event of the SSE level could sult in some yielding of miscellaneous electrical support com-ponents. Xn our engineering judgement, however, w~ are confident that the APW system and the plant elect:rical syst:ems plant as a whole to be would function as designed and would enable the brought= to cold shutdown conditions safely.

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