3F1088-07, Forwards Responses to 880830 Questions Re Emergency Feedwater,Per 880928 Commitment
| ML20205B470 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 10/12/1988 |
| From: | Widell R FLORIDA POWER CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 3F1088-07, 3F1088-7, NUDOCS 8810260249 | |
| Download: ML20205B470 (4) | |
Text
_ _ _ _.
E eee I
{ee ee) f e'
f i
eee j
coneonario=
October 12, 1988 i
I i
U.S.
Nuclear R9sulatory Commission I
Attentiont f,ocument Control Desk i
Washington, D.C.
20555 i
Subject:
Crystal River Unit 3 j
Docket No. 50-302 i
Operating License No. DPR-72 i'
Reorgency Feedwater j
Dear Sirt l
Attached are Florida Power Corporation's follow-up responses to your l
i August 30, 1988 questions as committed in our September 28, 19'P, i
(3F0988-20) correspondence.
j t
j i
Tf you have any question, please contact this office.
8 acerely, L
{
Rol C. Widell, Director L
Nuclear Operations Site support i
i REttRCW1wla l
l l
Attachment l
l xct Negional Administrator, Region II Senior Resident 2nspector
[
r
?
i l
l
[
g!A 2gggg ggaggg2
<.y l
~.,_e....,...,,,.m...,_._,..._e_
a rwa mes cme, I
4 Questim 02:
Themal Stratification in pipirg systens is known to roer. tit frun low ficw conditions.
Themal stratification can cause fatigue damage ani largo beniin; str You shculd acktress the possibility that thermi stratification existed in the piping system as a result of the backleakage and line coolirn, and acktress any damge to the pipin7 that my have resulted.
4 pa=nnes to m== tion #21 e
I EIBATIFIChTI(Mi Florida Power Cbrp3 ration's letter to the NRC dated S@tertber 28, 1988 h ibes the coniitions that could have irduced stratified ficws ard temeratures in the Daergency Feedwater piping to the "B" stavn Generator. The j
locations where the most severe coniitiers are believed to have existed, under both back leakage ani line cooling flows, have been evalustal by Florich Power Corporaticn.
The analyses conclu$e that the wximum possible p!.pirn stressers produced by stratification at cperatirg pressuns ard terpelature are within code allcwables.
The pipirg and surports at the locations evaluated will be inspected durity the October 1988 cutage, as di==M in the Septs ber 28, 1988 couuspedence, to further assure chmvje did not occur. Limitity the back leakage through M-43 and M-44 will preclude future stratification conocrns.
t a
Stratification durim back leakaoe - B&W analysis #32-1272908-00, "Heat losses throtgh DY Line", defines the highest leak rate that will mintain water in the DV line to be 0.003 gpn (fl0%).
Isak ratas Icuer thar, this will not permit any steam to enter the water t'illed portion of the pipino syatan. This steam counterflow is consideral necassary for stratified coniJticm to exist.
Therefore, the mxirum permissible systan inventory loss should be limited to 0.0027 gpe.
This will be egressni as 10.2 milliliters per mirute, cold water leakage to atmanrheric cxn11tions, ard will be the by:k leakage limit Jrposal upon M-43 and M-44, with the pipirn in its current insulatai configuration.
This same analysis also concludes that back leakage greater than 0.064 gpn vill eventually empty the "B"
Steam Generator's long horizontal pipiny run, elimitatiry any stratification correm in the systan (*0.02 gpn for the "A"
i Steam Generator). Back leakage between 0.0027 cpn ard 0.064 cpn results in intennadiate fill coniitions.
I The maasured leakage rates at Crystal River Unit 3 of 0 2-0-7 gpn iniicated l
that the line would have been subject to stratified cor1.nwa for a short period of time, an1 then would have resulted in a 1!ne m. tend g only steam.
The actual daJree of stratification is not known, be e 4:q mcdel was develcped to evaluate the worst corditions pass.ible.
A taTert ture stratification of tp to 400 degrees F was
=_wd whico ocnservativ41y neglected local preheatirg ard mixin).
The results of the analysis show the highest irduced thermi stresses to be 26.4 kai at the elbow cn the generator erd of the 140' horizontal pipe, ard 33.3 kai at the point of the greatest delta ta'perature stratification. The acrbined M1oad, pressuzu, and thermi str-are within ecde allcwables at these locations.
Dmpawe to Questimi 12 ocritirued:
Stratification durim line coolim - Scro degree of stratification may have existed in the horizontal runs durirg the 1 and 50 gpn cooling operations, as described in Florida Power Corpc, ration's letter to the NRC datal September 28, 1988, but to a lesser extent than *che bE.ck leakage condition dimMcui above.
This is due to the high initial taperature of the incrzning fill water which mixes to same degree with the following cooler water, reducirq the stratified delta taperature.
The highest taperature stratification is expccted to be less than 300 degrees F as expressed in the Septe::1ber conuspcMence.
The pipirq model develcped with a 300 degree F taperature difference resulted in much lower bending stresses than those for the back leakage case addressed earlier and further review determined the back leakage case to be the envelcping condition.
Cumtion i3:
In response to CAL number 4, ycu identified a number of r; ens why yru believe that the potential for water hamer was considered una. _cted by the back leakage. These reasons have been reviewed, and the statf feels that FPC should provide more substantially supported arguments to resolve the gaestion of whether a water hamer could or did occur.
Remonse to Oumtion f 3:
WATTRW99R; Florida Power Corporation has avaluated the waterhamer potential in the Dmrgency Fecdwater pipirg system during a back leakage cordition, which voidcd the Reactor Euildirq portion of the line.
As stated in a letter to the 18C dated September 28, 1988, both sinJ1e phase aM cordensation irduccd water hanter events were considered crulible, tuder certain flcu conditions, ard sure to to analyzed further.
A Gilbert Cmmonwealth, Inc. rr:; ort entitled
An Evaluation of Dergemy Feechratet Pipirg Systan hater Hamer Ioads with the Sy. stem Partially Vcided" dated CW.:cter 1988 concludes t6t fast fill, single phase waterhammer loads wtuid have inducA stresses above code allcsables, in scro localized a::cas, but below yield.
The analynes also conclude that the potential for cordensation IJrtuccd waterhamar existed at lcuer flows for the short pericd of tire it kutid take to ccmpletely fill the line frm a partially filled condition.
Since the potential for waterhamer did exist durirq several lino coolirg operations, an inspection of the piping and supports will be performed at the most susceptible locations durity the Octobe~ 1988 outage. This will detemine if any damage occurred.
Ritum waterhantor concoms will be alleviated by limiting back leakage thrugh IW-43 and FW-44 to 10.2 ml/ min, since leakage belcw this rate results in a hydraulically solid piping system up to the Steam L
Dasemse to Question #3 cmtirued:
Generator inlet piping, as addressed in the themal stratification infomation provided herein.
Potential fill cmditions- 'Ihe two conditions analyzed that could have occurred, but did not, were a fast fill transient of flows greater than 160 gpn and a slow fill acerario of 125 gpn.
'Ihe fast fill condition a = =~i tm Emergency Feedwater Ptmps starting sinultaneously, delivering approximately 1600 gpm to the "B" loop piping.
Calculated loads of 1340 lbs. force were input to the pipe stress analysis with the resulting strsw=a beirg below yield for all of the piping and suprt conponents.
'Ibe sics fill condition of 125 gpm, as described in the Septaber 28, 1988 correspondence, was evaluated for condensation induced waterhamer potential.
'Ihe potential would exist for a short period of time when the horizontal piping run was greater than 8'it full and filling.
Since the duration availabio for the formation of trapped water slugs was short, the probability of a condensation induced waterhamer proble occurring at this fill rate was 1cu.
Actual EFW fill conditions-Two flow rates were utilized by Florida Power Corporation to fill the "B" Emergency Feedwater piping loo) frun a voided condition.
A 50 gpn fill frun the Emergency Feedwater pip;ny was cuployed several times and a fill rate of less than 1 gpn was used orce frun a tenporary injection metering punp.
As stated in the Septaber 28, 1988 correspondence, the use of the injection circuit is not considered to have been a vaterhamer concern because of the low flow rato.
'Ibe 50 gpn fills, according to the evaluation, did have some waterhamer potential, but only when the horizontal pipirg was greater than 90% full and filling.
As with the 125 gpn situation, the timo for formtion of trapped water sltna was rhort, therefore the probability that same degree of waterhammer ocmrred was 1cw.
An inspection will be performed during the October 1988 outage to detomine if any damage cocurred that could have been induced by a waterhmner event.
mMm or 'I1pMAL seg7yEMIm MJD WIMLIEME MTEtE;
'Iho followirg is a sunmry of the inWicos to be perforwxi during the October 1988 outago in respence to tho thornil stratification and water hamer concerns discussed herein and in our Septanter 28,
- 1988, (3F0988-20) coriuspeiden
'Ihermal Stratification Inspection - Both enis of the 140' horizontal Emergency Foodwater (EEW) pipinJ to the "B"
steam generator will be inspected for external damage at the local supports.
Water Hamer Insocctions - Inspections will be performd on the horizcotal EEW pipinJ rua near the "B" steam generator and will include EEU-25A which is tho caly restraint utilizing concreto anchors.
If the inspections identify defects or deficiencies, the proper corrective actions will bo performed prior to returnirq the systm to cperable status.
Y