ML20029B510
| ML20029B510 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 03/04/1991 |
| From: | Cottle W ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GNRO-91-00040, GNRO-91-40, NUDOCS 9103110299 | |
| Download: ML20029B510 (10) | |
Text
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- 2 Entergy-5"';r """*"* '"*-
Onerations
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- s-M w b4s/ t4N, W. T. Cottle w e i r-am h mrr / t iva s,i ' W m X T U p: 'r March 4, 1991 U.S. Nuclear Regulatory Commission Mail Station F1-137 Washington, D.C.
20555 Attention:
Document Control Desk
SUBJECT:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 Summary of Calculations Regarding Precipitation in the SLCS Discharge Piping GNR0-91/00040 Gentlemtn:
On February 12, 1991 Entergy -Operations, Inc., Grand Gulf ~ Nuclear Station -
(GGNS) met with members of the NRC-Staff to discuss the results of calculations-performed by GGNS at the request of the Staff to confirm that excessive sodium pentaborate solution precipitation in-the Standby _
Liquid Control System _(SLCS) discharge piping does no.t occur.: As a follow-up to that meeting, the Staff requested GGNS submit a summary description of the calculational methodology and results.. The_ attachment to this letter provides'the_ requested'information.
in sddition. =during ths February 12, 1991 coeting the-NRC St aff asked Entergy Operations to consider revl: ting proposed changes to the.GGNS~ SLCS
-Technical Specifications submitted on. December 7, '1990: (1)_ clarification
'of proposed action statement a.3 and-(z) labeling changes.to proposed-i Figure 3.1.5-1.
Af ter careful consideration we believe_ _the -
Decomber 7, 1990 proposed enanges are cient, l
i
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l G9102264/SNLICFLR --1 c 0 910'3110299 910304 s 0C/
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9 March 4, 1991 GNRO-91/00040 Page 2 of 3 No further issues are associated with the proposed change to the SLCS Technical Specifications. We would appreciate your timely closure of this long-outstanding request.
Yours truly, A~
WTC/ PRS /mtc
attachment: Standby Liquid Control System Solution Temperature Change Calculation Summary cc:
Mr. D. C. Ilintz (w/a) f Mr. J. Mathis (w/a)
Mr. R. B. McGohee (w/a) i Mr. N. S. Reynolds (w/a)
Mr.11. L. Thomas (w/o)
Mr. Stewart D. Ebneter (w/a)
Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta St.,
N.W., Suite 2900 Atlanta, Georgia -30323 Mr. L. L. Kintner, Project Manager (w/a)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 11D21 Washington, D.C.
20555 G9102264/SNLICFLR - 2 1
At tachment to GNRO-91/00040 4
STANDllY lilQUID CONTROL SYSTEM S01,UTION TEMPERATURE CilANGE CAI.CUI.ATION
SUMMARY
s 09102264/SNLICFLR - 4
____--_.-..-.A
Attachr.ont to GNRO-91/00040 STANDBY LIQUID CONTROL SYS'iEM SOLUTION TEHpERATURE CilANGE CALCULATION SUMM/sRY I.
Calcul_a ti_on_Pu rpos e The current GGNS Technical Specifications (TS) allow the solution in the Standby Liquid Control System (SLCS) to have a sodium pentabor te concentration of 28.5 weight percent when at a solution temperature of 130'F.
The issue of whether such a solution in capable of being injected into the reactor vessel without excessive scxlium pontaborate precipitation occurring has been raised by the NRC.
To n ;sist in resolving this issue, a calculation was perforrned to determine how much the temperature of the SLCS process flow (starting from the SLCS pump discharge) changes due to ambient temperature condit ions (in the vicinity of the SLCS discharge piping) when being injected into the reactor vessel.
Figure I contains a schemnLic of the SLCS piping layout.
l The calculation consisted of two parts:
- 1) Calculation of the SLCS proccan flow amperature change under stendy state conditions (i.e., SLCS discharge piping warmed to SLCS process flow ternporat tre).
- 2) Calculation of the SLCS process flow temperature change immediat ely af ter SLCS initiation (i.e., SLCS discharge piping in the containment is at 70*F and the drywell portion of piping ir at 110*F).
The results of the calculation are to be used to demonstrate annlytically that the SLCS sodium pentaborate solution temperature along t.he entire SLCS discharge piping path remains above the 28.5 wc1ght percent sodium pentaborate solution saturation temperature of 114*F.
As long as the SLCS solution temperature remains great er than the saturation temperature in the discharge piping excessive precipitation does not occur.
II.
G6neral Assumptions The following are the major e umpt.lons used in both the steady state and transient. parts of he calculation:
- 1) The temperature of the SLCS sodium pentaborate solution (process flow) in assumed to be 130'F at the SLCS pump discharge.
- 2) The SLCS fIc. rate for two pumps is assumed to be 82.4 gpm.
3)
!.'o.:redit is taken for insulation on the SI.CS discharge piping.
G9102264/SNLICFLR - 5
Attachment to CNRO-91/00040
- 4) The ambient temperature in the containment is assumed to be 70'T (1.c., the SLCS discharge piping.in the contalonient is initially at, 70'r).
- 5) The ambient. temperature in the drywell is arsumed to be 110'r (i.e., the SLCS dischargo piping in the drywell is initially at 110'F).
- 6) The initial sodium pentaborate concentration of the process flow is assumed to be 28.5 weight porcent.
III. Steady Stato Condition Calculation Methodology The process flow temperature change due to ambient temperatures was eniculated by first determining the total heat transfer rate by free convection and radiation.
Then dividing the total heat transfer rato by the process fluid mass flow rate to obtain the enthalpy chango por pound mass (lbm). The temperature change in then calculated by dividing the enthalpy change by the specific heat of the SI.CS solution. These calculat. ions were performed neparately for each of ten pipe sections of the system piping modol.
IV.
S t_a_a dy_S t a.t o_C a l c_u l a tul on_R o s u l t s Once the piping reaches steady state temperatures, the t.otal temperaturo drop from when the solution leaves the pump dischargo until it reaches the renctor vessel is only 0.22'r, Therefore, the temperature losses to the ambient are very small and do not cause any excessive sodium pontaborato precipitation to occur since the resulting final solution temperature (129.78') remains above t,he saturation temperature (114*F).
V.
T r a n s i en t_Cond i t f on_Ca l cu l a.t ion _H o thod o,l ogy The temperature change of the first Ibm of the SLCS solution as it passes through the discharge piping from the SLCS pump until being injected into the reactor vessel was calculated by determining t.he amount of heat lost to the piping as this initial Ibm travels through the piping. The amount of heat lost to the dischargo piping by the very first Ibm of SLCS solution leaving the ShCS pump discharge upon SLCS initiation ir assumod to experience the greatest amount of heat loss by any lbm of SLCS solution. The basis for this assumption is that when the SLCS is first initiated, the SLCS piping will be the coldest. and the piping will subsequently warm up as the remaining SLCS solution passes through, until it reaches the steady stato condition discussed above. The transient calculation modeled the SLCS piping from the SLCS pump discharge to the reactor vessel in one foot incromonts.
The calculation also verified that the SLCS flow was turbulent at all locations in the discharge piping so as to assure thnt no thermal stratification occurred.
I G9102264/SNLICFLR - 6 i
Attachment to GNRO-91/00040 The first step was to calculate the traverse time through the pipe increment.
The SLCS flow rate used was 82.4 gpm for the common discharge piping and 41.2 gpm in the piping which is upcteam of the point where the discharge piping from each SLCS pur.p meets.
Dividing the SLCS flow rate by the cross sectional ares for the appropriate pipe diameter gave the SLCS solution velocity through the piping.
Dividing the 1 foot piping length by the solution velocity gave the traverse time for that pipo lacrement.
The second step was to calculate the area that the first Ibm of SLCS solution had in contact with the pipe wall for the appropriate diam'3ter of discharge piping.
8 The third step was to calculate the heat treasfer rate per ft of contact area for each increment of piping.
The calculation for the heat transfer rates was performed using a computer program. The heat transfer rate was calculated for each increment of piping.
The enthalpy change was then calculated as a prod 9ct of the heat transfer rate and the traverse time.
The temperature change was calculated by dividing the enthalpy change by the sFecific heat of i
the SLCS solution.
The preceding steps were performed separately for each increment of piping and each incremental temperature change was totaled to find the overall temperature change of the first ihm of SLC solution.
4 A calculation of the amount of heat required per foot of piping length was performed to determine how much time it would take to heat up the piping from ambient to 130'F.
The amount of time required for pipe heatup at various locations was determined by first calculating the initial heat transfer rate at that location.
The amount of heat required to heat up one foot of each diameter of piping was calculated.
~%c average (over time) heat transfer rate was assumed to be half of the initial heat transfer rate since the heat transfer tale varies almost linearly with the temperature difference between t.he SLC solution and the piping (this temperature dif ference goes from maximum to zero during the transient).
The heat required was then divided by the average heat t ransfer rate to determine the time required for pipe heatup.
The total time for pipe heatup (from To = SLC initiation) was calculated by determining the SLC process flow traverse time to i
that locat. ion and then adding the traverse time to the heatup time.
VI.
Transient Calculation Results The result obtained for the transient condition analyzed is that for two SLCS pumps cperating, 70'F ambient in the containment and 110*F ambient in the drywell:
the SLCS solution temperature as it enters into the reactor vessel is Ereater than ll7.2'F.
- Recall, the saturation temperature for a sodium pentaborate solution with a concentration of 28.5 weight percent is ll4*F.
G9102264/SNLICFLL - 7
Attachment to GNEO-91/00040 The total time for the discharge piping to heatup froni the ambient temperatures (70*F and 110*F) to the process flow temperature (130*F) was calculated to be less than 21 minutes and was less than 48 seconds if the 14 inch diameter llPCS discharge piping is neglected.
Since the SLCS process flow was verified to be turbulent at all piping locations and b ecause the initial lbm of SLCS solution reaches the reactor vessel at a temperature greater than the sat.uration temperature; no excessive precipitatioc of any nodium pentaborate occurs.
In addition, beccuse the time to heat the piping up in small and the initial Ibm temperature remains above the saturation temperature, any subsequent SLCS solution also remains above the saturation temperature.
VII. Sample Transient Calculation A sample calculation demonstrating the above described methods for the last complete 1 foot section of common 1-1/2" diamotor piping follows:
The traverse time for this 1 foot increment.:
T
= increment length / fluid velocity
.g
= 1 ft / 14.96 fps = 0.06685 seconds At this location the calculated initial SLCS solution temperature (t ) is 117.34'F. the pipe temperature (t ) is 110'F, the SLCh solution velocity is 14.96 ft/sec, anY! the internal pipe diameter is 1-1/2".
The heat transfer coefficient is given by (Source - Mark's Standard llandbook for Mechanical Engineers, 8th ed., page 4-64, equation 6c):
e, a
- o. :
h, = 160*( 14 0. 012 t,)V,
/ ( D,' )
where:
h, = mean value of h for entire surface (BTl'/hr f tF)
L = film temperature = (t i)/2 ('F) 4 t, e pipe wall temperature t = SLC solution-temperature b
V, = average fluid velocity (f t/sec)
D, = inside pipe diameter (inches)
= 160 * (1+0.012*113.67'F)
- 14.96 fps /(1.5")
8
= 3037.4 BTU /hr ft F The heat transfer rate at this location is therefore:
Q=h
- A
- AT m
a G9102264/SNLICFLR - 8
Attachment to GNRO-91/00040 where: h = mean film coefficient (BTU /hr ft**F) 8 A, = surface contact area (f t )
AT = SLC solution temperature pipe temperature ('F) 8 8
- 7.34'F
= 3037.4 BTU /hr ft *F
- 0.038 ft
= 847.2 BTU /hr = 0.235 BTV/sec The ent.hnipy change per Ibm of St.C selution while traversing this pipe increment:
All = h*To 1/2 t) where h=heattransferrateatthie. location-(BTU /sec)
T
= incre'-4nt traverse time (soc) u.in D 0.235 BTU /sec
- 0.06685 seconds = 0.01571 BTU
=
The temperature change across this incroacnt:
AT = All / c P
where: All = enthalpy change (BTU /lbm) c = SLCS solution specific heat (BTU /lbm'F)
= 0.01573 B10/lbm / 0.82488 BTU /lbm'F = 0.01905'r All of the values calculated above approximate the values calculated by the computer program algorithm.
The heatup time for this increment of piping (using half rate):
T,,g,,,p,,, = Q 1/2 r) I ((
- Apire - ( E* EI"*l"*
- b""8'h) l m
i
- AT)/2) l l
where: Q
,,,= heat transferred for increment-(BTU /ft) l h = mean va.ue of h for entiro surface (BTU /hr 8
l.
ft 'F)
A
= pipo increment's area (ft )
8 AT'= differer.m between the SLCS solution and the pipe tempe.atures-('F) 8
= 8.712 BTU /ft/((3037.4 BTU /hr ft 'F*
8 0.3927 fL *7.34'F)/2) = 0.002 hr = 7.2 seconds 09102264/SNL1CFLR._
j Attachment to CNRO 91/00040 I
The total time to heatup for this pipo section:
T,,g = T '
T,,,p,g + T t
2 I.tn A 1.tn*c il01 14'D l
0.5223 sec + 2.508 sec + 4.17 sec + 4.773 see +
=
i 7.2 sec j
19.1733 seconds
=
V I I I.,C_o.n. c.. l..u...s._i_ o.n.
n I
The results of this calculation prove excessivo precipitation of sodium pentaborate in the discharge piping la not a concern for tho conditions analyr.ed.
The initial lbm of SLCS solution experiencen no excessive precipitation, the piping reaches the process flow temperaturn (130*F) relatively quickly and once the piping is at.
i steady state the total temperature change of the solution from SLCS l
pumps to reactor vossol is-negligibic.
Therefore, it can be concluded that no excessive sodlum pentaborato precipitation occurs when the SLCS solution is maintained at the current TS maximum allowablo limits (130*F and'28.5 weight-percent).
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1 09102264/SNh1CFLR - 10
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k S_CS P! PING LAYOUT ~
1.5" s"
PUMP A 2'
17' 14" i
1.5" 1.5" 3"
12' a
~
62' 71' 3'
i SLCS 2"
1.5" g s
PUMP B 2'
13' I
i HPCS DISCHARGE PIPE CONTAINMENT DRYWELL
- NOT DRAWN TO SCALE Figure 1