ML19282C183
| ML19282C183 | |
| Person / Time | |
|---|---|
| Issue date: | 03/12/1979 |
| From: | Baer R Office of Nuclear Reactor Regulation |
| To: | Palmer W ECOLAIRE HEAT TRANSFER CO. |
| References | |
| NUDOCS 7903210159 | |
| Download: ML19282C183 (15) | |
Text
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UNITED STATES 3V i
NUCLEAR REGULATORY COMMis5 ION I
WASHINGTON, D. C. 20555
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1q 744ftd1 I2-Mr. William E. Palmer, President Ecolaire Condenser, Inc.
P. O. Box 2327 Lehigh Valley, Penn. 18001
Dear Mr. Palmer:
SUBJECT:
ORIEt1TED SPRAY C00 lit 1G SYSTEM TOPICAL REPORT 100P (TESTIf1G PROGRAM)
In your letter of May ll,1978, you requested our consideration of a number of questions concerning testing of the OSCS for nuclear plant ultimate heat sink service.
Our response to your. questions are presented in Enclosure flo.1.
Relatedly, with regard to meteorological aspects of design we suggest that you consider the techniques suggested in the reprint (Enclosure fio. 2) for scanning the weather record for the most adverse periods of thermal performance and water loss.
We hope that this information will be helpful to you.
Sincerely, d
i Robert L. Baer, Chief Light Water Reactors Branch flo. 2 Division of Project Management
Enclosures:
1.
Responses to Ecolaire Questions 2.
Reprint: " Selection of Design Meteorology for Safety Related Spray Pond Systems", by D. Myers and E. Rabin, Paper presented at AtiS Meeting, Winter 1975.
cc: See attached sheet 7soa216/ff
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RESPONSES TO ECOLAIRE QUESTIONS 0F MAY 11, 1978 HYOR0 LOGIC ENGINEERING SECTION, HMB, DSE General We have review!d your questions and concerns. In response, we suggest that your study simulate, as closely as possible, actual performance of the Oriented Spray Cooling System (OSCS) in the critical role this system would play in the nuclear plant. Any aspect of the simuidtion which is in question should always err in the direction of conservatism.
Specific Responses 1.
The choice of the prototype system is dependent on many variables.
We will not insist on a specific design or heat load, but you must show that the heat loads, operating conditions, cooling capacity and water loss in the system can be applied to an actual ultimate heat sink design under adverse operating conditions. The range of
, test conditions such as flowrates, heat loads and adverse meteoro-logical conditions must confir your predictive model.
't is unlikely that you will experience during your tests the combination of adverse meteorological and operating conditions which consitute the Design Basis of the ultimate heat sink. Therefore, you must show that your predictive model is capable of extrapolatiag 'nto those extreme' ranges of meteorological and operating conditions.
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2.
The factors involve <: in proving that the OSCS will perform as predicted, as outlired in response 1, must be established no matter where your test is conducted. It may be difficult to provide the necessary heat load from a nuclear plant not yet
.s licensed to produce full power. If you can provide the necessary heat load, however, it may be possible.
3.
Performance tests on the prototype will still be necessary.
If the Topical Report is approved, however, it may only be necessary to show that the predictive model of the Topical Report is con-firmed by limited onsite measurements, rather than a full-scale test.
4.
You must document the ability of your model to predict the per-formance if the spray configuration is changed. We have no basis
,for relying on the difference in performance between designs. You must confirm this.
5.
The performance of the whole pond is to be tested. The actual temper-ature returned to the plant and the quantity of drift loss are the variables of importance.
3-6.
The measured variables must adequately describe the performance of the pond. If these var', ables are closely related to per-formance of the entire system, then they should be measured.
The density of measuring instruments should be sufficient to describe the entire system in some 3-dimensional detail.
7.
We believe that many of the phenomer-n involved in water loss events are directly related to elevated temperatures in the cooling facility (e.g., convective currents which may significantly increase drift loss). Without significant added heat the test may be inconclusive.
8.
The purposes of the test would probably best be served by having a relatively constant heat load over the period of test.
It shou;d at least be constant for a period detennined to be long
, compared to the characteristic response time of the system.
9.
The tests are to confirm the applicability of the model, so a wide range of conditions is desirable. You will however, want to find a period of adverse weather to assess the extremes of pond performance.
If the period of your testing happens to fall in moderate weather, you may have to repeat the test during a worse period.
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lb. There is no requirement on the length of your test. A wide range of conditions will be necessary, and may take longer than 30 days, but the test program does not have to be continuous,
- 11. This is probably too short a period to see enough of a change in meteorological conditions. Other measurement programs such as Rancho Seco and North Anna have lasted longer.
- 12. This is up to you. The burden of proof of system perfomance is your responsibility.
- 13. You must basically prove your model's ability to conservatively predict performance. See the response to Ql.
14 Drift loss must also be established.
I believe the test you propose will be adequate for heat rejection performance.
l'
'Yes, if you justify all aspects of the test.
- 16. This seems reasonable, if you provide justification. Visual observations of the test should also be noted to catch any anamolies such as unstable plumes, etc.
- 17. In accordance with good experimental procedures.
- 18. Same as 16.
'19.
A performance test should also measure drift and evaporation, a:
well as seepage for your setup. While you may propose a very conservative relationship for the plant operating license, the
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5-performance test should provide a data base to back up your predictions.
- 20. This is not a correct statement. There are other sources of heat input at a nuc' ear plant such as diesel generators and electrical equipment. A preoperationil test will be necessary -
See the response to Q3.
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SMLECTION OF DESIGN METEOltOLOG Y F O lt SAFET Y RELATED Spit AY POND SYSTEMS D. Myc rs E. Rabin Bechtel Power Cor,. oration San Francisco SUM MA R Y The selection of conservative da-ign meteornlogical conditions is required to verify analytically the ability of a safety related spray pond system to meet its functional requirements. The Nuclear llegulatory Commission provides in Regulatory Guide 1.27 general criteria to be used in selection of design meteorology. Some confusion has existed concerning the application of the general criteria to specific cases, and it is the purpose of this paper to present a technique applicable to spray ponds.
Various selection criteria which have been used for spray ponds are discussed. such as:
1.
Highest average wet bulb temperature (thermal performance) 2.
Lowest dew point depression (thermal performance) 3.
Highest wind speed (water consumption) 4.
Highest dew point depression (water consumption).
A rapid anel yet more realistic technique has been developed which involves the use or a enefficient of performance (COP) anel a coefficient of water consumption (COWC).
Comparison of the results of the COP and COWC method with other selection criteria has shown the methnd to be superior in scicetion of conservative yet realistic design meteorology.
- Paper presented at the 1975 Winter Meeting, American Nuclear Society. Nov.
16 - 21. 19M.
INTRODUCTION In the last few years, spray ponds have been gaining popularity as sources of emergency cooling (Ultimate Heat Sinks) in nuclear power planL. As a result of the importance of this cooling in nuclear plants, various analyses are performed during design and construction of the plant to verify the ability of the spray pond system to meet its functional requirements. Two important functional requirements are an adequate supply of water for cooling and sufficient heat dissipation capability to limit cooling water temperatures.
In order to verify that a particular design meets these two requirements.
conservative design meteorology must be determined for two cases, maximum water loss and minimum heat transfer. The Nuclear Regulatory Commission provides in Regulatory Guide 1. 27 (Ref.1) gene ral criteria to be used in selection of design meteorology. Some confusion has existed concerning the apnlication of the general criteria to acecific cases, and it is the purpose of this paper to p.esent a technique apph.able to spray ponds.
Before considering selection techniques for design meteorology a brief discussion of the meteorological data base is in order. The approach most likely to prove successful in spray pond design is the use of long-term records from the nearest first-order National Weather Service Station.
These records are available from the National Climatic Center in
' Asheville, NC. Care should be exercised to assure that the climatic conditions of the station selected are representative of the site.
SELECTION TECHNIOUE.c; The design meteorological conditic.ns for spray ponds have been determined according to various selection criteria. Over the years improvements have been made in the selection criterir which tend to avoid excessive or in-adequate conservatism. The following criteria have been used in the past:
Se o
-w
a A COP and COWC can be derived for spray ponds by considering heat and mass transfer from a droplet.
T..e cooling of a droplet is due to the combined effect of convection and evaporation as shown in Figure 1.
For the droplet, the evaporation term can be written as O
=k A AC hfg, e
e where k is the mass transfer co-efficient, A is the droplet surface area, c
A C is the concentration difference between the droplet surface and the ambient air, and h the enthalpy of evaporation of water. The convection f
term can be expressed as Q =hA AT, where h is the convective heat C
C C
t ran s fe r coefficient, A is as defined before, and AT is the temperature difference between the droplet surface and the ambient air. The total haat and mass transfer becomes O=O
+Q
=A (h LT + k AC hfg )
(1 )
t c
e e
e In order to evaluate k andh empirical relations are used. For this e
e application the work of Ranz and Marshall (Ref. 2) was used to estimate the Nusselt and She vood numbers, hD
- 2. +0. 6 Re / 2 1/3 1
c Nu =
=
Pr (2) kD e
1/2Sc /3 1
Sh = D
. + 0. 6 R e
=
W v
'where k
the rmal conductivity of moist air
=
D diffusion coefficient for water vapor in air
=
D droplet diameter
=
Re Reynold's number
=
Pr
=
Prandtl number Sc Schmidt number
=
Assumn 6 a sigr convection such that heat and mass transfer into +'a droplet is taken positive, Equations 2 and 3 can be used in Equation }
to yield,
e Water Los s 1.
Maximum 30-day average dew point depression 2.
Maximum monthly average wind speed e
Heat Transfer 1.
Minimum daily average and 30-day averagr dew point depression 2.
Maximum daily average and 30-day average wet bulb tempe ratu re.
The criteria in each category above have in common that only one
.rateorological parameter is considered.
It is not precise to consider only one parameter since wind speed, wet bulb temperature, and relative humidity are all important parameters in spray pond performance and water consumption. We have found that less conservative conditions often result when only parameter is considered. Obviously one could synthesize conservative meteorology from the results of worsi case one parameter anatyses, but the conditions would be unrealistically conservative.
,A rapid and yet more realistic technique has been developed which involves the use of a' coefficient of performance (COP) and a coefficient of water consumption (COWC).
The coefficient of performance is a parameter whose value is proportional to the rate of change of spray dropict tem-perature considering convection and heat loss due to evaporation. The coefficient of water consumption is proportional to the water consumption rate, considering both evaporation and drift loss. Both coefficients require as input a given set of meteorological conditions (wind speed, wet bulb temperature, and relative humidity or dry bulb temperature) before
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a value can be assigned.
+h.-
D h(g 1/2 0 = A ( k (2+0. 6Re /2 1
Pr / 3) AT -
1 Sc /3 1
v (2 t 0. 6 Re
) AC)
(4) t D
D The relation above (COP) can be used to assign relative performance values to sets of meteorological conditions.
For water loss, the COP must be modified to include the effects of drift loss.
Drift loss from spray ponds is the translation of spray droplets by wind induced drag forces. While spray ponds are designed to minimize drift loss, losses on the order of a few tenths of a percent of the flow rate are not uncommon. Drift loss fraction can be expressed as a function of wind speed as shown in Figure 2 for a typical case.
Using the drift loss dependence on wind speed and the evaporation term from the COP, a COWC can be derived:
ND A v
1/2 1/3) AC + F COWC =
e c
D d
where N = number of droplets in the air at given time F *
"" " E "
d
$1 = nozzle flow rate COMPARISON OF SELECTION CRITERIA To illustrate the merit of the COP technique, a National Weather Service station was chosen and 26 years of data were analyzed using each of the criteria described above. The worst day fr,r heat transfer and the worst 30 days for water consumption were determined using each criterion above in the following manner. Daily average values of the criteria pa rameter, e. g., dew point depression, wet bulb temperatures, were obtained by summing the hourly values and dividing by the number of values per day. Daily wind speed averages are Root-Mean-Square averages.
Daily COP and COWC values were obtained from Equation 4 and S using daily average values of dry bulb, wet bulb, and wind speed.
The daily average values of each criteria parameter for the entire period of record were searched to locate the worst day. Running averages are used to determine the worst 30-day periods.
For.the various criteria the meteorological conditions for the worst day for heat transfer and the worst 30 days for water consumption are given in Table 1.
In order to evaluate the relative severity of the conditions, the cooling range of a spray pond was calculated for each of the heat transfer sets of meteorological parameters, and the water consumption rate was estimated for each of the water loss sets of conditions. The results are also given in Table 1 and indicate that the COP-COWC criterion is superior in selection ef conservative design meteorology for safety related spray ponds, while at the same time avoiding unrealistic cons e rvati s m.
The COP-COWC technique may be generalized to apply to any type of ultimate heat sink. All that is. required is that a coefficient be derived to represent the response of the particular type of ultimate heat sink to meteorological conditions.
REFERENCES 1.
U.S. Nuclear Regulatory Commission, Regulato ry Guide 1. 27, Revision 1, March 1974.
2.
Ranz, W.
E. and Marshall, W. R., J r.. "Evapo ration From D rop s," Chem. Enc. P rog., M, 173 (1952).
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TAI 1LE I COMPARISON OF SELECTION CRITERIA A.
' Thermal Performance Selection Meteorological Cooling Criteria Conditions o Range.
F Maximum Wet Bulb Temperature t 76.1/96.2/8.5 11.O Minimum Dew Point i
Depression 69.5/70.7/5.I 11.6 i
COP 75.9/86.3/2.7
- 9. 3 B.
Water Consumption Selection Meteorological Consumption Criteria Ce ndition s Rat e. gom Maximum Dew Point t
53.6/78.3/8.2 47.4 Depression Maximum Wind Speed t 69.3/96.1/9.4 45.O COWC i 54.4/77.5/9.0 48.3 Wet flulb Temperatu re, "F/ l)ry llulb Teinpe rat ii re, "V / Wi n<l Speerl, mph t
Daily ave rage for the rmal pe rfrirmance, in-clay.ive rage fo r water consumption
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em
Oc T,C DROPLET a
a I
V T
WIND d
e C;
F Figure 1.
Heat and Mass Transfer from a Droplet e
-4
-w
-e 0.03 2
9s U<
0.02 eu.
$0)
Hu.
0.01 E
O O
^
O 5
10 15 20 25 30 WIND SI'EED, MPH 0
Figure 2.
Drift Loss ar. a Function of Wind Speed N+
mm