ML19093A965
| ML19093A965 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/14/1978 |
| From: | Stallings C Virginia Electric & Power Co (VEPCO) |
| To: | Case E Office of Nuclear Reactor Regulation |
| References | |
| Download: ML19093A965 (14) | |
Text
RICHMOND,VIRGINIA 23261 April 14,. 1978:
- Mr. Edson G. Case, Acting Director Nuclear Reactor Regulation U. S. Nuclear Regulatory Connnission Washington, D. C.
20555 Attention:
Mr. Albert Schwencer, Chief Operating Reactors Branch 1
Dear Mr. Case:
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Serial No. 069A/Ol:fP78 PO&M/ ALH: das Docket Nos. 50~280 50-281 License Nos. DPR-32 DPR-37
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We submitted a letter to you on March 16, 1978 stating that certain infor-mation would be provided regarding our November 22, 1977 submittal for the per-manent solution of the low head safety injection and recirculation spray pumps net positive suction head problems.
We are still working with our A-E to pro-vide responses to all of your requests.
Responses to requests 1.0, 3.0, 9.0 and 12.0 are attached.
We will continue to forward responses to the remainder of your requests as the information becomes available.
Attachment cc:
Mr. J.P. O'Reilly
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RESPONSES FOR NRC REQUEST FOR ADDITION!,L INFORMATION SURRY POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-280/281 Attachment Request 1.0 Describe and justify. the analytical procedure used *to conservatively determine the maximum containment second peak pressure and maximum containment third peak pressure, respectively, for a spectrum of postulated cold leg breaks.
Response
The analytical procedure used to conservatively determine.the maximum containment second and third *peak pressures is that portion of the LOCTIC computer program dealing with mass and energy release rates.
A complete discussion of the method used for this calculation is presented in our response to question 8.0 and 8.1.
Additional conservatism has been applied to this method to maximize second and third peak pressures as listed below.
The c*ontainment second peak pressure is *maximized using the fallowing assumptions:
- 1.
Conservatively high mass and energy release rates calculated as indicated in response to questions 8.0.and 8.1
- 2.
The Tagami condensing coefficient discussed in response to question 3.1 that underestbnates condensing heat transfer
- 3.
The maximum air partial pressure allowed by the technical specifica-tion_ with maximum initial dry bulb and dew point temperature.
Maxi-mum initial dry bulb temperature minimizes the effectiveness of the heat sinks, and maximum initial dew point maximizes the initial total pressure.
- 4.
Use of Minimum ESF - Minimum ESF maxL~izes the release rates and mini-mizes quench spray flow.
The containment third peak pressure *is maximized using the following assumptions:
- 1.
Conservatively high mass and energy releases rates calculated as indicated in response to questions 8.0 and 8.1
- 2.
The maximum air partial pressure allowed by the technical specifica-tion with the minimum allowable dry bu;l.b temperature at 100 percent relative humidity.
The min~mum dry bulb temperature maximizes the containment air mass, and the 100 percent relative humidity assump-tion maximizes the inital total containment pressure.
- 3.
Use of Minimum ESF - Table 8 of Reference 1--1 demonstrates that Mini-mum ESF is the single failure assumption the maximizes the third peak, Reference 1-1 NPSH Report - Surry 1 & 2, forwarded to Mr. Edson G. Case, Acting Director of Nuclear Reactor Regulation, US NRC from Mr. C. M. Stallings, Vice Pre-sident - Power Supply and Production Operations, VEPCO, dated November 22, 1977.
e Request 3.0 For the case which results in the maximum containment second peak pressure and for the case which results in the maximum containment third* peak pressure, pro-vide the following information:
Request 3.1 A discussion of the conservatism in the heat transfer correlations used to calcu-late the heat transfer _from the containment atmosphere to *the passive heat sinks and vice versa:
Response
The heat transfer coefficient for condensation at surfaces inside the containment structure used in LOCTIC is the Tagami* condensing coefficient (Reference 3-1) and is presented in the following table:
MATERIAL Steel and painted concrete Where:
h t
tp Q
V hstag X
y
=
=
=
=
=
=
=
=
TIME During decom-pression At end of decompres-sion After decom-pression CONDENSING COEFFICIENT h=hmax (_t/tp}
h=hmax
=75 h=hstag + (hmax - hstag Tagami heat transfer coefficient, Btu/hr-sq ft-F time after rupture of primary system, sec time at end of decompression, sec energy released to *containment during decompres-sion, Btu containment free volume, cu ft 2 + 50x, Btu/hr - sq ft - F steam/air mass ratio EXP {-0.05 (t-tp)}
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The use of the Tagami condensing coefficient is very conservative, as exhibited in Figure 3.1-1.
The measured pressure transient was obtained from Test 3 of the Simulated Design* Basis Accident tests o.f the Carolinas Virginia Tube Reactor Containment (Reference 3-22.
The CONTEMPT best estimate calculation using the Uchida condensing coefficient generates a peak pressure 45 percent greater than the measured peak.
The use of the. Tagami condensing coefficient would yield a s:i.rriilar result.
Better agreement with the data is achieved using the TAEH average coefficient.
to calculate the condensing heat transfer.
Figure. JB of* Reference 3-2* indicates that the TAEH average coefficie*nt is four times the Uchida value at the time of peak pressure.
If the heat sink surface temperature is greater than the*dew point temperature, convective heat transfer to the containment atmosphere is calculated using a conservatively high constant heat* transfer coefficient value of 1.8 Btu/hr-ft2F.
It is conservative to overestimate heat transfer to the containment atmosphere.
This reversal occurs as the containment atmosphere is de.pressuring and approach-ing atmospheric pressure.
The heat transfer is considered as natural convection to air because of the mass energy releases to the containment are relatively small
.at the time (decay heat boil-off).
Kreith(Reference 3-3) recommends, for convecti~B from ve:1:tical plates in the tur-bulent region (Grashoff number greater than 10
) :
h k _0.021 (Gr Pr) 2/ 5 L
Where:
L
=
- height of heat. sink h
=
convective heat transfer coefficient k
=
thermal conductivity Gr
=
Grashoff number*
Pr
=
Prandtl number McAdams (Reference 3-4~ recommends, for free convection from vertical plates for Gr greater than 10, the correlation Nu= 0.13 (G~ Pr)l/3 The properties are evaluated at the mean film tew.perature.
Tl).e Grashoff number is proportional to the temperature difference between the heat sink and the contain-ment atmosphere and also is proportional to the height of the sink cubed.
Figures 3.1-2 and 3.1-3 prese~t sensitivity of the convective heat transfer co-efficient to the heat sink containment atmosphere temperature difference and the heat sink height,. respectively.
The curves demonstrate that, for very conserva-.
tive bounding values, the calculated heat transfer coefficient is about one-half of the value used in LOCTIC (1.8 Btu/hr-ft2F).
References 3-1 Takashi Tagami, "Interim Report on Safety Assessments and Facilities Establishment Project in Japan for Period Ending June, 1965 (No~.1),
February 28, 1966,Section IV.
e 3-2 Schmitt, R.C., et al, "Simulated Design Basis Accident Tests of the CaroJ.j_nas Virginia Tube Reactor Containment -- Final Report."
- r:N-14Q3, December 1970.
3-3 Kreith, F., Principles of Heat Transfer, International Textbook Company
(_1966).
3-4 McAdam, W. H., Heat Transmission, McGraw Hill (_19542.
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Request 9.0 Provide a detailed schematic drawing to show the modifications of the contain-ment recirculation spray system.
Response
See Figure 9.0-1 "Recirculation Spray Pump NPSH Modification"
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Request 12.0 Submit all cavitating venturi sizing calculations.
Describe the flow tests to be performed to verify both the system pressure drop and flow* 1.*ate with the ca-vitating venturi installed.
Response
Sizing of the venturis depends on the desired flow, the corresponding inlet pres-sure to the venturis and the lowest water temperature.
The cavitating venturis were sized for the minimum single pump runout flow condition during the injection phase.
The temperature of* the injected water from the RWST is 40 F to 45 F.
The minimum required runout flow value of 3,249 gpm was selected based upon dis-cussions with Westinghouse concerning the ECCS analysis.
The inlet pressure was determined for an empty RWST.* This means that the inlet pressure and hence the flow rates passed by the venturi will be higher for any other RWS"T level.*
- Thus, a single pump runout flow will_ be always be higher than the minimum required value of 3,249 gpm.
The inlet pressure to the venturi during the injection phase is a function of the.
atmospheric pressure, the elevation difference between the RWST and the venturis, piping system friction pressure loss, and the total dynamic head of the pump.
The friction loss and the pump head are flow dependent.
The system friction loss was fouild using as-built.piping drawings and the results of the*preoperational tests which were performed with the LHSI pumps installed in the system.
The pump head was found from the vendor's certified head flow curve developed from the shop tests.
The results are given in Table 12.0-1.
The venturi performance characteristics are then submitted to the ~anufacturer who determines the physical characteristics of ti1.e venturi.
A shop test to "prove" the sizing of the venturi is then conducted in the manufacturer's test loop.
After installation in the plant a performance test will be _conducted using one LHSI pump in the recirculation mode.
The maximum flow passed by the cavitating venturis depends on the inlet pressure.
Since the venturis are located close to the three branch flow split, each will have the same inlet pressure.
- Hence, only one of the three branches to the reactor coolant system ~ill be tested.
The flow path and instrumentation is sh.own in Fig. 12.0-1, "Installed Cavitating ven-turi Performance Test."
As showri. in the drawing, the safety injection branch line will be cut and.temporary piping will be routed back to the containment sump.
A throttle valve will be* utilized in the temporary piping to vary the downstream pressure.
The parameters that will be measured are the sump water level, the pump flow, the pump 'discharge pressure, the venturi inlet pressure, the pressure downstream of the temporary throttle valve, and the temperature of the.water.
With one LHSI pump running, the throttle valve will be opened in steps until a constant flow*is reached.
The valve will then be opened further to show that the maximum flow passed by the venturi for.a constant inlet pressure does not increas*e with decreasing downstream, pressure.
- -s-e e
The installed cavitating venturi performance will be acceptable if the measured*
maximum flow rate and corresponding venturi inlet pressure are within the respec-tive ranges predicted for the test conditions.
The predicted ranges depend upon conservatively high and low values for the system friction pressure loss and for*
the total dynamic head of the pump.
Table 12.0-1 e
CAVITATING VENTURI SIZING I)
Design Flow Total Flow Flow per venturi (1/3 Total)
II)
Design Vapor Pressure For RWST.at 40-45F III) Design Inlet Pressure A)
B)
C)
D)
E)
Atmospheric pressure Friction loss at design flow Pump head at design flow Elevation of RWST above venturis Intet pressure (_A+B+C+D) 3249 gpm 1083 gpm 0.3 ft 33.9 ft 88.7 ft 226.0 ft 42.8 ft 214.0 ft
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