ML20199K500
| ML20199K500 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 01/29/1998 |
| From: | Sepp H WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20070L384 | List: |
| References | |
| AW-98-1200, NUDOCS 9802060198 | |
| Download: ML20199K500 (18) | |
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Westinghouse Energy Systems
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,,,3,33 Electric Corporation AW 981200
.anuary 29,1998 Document Control Desk i
U.S. Nuclear Regulatory Commission Washington, DC 20555 A'ITENTION:
MR. T. R. QUAY APPLICATION FOR WITilllOLDING PROPRIETARY i
INFORMATION FROM PUllLIC DISCLOSURE SUlijECT:
RESPONSES TO FOLLOWON QUESTIONS REGARDING Tile AP600 TEST AND ANALYSIS PROGRAM - OSU FDR AND TAR
Dear Mr. Quay:
The application for withholding is submitted by Westinghouse Electric Company, a division of CBS Corporation (" Westinghouse"), persuant to the provisions of ;.aragraph (b)(1) of Section 2.790 of the Commission's regulations. It contains commercial strategic information proprietary to Westinghouse and customarily held in confidence.
The proprietary material for which withholding is being requested is identified in the proprietary version of the subject report. in conformance with 10CFR Section 2.790, Affidavit AW 981200 accompanies this application for withholding setting forth the basis on which the identified proprietary information may be withheld from public disclosure.
Accordingly, it is respectfully requested that the subject information which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10CFR Section 2.790 of the Commission's regulations.
Correspondence with respect to this application for withhciding or the accompanying affidavit should reference AW-981200 and should be addressed to the undersigned.
Very truly yours, llenry 5 Se p, er Regulatory and Licensing Engineering jml cc:. Kevin Bohrer NRC OWFN MS 12E20
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AITIDAVE COMMONWi!Al.Til OF PliNNSYINANI A:
ss COUNTY OF Al.lfGill!NY:
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liefore me, the undersigned authority, personally appeared llenry A. S ffidavit on behalf duly sworn according to law, deposes and says that he is authorized i
of Westinghouse fileeirie Company, a division of CilS Corporat on hbt f his knowledge, averments of fact set forth in this Affidavit are true and correct to t e es information, and belief:
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llenry A.hepp, Man (ger llegulatory and 1.icensing Engineering Sworn to and subscribed e this gd day befor of u __. r
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AW 981200 AFI'IDAVIT l
i COMMONWEALTil OF PENNSYLVANIA:
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t COUN'iY OF All.EGilENY:
1 Before me, the undersigned authority, personally appeared llenry A. Sepp, who, being by me duly sworn according to law, deposes and says that he is authorized to execute this Affidavit on behalf of Weeinghouse Electric Company, a division of CBS Corporation (" Westinghouse"), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge, information, and belief:
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y llemy A. Sepp, Manhger Regulatory and Licensing Engincering Sworn to and subscribed
- befor e this M9M day of h uar.#'
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1 AW.981200 (1)
I am Manager, Regulatory and Licensing lingineering, in the Nuclear Services Division, of the Westinghouse filectric Company, a division of CilS Corporation (" Westinghouse"), and as such, I have been speci0cally delegated the function of reviewing the proprietary infonnation sought to be withheld from public disclosure in connection with nuclear power plant licensing and rulemaking proceedings, and am authorized to apply for its withholdinF on behalf of the Westinghouse linergy Systems ilusiness Unit.
(2)
I am making this Af0 davit in conformance with the provirions of 10CFR Section 2,790 of the Commission't, regulations and in conjunction with the Westinghouse application for withholding accompanying this Af0 davit.
(3)
I have personal knowledge of the criteria and procedures utillied by the Westinghouse linergy Systems ilusiness Unit in designating information as a trade secret, privileged or as con 0dential commercial or Gnancial information.
(4)
Pursuant to the provisions of paragraph (b)(4) of Section 2.790 of the Commission's regulations, the following is furnished for consideration by the Commission in duermining whether the information sought to be withheld from public disclosure should be withheld.
(i)
The information sought to be withheld from public disclesure is owned and has been held in con 0dence by Westinghouse.
(ii)
The information is of a type customarily held in confidence by Westinghouse and not customarily disclos d to the public. Westinghouse has a rational basis for determining the types of information customarily held in con 0dence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of informatier in con 0dence. The application of that system and the substance of that system constitutes Westinghouse policy and provides the rational basis required.
Under that system, information is held in conGdence if it falls in one or more of l
several types, the release of which might result in the loss of an existing or potential l
competitive advantage, as follows:
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AW 981200 j
i (a)
'the information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other comp:1ies.
(b)
It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage, e.g., by optimization or improved marketability.
(c)
Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurar.ce of quality, or licensing a similar product.
(d)
It reveals cost or price infore ation, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.
(e)
It reveais aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to
".'.'stinghousC.
(f)
It contains patentable ideas, for which patent protection may be desirable.
There are sound policy reasons behind the Westinghouse system which include the following:
(a)
The use of such information by Westinghouse gives Westinghouse a competitive advantage over its competitors. it is, therefore, withheld from disclosure to protect the Westinghouse co'.ipetitive position.
l (b)
It is information which is marketable in many ways. The exter.t to which such l
I information is available to compet ' ors aiminishes the Westinghouse ability to 1
sell products and services involving the use of the information.
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(c)
Use by our competitor would put Westinghouse at a competitive disadvantage by reducing his expenditure of resources at our expense, j
(d)
Each component of proprietary information pertinent to a particular j
competitive advantage is potentially as valuable as the total competitive advantage, if competitors acquire components of proprietary information, any one component may be the key to the entire pui21e, thereby depriving Westinghouse of a competitive advantage.
(e)
Unrestricted disclosure would jeopardize the position of prominence of Westinghouse in the world market, and thereby give a market advantage to the competition of those countries.
(f)
The Westinghouse capacity to invest corporate assets in research and development depends upon the success in obtaining and maintaining a competitive advantage.
(iii)
The information is being transmitted to the Commission in confidence and, under the provisions of 10CI R Section 2,790, it is to be received in confidence by the Commission.
(iv)
The information sought to be protected is not available in public sources or available information has not been previously employed in the same original manner or method to the best of our knowledge and belief.
(v)
Enclosed is Letter DCP/NRCl234 (NSD NRC-98-5545), January 29,1998, being transmitted by Westinghouse Electric Company QV), a division of CilS Corporation
(" Westinghouse"), letter and Application for Withholding Proprietary Information from Public Disclosure, Ilrian A. hiclntyre (3V), to hir. T. R. Quay, Office of NRR. The proprietary information as submitted for use by Westinghouse Electric Company is in response to questions concerning the AP600 plant and the associated design certification application and is expected to be applicable in other licensee submittals in response to certain NRC requirements for justification of licensing advanced nuclear power plant designs.
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This information is past of that which will enable Westinghouse to:
(a)
Demonstrate the design and safety of the AP690 Passive Safety Systems.
(b) listablish applicable verification testing methods.
(c)
Design Advanced Nuclear Power Plants that meet NRC requirements.
(d)
IIstablish technical and licensing approaches for the AP600 that will ultimately result in a certified design.
(c)
Assist customers in obtaining NRC approval for future plants.
1 urther this information has sub.;tantial commercial value as follows:
(a)
Westinghouse plans to sell the use of similar information to its customers for purposes of meeting NRC requirements for advanced plant licenses.
(b)
Westinghouse can sell support and defense of the technology to its customers in the licensing process.
Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar advanced nuclear power designs and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information woulJ enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.
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o The development of the technology described in part by the informati(n is the result of applying the results of many years of experience in an intensive Westmghouse effort and the expenditure of a considerable sum of money.
In order for competitors of Westinghouse to duplicate this information, similar technleal programs would h,vc to be performed and a significant manpower elTort, having the requisite talent and experience, would I. ave to be expended for developing analytical methods and receiving NHC approval for those methods.
l'urther the deponent nyeth not.
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4e d' to Westinghouse 1etter DCI'/NHCl234 January 29.1998 Westinghouse Non l'roprietary IkNS$h
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r NRC REQUEST FOR ADDITIONAL INFORMA710N A
Question 440.573 (Revision 1)
Original NRC RAI:
Re: Prei,entation of data for Test SB18 in Section 5.l.2 of the OSU FDR.
In cornparmg Test Sill 9 to S1118:
Why is the transition from recirculation from draining in the Ch1Ts later in SB19 than in Sul8?
a.
b, is there a systematic explanation for differences in core levels and timing of events during the initial depressuritation phase?
c.
Why are the break flows higher in SB19 for the first 400 seconds?
If the differences are asenbed to the simulation of an elevated containment backpressure in SB19, provide a detailed explanation of the ways in which the contamment pressure influences early phase reactor / safety systems performance. It is not clear how the containment pressure is
- felt" by the RCS, since, for instance, critical now out the break and ADS valves should be insensitive to the ambient pressure. In addition, the discussion should address possible influences of the I;Ahts upon RCS response;i.e.,if the behavior noted in the OSU facility is in part related to that aspect of the loop design.
Original Westinghouse Response:
De difference in observed system performanc is attributed to simulating an increase in containment backpressure.
The mcrease in simulated containment backpressure results in the following; a.
One affect of the increased containment backpressure was to delay the draining of the Ch1T CLDLs in Test SB19 relative to their behavior observed for S818. Thus, the ChtTs did not begin to drain as early for test Sil19 as for test SB18. From Figure 5.1.3 9,it is noted that the general behavior of the draining remains the same between the two tests; that is, the CLBL nearest the break drains earliest, allowing its associated Ch1T to begin to also drain.
b.
ne observed differences in core levels and timing of events between test SB19 and SBl8 are the result of differences in the local pressure in the core region that are driven by the effects of a higher containment backpressure simulated for Test 5819. Specifically, the saturation temperature for SB19 is higher than that for test SBIR and the energy input to the working Guid from the core simulation is the same for tests SB19 and SB18. Dus, after the initial blowdown,it is expected that phenomena driven by boiling of core coolant will occur later in test SB19 than in test SRl8.
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NRC REQUEST FOR ADDITIONAL INFORMATION j
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He higher containment backpressure simulated in test SB19 is applied to the break separator. The quality l
c.
of break Dow is dependant upon its discharge backpressure. As the pressure in the break separator is higher l
for test SB19 than for test SBl8, the quality of the break flow for SB19 is lower that for 5B18. nus, for the same pressure drop across the break, a larger amount of liquid is discharged from the break early in test SB19 than for test SB18.
1 Additional NRC Comments / Questions on Original Westinghouse Response:
ne rationale (part (a) is still not clear. Why should backpressure have any significant ianpact early in the transient, when How is critical and (presumably) largely independent of backpressure? (Note: the Westinghouse response does not explain the behavior; it merely restates the question and attnbutes it to backpressure with no specific justificar'
he same question applies to part (b): granted that the saturation temperature at containment pressure ishigF tr, as long as the primary system pressure is greater than containment pressure, what is happening ins' s.id not significantly innuenced by the containment conditions (except at the interface, if the flow is noi.
e and the question specifically referred to the initial depressurization phase, when the primary pressure is still well above containment pressure. In addition, if the explanation in part (c) c' Ae (original] response is correct, and the liquid break Dow is higher for SB19, this would appear to decrease prit.a/ system inventory more rapidly and lead to an cather transition to CMT draining, rather that a later transition as observed in the test. And if containment pressure really innuenced early in vessel behavior, a lower containment pressure (SB18) would cause a higher ed fraction for the same quality, increasing the mixture levelit; the vessel, and presumably promoting the continuation oi := circulation, again the opposite of what was observed, i
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Supplemental Westinghouse Response to Additional NRC Comments / Questions:
Os erview A more detailed evaluation of OSU test SB19 and a comparison to OSU test SBl8 has been performed. Both tests i
were of a 2 inch break in the bottom of the cold leg (CL3) and assumed the same single failure of one ADS stage 4 valve to open. He,two tests were conducted with the same initial conditions and used the same actuation logic.
ne only intended difference in the two tests was the Break and ADS Measurement System (B AMS) was allowed to pressurite in SB19, in order to simulate the backpressure that would occur as a result of containment pressuritation
(
-in the AP600, his evaluation focuses on the early depressurization phase, the natural circulation phase, and initiation of ADS stages 1, 2 and 3.
For both tests, this encompasses the time teriod from the initiation of the break until approximately (
l'" seconds, when the ADS I actuation signal occurs. Figures 440.5731 and 440.573 2 (Figures 5.2.1 1 and 5.10.1 1 of the OSU Test and Analysis Report (TAR)) illustrate the phases of each test transient M0.573RI 2 T Westingtlouse l
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t' NRC REQUEST FOR ADDITIONAL INFORMATION A
for 51118 and Sil19, respectively. For each test, the initial depressuritation or blowdown phase ends at about 100 scconds and natural circulation occurs from [
l'** to about [
]* * ' seconds. The primary system pressure during the n*tural circulation phase is constant at about [
l'" psia, how ever, the pressure begins to f all rather in test Sill 9 coincident with the initiation of Core Makeup Tank (CMT) drai own.
CMT performance ne RAI questions focus on the performance of the CMTs in each test, and specifically, the obser ed transition from the recirculation phase to the draindown phase. This phenornena is best illustrated in Figures 440.573 3 and 440.573 4 (Figures 5.1.2 6 and 5.1.3 6 of the OSU Final Data Report (FDR)) for SB18 and SDl9, respectively.
For SBl8, both CMTl and CMT2 st.ow their respective balance lines drain and the CMT levels begin to fall at about(
)*" seconds. Intermittent filling and draining occurs in both cold leg balance lines (CLDLs), until about
[ ]**'second for CMTl and about [
l'" seconds in CMT2, at which time both CMTs continue to drain. The earlier draining of CMTl may occur since it is connected to CL3, where the break is located, in S1319, the CMTs exhibit a different behavior during this phase of the transient. CMTl shows no indication of CLDL draining and the level of CMTl is constant until about [
l'" seconds, when the balance line drains completely and CMTl transitions to draindown. CMT2 shows some slight drsining of its balance line but not near the amount of filling or draining observed in CMT2 of SBl8. CMT2 clearly transitions from recirculation to draindown at about [ j'" seconds in SB19.
Figures 440.573 5 and 440.573 6 [ Figures 5.1.216 and 5.1.316 of the FDR) confirm the CMT behavior in each test. The recirculation Dows are the same, about [ l'" gpm during recirculation, and increase to about [ ]'*'spm when draindown occurs.
The mitiation of CMT draindown can be caused be either Dashing in the top of the CMT as recirculating Guid heats the water in the top of the CMT and pressure is falling or due to uncoscring of the CLBL as the duid level in the cold leg falls due to loss of coolant inventory.
CMT Fluid Temperatures Fluid temperatures in CMTl are shown in Figues 440.573 7 and 440.573 8 (Time expanded plots of Figures 5.1.2. 80 and 5.1.3 80 of the FDR) for 5818 a,id SB19 respectively.
Note that the saturation temperatures for,both tests are the same for the first [
)*" seconds.
For SB 18, the uppermost Guid thermocouple. TF-529. " jumps" to saturation temperature at about [
)*" seconds.
His indicates steam in the top of the CMT and coincides with the initiation of CMT draining for this test SB19 exhibits the same behavior, but at a later time. Fluid thermocouple 17 529 " jumps" to saturation temperature at about [
l'" seconds, again indicating steam in the top of CMT). Rese plots confirm the earlier initiation of CMT draindown in SBl8, but do not indicate if Cashing or uncovering of the CLBL are the primary mechanism for the start of draindown.
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NRC REQUEST FOR ADDITIONAL INFORMATION 4
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Another difference is the fluid temperature at the top of CMTl at time 0, when the break occurs. CMTl is hotter in SBl8, at abaut [
l'" versus about l
)*" in SB19, and the heatup in SBl8 is (
l'" w hile there is a [
l'" second delay in the heatup of CMTl in SB19.
1 CLDL Performance Rt. collapsed liquid level in the downcomer is shown in Figures 440.573 9 and 440.573 10 (Figures 5.2. 42 and l
5.10-42 of the TAR) for SBl8 and SB19 respectively. The level during the early phases of the transient are very similar. The collapsed level in th downcomer is [
l*" the top of the CL (71.3*) during the blowdown phase and falls to the [
l'" of the CL at about [
]'" seconds in both tests. De downcomer collapsed level remains at the [
J'" of the CL until [
]*" seconds when it falls [
l'" of the CL (67,7").
ne mass of liquid and vapor in the CLs is shown in Figures 440.$7311 & 12, and 440.57313 & 14
{ Figures 5.2-60 & 61, and 5.10 60 & 61 ) in the TAR for Sal 8 and SB19, respectively. De mass of liquid and vapor liquid in CL3 for both tests are comparable over the first [
l'" seconds of the transient. Steam first
- appears at about [
l'" seconds in the CLs, however, about [
l'" the mass of steam is in CL3 as in the other CLs.
%c test data (downcomer level and CL vapor mass) indicates steam is present in CL3 after [
]'" seconds, which would allow the CLDL to begin to drain af ter that time. However, the heatup of the CMTl fluid is clearly different i
in each test, with SB19 having a delayed heatup and later draindown than 5B18, Initial Conditions To verify the test conditions were identical, Tables 5.1.21 and Tables 5.1.2 2 of the FDR, Initial Conditions for SBl8 and SB19, respectively, were co npared. Inital conditions for both tests were within acceptable limits.
The actual initial conditions were further compared to see if there were any notable differences, especially with regard to initial temperatures and pressuriter level, which could affect the initial primary system mass calculations.
Only one notable difference was detected. For SB18, the initial temperatures for thermocouple TF 529 in CMTl for SBl8 is recorded as [
l'" while CMT2 is [ j'" For SB19, CMTl and CMT2 initial temperatures are I
l'" and [
l'", respectively, for the same thermocouple. Rese readings, while within specifications, again indicate CMTl was hotter in SBl8 prior to the start of the test, i
Mass inventory Fesures 440.57315 and 440.57316 (Figures 5.l.2 62 and 5.1.3 62 from the FDR) show the break liquid and vapor volumetric flow rates for SBl8 and SB19, respectively. During the first [
l'" seconds of the transient the break liquid flows are higher for SB19 but the break vapor flows are higher for SB18. Since CMT injection also differs between the tests, but the collapsed liquid level is the same, an examination of total mass inventory during the initial phases of the two tests would indicate whether there was a net difference.
440.573RI 4 3 Westingttoute
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i Figures 440.57317 and 440.57318 (Time reduced plots of Figures 5.2.3 47 and 5.3.10-47 of the TAR) show the total mass inventory for each test. These plots show the first 1000 seconds of the trknsient. Comparison of the two plots show that 5H18 and SB19 hase similar mass inventories for the first [
l"' seconds of the transient. SB19 falls at a slightly higher rate between !
J seconds but by [
] seconds the difference in total mass in the
]
primary system is only about [
l'** lbm out of approximately [
j'** lbm, or [
)**' difference.
Boundary Conditior s The BAMS was allowed to pressurire during the transient for Figures 440.573-19 and 440.573-20
{ Figures 5.1.2 74 and 5.1.3 74) from the FDR show the BAHS
.tre as a fur ction of time. At the initiation of the test, the B AMS experiences a small pressure spike of about t l**' psia in the first [
)*** seconds of each test. For SBl8, the BAMS pressure then reduces to a steady value o.
ss than [
]**' psig. However, fo. au n y, l
the B AMS pressure increases to [
1**' psig at a linear rate over the f.ut [
l'*' seconds of the transient.
Conclusions The comparison of tests 5B18 and SB19 show that for the first 400 seconds of the transients, the tests are very similar with the exception of the transition of the CMTs from recirculation to draindown and in the volumeuic flow tates out of the break.
De difference in the CMT transition times result in ADS 1,2 and 3 actuations [
l'** seconds later in SB19 when compared to SB18. This difference occurs because ofintermittent draining of the CLBL for CMTl in SB18 allowing higher injection rates earlier in the transient and thereby reaching the CMT low level setpoint sooner. CMT2 contnbutes to the higher injection rate in SBl8 but to a lesser extent than CMTI.
A possible cause of this cather injection may be related to the higher initial temperature of CMTl in SBl8. The top of CMTl is clearly warmer and reaches saturation temperature much sooner in SB18, thereby allowing the CLBL to drain and steam to enter CMTl from the CLBL.
Although, the liquid break flew rate is higher in SB19, the net effect is the primary mass inventory during the first
[
l'** seconds is sery much the same in both tests. The higher break flow in SB19 appears to be offset by higher injection flows, e.g.., pressurizer drainmg. steam generator draining and CMT recirculation, resulting in similar downcomer levels and primary mass insentories early in the transient. The quality of the break flows is different between the two tests, with the vapor content of the break being higher in SBl8 than in SB19. This is probably the only effect the B AMS backpressure has on the test results early in the transient.
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Revised Westinghouse Responses to Additional NRC Ouestions/ Comments a) A review of the test data for the first 400 seconds of SBl8 and SB19 dus not indicate any major effect of the B AMS backpressure on test performance. As noted, the primary system respotse is very similar in both tests, with the exception of the CMT transition times from recirculation to draindown..t is postulated this difference is due to the initial higher temperature of CMTl in SBl8 which allows the Duld in the top of CMTl to reach saturation and initiate draindown sooner and is not an affect of the BAMS back essure.
b) Downcomer levels and primary mass inventories are very similar in ho S tests. The reactor vessel inventory and the core do sa not appear to be tifected by the B AMS backpressure. The s;..n pressure and saturation conditions are the same in both tests during the blowdown and natural circulation phases.
c) ne measured liquid break Dow is higher in SB19, but the quality of the break is different in the two tests, with measured steam Dow rates generally higher in SB18. However, the net effect on primary mass inventory is small between the two tests, which indicates the overall rnass How out the break for each test is similar.
In summary, backpressure in the BAHS does not appear to have induenced the core inventory or the CMT recirculation to draindown transition. Differences in the CMT performance appears to be attributable to the CMTl initial temperature difference, while within test specifications.
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NRC REQUEST FOR ADDITIONAL INFORMATION Figure 440.5731 through 1
Figure 440.573 20 are Westinghouse Proprietary Class 2 code a, h, e r
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Question 440.575 (Revision 1) i
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Original NRC rat:
Re: OSU TAR i
Two
- issues" are identified concerning the wre fluid thermocouples in Section 4.11 but no subsequent analysis or explanation of the issues is provided. Specifically, a.
Ilow did the Guid temperature histories at the center and perimeter differ?
b.
De "bes: average core temperature" is asserted to be represented by the center-rod temperatures, without quantitative justification. Why is this procedure preferable to a weighted average of the core a
and perimeter rods?
Origina# Westinghouse Response:
a.
Thermocouples at the periphery or perimeter of the heater rod bundle were lower than those measured at the center of the rod bundle by about 1015 degrees as the test pre 3ressed into the long term cooling portion of 'he transient, j
De attached Iwo time history plots [ Figures 440.57.41 and 440.575 2] of heater rod thermocouple data from test SB 18 illustrate the difference between measurements taken at the bundle center and the bundle periphery. Rod H1103 is near the bundle center and Rod B2 503 is at the bundle periphery, Two thermocouples were chosen for this illustration, both are at the 46.13 inch elevation.
ne first plot (Figure 440.5251] shows that duritig the initial cooldown of the transient, the two thermocouples behave in a very similar manner. After about 600 seconds into the transient, a temperature difference between the center and the periphery quickly deselops and maintains itself over the transient.
i ne second plot [ Figure 440.575 2] is an expanded t 'tw of data from the same two thermocouples from 500 seconds to 1000 seconds. From about 600 seconds alter initiation of the transient and beyond, the data of this plot suggest that a temperature difference of about 10 to 15 degrees generally exists between the two thermocouples, b.
De Guid terf crature measurement taken at the center of the rod bundle was used as representative of the core for the following reasons; l)
De radial power profile was Dat; that is, each rod received the same power.
2)
The power to Gow ration across the heater rod bundle, escept those at it's periphery, was essentially uniform.
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h nus, for a specific clevation, given a flat radial power profde, a constant power to flow ratio and the open lattice structure of the heater rod bundle, a radially uniform fluid temperature is espected. Although the effect is small, including the penpheral rods provides for conservatisely high steam generativ e stes.
Additional NRC Comments /Ouestions on Original Westinghouse Response:
Why do the center and peripheral temperature histories differ af ter about 600 seconds?
Supplemental Westinghouse Response to Additional NRC Comments / Questions:
The difference between the center (bl 103) and peripheral (D2 503) fluid temperature at the same elevation (46.13") in the heater core does not make an abrupt change at 600 seconds as might be implied by Figure 440.575 2.
Rather this difference can be seen over most of the test and can be shown to vary slowly during the initial transient before attaining a constant valuc of 15"F.
To illustrate this behavior, the temperature difference between the center and penpheral fluid temperature is plotted in Figure 440.575-3 for the entire test. In the long term, the difference is constant at about IST starting from about 500 seconds. De transition to this difference can be seen to occur at the beginning of the test.
To better examine the early portion of the test. Figure 440.575 4 shows the same fluid temperature difference (i.e.. center rod minus peripheral rod at elevation 46.13") for the first 1000 seconds of the test. The fluid temperature difference starts near reto at the initiation of the test, when the break occurs. After a slight positive increase, the periphery of the core becomes somewhat hotter until the difference reaches 157 at about 160 seconds. Then the temperature difference increases to zero at 220 seconds and then slowly increases from iero to IST from 220 seconds to 600 seconds.
Smce the flow distnbution through the core is not known, the behavior of the temperature difference durmg the test can only be surmised. Given that the radial rod power distnbution in OSU is constant and assuming the pumped flow through the core is constant prior to the break, the penphery of the core may hase a shghtly lower fluid temperature due to heat losses through the core barrel into the downcomer, After the break occurs and the flow through the core is no longer forced, the fluid temperature in the periphery may decrease at a slightly lower rate than the cent.er, perhaps due to metal heat input from the reactor vessel.
By 600 seconds, the system has depressurized and core inlet and outlet temperatures are now constant.. The fluid temperatures in the core attain a steady state condition with the center of the core 15T higher than the periphery. Again, this is likely due to heat losses from the periphery through the core barrel into the dow ncomer.
440.575RI 2 3 Westinghouse l
S' NRC REQUEST FOR ADDITIONAL INFORM ATION A
Figure 440.575 1 through Figure 440.575 4 are Westinghouse l'roprietary Class 2 code a, b, c m.s7sm-3 T Westinghouse