ML20091L235
| ML20091L235 | |
| Person / Time | |
|---|---|
| Site: | 05200004 |
| Issue date: | 08/28/1995 |
| From: | Quinn J GENERAL ELECTRIC CO. |
| To: | Quay T NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MFN-126-95, NUDOCS 9508290023 | |
| Download: ML20091L235 (20) | |
Text
GENuclearEnergy Ye C
$16S San Jose. CA 95125-1014 Mk BW air n A en 408 925-1005 (phone) 408 925-3991 (facsimile)
August 28,1995 MFN 126-95 Docket STN 52-004 Document Control Desk U. S. Nuclear Regulatory Commission Attention:
Theodore E. Quay, Director Standardization Project Directorate
Subject:
SHWR - Revised Schedule for TRACG RAIs Q901.75 - Q901.15S
Reference:
- 1. Letter from J. II. Wilson (NRC) to J. E. Quinn (GE), REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING TIIE SIMPLIFIED BOILING WATER REACTOR (SBWR) DESIGN (Q901.75 - Q901.158),
dated May 25,1995.
We are in receipt of the reference letter requesting additional information on the material presented in GE Licensing Topical Report (LTR) NED-32177, TRACG Computer Code Qualification, dated January 1993. We propose to respond to these RAls in two groups; the first group of responses will be provided the end of October,1995, and the remainder will be provided by the end of the year,1995. This schedule reflects the urgency of completing Revision C to the SBWR Test and Analysis Program Description (NED-32391), by August 31, 1995 such that the Staff can issue the DSER this fall. The 901-RAI response schedule also provides reasonable time to incorporate appropriate changes into the update of NED-32177, scheduled to be provided to the Staff in April,1996. The RAI responses will also reflect the discussions held with NRC and BNL to clarify some of the RAls.
I If you have any questions regarding TRACG please contact Bharat Shiralkar of our staff on 408-925-6889.
Sincerely,
/-
g4, Jame
. Quinn
[n q) 9508290023 950828 PDR ADOCK 05200004
(
A PDR
GENuclearEnergy
Attachment:
Status of Responses to RAls 901.75 - 901.158 cc:
P. A. Boehnert (NRC/ACRS) (2 paper copies w/att plus E-Mail w/att)
I. Catton (ACRS)
(1 paper. copy w/att plus E-Mail w/att)
S. Q. Ninh (NRC)
(2 paper copies w/att plus E-Mail w/att)
J. If. Wilson (NRC)
(1 paper copy w/att plus E-Mail w/att) 1 a
1
\\
1 Attachment to MFN 126-95 Status of Responses te RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Cunments The word " Qualification" is used thrdughout the report without ever being 10/31/95 901.75 5/25/95 defined. " Validation" and " Verification" are well defined words. It would appear that " Qualification" is used in place of " Validation.".
Each section of this report should demonstrate by itself, that TRACG has been validated for the specific model(s) cou 3idered in that section. This 10/31/95 901.76 S/25/95 requires a sufficiently detailed description of the experimental data base and the data range,.
The SBWR supplement to this report should consider the GE PIRT results e
n ng, which items must be validated. This systematic approach 10/31/95 901.77 5/25/95 should result in a comprehensive list of models to be validated and should include..
Were all model computations in the Qualification Report done with the same version of the code? State the code versions used. Describe how 10/31/95 901.78 5/25/95 GE proposes to demonstrate that the validations performed in preceding
_ years with.
In most sections of the Qualification Report, the nodalization of the 12/31/95 901.79 5/25/95 relevant TRACG model is described, but generally without justification.
For a meaningful code validation the nodalization should be justified,.
In many cases " good" or " satisfactory" agreement between simulation and experiment is claimed. Such qualitative statements are not adequate. A 12/31/95 901.80 5/25/95 meaningful quantitative comparison is required. This should include the following three steps:
(Section 3.1) The introduction to Section 3 states that the test data used f r qualification of TRACG for the prediction of void fractions cover a wide 10/31/95 901.81 5/25/95 range of flow conditions, pte.. ures, flow rates and inlet subcooling
" assuring..
(Section 3.1) Describe, in detail, the method used for void fraction 10/31/95 901.82 5/25/05 measurements in Sections 3.1.2, 3, and 4, as it can affect the value or weight given to a set of data.
(Section 3.1) No low pressure data are included in Section 3.1. During and after GDCS refill, the reactor vessel will be at pressures significantly 12/31/95 901.83 5/25/95 below the pressure of all the test data provided. Since the vapor-to-liquid density ratio.
(Sections 3.1.2 to 4) Provide additional details concerning the test apparatus and, in particular, about the void fraction measurement method 10/31/95 901.84 5/25/95 for the Christensen, Wilson and Bartolomei, as well as the EBWR data.
(Section 3.1.5) The PSTF Level Swell Tests of Section 3.1.5, refer to the TRACG two-phase level model (Section 3.2.7 of Model Report). The 10/31/95 901.85 5/25l95 definition of a two-phase level requires some arbitrary / reasonable definitions.
e a description of how a two-phase level is 10/31/95 901.86 5/25/95 measured and what it.is compared to.
Page 1
Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 3.2) This section only considers film boiling and core spray heat transfer. In the Model Report, Sections 3.2.9 and 10 consider interfacial 12/31/95 901.87 5/25/95 and wall heat transfer with many more heat transfer regimes. For interfacial heat transfer,.
Section 3.2.1) The film boiling evaluations of Section 3.2.1 state that THTF pressures are significantly higher than those of BWR transients.
10/31/95 901'88 5/25/95 What are the THTF pressures and how much are the correlations affected by the differences between.
j (Section 3.2.1) These high pressure data cannot be applied for code validation of film boiling after depressurization (i.e. In the range of about 2 12/31/95 901.89 5/25/95 bar), as would be required if the core were ever uncovered. Provide a justification for.
(Section 3.2.1) What is the sensitivity of the film boiling heat transfer to the given rod temperature data (i.e., what error in film heat transfer rates 10/31/95 901.90 5/25/95 would induce what error in rod temperatures), which clearly lag in response due to.
(Section 3.3) The comparison of TRACG code predictions against test 12/31/95 901.91 5/25/95 data from the CSHT facility is specific to ECCS liquid coolant entering the fuel bundles, which is not of interest in SBWRs. However,.
(Section 3.3) The descriptions of the tests and the model are inadequate.
in particular, a detailed description of Figures 3.3-3 and 3.3-4 is required 10/31/95 901'92 5/25/95 to permit a reader to follow the results. Provide additional explanation and description of.
(Section 3.4.1.3) Evaluate the effect of using heat slabs over the time 12/31/95 901.93 5/25/95 period of 50 to 60 s. Was this effect quantitatively evaluated, or is the last sentence of this sectbn conjecture?
(Section 3 5) This section assesses TRACG's capability to predict tube bundle pressure drops in the range of operating conditions (mass flow 12/31/95 901.94 5/25/95 range of test data - 140 to 2,040 kg/m2s; average full power mass flux
~1,020 kg/m2s). However,.
(Section 3.6.1) This section refers to "five rod groups" and to the rod that first showed BT being treated as a separate group. This description is 10/31/95 901.95 5/25/95 unclear. Is a sub-channel analysis being applied here, with a separation into five groups?
(Section 3.6.1) Describe the relative location of thermocouples 2 through 6 in Figure 3.6-1. They are apparently allin the upper section of the 10/31/95 901.96 5/25/95 bundle, but the response of Tc 4 is flat, while Tc 2 shows the largest oscillation amplitude.
(Section 3.6.*) Fig 3.6-2 is presented as TRACG results for comparison I
with the expuimental results of Figure 3.6-1. However, this figure does 12/31/95 901.97 5/25/95 not really present a validation of the test data, except.
Page 2
_ _ _ _ _ _ _ ~. _ _ _ _ _ _ _ _ _ _ _ _
Attachment to MFN 126-95 4
Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 3.6.2) How was the pressure increased in these tests? Figure 10/31/95 901.98 5/25/95
' ~
- so, why was a prescribed pressure vs. time imposed on the simulation,.
5
)
(Section 3.6.2) The report stated that the TRACG model used here is the i
"same" as for the oscillation tests. However, a different tube bundle was 10/31/95 901.99 5/25/95 used here (GE9 vs. GE11). Provide clarification of this discrepancy.
i l
(Section 3.6.2) A plot of CPR with a scale truncated at 1.0 does not P** * * **
- n f r the comparison of the experiment and the TRACG 12/31/95 901.100 5/25/95 simulation. Prov.de Justification why parameters equivalent to those of i
1 Figure 3.6-3 were not used.
10/31/95 901.101 5/25/95 (Section 3.7) Identify the FRIGG test that was selected.
(Section 3.7) FRIGG experiments that used a pseudo random binary 10/31/95 901.102 5/25/95 signal are available. Provide justification for not using one of those 4
experiments for validation.
(Section 4.2) Provide an explanation for why carryover and carry-under are only reported as functions of inlet quality. Mass flow rates or a related 10/31/95 901.103 5/25/95 parameter, such as stagnation pressure, should be considered as a j
separate, independent parameter.
1 (Section 4.2) The validation presented is in the range of normal operating 8
n nS ea n A n ms 18 88 g In paMcular i
10/31/95 901.104 5/25/95 during an MSLB scenario and during ADS operation, carryover could.
4 (Section 4.4.3) One purpose of the steady state heat transfer test was to eva a e "
e va@ng nhogen mncenkabon and steam Dow rates 12/31/95 901'105 5/25/95 on the PCC heat transfer characteristics". The comparison given does not
)
(Section 4.4.5) The methodology describing how this degradation parameter was established in the experiments is unclear. The text states 10/31/95 901'106 5/25/95 that it was " calculated by measuring the condensate flow rate", which is in itself contradictory.
(Section 5.1.1) The " mixture level" mentioned here is a two-phase level and not a collapsed level. Its progression downward during the test run is 10/31/95 901'107 5/25/95 estimated based on the differential pressure measurements, using the l
taps indicated in Figure 5.1-2....
l (Section 5.1.1) For the TRACG model, Figure 5.1-13 of Section 5.1.2 shows a bundle nodalization using 26 nodes. However, the test data of 10/31/95 901.108 5/25/95 Figures 5.1-3 to 6 are for " Data Nodes" 28 to 31. The results section i
(Section 5.1.1.3) implies.
4 4
Page 3 1
Attachment to MFN 126-95 l
l Status of Responses to RAls 901.75 - 901.158 l
i i
l l
Revised ID or RAI Source or Due Data No.
Date Rec'd NRC Comments (Section 5.i.1) Since this is a natural convection loop, the mass flows through the tube bundle, the bypass region and through the downcomer 10/31/95 901.109 5/25/95 4
should be determined. Are any data for these available, and if so, how do the..
l (Section 5.1.1) The reported void fraction distributions and the average rod temperature data generally show satisfactory agreement between 10/31/95 901.110 5/25/95 experiment and simulation. However, two anomalies should be addref, sed: Why do the TRACG predictions...
(Sect 6n 5.1.2) This section gives a partialjustification of the nodalization.
Under "further subdivisions".., "for more accurate representation," the l
12/31/95 901.111 5/25/95 nodalization of the lower plenum region is discussed. Two axial levels are j
used,...
j (Section 5.1.2) The early disagreement between TRACG break flow predictions and test data in Figure 5.1-19 is well discussed. However, a j
12/31/95 901.112 5/25/95 rationale for the significant underpredction of the break flow between 50 l
and 150 s should be provided.
(Section 5.1.2) For CCFL breakdown times between 90 and 130 s, "n ticeable changes"in upper plenum pressure drop are mentioned on 12/31/95 901.113 5/25/95 l
Page 5-17. In particular for the measurea data, no such changes can De readily identified in Figure 5.1-23.
(Section 5.1.2) Clarify the description and discussion of rod heat-up on Page 5-18. "Little or no heat-up" at the top elevation spplies for the test 12/31/95 901.114 5/25/95 data (when referred to the initial operating temperature) and for the...
l l
(Section 5.1.2.3, pago 5-17) A TRACG " hot rod" model is introduced and described. However, the staff could not find any reference to this " hot rod" j
10/31/95 901.115 5/25/95 modelin the Model Report. A description of this model should be included in the revised Model Peport.
(Section 5.1.3, Figure 5.1-33) Provide an explanation for the test data 12/31/95 901.116 5/25/95 bypass pressure drop spike at about 17 s.
(Section 5.1.4) All references to other sections of this report and to 10/31/95 901.117 5/25/95 references should be reviewed and corrected.
(Section 5.1.4) Various ECC flow rates are here given as fractions of those in previous tests, but the absolute values are not given in either 10/31/95 901.118 5/25/95 place. A table with the relevant flow rates and temperatures should be
. provided.
(Section 5.1.4) Tne text of Section 5.1.4.3, describing Figure 5.1-40 (core inlet flow), refers to unreliable core inlet flow data and states that dynamic 10/31/95 901.119 5/25/95 effects affected the accuracy of the density determination. How is tne test core inlet flow.
(Section 5.1.4) Figure 5.1-45 shows two separate test data traces, 10/31/95 901.120 5/25/95 differing from most other figures with rod temperatures. What is the second (lower) trace? (See also Figures 5.2-20 and 21.)
Page 4
I Attachment to MFN 126-95 l
l Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Sourco or Due Date No.
Date Rec'd NRC Comments (Section 5.1.4) Although no void fraction data were presented with the 10/31/95 901.121 5/2b/95 results of this section, the conclusions of Section
,.4.4 claim good performance of the void distribution models. F.nner,..
(Section 5.2) This report should be free-standin and should demonstrate qualification of the TRACG code. This section contains insufficient detail 10/31/95 901.122 5/25/95 in the description of the test facility and of the TRACG model. No rationale for the selected TRACG.
(Section 5.2.2) The discussion of Figure 5.2-3 states that an attenuation f the depressurization rate at 11.5 s was ot. saved. A slightly lower 12/31/95 901.123 5/25/95 depressurization rate was observed at about 18 s, but not at 11.5 s.
Provide a basis substantiating the.
(Section 5.2.2) Figures 5.2-6 and 7 are claimed to show a " faster 12/31/95 901.124 5/25/95 reduction" of the bypass and bundle inventories for the time period of 40 to 64 s. If DP is accepted as a measure of inventory, then.
(Section 5.3.2) Table 5.3-1 lists the tests to be modeled by TRACG, along w th the rationale for why these tests were selected. Tests B01 and B07 10/31/95 901.125 5/25/95 are both main steam line breaks, however, there is no description of what the difference between.
(Section 5.3.2) Aside from the arrangement of cooling water inventories, there are additional differences between the SBWR design for which GIST 10/31/95 901.126 5/25/95 was built, and the current design. In particular, the reference to ADS components,.
(Sectiom 5.3.4) Table 5.3-1 states that Test 807 (core uncovery and subsequent heat-up) would be the only SBWR-related test where these 10/31/95 901.127 5/25/95 phenomena were observed. However, this was not discussed in the text and.
(Section 5.3.4, Page 5-76) The report states that Figure 5.3-12 shows that test and calculation show onset of GDCS flow within 12 s of each 10/31/95 901.128 5/25/95 other. However, the figure shows at least 70 s (less than 450 s vs. more than 520 s). Explain this discrepancy.
(Section 5.3.4) Figure 5.313 shows some disagreement for the annulus pressure drop between test and predictions during depressurization ( 50 12/31/95 901.129 5/25/95 to 200 s) and, in Figure 5.3-14, the core pressure drop disagrees after GDCS onset. However, (Section 5.3.4) Provide an explantion for why a GDCS flow over-12/31/95 901.130 5/25/95 prediction after calibration against test data can be justified by a test data uncertainty of 10%. Since the test data were used as E. basis, (Section 5.3.4) There are some disagreements in the annulus pressure drop data, in particular in the 50 to 150 s range, and some in the pos!-300 12/31/95 901.131 5/25/95 s range. These should be discussed and quantified to substantiate the subjective conclusion that..
l l
i Page 5 m
Attachment to MFN 126-95 Status of Responses to RAIs 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 5.4.3) The detailed qualitative description of the accident scenario points to the importance of keeping the lower plenum two-phase 12/31/95 901.132 5/25/95 level below the side entry orifices (SEO). However, the results section stated that this was the case.
(Section 5.4.3) The discussion of Figure 5.4-7 is not clear. The figure shows vapor velocities, which tum negative at about 13 s for the 12/31/95 901.133 5/25/95 peripheral bundles, it is not clear how this indicates transition to liquid downflow at about 10 s, and.
(Section 5.4.3) Apparently the SEO pressure drop is not an orifice DP, but a measurement across taps 0.567 m apart. The text description and 12/31/95 901.134 5/25/95 data for Figure 5.4-8 differ. Only at close to 20 s (not 10 s) does the measured pressure difference.
(Section 5.4.3) The calculated pressure drop data of Figures 5.4-8 to 14 12/31/95 901.135 5/25/95 show oscillations of differing frequencies, which are not observed in the test data. Provide a rationale explaining this behavior.
(Sections 5.5.1 & 5.5.2) The description of the facility, the test procedure (aM also ome MG mMel b Secdon 5.5.3M) me adequate, M, h 10/31/95 901.136 5/25/95 test itself is never identified. It is initially referred to as "a system response test".
(Section 5.5.3) Nine almost straight lines are presented on nine graphs and, at the selected scales, agreement between test and experiment 12/31/95 901.137 5/25/95 appears excellent. Since the test was run to demonstrate the operation of the PCCS,..
(Section 5.5.3, Figure 5.5-5) The report states that the initial peak pressure in the drywell is well-predicted, however, the figure does not 12/31/95 901.138 5/25/95 support this conclusion. The report should provide a blow-up of that region and should explain.
(Section 5.5.3) Explain the differences between Figures 5.5-7 and 8 10/31/95 901.139 5/25/95 (same title, same straight lines).
(Section 5.5.3) Using the poollevel as an indicator of heat removalis a relatively inaccurate integral reading, telling little about the actual heat 12/31/95 901.140 5/25/95 removal conditions. Also, over the time period of 17 hr the predicted pool level drop is.
(Section 5.5.3) TRACG apparently over-predicts the PCCS heat removal 2
rate. Ms shouM reduce the drywell pressure. Explain why the drywell 12/31/95 901.141 5/25/95 pressure agreement is good, with an over-prediction in PCCS heat removal.
(Section 5.6) Provide a discussion explaining why the reference natural cWadon expehent was not skndated, sbce R is mud mme relevanMo 10/31/95 901.142 5/25/95 SBWR applications than the forced flow experiment. Apparently, the information.
Page 6
Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'dl NRC Comments (Section 7.2) The data shown in Figures 7.2-2 and 3 appear to apply during recirculation pump coast-down time. Only the transition to a 10/31/95 901.143 5/25/95 natural circulation mode and the flow under those conditions are of interest for SBWR applications.
(Sections 7.2 & 7.3) Provide a detailed description of the test conditions 12/31/95 901.144 5/25/95 and the data measured during the plant tests and for the different time periods.
(Section 7.3) During the Hatch MSIV Closure Test, the quenching of s eam h incoming feedwater played an essendal mie. Mat actuaHy 12/31/95 901.145 5/25/95 happened to the feedwater flow during this test? Was it generally set to match steamline flow; had it been tripped?
In Section 3.2.12, the Model Report points out need for a quenching heat transfer model during reflood, which apparently is available as an option in 10/31/95 901.146 5/25/95 TRACG. However, the Qualification does not mention this model. Has it be.en validated..
(Figures 3.1-10 and 11) Provide the units of vapor flux on the abscissa 10/31/95 901.147 5/25/95 scale..
(Section 3.1.5) Table 3.1-5 lists four tests with top break and two with bottom break. Why are only the first two of the top break tests simulated 10/31/95 901.148 5/25/95 with the TRACG model? Was there a problem wFh the other two top break tests (5801-19 and 5702-16)?
10/31/95 901.149 5/25/95 (Section 3.3) Provide the name of the "CSHT" facility.
(Equation 3.3-1) No notation is provided for this equation. The staff notes that the corresponding equation in the Model Report (Equation 3.2-54) 10/31/95 901.150 5/25/95 differs slightly and is only partly defined there. Provide notation for the equation and define.
(Section 3.4) This section should be enhanced by including figures of the 12/31/95 901.151 5/25/95 vessel pressure vs. time.
(Page 3-99) Apparently the figure titles on this page are reversed. Figure 3.9-3 snows " Energy Release", which is more commonly referred to in the 10/31/95 901.152 5/25/95 text as " integrated power". For clarity, also indicate that it is integruted power.
gwes 4.2-2 & 5) Me reWsed hgwe Wes. Bom 6gwe Wes are 10/31/95 901.153 5/25/95 mislabeled; carryover is shown.
(Page 5-3) The mixture level of 0.254 m (top of Page 5-3) appears to be 10/31/95 901.154 5/25/95 in error. Confirm that level is 2.54 m (100 in.), which would roughly correspond to the elevation shown in Figure 5.1-6.
- 9*
10/31/95 901 155 5/25/95 line in Section 5.1.3.3 should be to Figure 5.1-35 (not 5.3.1.9).
(Section 5.1.4, Page 5-43) The reference to Figures 5.1-44 and 45 in the 10/31/95 901.156 5/25/95 text appears wrong. Confirm that figure numbers and discussion refer to mld plane and upper elevation (not 0.89 m elevation).
4 Page 7
Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 5.3.1) is the reference to recirculation line breaks in the second 10/31/95 901.157 5/25/95 paragraph of this section an error, since GIST was established for SBWR-related tests. If not, provide an explanation.
(Page 5-130, first line) In a TRACG model, how does one fill the system 10/31/95 901.158 5/25/95 with water?
1 Page 8
O GENuclearEnergy
$NSnSe'wWgN#*'
??SE$A enWT ISSSan. lose CA 9S12S-1014 408 92S-100S (phone) 408925 3991 (!?csimile)
August 28,1995 MFN 126-95 Docket STN 52-004 Document Control Desk U. S. Nuclear Regulatory Commission Attention:
Theodore E. Quay, Director Standardization Project Directorate
Subject:
SBWR - Revised Schedule for TRACG RAls Q901.75 - Q901.158
Reference:
- 1. Letter from J. H. Wilson (NRC) to J. E. Quinn (GE), REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING THE SIMPLIFIED BOILING WATER REACTOR (SBWR) DESIGN (Q901.75 - Q901.158),
dated May 25,1995.
We are in receipt of the reference letter requesting additional information on the material presented in GE Licensing Topical Report (LTR) NED-32177, TRACG Computer Code Qualification, dated January 1993. We propose to respond to these RAls in two groups; the first group of responses will be provided the end of October,1995, and the remainder will be provided by the end of the year,1995. This schedule reflects the urgency of completing Revision C to the SBWR Test and Analysis Program Description (NED-32391), by August 31, 1995 such that the Staff can issue the DSER this fall. The 901-RAI r:sponse schedule also provides reasonable time to incorporate appropriate changes into the update of NED-32177, scheduled to be provided to the Staff in April,1996. The RAI responses will also reflect the
{
discussions held with NRC and BNL to clarify some of the RAIs.
If you have any questions regarding TRACG please contact Bharat Shiralkar of our staff on 408-925-6889.
l Sincerely, s'
4J.
9
~
GENuclearEnergy
Attachment:
Status of Responses to RAIs 901.75 - 901.158 cc:
P. A. Boehnert (NRC/ACRS) (2 paper copies w/att plus E-Mail w/att)
I. Catton (ACRS)
(1 paper copy w/att plus E-Mail w/att)
S. Q. Ninh (NRC)
(2 paper copies w/att plus E-Mail w/att)
J. H. Wilson (NRC)
(1 paper copy w/att plus E-Mail w/att) l 1
Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments The word " Qualification" is used throughout the report without ever being 10/31/95 901.75 5/25/95 defined. " Validation" and " Verification" are well defined words. It would appear that " Qualification" is used in place of" Validation."
Each section of this report should demonstrate by itself, that TRACG has been validated for the specific model(s) considered in that section. This 10/31/95 901.76 5/25/95 requires a sufficiently detailed description of the experimental data base and the data range.
The SBWR supplement to this report should consider the GE PlRT results in determining, which items must be validated. This systematic approach 10/31/95 901.77 5/25/95 should result in a comprehensive list of models to be validated and should include.
Were all model computations in the Qualification Report done with the same wson ome Me? SWe h code wrsions used Desch how 10/31/95 901.78 5/25/95 GE proposes to demonstrate that the validations performed in preceding years with..
In most sections of the Qualification Report, the nodalization of the 12/31/95 901.79 5/25/95 relevant TRACG model is described, but generally without justification.
For a meaningful code validation the nodalization should be justified, in many cases " good" or "satisfacQry" agreement between simulation and experiment is claimed. Such qualitative statements are not adequate. A 12/31/95 901.80 5/25/95 meaningful quantitative comparison is required. This should include the i
following three steps:
(Section 3.1) The introduction to Section 3 states that the test data used f r qualifi ation of TRACG for the prediction of void fractions cover a wide 10/31/95 901.81 5/25/95 range of flow conditions, pressures, flow rates and inlet subcooling
" assuring..
(Section 3.1) Describe, in detail, the method used for void fraction 10/31/95 901.82 5/25/95 measurements in Sections 3.1.2,3, and 4, as it can affect the value or weight given to a set of data.
i (Section 3.1) No low pressure data are included in Section 3.1. During ad anemDCS mEH, me machsseM be at pmsswes sigMcaMy 12/31/95 901.83 5/25/95 below the pressure of all the test data provided. Since the vapor-to-liquid density ratio.
(Sections 3.1.2 to 4) Provide additional details concerning the test apparatus and, in particular, about the void fraction measurement method 10/31/95 901.84 5/25/95 for the Christensen, Wilson and Bartolomei, as well as the EBWR data.
(Section 3.1.5) The PSTF Level Swell Tests of Section 3.1.5, refer to the aSe m
n p4 h 10/31/95 901.85 5/25/95 definition of a two-phase level requires some arbitrary / reasonable definitions.
10/31/95 901.86 5/25/95 measured and what it.is compared to.
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AttSchment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAl Source or Due Date No.
Date Rec'd NRC Comments (Section 3.2) This section only considers film boiling and core spray heat transfer. In the Model Report, Sections 3.2.9 and 10 consider interfacial 12/31/95 901.87 5/25/95 and wall heat transfer with many more heat transfer regimes. For interfacial heat transfer,.
Section 3.2.1) The film boiling evaluations of Section 3.2.1 state that THTF pressures are significantly higher than those of BWR transients.
10/31/95 901.88 5/25/95 What are the THTF pressures and how much are the correlations affected by the differences between.
(Section 3.2.1) These high pressure data cannot be applied for code validation of film boiling after depressurization (i.e. in the range of about 2 12/31/95 901.89 5/25/95 bar), as would be required if the core were ever uncovered. Provide a justification for.
(Section 3.2.1) What is the sensitivity of the film boiling heat transfer to eg r d temprature data (i.e., what error in film heat transfer rates 10/31/95 901.90 5/25/95 would induce what error in rod temperatures), which clearly lag in response due to.
(Section 3.3) The cort.parison of TRACG code predictions against test 12/31/95 901.91 5/25/95 data from the CSHT facility is specific to ECCS liquid coolant entering the fuel bundles, which is not of interest in SBWRs. However,.
(Section 3.3) The descriptions of the tests and the model are inadequate.
in Particular, a detailed description of Figures 3.3-3 and 3.3-4 is required 10/31/95 901.92 5/25/95 to permit a reader to follow the results. Provide additional explanation and description of.
(Section 3.4.1.3) Evaluate the effect of using heat slabs over the time 12/31/95 901.93 5/25/95 period of 50 to 60 s. Was this effect quantitatively evaluated, or is the last sentence of this section conjecture?
(Section 3.5) This section assesses TRACG's capability to predict tube bundle pressure drops in the range of operating conditions (mass flow 12/31/95 901.94 5/25/95 range of test data - 140 to 2,040 kg/m2s; average full power mass flux l
-1,020 kg/m2s). However,.
(Section 3.6.1) This section refers to "five rod groups" and to the rod that first showed BT being treated as a separate group. This description is 10/31/95 901.95 5/25/95 unclear. Is a sub-channel analysis being applied here, with a separation into five groups?
(Section 3.6.1) Describe the relative location of thermocouples 2 through 6 in Figure 3.6-1. They are apparently allin the upper section of the 10/31/95 901.96 5/25/95 1
bundle, but the response of Tc 4 is flat, while Tc 2 shows the largest oscillation amplitude.
(Section 3.6.1) Fig 3.6-2 is presented as TRACG results for comparison e exp en al res s omgm 3M Howem, Ws Sgm does 12/31/95 901.97 5/25/95 not really present a validation of the test data, except.
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9 Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 stevised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 3.6.2) How was the pressure increased in these tests? Figure 3.6-3 implies that this was achieved through an increase in inlet flow. If 10/31/95 901.98 5/25/95 so, why was a prescribed pressure vs. time imposed on the simulation,.
(Section 3.6.2) The report stated that the TRACG model used here is the "same" as for the oscillation tests. However, a different tube bundle was 10/31/95 901.99 5/25/95 used here (GE9 vs. GE11). Provide clarification of this discrepancy.
(Section 3.6.2) A plot of CPR with a scale truncated at 1.0 does not Erovide a validation for the comparison of the experiment and the TRACG 12/31/95 901.100 5/25/95 simulation. Provide justification why parameters eenivalent to those of Figure 3.6-3 were not used.
10/31/95 901.101 5/25/95 (Section 3.7) Identify the FRIGG test that was selected.
(Section 3.7) FRIGG experiments that used a pseudo random binary 10/31/95 901.102 5/25/95 signal are available. Provide justification for not using one of those experiments for validation.
(Section 4.2) Provide an explanation for why carryover and carry-under are only reported as functions of inlet quality. Mass flow rates or a related 10/31/95 901.103 5/25/95 parameter, such as stagnation pressure, should be considered as a separate, independent parameter.
(Section 4.2) The validation presented is in the range of normal operating data only. Consideration of LOCA conditions is missing. In particular 10/31/95 901.104 5/25/95 during an MSLB scenario and during ADS operation, carryover could.
(Section 4.4.3) One purpose of the steady state heat transfer test was to walua e ee a@ng Mogen cacenuadon and steam now rams 12/31/95 901.105 5/25/95 on the PCC heat transfer characteristics". The comparison given does not (Se.: tion 4.4.5) The methodology describing how this degradation parameter was established in the experiments is unclear. The text states 10/31/95 901.106 5/25/95 that it was " calculated by measuring the condensate flow rate", which is in itself contradictory.
(Section 5.1.1) The " mixture level" mentioned here is a two-phase level and not a collapsed level. Its progression downward during the test run is 10/31/95 901.107 5/25/95 estimated based on the differential pressure measurements, using the taps indicated in Figure 5.1-2.
a (Section 5.1.1) For the TRACG model, Figure 5.1-13 of Section 5.1.2
- " "* 9 10/31/95 901.108 5/25/95 Figures 5.1-3 to 6 are for" Data Nodes" 28 to 31. The results section (Section 5.1.1.3) implies.
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Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 s
Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 5.1.1) Since this is a natural convection loop, the mass flows through the tube bundle, the bypass region and through the downcomer 10/31/95 901.109 5/25/95 should be determined. Are any data for these available, and if so, how do the.
(Section 5.1.1) The reported void fraction distributions and the average r d temperature data generally show satisfactory agreement between 10/31/95 901.110 5/25/95 experiment and simulation. However, two anomalies should be addressed: Why do the TRACG predictions..
(Section 5.1.2) This section gives a partial justification of the nodalization.
Under "further subdivisions"... "for more accurate representation," the 12/31/95 901.111 5/25/95 nodalization of the lower plenum region is discussed. Two axiallevels are
- used, (Section 5.1.2) The early disagreement between TRACG break flow 12/31/95 901'112 5/25/95 rationale for the significant underprediction of the break flow between 50 and 150 s should be provided.
(Section 5.1.2) For CCFL breakdown times between 90 and 130 s,
" noticeable changes" in upper plenum pressure drop are mentioned on 12/31/95 901.113 5/25/95 Page 5-17. In particular for the measured data, no such changes can be readily identified in Figure 5.123.
(Section 5.1.2) Clarify the description and discussion of rod heat-up on Page 5-18. "Little or no heat-up" at the top elevation applies for the test 12/31/95 901.114 5/25/95 data (when referred to the initial operating temperature) and for the.
(Section 5.1.2.3, page 5-17) A TRACG " hot rod" model is introduced and described. However, the staff could not find any reference to this " hot rod" 10/31/95 901.115 5/25/95 modelin the Model Report. A description of this model should be included in the revised Model Report.
(Section 5.1.3, Figure 5.1-33) Provide an explanation for the test data 12/31/95 901.116 5/25/95 bypass pressure drop spike at about 17 s.
(Section 5.1.4) All references to other sections of this report and to 10/31/95 901.117 5/25/95 references should be reviewed and corrected.
(Section 5.1.4) Various ECC flow rates are here given as fractions of those in previous tests, but the absoiute values are not given in either 10/31/95 901.118 5/25/95 place. A table with the relevant flow rates and temperatures should be provided.
(Section 5.1.4) The text of Section 5.1.4.3, describing Figure 5.140 (core niet flow), refers to unreliable core inlet flow data and states that dynamic 10/31/95 901.119 5/25/95 effects affected the accuracy of the density determinatjon. How is the test core inlet flow.
(Section 5.1.4) Figure 5.1-45 shows two separate test data traces, 10/31/95 901.120 5/25/95 differing from most other figures with rod temperatures. What is the second (lower) trace? (See also Figures 5.2-20 and 21.)
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i Attachment to MFN 'i26-95 i
l Status of Responses to RAls 901.75 - 901.158
)
Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments 1
l (Section 5.1.4) Although no void fraction data were presented with the 10/31/95 901.121 5/25/95 results of this section, the conclusions of Section 5.1.4.4 claim good performance of the void distribution models. Further, (Section 5.2) This report should be free-standing and should demonstrate qualf cation of the TRACG code. This section contains insufficient detail 10/31/95 901.122 5/25/95 in the description of the test facility and of the TRACG model. No rationale for the selected TRACG..
(Section 5.2.2) The discussion of Figure 5.2-3 states that an attenuation
- *E* * *
^*9 12/31/95 901.123 5/25/95 depressurization rate was observed at about 18 s, but not at 11.5 s.
Provide a basis substantiating the.
(Section 5.2.2) Figures 5.2-6 and 7 are claimed to show a faster 12/31/95 901.124 5/25/95 reduction" of the bypass and bundle inventories for the time period of 40 to 64 s. If DP is accepted as a measure ofinventory, then..
(Section 5.3.2) Table 5.3-1 lists the tests to be modeled by TRACG, along e ra ak for wWese tests wem selected. Tests 801 and 807 10/31/95 901.125 5/25/95 are both main steam line breaks, however, there is no description of what the difference between.
(Section 5.3.2) Aside from the arrangement of cooling water inventories, em a aMonal Memnces Ween me SBM design for wM GST 10/31/95 901.126 5/25/95 was built, and the current design. In particular, the reference to ADS components, (Sectiom 5.3.4) Table 5.3-1 states that Test B07 (core uncovery and s@sequed MatM wouW k N only SBEMated tesMem mese 10/31/95 901.127 5/25/95 phenomena were observed. However, this was not discussed in the text and.
~
(Section 5.3.4, Page 5-76) The report states that Figure 5.3-12 shows j
that test and calculation show onset of GDCS flow within 12 s of each j
10/31/95 901.128 5/25/95 other. However, the figure shows at least 70 s (less than 450 s vs. more than 520 s). Explain this discrepancy.
(Section 5.3.4) Figure 5.3-13 shows some disagreement for the annulus pressure drop between test and predictions during depressurization (~50 12/31/95 901.129 5/25/95 to 200 s) and, in Figure 5.3-14, the core pressure drop disagrees after GDCS onset. However, (Section 5.3.4) Provide an explantion for why a GDCS flow over-12/31/95 901.130 5/25/95 prediction after calibration against test data can be justified by a test data uncertainty of 10%. Since the test data were used as a basis, (Section 5.3.4) There are some disagreements in the annulus pressure drop data, in particular in the 50 to 150 s range, and some in the post-300 12/31/95 901.131 5/25/95 s range. These should be discussed and quantified to substantiate the subjective conclusion that..
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Attachment to MFN 126-95 9
Status of Responses to RAls 901.75 - 901.158 l
Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 5.4.3) The detailed qualitative desenption of the accident s enari p ints to the importance of keeping the lower plenum two-phase 12/31/95 901.132 5/25/95 level below the side entry orifices (SEO). However, the results section stated that this was the case,...
(Section 5.4.3) The discussion of Figure 5.4-7 is not clear. The figure shows vapor velocities, which turn negative at about 13 s for the 12/31/95 901.133 5/25/95 peripheral bundles. It is not clear how this indicates transition to liquid downflow at about 10 s, and..
(Section 5.4.3) Apparently the SEO pressure drop is not an orifice DP, but a measurement across taps 0.567 m apart. The text description and 12/31/95 901.134 5/25/95 data for Figure 5.4-8 differ. Only at close to 20 s (not 10 s) does the measured pressure difference.
(Section 5.4.3) The calculated pressure drop data of Figures 5.4-8 to 14 12/31/95 901.135 5/25/95 show oscillations of differing frequencies, which are not observed in the test data. Provide a rationale explaining this behavior.
(Sections 5.5.1 & 5.5.2) The description of the facility, the test procedure (an als e
el e
n.
are a equate, ht, me 10/31/95 901.136 5/25/95 1
test itself is never identified. It is initially referred to as "a system response test".
(Section 5.5.3) Nine almost straight lines are presented on nine graphs and, at the selected scales, agreement between test and experiment 12/31/95 901.137 5/25/95 appears excellent. Since the test was run to demonstrate the operation of the PCCS, (Section 5.5.3, Figure 5.5-5) The report states that the initial peak pressure in the drywell is well-predictad, however, the figure does not 12/31/95 901.138 5/25/95 support this conclus;on. The report should provide a blow-up of that region and should explain.
(e n
xpla e
erences beWen Rgwes 5.54 ad 8 10/31/95 901.139 5/25/95 (same title, same straight lines).
(Section 5.5.3) Using the poc' % vel as an indicator of heat removal is a rela ely inacewam integM wnMg Mng little about the actual heat 12/31/95 901.140 5/25/95 removal conditions. Also, on the time penod of 17 hr the predicted pool level drop is..
(Section 5.5.3) TRACG apparently over-predicts the PCCS heat removal rate. This should reduce the drywell pressure. Explain why the drywell 12/31/95 901.141 5/25/95 pressure agreement is good, with an over-prediction in PCCS heat removal.
(Section 5.6) Provide a discussion explaining why the reference natural r ulation experiment was not simulated, since it is much more relevant to 10/31/95 901.142 5/25/95 SBWR applications than the forced flow experiment. Apparently, the information.
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Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 7.2) The data shown in Figures 7.2-2 and 3 appear to apply during recirculation pump coast-down time. Only the transition to a 10/31/95 901.143 5/25/95 natural circulation mode and the flow under those conditions are of interest for SBWR applications.
(Sections 7.2 & 7.3) Provide a detailed description of the test conditions 12/31/95 901.144 5/25/95 and the data measured during the plant tests and for the different time periods.
(Section 7.3) During the Hatch MSIV Closure Test, the quenching of steam h Mcombg feedwate$ayed an essedal mie. Mat actuah 12/31/95 901.145 5/25/95 happened to the feedwater flow during this test? Was it generally set to match steamline flow; had it been tripped?
In Section 3.2.12, the Model Report points out need for a quenching heat transfer model during reflood, which apparently is available as an option in 10/31/95 901.146 5/25/95 TRACG. However, the Qualification does not mention this model. Has it been validated.
(Figures 3.1-10 and 11) Provide the units of vapor flux on the abscissa 10/31/95 901.147 5/25/95 scale..
(Section 3.1.5) Table 3.1-5 lists four tests with top break and two with bottom break. Why are only the first two of the top break tests simulated l
10/31/95 901.148 5/25/95 with the TRACG model? Was there a problem with the other two top break tests (5801-19 and 5702-16)?
10/31/95 901.149 5/25/95 (Section 3.3) Provide the name of the "CSHT" facility.
(Equation 3.3-1) No notation is provided for this equation. The staff notes that the corresponding equation in the Mode! Report (Equation 3.2-54) 10/31/95 901.150 5/25/95 differs slightly and is only partly defined there. Provide notation for the equation and define.
(Section 3.4) This section should be enhanced by including figures of the 12/31/95 901.151 5/25/95 vessel pressure vs. time.
(Page 3-99) Apparently the figure titles on this page are reversed. Figure 3.9-3 shows " Energy Release", which is more commonly referred to in the I
10/31/95 901.152 5/25/95 text as " integrated power". For clarity, also indicate that it is integrated power.
gwes O
em s gwe es.
gum es am 10/31/95 901.153 5/25/95 mislabeled; carryover is shown.
l (Page 5-3) The mixture level of 0.254 m (top of Page 5-3) appears to be 10/31/95 901.154 5/25/95 in error. Confirm that levelis 2.54 m (100 in.), which would roughly correspond to the elevation shown in Figure 5.1-6.
- 9" 10/31/95 901*155 5/25/95 line in Section 5.1.3.3 should be to Figure 5.1-35 (not 5.3.1.9).
(Section 5.1.4, Page 5-43) The reference to Figures 5.1-44 and 45 in the 10/31/95 901.156 5/25/95 text appears wrong. Confirm that figure numbers and discussion refer to mid plane and upper elevation (not 0.89 m elevation).
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.o Attachment to MFN 126-95 Status of Responses to RAls 901.75 - 901.158 Revised ID or RAI Source or Due Date No.
Date Rec'd NRC Comments (Section 5.3.1) is the reference to recirculation line breaks in the second 10/31/95 901.157 5/25/95 paragraph of this section an error, since GIST was established for SBWR-i related tests. If not, provide an explanation.
(Page 5-130, first line) In a TRACG model, how does one fill the system l
10/31/95 901,158 5/25/95 with water?
i
'Je, s ;*
d D
93 1*
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i 4
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