ML20117P789
| ML20117P789 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/12/1987 |
| From: | INTERNATIONAL TECHNICAL SERVICES, INC. |
| To: | |
| Shared Package | |
| ML20116D885 | List:
|
| References | |
| FOIA-96-237 NUDOCS 8708190171 | |
| Download: ML20117P789 (17) | |
Text
._
l Tedinim1 Evaluaticn of BG&E Topical Report:
mas amputer a:x5e Rw+ne Transient Analysis Mnrb1 Qualification e
l m.=_
maw.
w r-International Technimi services, Inc.
420 Iexirgton Avenue New York, New York 10170 f *JQbilc &
gIsh&
TMEE OF OCtfrDTIS Page 1.0 sunnary..........................
1 2.0 Introduction..........................
2 3.0 Topical Objectives.......................
2 4.0 Ocuputer Modeling.......................
2 4.1 REIRAN02A OD03...........
2 4.2 Nodalizations........................
3 4.3 Models..........................
4 5.0 Plant Test Ocuparison.....................
5 5.1 Multiple Secondary Side Malfunction Event.........
5 5.2 Four Punp coastdown frun 20% Power............
6 5.3 Paar+^r Coolant Operation Pung nwhination Flow Tests at Hot Zero Power.............
7 5.4 One Puup Coastdown from 80% Pcwer.............
7 5.5 Total Ioss of Flow / Natural Ciru11ation Test frtan 40% Power....................
8 6.0
'IRAC Analysis 0:mparison....................
9 6.1 Cooldown to PHR Entry Using ADVs and APS.........
9 6.2 Runaway Main Feedwater to One Steam Generator...... 10 7.0 IDFT Test Otmparison...................... 10 7.1 I4-1 Test......................... 11 7.2 In-3 Test.........................
11 8.0 Conclusions and Pwvnmm1dations................ 13 9.0 References........................... 14 l
1 i
1
1.0 Sumary The Baltimore Gas and Electric Coupany (BG&E) =*mitted a. topical iwi. [1] for the purpose of @=% tion of the BG&E best-estimate REIRAN thermal-hydraulic analysis capability.
BG&E. ra ded ocuparison of five plant transients; these are (1) Multiple Secondary Side Malfunction Event, (2) Pour Rap Coastdown frun 204 Power, (3) Reactor Cbolant Operation Pump Ocubination Flow Tests at Hot Zero Power, (4) One Punp Coastdown fran 80%
Power and (5) Total Ioss of Flow / Natural Ciru11ation Test frua 404 Power).
BGEE also r __ T M two 'IRAC analyses; (6) Cooldown to RHR Entry Using ADVs and (7) APS and Runaway Main Pantater to One Steam Generator.
'I%c IDFT tests simulated for ocuparison with REIRAN calculations are IA-1 and I4-3.
It is.our general conclusion that the applicant has presented thorough analyses, considering sensitivities to nadalizations, waials and physical parameters.
We feel that they have exhibited a good ursumi.anding of the REIRAN code and the manner in which its applications to simulate plant transients is conducted, ard demonstrated that the staff nw=hars who performed these analyses have adequate skills to analyze the results of such applications. Although their use of the control systes was not examined in detail and none of the transients analyzed tested their ability to use the j
control systems
- fully, their skill and understanding of the code
{
demonstrated in the dim== ion of the results in the report gives us 1
reasonable assurances that the B%E staff also pnamaan the ability to unial the control systems with the code.
4 I
1 1
- -.-.- -- -.~ _
J l
l 2.0 Introduction i
j
'Ihe Baltimore Gas and Electric Q:spany (BGEE) sukaitted a topical report [1,2,3) for the purpose of h*'antation of the BG&E best-estimate REIRAN thermal-hydraulic analysis capability.
BG&E MAed crrparison of five plant transients, two 'IRAC analyses and two IDFT tests b, h REIRAN t'
calcallations.
We have reviewed the applicant's efforts to qualify REIRAN wdala for use in the analysis of the Calvert Cliffs plant.
Our evaluation ll is===arized in this awl.
i 4
i 3.0 Topical Report Otdectives i
l It was BG&E's stated intent to demonstrate (i) the capability of BG&E analysts to properly develop REIRAN medala of the Calvert Cliffs plant, a j
M= tion Engineering design, (ii) to perform calculations.with these medalm to sins.tlate rnalistic plant transient response, and (iii) to ocupare j
the results to maa=wed plant data, another best estimate computer code I
('IRAC), and experimental data (IDFT).
In addition, medal enM ncement and i
j appropriate sensitivity studies were performed by BME to provide greater.
j insight and a better ursiu..A of modeling Calvert Cliffs with REIRAN.
^
4 i
One of BG&E's objectives in h*=qting their analyses and results in j
this topical report was to present their effort in performing a code verification in accordance with NRC Generic Istter No.83-ll (4) a i
I j
4.0 Otmputer Modeling 1
4.1 REIRAN02 MOD 03 4
i i
'Ihe applicant used REIRAN02AOD03 to perform analyses presented i
2 N
i I
1 in their tcpical report.
'1his version, which has not been approved, contains cuu actions of code errors discovered during the review of l
REIRAN02/)OD02 [5] which were inplemented at the request of tiw NRC.
However, in addition to error correction, some ra$el modifications were also made to this version (6].
'Ibe NRC staff has not yet reviewed the code to assure that these model revisions were apprtpriate, accurate and properly inplemented. However, the use of this version by BG&E is acceptable in the context of this topical report.
i 4.2 Nevhlization BME developed three nodalizations for Calvert Cliffs: (1) a detailed one-loop el for transients with nearly symetric loop cxniiticms; (2) a split-core two-loop model (two cold legs were 1tmped together) for transients which result in asymetric plant conditions; and (3) a "four-loop" wvh1 which in fact has only two loops, but which wvbls all four cold legs discretely to study flow patterns during flow tests or transients which can be inpacted by one or more RC punps on a coastdown.
'Ihe applicant has selectively and appropriately used one of these nevhlimtion schemes for each transient depending upon the ey=+ai plant behavior and has, in addition, provided acceptable justifications for sudi selection, in scane caaaa baai upon sensitivity analysis.
'Ihe one-loop wvial was used in a four punp coastdown and a conparative study with 'IRAC for cooldown to RHR entry usin; ADVs and APS.
An obvious advantage of this nodalization is the cmputer code speed obtained by a ihplified model, while an obvious disadvantage is lack of detail. BG&E ?-,rr :d.rnted an awareness of these trade-offs.
s Use of a split-core model is a state-of-the-art technique for an asymetric plant behavior which can influetce the core physics due to reactivity faarthmCk fIUD the aSymetric tenperature distribution caused by different cold leg fluids and the mixirg of 'these fluids in the core. 'Ihis nevh1Mtion was used by B%E for analysis of the multiple secondary side 3
_ _ _. _ _ _ _ ___ _ _. _._ ___ _. _. _.~
malfunction event, a natural ciru21ation test frun 40% power, and a runaway main faarhater to one steam generator event as part of a set of PIS-limiting system transient analyses.
'the four-loop model explicitly andala eacts of the four cold legs, including two cold legs per loops, a unique problem to CE plants.
'Dtis model is used when individual cold leg /RCP transients are analyzed sucis as three QLivert Cliffs start-1Jp tests; a four plup coastdoWn fran 20%
power, SC operational ptmp ocabination flow tests at hot zero power, and a one puup coastdown fran 80% power.
In all three of these plant endala, the RE' IRAN md14hrium pressurizer was used in ocabination with a single-node representation of the pr=manirizer.
In order to overonme the piracy intrM=d during the ocmputation of a rapid insurge/outsurge transient, BG&E intends to use the Temperature Transport Delay Time Model (TIUr) available in REIRAN. BG&E has demonstrated that they are aware of the limitations of the TIUr model and the rar. =dlihelum model and of their ranges of applL: ability.
'Iha steam generator secondary side is modeled as a four volume recirculating steam generator with a best estimate recirculation ratio in the two-loop and four-loop plant nadalizations, while the one-loop nodalization only uses a one volume steam generator.
Transients for which BG&E intends to use the one-volume model have been dMiacad thoughtfully and are listed in Table 1.
In addition, IE&E obtained frcun Energy Irwigated and modified a IDFT REIRAN-01 I4-5 deck to mndal the IDFT facility using REIRAN-02/)OD03 for similaticri of two tests; IA-1 and IA-3.
4.3 Iggjals BG&E has qualified a portion-of'their REIRAN code andaliaq for the Calvert Cliffs plant, and in addition, they have provided db-ions 4
~
indicating their enderstanding of the details and limitations of certain of those wels, incitriing the non-equilibrium model, the bubble rise w*1, the TIDF model and they have dimW thoughtfully the impact of various steam generator nodalizations.
'Ihese discussions are important aspects of demonstrating their ability to use the code and analyze the results.
In addition, the transients analyzed required sufficient use of the REIRAN control systems w*1ing that BG&E has adequately d=ma = Luted its ability to use those input w*1m to represent the plant's control systens.
TABLE 1.
BG&E Nodalization Selection REIRAN SG SECONDME SIDE M) DEL Ch.14 UHWIED FSAR EVDir SINGIE NO W MJLTIFIE.NOCE l
RCSD X
i IDF X
SR X
CEAD X
CEAW X
CEAE X
EL X
IDL X
IDEW X
MM X
l IDAC X
M31B X
SGIR X
EWIB X
5.0 Plant Transient OmoariggDS 5.1 R11ticle Secondary Side Malfunction Event A reasonable agreement was obtained between the REIRAN 5
cala11ated results and data of the asymetric cooldown durirg the first 200 l
seconds of the event.
BG&E, by performance of a sensitivity study, I
indicated that use of the TIUr inndal reduced the peak pressure frca 2338 psia to 2310.7 psia which is closer to the measured 2306 psia, and increased the peak pressurizer level by about two inches closer to plant data. Timing of these occurrences, however, were not affected by the use of this model.
l Although, the results began to differ after roughly 200 seconds into the transient, BME recognized and dimW the fact that this was due to the uncertaihty in the stuck open 'IBV position.
A series of sensitivity studies was conducted to determined which parameters would affect the transient results.
In the supporting @==rit presented by the applicant (3), BG&E analysts damnnstrated a thortogh tit darxiing of the transient by prwiding an explanation of each substantial change in slope of plant parameters arx1 how they inpact each other.
'Ibe applicant should be encouraged to prwide future subnittals in this depth.
5.2 Four Puno Coastdown from 20% Power Measurements were made of the total RCS flw for the first 55 seconds after reactor trip to obtain RCS flow data during a four puup coastdown at 20% of full power.
~
RETIPAN calculated flow was within roughly 3% of measured flow for the first 35 seconds of the transient where the flow measurment accuracy is 2%.
A closer a.aeiisnt was obtained with the four-loop model w
than with the single-loop inndal due to the finer nodalization and more j
accurate t wresentation of RCS flow paths and pressure losses.
BG&E iniicated an understarxiing of the accuracy of these inndals and the uncertainties in plant data.
l 6
1 i
5.3 Banctor Cbolant thration P== 'T=hination Flow Tests at Hot 4.
i Fifteen various ocenbinations of flow tests were conducted at hot j
stand-by to evaluate operating punp cxanbination flow distribution.
The RIHRAN four loop model was modified to include a cross flow junction betzeen the two identical downoamer voltanes used for this analysis, to permit sudi cross f1bw to occur when the coastdown is asynsastric.
BG&E also irput an explicit locked rotor reverse flow pressure loss coefficient to improve modeling.
j Statistical analysis was performed with the mananid plant data i
and RIHRAN cxmputed results were ocupared to the mean value of the data. In twelve out of fourteen cases studied, the m*ad results were within two standard deviations (95.5% of data) of manaired data. One of the remaining
)
tests had insufficient data points to be meaningful and in the other test, the ocmputed flow differed fran the mean by 4.1%.
a i
5.4 One P=n Natdmn fran 80% h The objective of this test was to maanne single RCP coastdown i
data ala validate the low RCS flow trip fraa 80% power with one RCP secured.
1he four-loop andal was used in the analysis.
Model enhancements including dowrnmar cross flow and realistic RCP reverse pressure loss ocefficient were used. Other plants conditions were adjusted to reflect conditions at 80% power.
Although the ocmputed pressurizer praamns and hot and cold leg temperatures originally did not agree well and the total BCs flow under-l predicted plant data by 1 to 4 % over the 60 second period, these i
i differences were attributed by BG&E to differences in 7BV and ADV opening times.
BGEE then used revised data, adjusted the TBV and ADV input to the 7
i m
1 l
~
1 l-code and obtained better agreement.
l BGEE performed a sen itivity stady in idtidi RCP noment of j
inertia and rated torque were varied.
It was found that by either increasing pump prnarzt of inartia by 10% or ckcreasing pung torque by 10%,
temporal f1w rate increased closer to maammx1 data.
It was also found that adding a downoamer cross flw path and realistic BCP reverse flw loss l
factor resulted in higher Rcs flw than the initial model after 18 seconds into the* transient and ocupared more closely with the data (79.1% versus 78%
for the base case and 80% for plant data). For t % base case with data w 3
cross-flw and RCP reverse flw model coefficiarits, RETRAN uh3icvudicted BCS total flw (i.e., cuer-predicts flw reductio 1 in the shutdown loop) by 0.4% to 3.9%.
These par _kic studies indicate 13G&E's ability to seek out the <w=an of differences between plant data and camputational results.
5.5 Tcfal 1r== of Flw/ Natural Cirmlation 'Dast from 40% Power This test was conducted to determine the pahflw ratio during natural circulation. Key parameters were recorded for only the first 60 secorxis of this transient although the transiant lasted much longer.
Therefore, calculational result acaparison was made~ for this 60 second period.
For this sina11ation, the REIRAN two-loop nrvial was modified to be initialized at thei 40% power conditions.
Ag_;_ _it between the plant data and R? IRAN 'results in RCS fim, pressurizer pressure and pressurizer level was gcod; however, hot and cold leg tasperatures and therefore the secondary side pressures did not agree well.
The temperatures differed by about 5'F :and the pressure by roughly 25 psi.
(During this time period, the hot and leg temperatures deconaw roughly 10*F and 5'F, respectively and the net change in the secondary pressure was approximately 75 psi.)
The topical report d4===a=
the comparison of the onset and magnitude of the natural circulation fle.t well after 60 seconds (five 8
\\
i 4
minutes), and BG&E indicated that this diammaion was haamd upon the record of the test written by the operator rather than upon recorded =aamie.
i 6.0
'IRAC Analysis hviam
'Iha Ios Alamos National Iaboratory (IANL) developed a finely detailed StAC-PF1 nodalization of the calvert Cliff plant including a three dimensichal vessel with modeling of lower plenum mixing pipes.
Both steam generators and the pressurizar were modeled using malti-voltane multi-node nodalizations.
The two StAC analyses presented by BG&E were p rformed by IANL.
For sinailation of two transients performed by IANL, it appears that 33&E's objective was to perform their cWn best-estimate analysis for eacts of these transients, and not to simulate the IANL camputation of the transient by using exactly the same assunptions.
'Ihus our review of these two analyses was not f e iaad upon the degree of imga.L or dis 4s.L between the results obtained by the two oodes, but was fomaad upon BG&E's t.A aanding of their own results and the reasons for differences frun the
'IRAC results.
6.1 Cooldown to RHR Entry Usim ADVs and APS l
i l
The REIRAN ane-loop andal was used in the comparison of this transient with the results from using a finely detailed TRAC nodalization.
'IWo major differences between the initial BG&E cciculations and those of IANL using these codes are: (1) the pr===trizer emptied in the REIRAN analysis while 'IRAC did not predict pressurizer emptying; and (2)
TRAC predicted faster cooldown after 6000 seconds than REIRAN.
Reanalysis of this transient by BG&E after the initial =*=ittal showed that difference (1) was due to different assunptions about the use of charginJ flow in the analysis and the time at whicta charging was assumed to be restored for level 9
l i
{
control. With these changes, IEEE reported that REIRAN did not predict the pressurizar captying.
Difference (2) was attributed to the Whical j
modeling of the ADVs ard, after BG4E altered its el, differences between j
the two calcx11ations were said to have been " resolved".
I j
6.2 Runaway Main F=aduatar to One Shwam Gerhetcr 4
j This analysis was performed as part of the NRC sponsored l.
pressurized thermal shock project.
i j
'Ihe PORV reached its setpoint and the pressurizer level rose to the top roughly 500 seconds earlier in the REIRAN analysis than in the 'IRAC calcx11ation because the TRAC model did not. allow Wimp presrurizer heaters to reactivate after pressurizer liquid level returned above a programmed f
level setpoint. Furthermore, BG&E indicated that the reason REIRAN ocaputed that the pressurizer level rose to the top over 1000 seconds earlier than l
'IRAC was hanause of the large difference in HPSI flow rate which resultad
{
frtza the different pressures predicted.
i j
'Ihe minium downmmar temperature was ocmputed to be 350*F by i
REIRAN, whereas 'IRAC ocmputed mininnan average downoomer tenperature of i
400*F.
'Ihe hot leg temperatures also show a similar difference between a
)
REIRAN and 'IRAC.
Overall, the :esults exhibited similar trends despita i
large differences in the ocmputer code medala and the degree of detail and capabilities in plant nadalizations.
7.0 IDFT Test Camparison BG&E mrdified an I4-5 RETIRAN-01 medal supplied by Energy Incorporated to ardal IE-1 and I6-3.
These experiments are secondary system initiated events: 16-1 was a loss of steam load anticipated transient; and 16-3 was an i
excessive load increase anticipated transient.
10 j
i
f 1
l i
I i
1 j
7.1 IDFT Test IE>-1 j
l l
1he minilational results gitad (steam generator dczna
{
pressure, secondary side liquid level, praasnirizar pressure and level and coolant temperature in the intact loop steam generator primary side inlet plema) in the topical report did not agree with the test data.
After a i
3 i
sensitivity study with th to the Interfacial Heat Transfer Ocefficient l
(Df!C) was performed, BG&E concluded that RE3RAN does not permit a varying j.
Df!C to sina.tlata this sort of transient involving a. rapid pressurizer i
insurge follound by an equally rapid outsurge. The use of a large value of f
DfIC (27500 BIU/HR-FT _.F) properly calculated the insurge portion but not 2
l the outsurge portion hamiina it mn=M aw==aiva energy transfer from the j
steam W11d1 resulted in a lower pressure, Wildt in turn mnand too much pressurizar liquid to flash during the outsurge.
Cou+.11ngly, the use 2
of a low value (10 B1U/HR-FT _.F) of Df!C predicted plant data more tinmaly j
during the cutsurge portion than the origiral calculation Wildt used large l
DfIC; however, pressurizar pressure and level were not well ocsputed during j
j the insurge.
BG&E found that 400.0 BIU/HR-FT
- F gave a better overall fit '
2 to the data.
4 2
In this analysis, the BG&E RE3RAN primary and secondary pressure transient behavior did not follow the plant data precisely. We concur with BG&E's conclusion that this deviation is attributable to lack of basic data
)
regarding the details of Main Steam Flow Control Valve operaticas during the transient, and that the absence of sudt data makes it virtually inpassible to obtain exact correlation.
i i
i 7.2 IDFT Test II>-3 After BG&E added the use of the TIUr option, the primary side parameters, e.g., pressurizar pressure and h'ot leg tanparatures agreed well between the test data ard REIRAN results.
The cxmputed coolant 11
temperature in the intact loop steam generator primary side inlet plenum lagged the test data by roughly 25 aamrxis.
'Ihis diffexence was attributed to uncertainty in the data.
'Ihe ocmputed and test steam generator dcane pressures began to diverge at about 50 seconds due to the earlier REIRAN reactor trip and the resultirq earlier closure of the MSFCV. 'Ihe reason for the pressurizer level divergence starting at about 50 aamnds was attributed
[
to less energy being available to be deposited in the secondary due to the early scram and to a higher terminal steam flow and feedwater flow in the REIRAN /alculation.
i 12
1, 4
i.
3 4
8.0 Ctmclusions ard Recamandations a
4 i
IKi&E staff have deerzistrated their ability to develop input undals for best estimate otsputation of plant transients in the Calvert Cliffs Nuclear j
Power Plant, and to perform the supporting sensitivity studies to aid in l
determination of the appropriate model selection and nodalization. BG&E has I
~
developed three nodalizations idtidt it proposes to use; BG&E has g n id dimmaions and justifications of their nndalizations for certain of the transients (as indicated in the foregoing text), and suda nadalizations should therefore be considered qualified for future use.
It is r=er==manded that in future licensing applications, model selection be justified on a transient by transient basis.
BG&E nay, bcWever, rely upon and reference
).
- the dim==ians contained in this application idien making sudt undal l
. election.
BG&E staff have further desonstrated their ability to thorou;$ly analyze a transient.
It is rarv==anded that in future licensing sutzaittals BG&E be requested to =*=it analyses of the detail and thoroughnees provided in their analysis of Multiple Secondary Malfunction Event.
13
/
1 9.0 Referimons
(
l i
1.
REE 'Ibpical Report A-85-11, "RFIRAN Oxtputer (bde Reactor System l
Transient Analysis 14mdal Qualification," January 31, 1986.
t 4
2.
Istter fran J.A. Tiernan (BG&E) to NRC, dated February 24, 1987, i
- "REIRAN Review - Subnittal of Additional Information".
3.
Intter frun J.A. Tiernan (BG&E) to NRC, dated June 9,1987, "REIRAN Review - subnittal of Additional Information".
4.
USNRC Generic Intter No. 83-11, " Licensee Qualification for Performing Safety Analyses in Support of Licensing Actions,"
February 8, 1983.
5.
Istter frun P.B. Abramson (ANL) to J. Otrter (NRC), "Tectinical Evaluation Report: REIRAN-2AOD02," May 31,1983.
6.
Istter frun T.W. Scfinatz (IERA) to C.O. 'Ihnenan (NRC), "REIRAN - A hemo for Transient 'Ihermal-Hydraulic Analysis of Ocuplex Fluid Systems," February 4, 1985.
14
ENCLOSURE 3 CALVERT CLIFFS, UNITS 1 AND 2 SYSTEMATIC ASSESSMENT OF LICENSEE PERFORMANCE 4
1 Functional Areas 1.
Management Involvement in Assuring Quality.
Technical review of the submittal indicates that the management reviews are timely and technically appropriate.
j Rating: Category 2 2.
Approach to Resolution of Technical Issues from a Safety Standpoint.
N/A i
1 3.
Responsiveness to NRC Initiatives The licensee is very cooperative to the staff initiatives.
4 I
Rating: Category 1 4
4.
Enforcement History N/A a
5.
Operational and Construction Events N/A J
6.
Staffing (including Management) l N/A 7.
Training and Qualification Effectiveness N/A i
Reference:
NRC Manual Appendix 0516 - Systematic Assessment of Licensee Performance 1