ML20136G186
| ML20136G186 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/10/1997 |
| From: | Hebert J Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20057G447 | List: |
| References | |
| JRH-97-055, JRH-97-55, MN-97-19, TAC-M94834, NUDOCS 9703170231 | |
| Download: ML20136G186 (34) | |
Text
4 MaineYankee RELIABLE ELECTRICITY SINCE 1972 329 BATH ROAD + BRUNSWICK, MAINE 04011 + (207) 798-4100 March 10,1997 MN-97-19 JRH-97-055 I
i UNITED STATES NUCLEAR REGULATORY COMMISSION Attention: Document Control Desk Washington, DC 20555
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b)
Letter, C.D. Frizzle (Maine Yankee) to W.T. Russell (USNRC), " Submittal of Maine Yankee SBLOCA Licensing Analysis in Compliance with 10 CFR 50.46 and in Satisfaction of TMI Action items ll.K.3.30, ll.K.3.31, and ll.K.3.5", MN-96-056, dated April 25,1996.
(c)
Letter, E.H.Trottier (USNRC) to C.D. Frizzle (Maine Yankee), " Request for Additional Information - ANF-RELAP SBLOCA Analysis (TAC No. M94834)",
dated June 25,1996.
(d)
Letter, C.D. Frizzle (Maine Yankee) to F.J.Miraglia (USNRC), " Response to USNRC Request for Information (RAI)- Maine Yankee SBLOCA Analysis", MN-96-145, dated October 18,1996.
(e)
Letter, D.H.Dorman (USNRC) to C.D. Frizzle (Maine Yankee), " Request for AdditionalInformation on SBLOCA Analyses Related to an Item-of-Loop-Seal-Induced-Core-Uncovery - Maine Yankee Atomic Power Station (TAC No.
M94834), dated October 28,1996.
(f)
Letter, J.R.Hebert (Maine Yankee) to USNRC, " Transmittal of the Maine Yankee SBLOCA ANF-RELAP Nodalization Diagrams", MN-96-180, dated November 27,1996.
Subject:
Maine Yankee SBLOCA Analysis: Response to USNRC Request for Additional Information and Reqqest for Supplemental Information Gentlemen:
This letter, and the information attached, is being submitted in response to USNRC requests associated with the Maine Yankee SBLOCA licensing analysis, Reference (b). The USNRC requests are both of the form of a Request for Additional Information (RAl), Reference (e), and verbal requests for supplementalinformation made during phone calls between Maine Yankee and the NRC on November 14,22, and 27,1996.
Maine Yankee has previously provided information, Reference (d), regarding the earlier USNRC questions, Reference (c). Additionally, per USNRC verbal request, we have previously transmitted a copy of the SBLOCA ANF-RELAP nodalization diagram, Reference (f).
Portions of the responses to the USNRC requests are considered proprietary by the Maine Yankee vendors performing this work. Therefore, contained as Attachment 1 to this letter are f.5) JM$
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MaineYankee 1.
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UNITED STATES NUCLEAR REGULATORY COMMISSION MN-97-019 l
ATTENTION: Document Control Desk Page 2 I
affidavits executed by the Yankee Atomic Electric Company and the Siemens Power Corporation pursuant to the requirements of 10 CFR 2.790(b)in support of the withholding of the proprietary.
information from public disclosure.
5
' Attachment 2 contains the full and complete proprietary responses to the USNRC requests.
l Maine Yankee requests that the information in this Attachment be withheld from public disclosure.
' contains the non-proprietary version of the same responses as in Attachment 2.
Per request of the USNRC, we are also sending a copy of the complete submittal to Dr. Cari 4
l-Beyer of the Pacific Northwest National Laboratory.
If the Staff has additional questions or comments on the attached information,' please contact Mr. Robert P. Jordan of Maine Yankee at (207) 798-4243.
(-
4:
Very truly yours, S
m/
ames R. Hebert, Manager l
Licensing & Engineering Support Department -
i c:
Mr. H. J. Miller Mr. D.H. Dorman
' Mr. J. T. Yerokun Dr. C. Beyer -
Mr. U. Vanags (w/o Attachment 2)
Mr. P. J. Dostie (w/o Attachment 2) nrc31
MaineYankee MN-97-019 ATTACHMENT 1 AFFIDAVITS YANKEE ATOMIC ELECTRIC COMPANY SIEMENS POWER CORPORATION nrc31
=,
d AFFIDAVIT PURSUANT TO 10CFR2.790 Yankee Atomic Electric Company
)
Nuclear Services Division
)
Commonwealth of Massachusetts
)
Worcester County
)
SS:
i -
1, S. P. Schultz, depose and say that I am the Vice President of Yankee Atomic Electric
_ Company, duly authorized to make this afildavit, and have reviewed or caused to have reviewed the information which is identifled as proprietary. I am submitting this aftldavit in accordance with the provisions of 10CFR2.790 of the Commission's regulations for withholding this information.
e l
The information for which proprietary treatment is sought is the response contained in the j
proprietary enclosure to Maine Yankee letter MN 97-19, Maine Yankee Atomic Power Company to U. S. Nuclear Regulatory Commission.
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 determining l
whether the infonnation sought to be withheld from public disclosure, included in the referenced document, should be withheld.
1.
.The material contained in this transmittal was obtained at considerable expense to Yankee Atomic Electric Company and Maine Yankee Atomic Power Company and l
the release of which would seriously affect our competitive position.
[
2.
The material contained in this transmittal is of the type customarily held in j_
confidence and not customarily disclosed to the public.
3.
_ 'Ihis information is being transmitted to the Commission in confldence under the l
provisions of 10CFR2.790 with the understanding that it is to be received in confidence by the Commission.
1 4.
This infonnation is for Commission internal use only and should not be released to persons or organizations outside the Directorate of Regulation and the ACRS j
without prior approval of Yankee Atomic Electric Company. Sheuld it become necessary to release this information to such persons as part of the review procedure, please contact Yankee Atomic Electric Company.
Further deponent sayeth not.
Sworn to before me this M
27th day of February,1997 S. P. Schultz Vice President Y.
1]ALW
~
l flotary Pubile Donna L Pelletter, Notary Pub;!c State of Maine My Commission Expires 12/12/0S j
4 4
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p AFFID AVIT I
. STATE OF WASHINGTON )
l
) ss-j-
- COUNTY OF BENTON
)
j-
~, R. A. Copeland, being duly sworn, hereby say and depose:
I j,
1.
I am a member of Product Licensing for Siemens Power Corporation
("SPC"), and as such I am authorized to execute this Affidavit.
i 2.
l.am familiar with SPC's detailed document control system and policies i
which govern the protection and control of information.
i j
3.
I am familiar ~ with the Siemens Power Corporation information in TMH:97:024, " Responses to NRC's Request for Additional Information (RAl) on Maine Yankee SoLOCA Analysis Submittal-Supplement," dated January 31,1997, referred to as f
" Document."
Information contained in this Document has been classified by SPC as proprietary in accordance with the control system and policies established by SPC for the h
control and protection of information.
4.
The Document contains information of a proprietary and confidential nature and is of the type customarily held in confidence by SPC and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in the Document as proprietary and confidential.
4
}
5.
The Document has been made available to the U.S. Nuclear Regulatory Commission in confidence, with the request that the information contained in the Document will not be disclosed or divulged.
i
6.
The Document contains information which is vital to a competitive advantage of SPC and would be helpful to competitors of SPC when competing with SPC.
7.
The information contained in the Document is considered to be proprietary by SPC because it reveals certain distinguishing aspects of SPC licensing methodology which secure competitive advantage to SPC for fuel design optimization and marketability, and includes information utilized by SPC in its business which affords SPC an opportunity to obtain a competitive advantage over its competitors who do not or may not know or use the information contained in the Document.
8.
The disclosure of the proprietary information contained in the Document to a competitor would permit the competitor to reduce its expenditure of money and manpower and to improve its competitive position by giving it valuable insights into SPC licensing methodology and would result in substantial harm to the competitive position of SPC.
9.
The Document contains proprietary information which is held in confidence by SPC and is not available in public sources.
10.
In accordance with SPC's policies governing the protection and control of information, proprietary information contained in the Document has been made available, on a limited basis, to others outside SPC only as required and under suitable agreement providing for nondisclosure and limited use of the information.
11.
SPC policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.
12.
Information in this Document provides insight into SPC licensing methodology developed by SPC. SPC has invested significant resources in developing the methodology as well as the strategy for this application.
Assuming a competitor had available the same b #wwd data and incentives as SPC, the competitor might, at a minimum, develop the information for the same expenditure of manpower and money as SPC.
4 THAT the statements made hereinabove are, to the best of my knowledge, information, and belief, truthful and complete.
FURTHER AFFIANT SAYETH NOT.
l J
SUBSCRIBED before me this $0" g, g4 day of NOW.1997.
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- 0.$+/
,Op wggg Sue M. Galpin NOTARY PUBLIC, STATE OF WASHINGTON MY COMMISSION EXPIRES: 2/27/00
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MaineYankee MN-97-019 l
J 4
i ATTACHMENT 3 NON-PROPRIETARY RESPONSES IQ USNRC SBLOCA QUESTIONS nrc31
SupplementalInformation Related to FROSSTEY-2 Code Modifications Maine Yankee submitted the SPC SBLOCA Analysis including the description of the FROSSTEY-2 code and its use in Reference 1. The NRC review of the analysis resulted in a request for additional information (Reference 2). Maine Yankee responded to the request in October 1996 (Reference 3).
A telephone conversation was subsequently held on November 22,1996 between NRC, NRC contractor at PNL (technical reviewer), MY, SPC, and YNSD to discuss status. Based on the discussion, Maine Yankee committed to provide additional information related to FROSSTEY-2 code modifications. The additional information is contained below.
Item 1 The FROSSTEY-2 code was modilled to change the gap conductance iteration logic. The modification was tested by running [
]. The comparison of FROSSTEY-2 predictions with and without the modification showed no impact for this test rod. Based on this, it was concluded in Reference 3 that there would be no impact on the IFA experimental rods which comprise the code uncertainty database. However, PNL observed that this test rod contained [
] and the choice of this rod to verify the modification was questioned.
A review of the engineering calculation documenting the gap conductance iteration logic modification showed that [
] was chosen since the data file for this rod was available online and was part of the code's test suite. It is recognized that this rod is not as representative of commercial fuel rods as other rods in the FROSSTEY-2 test matrix. A comprehensive evaluation of the impact was undertaken and is described below under " Supplemental Information."
Item 2 In Reference 3, the impact of the annular pellet modillcation and its conservatism was discussed. Based on the test case results presented in Reference 3, the code modifications tended to reduce the code uncertainty and hence, the use of the original (i.e. larger) code uncertainty would be conservative. MY committed to providing further assessment of this modification during j
the November 22,1996 telephone communication.
A review of the engineering calculation documenting the annular pellet modification was performed. The assessment of Reference 3 was based on comparing ccde predictions before and after the modification for a limited portion of the code benchmark data. Based on this limited assessment, it was concluded that the annular pellet modification would tend to decrease the calculated code uncertainty. It is recognized that this evaluation did not fully reflect the code uncertainty database. The further evaluation of the modification's impact was performed using the entire code's uncertainty data base and is described below.
Supplemental Information All of the IFA test rods in the FROSSTEY-2 code uncertainty data base were rerun using code versions corresponding to gap conductance logic and annular pellet modifications. Table 1 provides a summary of the differences between mean predicted and measured centerline temperatures for gap conductance iteration logic and annular pellet modifications. To accurately assess the impact of the code modifications, the compariyens are made based on the same burnup intervals and data points as used in the FROSSTEY-2 uncertainty evaluation methodology.
The modification of the gap conductance iteration logic resulted in no change in the mean centerline temperature predictions for the [
).The[
] exposure intervalis most Page 1
m 1"
6 l
limiting since the [
] occur j!
- centerline temperature predictions. Table 1 also provides the changes in mean centerline in this interval. The remaining intervals show a larger but still relatively small reduction in mean temperature for the annular pellet modification. 'Ihe modification resulted in an insignificant j
change in the predicted mean centerline temperature predictions for the [
] exposure interval
[
]. [
] intervals showed larger changes compared to the [
] interval.
)
Based on the comparisons presented in Table 1, it is concluded that the modifications have 1
a very small impact on the code uncertainty for the limiting exposure interval. The change in the 1
code uncertainty for the remaining non-limiting exposure intervals is projected to be small.
I As stated in Reference 3, discrepancies in free gas volume input were identifled in the data sets of IFA rods comprising the FROSSTEY-2 code uncertainty database. These have been corrected and the code's input capabilities have been extended to allow the explicit modeling of the thermocouples located in the annular regions of the experimental rods. Additionally, during
[
the preparation of this supplemental information, inconsistent settings of input options were found for two of the rods. All discrepancies have been addressed in the results shown in Table 1.
The previously calculated code uncertainty valaes are being updated to reflect the re-validation of the code against experimental data. 'Ihe impact of the updated code uncertainty will be addressed according to YNSD Quality Assurance Program procedures and dispositioned in
{
compliance with 10CFR50 requirements.
References 1)
Letter, C. D. Frizzle (MYAPC) to W. T. Russell (USNRC), " Submittal of Maine Yankee SBLOCA Licensing Analysis in Compliance with 10 CFR 50.46 and in Satisfaction of'INI Action Items II.K.3.30, II.K.3.31 and II.K.3.5 " MN-96-056, April 25,1996.
2)
Letter, E. H. Trotuer (USNRC) to C. D. Frizzle (MYAPC), " Request for Additional Information
- ANF-RELAP SBLOCA Analysis (TAC No. M94834)," June 25,1996.
3)
Letter, C. D. Frizzle (MYAPC) to F. J. Miraglia (USNRC) " Response to NRC Request for Additional Information (RA!) - Maine Yankee SBLOCA Analysis," MN-96-80, October 18,1996.
Page 2
Exposure Centerline Mean Predicted Minus Net Impact of Change")
Interval Measured Temperature Difference
(*F)
(GWD/MTU)
('F)
FROSSTEY-2 Code Version Original Gap Annular Gap Annular Conductance Pellet Conductance Pellet Logic Logic lProprietan)information Withheld)
Computed as the change in Centerline Mean Predicted Minus Measured Temperature attributed to the respective modification.
Table 1 Comparison of Mean Predicted Minus Measured Centerline Temperature Differences for Gap Conductance Iteration Logic and Annular Pellet Modifications 1
a i
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Page 3 l
I
TMH:97:024 l
Attachment B j
Page B-2 j
LooD-Seal-Induced-Core-Uncoverv Question:
a The results of small-break loss-of-coolant accident (SBLOCA) analyses provided by the industry for pressurized-water reactors (PWRs) show that a loop-seal-induced-core-4 uncovery may occur for breaks located at or near the top of the reactor coolant pump (RCP) discharge leg. The resulting peak cladding temperature of 1000 'F to 1500 *F may last for extended periods of time. Under these conditions, the metal-water reaction may resultin significant core wide and peak local oxidations, which must meet the acceptance l
criteria of 10 CFR 50.46(b) for oxidation limits and long term cooling.
l For SBLOCAs with the break location at the top of the RCP discharge leg and break cross-
}
sectional areas of about 0.005 to 0.02 ft', reactor coolant system (RCS) pressure holds i
constant at a relatively high value because the energy added to the RCS from decay heat I
power is matched by the heat removal through the steam generators (SGs) and the energy i
foss through the break. For these break sizes, which are large enough to prevent the refilling of the RCS with emergency core cooling system (ECCS) injection, but small enough to avoid the RCS depressurization following establishment of such a pressure l
plateau, the RCS two-phase level eventually decreases to the elevation of the break at the top of the discharge leg and stabilizes at this level. During this stage of a SBLOCA, the steam generated in the core passes through the SGs to the break. Calculations show that about 90 to 95 percent of the steam generated in the core is condensed in the SGs, and l
a low steam flow rate exits the SGs into the loop seal region. Since the low steaming rate 1
is insufficient to entrain and remove water from the loop seal region, the hydrostatic head l
In the loop seal remains at high levels as steam bubbles through the loop seal region to l
the break. Since the SGs will not condense all of the steam in the SGs for this range of j
small breaks, the low rate of steaming from SG to the loop seal causes a pressure buildup in the reactor vessel upper plenum to balance the hydrostatic head of water in the loop j
seal. If the elevation of the lower portion of the loop sealis below the top elevation of the i
core (as in Maine Yankee), the pressure buildup in the reactor vessel upper plenum may i
become large enough to cause the core to uncover. Depending upon the break size, break orientation, decay heat level, vertical elevation of the loop seal and ECCS pump i
head characteristics, the loop-seal-Induced core-uncovery may develop and exist for extended period of time. The peak cladding temperature may be in the range of 1000 to 1500 'F for an extended period of time and raises concerns regarding the resulting metal-l water reaction exceeding the limits of 10 CFR 50.46(b).
The attached non-proprietary submittal by Framatome Technologies, incorporated provides additional information to describe the staff concerns and the associated phenomena. You are reauested to provide results of relevant calculations and to addrest, concerns associated with RCP loop seal clearina and break orientation, and compliance with the reaulrements of 10 CFR 50.46(bt includina concerns reaardina metal-water reaction and lona term coolina.
Response
Based on this question and the referenced Framatome submittal, there appear to be two separate issues. The first is whether or not very small breaks (0.005 to 0.02 ft') can lead to core uncovery because ofinsufficient venting of steam through the loop seals. The second is whether L
.-.. _. _. _. _ ~ _ _. _ _..
TMH:97:024 i
Attachm:nt B Paga B-3 the loop seals could reform and cause core uncovery in the long term cooling phase of an 1
SBLOCA, given a particular break size and orientation. Since these are somewhat separate issues, they will be addressed separately.
i To address the first issue, two smaller SBLOCA calculations were performed: a 0.005 ft break 2
I
' and a 0.02 ft' break. In the 0.005 ft break (run to 12,000 s), the primary system remained 2
mostly liquid-filled because the high pressure safety injection (HPSI) flow quickly balanced the i
break flow. Therefore, loop seal-induced core uncovery did not occur. Throughout the entire i
event, the mixture levelin the reactor vessel remained above the elevation of the core. Thus, no core heatup occurred. Results of this calculation are shown in Figures 1 to 5.
2
]
In the 0.02 ft break (run to 10,000 s),' more voiding occurred in the primary system. However, the mixture level remained above the top of the core. As a result, no core heatup was calculated. One intact loop cleared relatively early; later, when that loop seal began to replug, the other loop seals began to clear and vent steam. For the last hour of the transient, all three 3i loop seals were plugged with liquid, but sufficient vapor continued to bubble through the loop -
seals to prevent any core uncovery. Results of this calculation are shown in Figures 6 to 10.
The results of these two calculations, combined with the results of the 0.05 ft case (which was 2
i part of the break spectrum analysis previously submitted), demonstrate the range of loop seal phenomena which could occur with such small break sizes: liquid-filled loop seals (0.005 ft 2
. break), loop seals partially filled but with adequate steam venting (0.02 ft ),..and cleared loop 2
2 seals (0.05 ft ). In all three cases, no core heatup was calculated to occur and metal-water reaction was not an issue. Thus, the conclusion is that such small break sizes do not result in l,
loop scal conditions that cause com uncovery and subsequent heatup.
I The second concern, related to break orientation, [
). The issue, as deduced from the NRC question, is whether or not the loop seals replug as ECCS refills the downcomer.
This situation is postulated if the liquid cannot spill out through the break; that is, if the break is on the top of the cold leg instead of the bottom. The implementation of (
l i
1 4
)
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' TMH:97:024 Attachment B P:ga B-4 l',
i 1
Maine Yankee Cycle 15 SBLOCA. Analysis Smaller Small Break Calculation, 0.005 sq f t Break 2500.0' c
a Pressurizer e
o sG-1
' SG 2000.0
,___,3g_3
.m t
.9 y 1500.0 e
LJ g 1000.0 e
E u00.0
.0
.0 2000.0 4000.0 6000.0 8000.0 10000.0 12000.0 Time (sec) 2 Figure 1 - Pressurizer Pressure ke 0.005 ft Break Calculation
l TMH:97:024 l-
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Pags B-5 l-i i
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. Maine Yankee Cycle 15 SBLOCA Analysis i
Smaller Small Break Calculation, 0.005 sq f t Break 120.0 i
i i
l 100.0 O
'l f-N Eo 80.0 t
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.0 -
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.0 2000.0 4000.0 6000.0 8000.0 10000.0 12000.0 Time - (sec) j.!
Figure 2 - Break Mass Flow Rate for 0.005 ft Break Calculation 2
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TMH:97:024 -
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1 Maine Yankee Cycle 15 SBLOCA nolysis j
Smaller Small Break Calculation, 0.005 sq f t Break 1.2 -
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.8 C
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r
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....... i........... '...
.0 2000.0 4000.0 6000.0 8000.0 10000.0 12000.0 Time (sec)
Figure 3 - Break Void Fraction for 0.005 ft: Break Calculation
TMH:97:024 j
Att:chment B Pags B-7
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j i
2 Maine Yankee Cycle 15 SBLOCA. Analysis Smaller Small Break Calculation, 0.005 sq f t ' Break
- O 3 - 50.0 3
e o Primary System e
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.. i... i....
.0 2000.0 4000.0 6000.0-8000.0 10000.0 12000.0 Time (sec)
Figure 4 - Total Primary System and Reactor Vessel Mass for 0.005 ft Break 2
Calculation
TMH:97:024 Atttchm:rit B~
Pags B-8 4
4 Maine Yankee Cycle 15 SBLOCA Analysis 4
Smaller Small Break Calculation, 0.005 sq ft Break 3000.0 e
a Vapor Temperature 4
e o Clad Temperature 2500.0
+
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v i
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.0
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.o 2000.0 4000.0 6000.0-8000.0 10000.0 12000.0 Time (sec) 2 Figure 5 - Hot Assembly Vapor and Clad Temperature (Node 19) for 0.005 ft Break Calculation l'
TMH:97:024
' Atttchment B
"~
Pags B-9 i
2 i
l i
t Maine Yankee Cycle 15 SBLOCA Analysis Smaller ' Small Break' Calculation, 0.02 sq f t Break 2500.0 e
o Pressurizer e
o SG-1 2000.0 SG-2
- gg_3 l
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.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0 8000.0 9000.0 10000.0 Time (sec) 2 Figure 6 - Pressurizer Pressure for 0.02 ft Break Calculation i
,1
TMH:97:024 Attachmsnt B Paga B-10 i
Maine Yankee Cycle 15 SBLOCA Analysis i
Smaller Small Break Calculation, 0.02 sq f t Break 600.0 l
500.0 9x 400 0 0
1 0 300.0 0
S 200.0 e
. i m
.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0 8000.0 9000.0 10000.0 Time (sec)
Figure 7 - Break Mass Flow Rate for 0.02 ft' Break Calculation
~
TMH:97:024 Attachm:nt B Paga B-11 1
Maine Yankee Cycle 15 SBLOCA Analysis j
Smaller Small Break Calculation, 0.02 sq f t Break 1
1.2 10
.8 8
5
.6 y
q e
s l
l u.
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.4
.2
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=
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.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0 8000.0 9000.0 10000.0 Time (sec) 2 Figure 8 - Break Void Fraction for 0.02 ft Break Calculation
~
l TMH:97:024 Attichnunt B l
Paga B-12 l
Maine Yankee Cycle 15 SBLOCA Analysis
-Smaller Small Break Calculation, 0.02 sq f t Break
+
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...i............i...,
i.
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O2 20.0 O
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.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0 8000.0 9000.0 10000.0 Time (sec) 2 Figure 9 - Total Primary System and Reactor Vessel Mass for 0.02 ft Break Calculation l
~
TMH:97:024 Attachmunt U Pega B-13 i
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+
6 f
4 4
1.
4.
Maine Yankee Cycle 15 SBLOCA Analysis Smaller Small Break Calculation, 0.02 sq f t -Break 3000.0 e
c 3 Vapor Temperature c
o Clod Temperature 2500.0
.......................................P.ql.LYL.77.M.f......................................
C 2000.0 v
1 E 1500.0 ba E*
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.o
,,,,...,,,,,,,.w.t,,..
.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0 8000.0 9000.0 10000.0 Time (sec)
Figure 10 - Hot Assembly Vapor and Clad Temperature (Node 19) for 0.02 ft' Break Calculation
TMH:97:024 Attachm:nt B Paga B-14 TOODEE2 Mathematical Models The following information supplements SPC's previous response to Question 2 of the NRC's RAI on the Maine Yankee SBLOCA analysis. Question 2 relates to TOODEE2 mathematical models.
Supolemental Response:
Two issues are associated with Question 2, one is general and the other is specific. They are:
- 1) quantify the error due to neglecting second and higher order terms particularly at the fuel centerline as R approaches zero and justify the adequacy of the first order difference approximation by showing small truncation errors; and 2) assess and quantify the effects of truncation errors of the terms with second and higher order derivatives on the calculated SBLOCA PCT for Maine Yankee.
In response to these issues, SPC performed two analyses: (1) the first analysis derived and quantified the error terms analytically, and (2) the second analysis demonstrated the effect of 4
the truncation error of the second and higher order derivative terms by comparing results i
obtained using the TOODEE2 numerical method against results from a closed-form analytical solution.
Description and results of first analysis The heat conduction equation solved in TOODEE2 with cylindrical coordinates is presented as Equation (A 1) of Appendix A of NUREG-75/057. An adiabatic boundary condition is imposed 4
on the fuel rod centerline. This is accomplished by setting all coefficients in the radial direction in the difference equation to zero at the radial center.
I i
The errors associated with neglecting higher order terms in the Taylor series expansion were derived and evaluated for both steady-state and transient conditions. This derivation and the error results are detailed in the discussion titled:" Spatial Discretization Error in the Radial Heat Conduction Equation in TOODEE2 Code," which follows.
Except for the innermost node (i=2), the magnitude of the higher order terms is shown to be very small and negligible. For the steady-state case it is shown that the temperature error at the innermost node decreases as the number of equally-spaced nodes increases, equivalent to decreasing Ar (i.e., r4 at the innermost node).
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Description and results for second analysis The purpose of the second analysis is to demonstrate the effect of the truncation error of the second and higher order derivative terms by comparing results obtained using the TOODEE2 numerical method against results from a closed-form analytical solution. The existing TOODEE2
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TMH:97:024 Attrchmsnt B Paga B-15 code would require significant modification to perform this calculation because features such as temperature dependent properties, fuel deformation models, metal-water reaction calculations, and heat transfer correlations are hardwired into the code. Therefore, to focus on the issue of truncation errors in the conduction solution, a one-dimensional heat conduction code with heat generation using the numerical solution scheme of TOODEE2 was developed. Steady-state calculations were performed since the focus of this issue is errors due to spatial discretization.
An analytical steady-state solution for radial heat conduction with heat generation was obtained and the equivalent solution was computed using the code with the TOODEE2 numerical solution.
Both calculations used a consistent set of constant material properties, boundary conditions, channel and gap heat transfer coefficients, and fuel rod conditions similar to those calculated for the Maine Yankee SBLOCA near the time of PCT. Since the Maine Yankee calculation uses 8 fuel nodes, a plot of the numerical solution using 8 fuel nodes is shown against the results of the.
closed-form analytical solution in Figure 1. The temperature differences between the analytical and numerical solutions are quite small, further demonstrating that the higher order terms in TOODEE2 can be neglected.
Conclusions (1)
The impact of neglecting the second and higher order derivative terms in the TOODEE2 numerical solution is quite small; therefore, the TOODEE2 code is acceptable for calculating conduction in a nuclear fuel rod.
(2)
The effects of truncation errors due to neglecting the second and higher order derivative terms on the calculated SBLOCA PCT for Maine Yankee is small and not significant.
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