ML20211Q705
| ML20211Q705 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/18/1987 |
| From: | Whittier G Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 8476L-GDW, GDW-87-33, MN-87-16, NUDOCS 8703030167 | |
| Download: ML20211Q705 (8) | |
Text
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MAIRE HARHEE 'MOMICPOWER00MPARUe
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(207) 623-3521 e
February 18, 1987 GDH-87-33 HN-87-16 United States Nuclear Regulatory Commission Attention: Document Control Desk Hashington, D. C.
20555
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter to HYAPCo dated January 29, 1987
Subject:
Response to NRC Questions on Cycle 10 Core Performance Analysis Report Gentlemen:
Attachment I documents Maine Yankee's response to the questions contained in Reference (b).
This information was provided to the staff in our February 9,1987 telecon.
Please contact us if you have any questions or require any additional information.
Very truly yours, l
MAINE YANKEE ATOMIC POWER COMPANY kb AV G. D. Whittler, Manager Nuclear Engineering and Licensing GDW/hbg Enclosure cc: Mr. Ashok C. Thadani Mr. Richard Vollmer Mr. Pat Sears Mr. Cornelius F. Holden
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MAINE YANKEE ATOMIC POWER COMPANV ATTACHMENT 1 Response to NRC Ouestions on the Maine Yankee Cycle 10 Reload Submittal Ouestion 1.
The statement is made on Page 76 that the FSAR power distribution, evaluated at full power heat flux, results in a lower DNBR than any of the Cycle 10 predicted power distributions within the symmetric offset pre-trip alarm band, evaluated for their respective maximum power level limit as defined in the PDIL for Cycle 10. This appears to contradict the results shown in Table 5.9 (erroneously referred to as Table 5.11 in the text).
Please comment on this discrepancy.
Answer 1.
The text of the first paragraph on Page 76 of the Cycle 10 Core Performance Analysis Report is incorrectly worded.
It should read:
As a starting point the safety analysis assumes the FSAR design power distribution (Fz - 1.68 and Fl elta H = 1.49) shown in Figure 5.2.
As indicated in Table 5.9, the Cycle 10 predicted power distribution within the S/0 LCO band at the 100% power PDIL, defined in Figure 4.9, results in the lowest DNBR for Cycle 10.
Both the 100% and 94% power PDIL power distributions result in a lower DNBR than the FSAR design power distribution, evaluated at the full power heat flux.
The text on Page 76 erroneously refers to Table 5.11, instead of Table 5.9.
Table 5.9 is the appropriate reference.
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M AINE YANKEE ATOMIC POWER COMPANV Ouestion 2.
The fresh fuel SAFDL is assumed to be bounding for all fuel batches. The justification is given that the fresh fuel contains the core-wide maximum power pin throughout the cycle and the SAFDL for any previously exposed fuel batt.h is greater than or equal to the ratio of the peak power of that batch divided by the peak power of the fresh fuel batch multiplied by the SAPDL for the fresh fuel batch. How was this verified for transient conditions? Describe, for example, how verification is made that the maximum post-drop LHGR does not violate the limiting centerline melt SAFDL for any fuel batch in the event of a CEA drop.
Answer 2.
The ratio of the maximum radial pin power in each fuel batch to the maximum in the core are provided each cycle in Tables 3.5 through 3.7 for the regulating bank insertions to illustrate the magnitude of the SAFDL margin in the exposed fuel. These margins are calculated in Table 1 using the LHGR SAFDL limits from Table 3.4 for BOC and E0C conditions, showing a minimum of 6.7% margin for Type N fuel, 19.9% for Types L and H fuel, and 23.4% for Type E fuel for All Rods Out (AR0) and the regulating CEA bank insertions.
The flyspeck physics analysis each cycle provides an explicit three-dimensional calculation of the LHGR at each location in the core.
The maximum LHGRs for each batch are compared to their respective limits each cycle by the calculated quantity PL (power to fuel limit on LHGR),
which is a function of CEA insertion and symmetric offset conditions.
The flyspeck physics analysis shows LHGR margins comparable to or greater than those calculated by this radial pin power ratio method.
This is because the fresh fuel typically has larger axial peaking factors, and the differences in axial peaking factors in the exposed batches are small relative to the magnitude of the SAFDL margins. As such, the ratio method can be used to demonstrate that significant SAFDL margins exist.
The regulating bank CEA insertion cases are examined by the ratio method since they represent the nominal radial peaking conditions for CEA movement along the Power-Dependent Insertion Limit (PDIL) for both CEA insertion and CEA withdrawal.
These cases also represent the largest perturbations to the core power distribution, resulting in the most probable means of increasing relative power in the exposed fuel.
If a significant SAFDL margin exists under regulating CEA group insertion, it will surely exist for the other Anticipated Operational Occurrence (A00)
SAFDL criteria incidents.
This is illustrated in Tables 2 and 3, which provide the ratios of maximum radial relative pin powers for Types L, or M, and N fuel, respectively, for selected A00 SAFDL criteria incident cases for Cycle 10.
These cases include:
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MAINE YANKEE ATOMIC POWER COMPANY CEA subgroup withdrawal (Bank SA or SB withdrawal from Bank 5 in)
CEA group, subgroup withdrawal, and subgroup movement margins to SAFDL limits by batch are explicitly evaluated each cycle as part of the flyspeck physics analysis described above. None of the cases in Tables 2 and 3 show the exposed fuel SAFDL margins to be less than those of the minimum of the regulating CEA insertion cases.
CEA drop at HFP (ARO and Bank 5 in pre-drop conditions)
The CEA drop results are most limiting at the higher power levels and, as such, HFP cases are shown. CEA drop penalties are applied in the flyspeck analysis as a function of power level, as shown each cycle in Figure 4.11.
These penalties are based on the increase in peaking in the fresh fuel. The cases in Tables 2 and 3 show the exposed fuel SAFDL margins to be within 11. of the minimum of the regulating CEA inserticn cases.
This is to be expected since, although the CEA drop is a severe local effect, the area of maximum peaking is far away from the drop, yielding similar relative power increases in each batch and resulting in similar SAFDL margin relative to the pre-drop condition.
Different moderator density conditions (HZP with ARO or Bank 5 in) l Incidents such as excess load, loss of load, loss of feedwater, and loss of coolant flow result in changing moderator density l
conditions. The ' change from HFP to HZP conditions is a significant I
change in moderator density to illustrate the effect of this variable. None of the cases in Tables 2 and 3 show the exposed fuel SAFDL margin to be less than those of the minimum of the regulating CEA insertion cases.
The maximum radial relative pin power ratio method will continue to be used to demonstrate that significant SAFDL margin exists.
It is recognized that, if significant margin does not exist, an explicit evaluation of the A00 SAFDL incidents will be required to demonstrate that the fresh fuel SAFDL is bounding. Given the present three-batch, low leakage fuel management, it is likely that significant SAFDL margin in the exposed fuel will be maintained.
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MQlNE YONKEE AVOMIC POWER COMPANY Question 3.
The allowable negative limit for the MTC has been extended to -2.96 for Cycle 10 as compared to -2.81 for the previous cycle.
Explain how this was accounted for in the Cycle 10 steam line rupture accident.
Answer 3.
An explicit reactivity balance calculation was performed for the Steam Line Rupture (SLR) accident for Cycle 10.
This balance evaluates the various reactivity components to demonstrate that the reactor will remain subcritical post-SLR, and in a conservative fashion demonstrates that fuel failure limits are not exceeded. One component explicitly used in the Cycle 10 reactivity balance was the Cycle 10 moderator defect curve. This curve incorporates the Cycle 10 characteristic of a more negative HTC.
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O' MAINE YANKEE ATOMIC POWER COMPANY TABLE 1 Maine Yankee Cycle 10 LHGR SAFDL Limits and SAFDL Marain for Each Fuel Tvoe l
Fuel Time in Cycle Life Parameter Types HQC EQC LHGR SAFDL E
21.3 20.6 Limit (kW/ft)
L, M 20.9 19.8 (Table 3.4)
N 22.2 20.9 P
23.1 22.2 Maximum Ratio of E
0.706 0.694 Maximum Relative Pin L, M 0.725 0.710 Power in Each Fuel Type N
0.886 0.878 to Maximum in-Core for P
1.000 1.000 l
AR0 and Regulating CEA Insertions (Tables 3.5 - 3.7)
Minimum SAFDL Margin for E
23.4 25.2 Each Fuel Type Relative L, M 19.9 20.4 to Fresh Fuel for ARO N
7.8 6.7 and Regulating CEA P
0.0 0.0 Insertions (%)*
l l
SAFDL of fresh fuel
MAINE YANKEE ATOMIC POWER COMPANY TABLE 2 Maine Yankee Cycle 10 Ratio of Maximum Radial Relative Pin Powers Maximum in Tynes L or M Fuel to Maximum in Core Additional Cases Time in Cycle Life CEA~
Conditions Confiauration HQC EQC HFP Bank 5A Hithdrawn 0.603 0.647 Bank 5B Hithdrawn 0.650 0.656 HFP ARO and Dropped A 0.718 0.711*
AR0 and Dropped B 0.711 0.719*
Bank 5 In and Dropped A 0.687 0.703 Bank 5 In and Dropped B 0.652 0.694 HZP ARO 0.640 0.690 Bank 5 In 0.549 0.691
- Ratios greater than those for Types L or M fuel in Table 1 which reduce SAFDL margin for Types L or M fuel from 20.4 to 19.4%.
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MAINE YANKEE ATOMIC POWER COMPANY TABLE 3 Maine Yankee Cycle 10 Ratio of Maximum Radial Relative Pin Powers Maximum in Tyne N Fuel to Maximum in Core Additional Cases CEA Time in Cycle Life Conditions Confiauration HQC EQC HFP Bank 5A Hithdrawn 0.862 0.810 Bank 5B Hithdrawn 0.834 0.779 HFP ARO and Dropped A 0.875 0.811 ARO and Dropped B 0.872 0.817 Bank 5 In and Dropped A 0.885*
0.842*
Bank 5 In and Dropped B 0.881 0.839 HZP ARO 0.863 0.804 Bank 5 In 0.863 0.838
No reduction in SAFDL margin for Type N fuel I
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