ML20217K941
| ML20217K941 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/30/1998 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9804070339 | |
| Download: ML20217K941 (9) | |
Text
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Northern states Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. E.
Welch, MN 55089 March 30,1998 10 CFR Part 50 Section 50.90 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING STATION Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Response to March 16 and 19,1998 Requests for Additional Information for License Ammendment Request dated March 6,1998 On March 16 and 19,1998, the NRC Staff requested additional information regarding our License Amendment Request dated March 6,1998, which proposed changes to the Technical Specifications to update the heatup and cooldown rate curves, incorporate the use of a pressure and temperature limits report, and change the pressurizer power operated relief valves operability temperature. Our response I
to the March 16,1998, request for additional information is provided as Attachment
- 1. Our response to the March 19,1998, request for additional information is I
provided as Attachment 2. In these attachments NSP makes no new commitments.
If you have any questions concerning this supplemental response, please contact j
John Stanton at 612-388-1121 x4083.
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l Joel P. Sorensen i
j Plant Manager 3n' a-Prairie Island Nuclear Generating Plant f
l 9804070339 980330 PDR ADOCK 05000282 p
USNRC NORTHERN STATES POWER COMPANY l.
March 30,1998 Page 2 l
f c:
Regional Administrator-Ill, NRC NRR Project Manager, NRC Senior Resident inspector, NRC State of Minnesota, Attn: Kris Sanda J. E Silberg Attachments:
Affidavit Response to March 16,1998 Request for Additional Information for License Ammendment Request dated March 6,1998
- Response to March 19,1998 Request for Additional Information for License Ammendment Request dated March 6,1998 J
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t UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET NO.
50-282
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50-306 Response to March 16 and 19,1998 Requests for Additional Information for License Amendment Request dated March 6,1998
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Northern States Power Company, a Minnesota corporation, with this letter is submitting information to support a requested license amendment.
This letter contains no restricted or other defense information.
l NORTHERN STATES POWER COMPANY By
[/oel P Sore'nsen Plant Manager Prairie Island Nuclear Generating Plant On this the%D day ofAck lW before me a notary public in and for said county, personally appeared Joel P Sorensen, Plant Manager, Prairie Island Nuclear Generating Plant, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of the Northem States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay.
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Response to March 16,1998 Request for Additional information for License Ammendment Request dated March 6,1998 Question 1:
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Why do the measured saturated activities for capsule R from the two most recent submittals (Ref.1 and Ref. 3) for Units 1 and 2 change in different magnitudes and g
direction from previous submittals (Ref. 2 and Ref. 4) given the fact that the history of l
the capsules is so similar?
Ref.1 WCAP-14779, Rev. 2," Analysis of Capsule S from the Northern States Power Company Prairie Island Unit 1 Reactor Vessel Surveillance Program",02/98.
Ref. 2 WCAP-11006, " Analysis of Capsule R from the Northern States Power Company Prairle island Unit 1 Reactor Vessel Surveillance Program",02/86.
Ref. 3 WCAP-14613, Rev. 2, " Analysis of Capsule P from the Northern States Power Company Prairie Island Unit 2 Reactor Vessel Surveillance Program",02/98.
Ref. 4 WCAP-11343, " Analysis of Capsule R from the Northern States Power Company Prairie Island Unit 2 Reactor Vessel Surveillance Program",12/86.
I Resnonse:
There are three factors that are affecting the differences in the measured saturated activities for Capsules R withdrawn from Units 1 & 2:
- 1. Updates to the methodology,
- 2. Updates to the basic nuclear parameters, i.e. decay constants, target atomic weight fractions, and fission yields, etc.., and
- 3. Radial gradient factors correcting the activities to the capsule center.
I Table 1 shows a comparison of the measured activities showing these combined effects.
The methodology employed in both original reports (Refs. 2 & 4) assumed a generic, design basis core source distribution, in which cycle-to-cycle flux variations were not considered. Thus the saturated activity is derived from Eq. 6-3 of the referenced reports as:
i
m v
Attachn nt 1 P ge 2 A
. Saturated Activity =,
[pl (1 - c'"> )e*<
j=1 man
- where,
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measured specific activity (dps/g)
A
=
Pj average core power level during irradiation period j
=
Pmo maximum or reference core power level
=
A
=
decay constant of product nuclide length of irradiation period j tj
=
to decay time following irradiation period j
=
total number ofirradiation periods n
=
As plants began to change core management by moving from an out-in fuel loading pattern to low-leakage or in-out patterns, cycle-to-cycle flux variations became apparent. The methodology for calculating the reaction rates (and saturated activities) evolved to account for changes in sensor reaction rates caused by variations in flux level induced by changes in the core spatial power distributions from cycle to cycle. Thus as shown in Refs 1 & 3, the saturated 1
activity derived from the reaction rate equation in the referenced reports is:
l A
Saturated Activity =,
p i
[ p 'ax C,(1 - e~"')e"'
j=1 m
- where, Cj Calculated ratio of $(E > 1.0 MeV) during irradiation period j to the time
=
weighted average $(E > 1.0 MeV) over the entire irradiation period For a single cycle irradiation, Cj, is taken to be 1.0. However, for multiple cycle irradiatior's, Pracularly those employing low leakage fuel management, the additional Cj erm should be t
employed. The impact of changing flux levels for constant power operation can be quite significant for sensor sets that have been irradiated for many cycles in a reactor that has transitioned from non-low leakage to low leakage fuel management or for sensor sets contained in surveillance capsules that have been moved from one capsule location to another.
Although the Prairie Island units appear to have similar operating histories, tim spatial core power distributions have been significantly different such that the Cj's for the Capsule R irradiation is quite different as shown below:
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~
P:g3 3 Prairie Island Unit 1 Prairie Island Unit 2 Cyde ME > 1.0 MeV)
Q 4(E > 1.0 MeV)
Q 1
1.42E+11 0.967 1.39E+11 0.919 2
1.28E+11 0.871 1.45E+11 0.958 3
1.57E+11 1.067 1.49E+11 0.985 4
1.51 E+11 1.026 1.51E+11 1.000 5
1.59E+11 1.080 1.67E+11 1.106 6
1.59E+11 1.084 1.52E+11 1.005 7
1.32E+11 0.897 1.46E+11 0.964 8
1.73E+11 1.177 1.34E+ 11 0.888 9
1.26E+11 0.855 1.86E+11 1.229 Average 1.47E+11 1.51 E+11 For the true integrating reactions, i.e. the long-lived product reactions, the reaction rates are generally not impacted by the effect of the changing flux levels, however, for the short-lived reactions, the impact is more significant. Therefore, there is very little difference in the saturated activities of the long-lived reactions, e3Cu, "Co, 238U,and Np. However, for the 237 "Fe and 58Ni reactions, the act:vities differ in magnitude and direction between the units which is due to the Cycle 9 flux relatve to the average as shown by the Cj terms above.
The second factor causing the differences in the reported saturated activities is due to the nuclear parameters used in the evaluations. These data, decay constants, target atomic weight fractions, fission yields, etc. have been updated by intemational consensus bodies and published. These changes would act in equal magnitude and direction for both units.
A third factor that acts in equal magnitude and direction in both units is the effect of radial gradient corrections to the geometric center of the surveillance capsule. As noted in Tables 6-8 for Capsules R of References 2 and 4, the reported saturated activities have been gradient corrected to the capsule center position. The latest submittals (References 1 and 3) report saturated activities that have not been radially gradient corrected, however, radial corrections are included in the reported reaction rates. Figures 4-2 in all four referenced reports show the dosimeter position relative to the core. The Fe wires are placed in the front portion of the capsule closer to the core than the Cu, Ni, or Co wires and the U and Np fission monitors are located at the geometric center.
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Table 1 Comparison of Capsule R Saturated Activities from Prairie Island Units 1 and 2 Prairie Island 1 Prairie Island 2 Table 6-8 Table 6-8 Table 6-8 Table E-8 WCAP WCAP WCAP WCAP 11006
'14779d2
%_dtff 11343 14613r2
% diff
- Cu-(n.a)
Top Mid 4.90E+05 4.29E+05 14.3 %
4.84E+05 4.17E+05 16.2 %
Bot Mid 5.06E+05 4.43E+05 '
14.2 %
5.20E+05 4.48E+05 16.0 %
"Fe (n,p)
Top 5.42E+06 6.09E+06
-11.0%
5.85E+06 5.62E+06 4.1%
Top Mid '
4.89E+06 5.49E+06
-10.9%
5.38E+06 5.17E+06 '
4.0%
Middle 5.07E+06 5.69E+06
-10.9%
5.79E+06 5.53E+06 4.6%
Bot Mid 5.12E+06 5.76E+06
-11.1 %
5.59E+06 5.36E+06 4.2%
- Bottom 5.28E+06 5.93E+06
-11.0%
6.31E+06 6.07E+06 4.0%
Bottom 6.18E+06 5.94E+06 4.1%
"Ni (n.p)
Middle
.7.46E+07 - 7.59E+07
-1.6%
9.42E+07 7.14E+07 31.9 %
"Co (n,y)
Top 1.10E+08 1.31E+08
-16.2%
1.03E+08 1.21E+08
-14.9%
Bottom 1.20E+08 1.44E+08
-16.7%
1.12E+08 : 1.33E+08
-15.8%
Bottom 1.45E+08 l
"Co (n,y) Cd
. Top 4.37E+07 5.24E+07
-16.7%
Bottom 4.44E+07 5.33E+07
-16.7%
- 'U (n,f)
Middle 1.14E+07 1.20E+07
-5.3%
1.24E+07 1.22E+07 1.4%
- 7Np (n,f)
Middle 8.19E+07 8.12E+07 0.8%
7.37E+07 7.25E+07 1.7%
l r
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Response to March 19,1998 Request for Additional Information for License Ammendment Request dated March 6,1998 Note:
Referenced reports are identified in Question 1 of Attachment 1, " Response to March 16,1998 Request for Additional information for License Ammendment Request dated March 6,1998" Question 1:
How can the cycle specific fluxes from Capsules R removed from Prairie Island Units 1 and 2 be so different since they are located at the same respective location in each reactor and irradiated for approximately the same period of time prior to being removed fo!!owing Cycle 97
Response
Although the Prairie island units appear to have similar operating histories, the spatial core power distributions have been significantly different. For Unit 1 Cycle 8 a fresh assembly resided adjacent to Capsule R, while in Cycle 9 a low enrichment once bumt assembly (reactivity equivalent to a twice bumt assembly) occupied that core location. In Unit 2 the situation was reversed. For Unit 2 Cycle 8 a twice bumt assembly resided adjacent to Capsule R, while in Cycle 9 a fresh assembly occupied that core location.
Question 2:
Why is there only one bare "Co(n,y) activity from the bottom position reported in Reference 2 but two reported in Reference 17
Response
1 Two bare Co foils were removed from Capsule R of Unit 1 and analyzed. In the original Capsule R report (Reference 2) these two samples were averaged together and reported as one bottom sample. In the latest submittal (Reference 1), the two samples were analyzed and reported separatey. The difference between the reported activities is as described above in the response provided to the 03/16/98 NRC question.
Page 2 -
Question 3:
Why are assU(n,f) reactions labeled " corrected" reported in Tables 6-8 for Capsules R in References 2 and 4 but not used?
Response
238 Tables 6-8 for Capsules R in References 2 and 4 show the measured saturated U(n,f) 23s (n,f) activity and denoted with table note (c). A activity and a corrected measured saturated U
235 0.85 multiplicative factor was applied as a correction to account for 305 ppm U impurity and 23e the build-in of Pu. Additionally in Tables 6-8 of References 2 and 4 a calculated saturated
'88U(n,f) activity is presented, it should be noted that in both referenced reports the calculated saturated asU(n,f) activity should be moved down one line and compared with the corrected 2
activity. The reported C/E ratio is the calculated to corrected activity ratio.
In Tables 6-9 of References 2 and 4, the results of the fast neutron dosimetry are presented for each unit as the measured and calculated saturated activity, fast neutron flux, and fast neutron 23s (n,f) activity is indeed used in the evaluation.
fluence, it should be noted that the corrected U
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