1CAN039703, Submits Addl Info Re RCS Pressure & Temp Limit Tech Spec Change.Tech Specs,Encl
| ML20136B280 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 03/04/1997 |
| From: | Mims D ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20136B284 | List: |
| References | |
| 1CAN039703, 1CAN39703, NUDOCS 9703100230 | |
| Download: ML20136B280 (12) | |
Text
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-== E ma s a 233 RuzeL M AR 72801 4
Tel 501853-5000 l
March 4,1997 i
1CAN039703 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station PI-137
[
Washington, DC 20555
Subject:
Arkansas Nuclear One -' Unit 1 Docket No. 50-313 License No. DPR-51 Additional Information Regarding RCS Pressure And Temperature Limit Technical Specification Change Request Gentlemen:
By letter dated November 26,1996 (ICAN119608), and supplemented by letter dated December 17,1996 (ICAN129604), Entergy Operations requested changes to Arkansas Nuclear One Unit 1 (ANO-1) Technical Specification (TS) 3.1.2 concerning the Reactor Coolant System pressure and temperature (P/T) limits. In subsequent conversations, the staff requested additional information to be submitted to support to TS change, this additional information is included as Attachment I to this letter.
In addition, ANO-1 has concluded that a reference to "RCS PRESSURE AT "A" HOT LEG TAP (PSIG)" as the label for the Y axis on figures 3.1.2-1, 3.1.2-2, and 3.1.2-3 in the original letter (ICANI1%08) could be misleading and more appropriately should be labeled as "RCS PRESSURE AT HOT LEG TAP (PSIG)". The analysis for the 32 effective full power year figures supports reading RCS pressure from either hot leg tap (A or B). The current TS 3.1.2 figures depict this axis as " Indicated Reactor Coolant System Pressure, psig (at RCS Hot Leg Tap)." The word " indicated" was not carried forward because it could mistakenly be assumed that instrument uncertainties were included in the revised TS figures. As stated in the previous submittal, the appropriate instrument uncertainties will be included in the operating procedures. Attachment 2 of this letter contains the three revised TS figures (3.1.2-1,3.1.2-2, and 3.1.2-3). The attached changes are consistent with the current TS requirements and do not affect the conclusions of the no significant hazards determination of the November 26, 1996, submittal.
Very truly yours, g
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Dwi C. Mims Director, Nuclear Safety DCM/rde
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> U. S. NRC March 4,1997 1 A039703 Page 2 of 2 cc:
Mr. Leonard J. Callan Regional Administrator U. S. Nuclear Regulatory Commission i
Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Mr. George Kalman NRR Project Manag n IV/ANO-1 & 2 U. S. Nuclear Regulatu mmission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852 s
i E
ATTACHMENT 1 ADDITIONAL INFORMATION SUPPORTING TS CHANGE i
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3 ATTACHMENT 1 ADDITIONAL INFORMATION SUPPORTING TS CHANGE 1
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. Attachment 1 Page1 Responses to request for additional information on ANO-1 P/T submittal Guestion Number 1:
It is stated in the submittal that "The FTI cavity dosimetry database, which was developed in the Cavity Dosimetry Benchmark Experiment demonstrated a slight bias in the calculations.
The energy dependent bias removal function, h, was developed...". To the effect that h g
g amounts to a spectral modification movide the values of h for E > 1.0 MeV. h is also 4
g g
defined as a " bias removal constant for group g". Does this mean that h is plant independent and applicable to all measurements i.e. unlike the variability implied by "g removal function"?
Response To Ouestion Number 1:
(A)
The bias removal process can be described either as a function (f) of energy (E),
h = f(E),
i or can be expressed discrew.y by energy group ("g"), as h, which is a constant for g
each group. The discrete form is used in practice.
(B)
The h s were determined in the Cavity Dosimetry Benchmark Analysis, and do not g
involve (in any way) the ANO-specific dosimeter activities presented in the submittal (Tables B2 - B4). The numerical values of the h s are given in Table (1).
g (C) h is plant independent, and is also independent oflocation and of dosimeter type.
g (D)
Application of the bias removal function (h ) to the DORT-calculated fluence g
produces the "best-estimate" (un-biased) fluence. Typically, this amounts to less than a 5% change in the magnitude of the calculated fluence. (The h,is not applied to the measurements.)
(E)
The following describes the development of the bias removal factors.
Introduction One of the primary goals of the Cavity Dosimetry Program was to develop a calculational-based methodology that could be used to accurately determine the neutron fluence in the reactor vessel and/or in the surveiPance capsules. It is also necessary for the methodology to accurately calculate the energy / s adent dosimeter responses in the cavity dosimetry. The measurement results of the cav% J. timetry program were used in a statistical analysis to identify and quantify the inheter: vwgy dependent bias in the calculated fluence. This calculational bias is a function of tne methodology and/or the ENDF/B6 data. As such, it is general, not specific to the Cavity Dosimetry Experiment and therefore applies to all analyses that use the methodology described in Section C of the submittal. The term "blas factor" (sometimes called " bias function") is defined as the set of energy-dependent factors, h, that g
when applied on a group-by-group basis, remove the bias in the calculated fluence over a
i i
Page 2 specified energy range. The concept of the bias removal factor is discussed in detail in the following.
The Bias Removal Factor Concept This section describes the simple concept behind the bias removal factor techrdque developed in the following sections. First, define the tme value of some arbitrary physical quantity, Q, as Q"". Secondly, define C as the value of the same physical quantity as determined by some analytical process. Finally, define M a.= the value of the same physical quantity determined by some measurement process. In general, C
- Q"*,
M
- Q " ",and M*C The goal is to determine the best estimate of the true value, Q ", which in a 8
calculational-based methodology is defined by:
(1)
Q""=Cemco The bias in the measured quantity (B.) is removed by calibrating the measurement methodology to certified standards traceable to the National Institute of Standards and Technology. The bias in the calculated quar.tity (Bc) is determined by:
(2)
Bc = C - M The bias in C can be removed either additively or multiplicatively, that is:
(3)
Cameo = C - Bc or, (4)
Cmamco = C x h '
Where h = fIC,M,C/M)
Naturally, Q"" would differ from Q"" over a range that is defined as the product of Q""
and the uncertainty in Q"", that is, (5)
[Q"" - U(Q"")] s Q"" s (Q"" + U(Q"")]
or (6)
(Cmauno x (1-U)] s Q"" s [Cmamco x (1+U)]
Combining (4) and (6) yields
1 l
i Attachment 1 Page 3 (7)-
.[C x h x (1-U)] s Q"" s [C x h x (1+U)] -
or, since h = f(C,M,C/M),
(8)
[C x f(C,M,C/M) x (1-U)] s Q"" s [C x f(C,M,C/M) x (1+U)]
Equation (8) states that the true value of a hypothetical physical quantity that has been determined by both measurements and calculations can be expressed as a function of the calculated value, the measured value, and the ratio of the calculated and measured values.
The preceding generalized discussion expresses the theory upon which the determination of the bias in the fluence is based. In moving from the general to the specific, however, there are a number of significant differences, which will now be discussed.
The neutron fluence, which is the quantity ofinterest, is not (and cannot be) measured directly. Instead, a quantity that is related to the flux in a known way (the dosimeter response) is measured. This means that M, C, and C/M do not have the same relationship to neutron flux.(4) that they had in the previous theoretical discussion, but the fundamental idea i
still applies.
The physical quantity ofinterest is the flux integrated over some energy range, say E > 1.0 MeV. The measured quantity is a dosimeter response that is related to the flux in a known way, but which is integrated over a different energy range. Because of this energy-coverage i
disparity between the measured quantity and the quantity ofinterest, the bias removal function developed for the actual fluence calculational methodology must be a function of energy.
Expressed discretely, the bias removal function would have the following form:
(9) h, =f(C,, M, ( c, ))
M and it would be used to determine the best-estimate flux in this way:
(10) 4"87 = E. (4"k), x h;'
where g = energy index (4""), = calculated neutron flux in group 'g' h,
= bias removal factor for group 'g'
1 t
Page 4 The final methodology must be able to determine the fluence at numerous locations in the reactor vessel. Given the geometrical configuration, it would be reasonable to think that a space-dependent bias would be present; for example, with a space dependent bias, the best-estimate fluence at the inside surface would have been obtained using a different set of bias factors than those that would have been applied to obtain the best estimate fluence at the T/2 location. This example poses one of the fundamental questions that the Cavity Dosimetry Benchmark Experiment was designed to answer: whether there is a space-dependent bias in the calculational methodology To gather the data necessary to answer this question, dosimetry was placed at numerous locations throughout the cavity and in two standard (unirradiated) surveillance capsules in the vessel. The in-vessel and one string of ex-vessel dosimetry were located at the same azimuthal position. The results were evaluated and
)
analyzed, and it was found that there is no significant location bias. The biases calculated using the measured data from the cavity dosimetry were statistically indistinguishable from the biases calculated using the in-vessel dosimetry. Since the energy-dependent bias did not change significantly from the in-vessel locations to the ex-vessel locations, it is inferred that it could not have changed much in the vessel. Based on this reasoning, one universally-applicable set of energy-dependent bias factors was developed, using data from both the in-vessel and the ex-vessel dosimetry measurements.
The bias removal factor, h,, is a function of energy only. As discussed previously, there is no position bias, so it applies at all positions ofinterest, as long as they are not outside of the beltline region. In out-of-beltline regions, the calculated flux is not reliable, apriori, so the bias factors under consideration here do not apply for calculated fluxes outside the beltline agion.
Page5 TABLE 1 BIAS REMOVAL FACTORS (E > 1 MeV)
Energy Group Upper Energy, MeV h,
1 17.33
~1.020 2
14.19 1.022 3
12.21 1.022 4
10.0 1.021 5
8.607 1.020 6
7.108 1.020 7
6.065 1.022 8
4.966 1.019 9
3.679 1.014 10 3.012 1.004 11 2.725 0.988 12 2.466 0.982 13 2.365 0.979 14 2.346 0.977 15 2.231 0.970 16 1.921 0.960 17 1.653 0.952 18 1.353 0.913 19 1.003 Ouestion Number 2:
l Referring to the C/M results for Np-237 and U-238 which is stated to be under review and investigation: is it possible that the results will alter the contents of this submittal?
Response To Ouestion Number 2:
It is not possible that the results of the investigation of the U and Np bias would change the j
results of this analysis. This is explained below.
Since a calculational-based methodology was utilized, the measurements are used only to check the calculations. The calculated flux results were not adjusted to agree with the measurements. The calculated fluence was judged to be correct (uncertainty less than 20%)
based on statistical comparisons of the measured dosimeter activitics to the corresponding calculated activities. The Uranium C/M data were included in the bias and uncertainty i
analysis, but the Np data were not.
It is expected, based on the results of the other dosimeters, particularly Nb, that the resolution of the biases in the U and Np results will have the effect ofimproving the C/M ratios, (i.e.
.~
. Attachment 1 Page 6 L
bringing them closer to unity) thus improving the agreement between calculations and measurements and providing further confidence in the calculations. No changes to the calculated results would occur.
1 Ouestion Number 3:
In section D " Uncertainty" it is stated that, "The mean measured uncertainty associated with i
the ANO-1 cavity dosimetry is 7.44%". Given that in the equivalent location in PSA the uncertainty was over 10%, clarify what does the 7.44% represent. Are geometry (location) and material (density and composition) contributions to the uncertainty included? If not, why not and ifyes, how?
Response To Ouestion Numberl The quoted 7.44% uncertainty is dermed as the mean uncertainty in the measured specific j
activity (pCi/ gram) of the dosimetry that was employed in the ANO cavity over cycles 10 - 12. Since this is the uncertainty in the specific activity (not the uncertainty in the
" measured fluence"), it is independent oflocation and of all of the many other factors that affect the magnitude of the flux to which the dosimeter was exposed (such as density and composition).
The primary factors that were included in the determination of the uncertainty in the measured specific activities are:
- 1. Counting error
- 2. Error introduced in measurement methodology to obtain pCi/ gram (from CPM):
self attenuation correction geometry correction (offset, distance, shape, etc.)
mass and purity concentration (aliquot) competing x-rays (Nb)
The 7.44% measurement uncertainty is used as one component (among several) in a statistical process to show that the ANO-specific uncertainty falls within the FTI Standard Fluence Uncertainty (Table D-3). This is discussed in detail in the B&WOG Fluence and Uncertainty Topical Report, planned for submission in late March or early April.
P:gs 7 Question Number 4:
In section D it is also stated that "These values and the CM comparisons for each dosimeter indicate that the ANO-1 benchmark uncenainty can be combined with the FTI database".
There is no justification for this statement in the sense that no statistical adjustments were presented that the two data groups belong to the same population and, thus, could be combined. Please explain how you reached this conclusion.
Response To Ouestion Number 4:
In order to confirm that the generic calculational methodology produced acceptable results in this plant-specific analysis, it was necessary to show that, (1) the uncertainty in the ANO-specific measured dosimeter activities is consistent with the uncertainty in the measured dosimeter activities in the FTI database, and (2) the CM comparison in the ANO-specific benchmark is consistent with the CM benchmark uncertainties in the FTI database. While it can be shown that the ANO-specific uncertainties can be combined statistically with the FTI database uncertainties, it is not necessary to do so for purposes of this submittal, and it has not been done. The intent of the quoted passage was only to convey the fact that the ANO-specific uncertainties " fit" within the database uncertainties.
Question Number 5:
(The following is a paraphrase of an additional (verbal) question asked on February 27,1997).
There are some large discrepancies between the CM results of the Ni dosimeters between cycles 10,11, and 12 (Tables B2, B3, and B4). This is also true for the U-238 dosimeters.
Does this have an effect on the reponed fluences?
Response To Ouestion Number 5:
No, the discrepancies (systematic and random deviations) have no effect on the reported fluence results because FTI does not use the plant-specific measured results to adjust the calculated fluence. In accordance with specific provisions of the Draft Regulatory Guide 1053, the plant-specific CM results are used only to check (or " benchmark") the calculated results. The reported fluences were obtained by calculations alone, and do not involve the measurements in any way.
o ATTACHMENT 2 PROPOSED TECHNICAL SPECIFICATION CHANtJCS (pages 20a. 20b. and 20c) l