ML20027C497
| ML20027C497 | |
| Person / Time | |
|---|---|
| Issue date: | 09/15/1982 |
| From: | Thomas C Office of Nuclear Reactor Regulation |
| To: | Scherer A ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| References | |
| NUDOCS 8210180023 | |
| Download: ML20027C497 (4) | |
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SEP 151982 Combustion Engineering, Inc.
ATTN: Mr. A. E. Scherer Director Nuclear Licensing 1000 Prospect Hill Road Windsor, Connecticut 06095
Dear Mr. Scherer:
Subject:
Request Number 1 for Additional Information on CENPD-266(P)
We are currently reviewing Combustion Engineering Inc., Licensing Topical Report CENPD-266(P) entitled "The ROCS and DIT Computer Code for Nuclear Design" dated December 1981.
The initial review reveals the need for the additional information indicated i
in the enclosure.
This infonnation is necessary to complete the review - its expeditious sub-mittal will therefore be to Combustion Engineering's advantage. Please advise us as soon as possible of your planned submittal date to permit us, in turn, i
to develop a review schedule. To provide for a timely continuation of the review, we suggest the response by November 1,1982 Sincerely.
Cecil l0.khomas,ActingChief Standardization and Special Projects Branch Division of Licensing
Enclosure:
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SEP 101992 CORE PERFORMANCE BRANCH QUESTIONS ON THE ROCS AND DIT COMPUTER CODES-CENPD-266-P (TACS 47469) 1.
Although comparisons of power distributions between the NEM and H0D methods are given, other important physics parameters such as rod worths, reactivity coefficients, and critical boron concentrations are only calculated usin'g the H0D method. Since the calculational uncertainties for these parameters were obtained from ROCS comparisons with measurements, what calculational uncertainties can be attributed to the NEM?
2.
Comparisons of power distributions between the NEM and H0D methods were done with two different nodal codes; ROCS (HOD) and HERMITE(NEM).
Describe any differences which are expected between ROCS (NEM) and HERMITE(NEM).
3.
. Since the ROCS (NEM) scheme is mentioned as a replacement for PDQ in generating the coefficient libraries for the incore detector code, we will require comparisons of ROCS (NEM) and experiment and/or.
ROCS (NEM) and PDQ.
Provide a comparison of PDQ generated coefficients with ROCS (NEM) generated coefficients.
4.
Will the use of ROCS /DIT and the MC module eliminate the need for a bias correction factor for pin peaking near water holes?
5.
Are the boundary conditions used in the BOC, MOC and EOC PDQ calculations in Figures 2-4 through 2-6 the same as those employed
-in other cycles and other plants? Briefly explain.
6.
Figures 2-4 through 2-6 show comparisons of the H0D and NEM methods with PDQ for 2D midplane power distributions. Comparisons showing 2-D axially integrated distributions would be more informative
.since they could show the effects of axial leakage.
Furthermore, for the M0C and E0C statepoints, they would reflect the axial non-uniformity of the exposures. Please supply axially integrated 2-D distributions showing the percent deviations.
7.
The errors shown in Figure 2.9 are for early cycle and at 50 percent power.
Please show, in a similar manner, errors for other exposures l
and at full power.
8.
Are the power coefficients given in Reference 2.16 still valid?'
Discuss the sensitivity of the measured power coefficients with fuel design, in particular with fuel enrichment and with soluble boron and comment on the adequacy of the correlation used.
9.
Please discuss the limitations of the fine-mesh imbedded method for obtaining pin power distributions.
- 10. Which data library is used in the DIT production calculations, the 85-group or the 41-group set?
Y a;
. 11 Gadolinia is mentioned as a burnup chain in DIT.
It the use of gadolinia is contemplated in CE cores, is any additional information available which would validate the gadolinia modeling?
12.
Please explain how ROCS is used (and hence how k is evaluated) during periods of operation characterized by var $Ng conditions.
Over what total length of a typical cycle are the operating con-ditions variable? What is the uncertainty in k,ff for such operations?
- 13. The number of measured statepoints is larger than the number of
^
calculated statepoints, according to page 4.4.
Please describe the interpolation strategy which can " produce a calculated reactivity at one of the measured critical conditions." Discuss the uncertainties associated with both measured and calculated, on the one hand, and measured and interpolated, on the other.
14.
Most of the 1281 data points presented in Figure 4.1, page 4.26, are scattered around a reactivity value of -0.251 for core average exposures larger than 10,000 mwd /t.
However, for core average exposures in the range from 0 to 10,000 mwd /t there seems to be a clear bias.
This needs to be explained.
15.
Section 4.1.2 summarizes the results of the calculative uncertainties.
No direct results showing calculated and measured bundle-average or axial power distributions have been given for any of the plant -
and cycle-specific statepoints for which standard deviations have been presented in Tables 4.2 through 4.9.
Please show comparisons
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of measured and calculated bundle-average and axial power distributions at specific points in a cycle, for the reactors and cycles referred to in the above section.
16.
There are two entries for Calvert Cliffs II Cycle 3 in Table 4.16 and no data given for Calvert Cliffs I.
The text in Section 4.1.3, page 4.11 mentions four reactors.
Please correct.
- 17. Describe the calculational procedure carried out with ROCS /DIT and specify which ROCS parameters are used in determining CEA bank worth.
- 18. Table 4.19 gives a summary of the differences between measurement and calculations of rod bank worths, in terms of their means and standard deviations, x and S, respectively.
Please show individual n
values of the calculated and the measured results which have been used to form the differences in the summary Table 4.19.
19.
Please describe the steady state (initial) condition of the core just prior to each of the upset conditions discussed in Section 4.2 and define the reactivity worth as it applies to the states of the core in the upset conditions.
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. 20.
Please specify which calculations for the upset conditions discussed in 4.2 were carried out in two dimensions and which in three dimensions, giving reasons and criteria. Similarly, please indicate whether full or quarter core geometries were used for the analyses of the upset conditions.
21.
It is stated in the concluding paragraphs of Section 4.2.1, p' age 4.21 that normal rod bank reactivity results have been taken from the first cycle only calculations, Table 4.18.
What can be said about the applicability of the results of these analyses to later cycles?
22.
It is mentioned in Section 4.2.2, page 4.22 that all ROCS calculations simulated instantaneous rod motion with (prompt) thermal-hydraulic feedbacks "on."
Please explain what feedback mechanisms are implied in this statement.
- 23. ' The one-sided tolerance limits for the random error in pin peaking as calculated by ROCS and MC has been established for F F
and F using differences between ROCS /DIT and measuremhnts! It appeaff that data obtained from certain cycles / reactors have not been included in the combined uncertainty evaluation.
Please comment.
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