ML20217J072
| ML20217J072 | |
| Person / Time | |
|---|---|
| Issue date: | 10/18/1999 |
| From: | NRC (Affiliation Not Assigned) |
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| ML20217J058 | List: |
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| PROJECT-702 NUDOCS 9910220267 | |
| Download: ML20217J072 (5) | |
Text
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1 UNITED STATES g
j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 3066160001 o
.....,o 1
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TOPICAL REPORT EMF-2158(PL REVISION 0.
"SIEMENS POWER CORPORATION METHODOLOGY FOR BOILING WATER REACTORS:
EVALUATION AND VALIDATION OF CASMO-4/Ml_CROBURN-82"
1.0 BACKGROUND
i l
Topical Report EMF-2158(P), Revision 0,' describes the methodology behind the application of the Siemens Power Corporation's (SPC's) boiling water reactor (BWR) neutronics design code system (Reference 1). The code system consists of two codes: the lattice spectrum / depletion code (CASMO-4), and the steady-state reactor core simulator code (MICROBURN-B2).
Together these two codes are used to perform initial and reload core design, calculate parameters for safety analyses, and perform off-line and on-line core monitoring functions.
CASMO-4 and MICROBURN-82 have received benchmark approval for use in commercial reactor applications. The new code system replaces the existing neutron codes used for the current SPC BWR neutron design and safety methodology (Reference 2).
l The new SPC code system incorporates edvanced model features that are essential for today's
)
new core design. One of these features is the inclusion of the pin power reconstruction method.
This report establishes a methodology evaluation and validation criteria by which a new neutronics design code o' We system would be assessed for application to BWR neutronics design. These criteria are c.tablished to address the need for more accurate modeling for current and future reactor core / fuel lattice designs and operations. This report contains the results of the application of these criteria to assess the calcuistional results of CASMO-4 and MICROBURN-B2 to SPC. The evaluation and validation of the SPC code system is benchmarked with data from a variety of operating reactor core /fuellattice designs.
2.0 TECHNICAL EVALUATION
The upgraded SPC BWR neutronics design code system consists of the CASMO-4 lattice spectrum / depletion code and the MICROBURN-82 steady-state reactor core simulator code.
The CASMO-4 code, was developed by Studvik of America, and the MICROBURN-B2 code was developed by Siemens. MICROBURN-82 has been applied to European BWR core designs, and benchmarked against European BWRs.
The CASMO-4 code determines a multi-group heterogeneous medium neutron spectrum in a fuel lattice consisting of fuel rods, bumable poison rods, water rod / channels, and structural components. CASMO-4 homogenizes the heterogeneous lattice spectrum into a neutronically equivalent homogeneous medium, determines the pin power distributions, and depletes 9910220267 991018 PDR TOPRP EMVEXXN C
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nuclides in fuel and burnable poison pins; CASMO-4 uses a variety of nuclear data libraries, ranging from BNL-84, JEF-1, JEF-2.1, END/B-V, END/B-Ill, END/B-IV, and END/B-V.'
The main data output from CASMO-4 is a set of the following two neutron energy group data (1)
' a microscopic and macroscopic cross-section for a spatially homogenized lattice, and (2) pinwise power distribution, exposure distribution, and energy deposition in various components of a fuellattice. The output data from CASMO-4 is processed by an auxiliary code into a lattice neutronic data library for the MICROBURN-B2 core simulator code.
The MICROBURN-B2' code determines core-wide nodal exposure and nuclide density distribution., channel inlet flow distribution, and fuel thermal performance parameters such as linear heat generation rate, axial planer linear heat generation rate (APLHGR), and critical power ratio. These predicted results are used to design fuel cycles, to assess safety limit margins, and to monitor operating reactor cores.
The local pin power distributions calculated by the MICROBURN-B2 code are validated by comparison with results from higher order methods and pin gamma scan measurements. A substantial colorset of geometries were simulated and the resulting pin power distributions were simulated; the resulting pin power distributions were cc..ipared with the predicted values of MICROBURN-82 and CASMO-3/CASMO-4. Comparisons were also made with Quad Cities Unit 1 and KWU-S gamma scan measurements, to determine the uncertainties of predicted local
. pin power distributions.
The SPC core monitoring system utilizes the Transverse-Incore-Probes (TIPS) to determine j
(measured) incore power distribution. - Although the core simulator model uses the MICROBURN-B2 code to calculate (predict) incore power distribution, the TIP obtained measured power has associated with it a statistical uncertainty. To determine the magnitude of this uncertainty, a statistical analysis is performed of the predicted-versus-measured TIP
- distributions and local pin power distributions using NRC-approved statistical methods (Reference 2).
1 3.0 STATISTICAL ASPECTS OF CASMO-4/MICROBURN-B2 The statistical aspects of CASMO-4 and MICROBURN-82 consist of applying appropriate statistical techniques (Reference 2) to the CASMO-4/MICROBURN-B2 code system database.
The statistical analysis procedure in this approved reference is employed to determine the uncertainties in the measured power distribution of the CASMO-4/MICROBURN-B2 code
. system.
The procedure consists of determining the measured nodal power distribution and the measured
~ maximum pin power distribution in a node with their associated uncertainties. Similarly, the
. measured bundle power and the measured maximum pin power in a bundle, with their associated uncertainties, are also determined. The staff reviewed the methodology for determining these uncertainties in an earlier submittal (Reference 2).
SPC compared the calculated power distribution and the measured power distribution. SPC then used these comparisons to verifv the results of the evaluation of the calculated power
(g-4 3-distribution uncertainty from the calculated TIP distribution uncertainty. The data base used for verifying these uncertainties consisted of full-core measurements from C-lattice and D-lattice
- reactors.f Detailed information on the data base is in Table 9.1 of Topical Report EMF-2158(P).
Comparison of the measured power distribution uncertainties for the new
' CASMO-4/MICROBURN-B2 code system, and the associated criteria reported in Section 5.3 of Topical Report EMF-2158(P), are in Table 9.0 of the topical report.. The comparisons show that the measured power distribution uncertainties of the new code system are less than the acceptance criteria as specified in Section 5.3 of the topical report. The staff agrees with these usults.
4.0L EVALUATION OF THE CASMO-4/MICROBURN-B2 METHODOLOGY
-4.1.
- CASMO-4 p
The CASMO-4 code is capable of generating heterogeneous medium multi-group neutron spectrum and " calculating burnup chain equation solutions for heavy nuclides, fission product nuclides, and poison nuclides in each fuel pin. CASMO-4 uses deterministic transport methods.
- At the pin cell level, it exclusively uses the collision probability method to collapse the 40/70 group nuclear data into multi-group data. At the lattice level, it uses a characteristics method for the neutron transport equation solution. One improvement of CASMO-4 over its predecessor CASMO-3 is that CASMO-4 does not need to perform any pin cell spatial homogenizaton to perform a 2-D lattice-wide transport calculation, a highly desired feature when dealing with
' bumable poison rods with high gadolinia concentration (Reference 3).
The primary use of CASMO-4 within the SPC neutronics method is to determine two groups of homogenized microscopic and macroscopic cross L dion data as well as pin power and bt mup distributions for fuellattices.
4.2 MICROBURN-B2 MICROBURN-B2 is an improved version of the NRC-approved MICROBURN-B simulator code.
- MICROBURN-B2 so!ves the two-group neutron diffusion equation based on the interface current
. method. It is capable of calculating the bumup chain equation solutions for heavy nuclides and burnable poison nuclides. It is also capable of determining the nodal power, bundle flow, and void distribution, as well as of determining pin power distributions and thermal margins to technical specification limits. MICROBURN-B2 incorporates several new and advanced features, such as the advanced nodal expansion method solution of diffusion equation, nodal
- bumup and spectral history gradient model, and a pin power reconstruction model. All these features enable MICROBURN-B2 to obtain more accurate nodal and pin power distributions l
' (Retet ance 4).
Analysis conducted by SPC shows that the application of MICROBURN-B2 to BWR core
~ designs would not necessitate changes to the SPC's approved safety analysis methodology.
MICROBURN-B2 is compatible with the approved safety aaalysis codes and is consistent with the approved neutronics safety methodologies cf SPC presented in fteference 2.
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5.0
- VAL DATION OF CASMO-4/MICROBURN 82 METHODOLOGY
- The validation of the CASMO-4 code is based on critical experimenis, such as those conducted
-_ st KRITZ (Reference 5) and those conducted by Babcock and Wilcox (B&W) (Reference 6).
. These experiments provided critical K-effective and pin-by-pin fission rate measurements.
Additional validation data included Doppler resonance measurements, and isotopic inventory
' ' measurements, such as those Irom Yankee Rowe, which provides what is considered to be i acceptable measured d ta 7.an W industry (Reference 7),
In addition to these measurements, comparisons with results from Monte Carlo sin'JIStion Codes
.(such as MCNP, Reference 8), which are generally accepted by the industry, were also performed to further validate the overall methodology of the CASMO-4 code. Ganma scan measurements data of pin power distribution was also utilized in the validation prc cess of CASMO-4 and MICROBURN-B2.--The analysis showed that the CASMO-4 lattice spectrum / depletion code produces a level of accuracy acceptable for SPC BWR fuel bundle and core design. SPC chose six operating BWR reactors to validate the CASMO-4/MICROBURN-B2 code setemi SPC conducted analyses on hot operating conditions critical K-effective measurements, TIP measurements, and cold critical measurements for a very large number of fuel cycles. These fuel cycles were specifically chosen to contain various types of fuel mechanical designs from different vendors throughout the world. The results of the analysis indicated that the CASMO-4/MICROBURN-82 code system accurately predicts core physics
. parameters._ Analysis of the predicted accuracy was found to be independent of core loading patterns, fuel assembly types, and core operating modes. A tabulation of these physics
. parameters (validation criteria) appear in Tables 5.1, 5.2, and 5.3, along with the tabulated results of the analysis, in Chapter 7 of Reference 1. The staff agrees with these results.
6.0 CONCLUSION
The staff has reviewed the analyses in Topical Report EMF-2158(P), Revision 0, "Siemens
- Power Corporation Methodology for Boiling Water Reactors: Evaluation and Validation of CASMO-4/MICROBURN-B2," and concludes that on the basis of its findings, Topical Report EMF-2158(P), Revision 0, is acceptable for licensing evaluations of BWR neutronics designs and applications in accordance with SPC's agreement (Reference 9), subject to the following conditions:
1.
The CASMO-4/MICROBURN-B2 code system shall be applied in a manner that
. predicted results are within the range of the validation criteria (Tables 2.1 and 2.2) and i measurement uncertainties (Table 2.3) presented in EMF-2158(P).
2.
The CASMO-4/MICROBURN-B2 code system 3all be validated for analyses of any new fuel _ design which departs from current orthogonal Im&e designs and/or exceed gadolinia and U-235 enrichment limits.
3.
The CASMO-4/MICROBURN-B2 code system shall only be used for BWR licensing
- analyses and BWR core monitoring applications.
4.
The review of the CASMO-4/MICROBURN-B2 code system should not be construed as a generic review of the CASMO-4 or MICROBURN-B2 computer codes.
I
. 5.
The CASMO-4/MICROBURN-B2 code syste is approved as a replacement for the CASMO-3/MICROBURN-B code system used in NRC-approved SPC BWR licensing methodology and in SPC BWR core monitoring applications. Such replacements shall be evaluated to ensure that each affected methodology continues to comply with its SER restrictions and/or conditions, i
6.
SPC shall notify any customer who proposes to use the CASMO-4/MICROBURN-82 code system independent of any SPC fuel contract that conditions 1 through 4 above must be met. SPC's notification shall provide positive evidence to the NRC that each customer has been informed by SPC of the applicable conditions for using the code system.
i
7.0 REFERENCES
1.
Letter from James F Mallay (SPC) to the U.S. Nuclear Regulatory Commission, submitting Topical Report EMF-2158(P), Revision 0, "Siemens Power Corporation Methodology for Boiling Water Reactors: Evaluation and Validation of CASMO-4/MICROBURN-B2," December 30,1998.
2.
Exxon Nuclear Methodology for Boiling Water Reactors-Neutronic Methods for Design and Analysis," XN-lJF-80-19 (A), Vol.1 (March 1983), Supplements 1 and 2, and j
- Benchmark Results for the CASMO-3G/MICROBURN-B Calculation Methodology,"
XN-NF-80-19(P)(A), Vol.1, Supplements 3 and 4 (November 1990).
3.
D. Knott, B.H. Forssen, and M. Edenius, "CASMO-4, A Fuel Assembly Burnup Program, Methodology," STUDSVIK/SOA-95/2, Studsvik Proprietary (September 1995).
4.
H. Moon, "MICROBURN-B2: Steady State BWR Core Physics Method," EMF-1833(P),
Rev. 2, Siemens Power Corporation (September 1998).
5.
R. Person, E. Blomsjo, and M. Edenius, "High-Temperature Critical Experiments with H 0-Moderated Fuel Assemblies in KRITS," Technical Mtg. No. 2/11, NUCLEX 72 2
(1972).
6.
L.W. Newman, "Urania-Gadolinia: Nuclear Model Development and Critical Experiment Benchmark," BAW-1810, B&W Company (April 1984).
7.
R.J. Nodvik, et al., " Evaluation of Mass Spectrometric and Radiochemeical Analysis of Yankee Core 1 Spent Fuel," WCAP-6068 (1966).
8.
J. Briesmeister, "MCNP-A General Monte Carlo Code for Neutron and Photon Transport, Version 3 A," LA-7396-M Revision 2 (1992).
9.
Letter from James F. Mallay (SPC) to the U.S. Nuclear Regulatory Commission, "SER Conditions for CASMO-4/MICROBURN-82," September 9,1999.
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PrincipalContributor: A. Attard Date: October 18, 1999