ML20116K458
| ML20116K458 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 11/11/1992 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-M84443, TAC-M84444, NUDOCS 9211170202 | |
| Download: ML20116K458 (7) | |
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GALTIMORE -
GAS AND ELECTRIC 1650 CALVERT CUFFS PARKWAY. LUSBY, MARYLAND 20657-4702 ROBERT E, DENTON Vict PRESIDENT nucle AN ENERGY (410) 260-4 ens November 11,1992 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Response to NRC Request for Additional Information Regarding the Spent Fuel Pool Enrichment Limit License Amendment (TAC Nos. M84443: M84444')
REFERENCE:
(a)
Letter from Mr. G. C. Creel (BG&E) to NRC Document Control Desk, dated September 1,1992, License Amendment Request; Spent Fuel Pool Enrichment Limit (b)
Evaluation of AMPX KENO Benchmark Calculations for IIigh -
Density Spent Fuel Storage Racks, S. E. Turner and M.- K. Gurley, Nuclear Science and Engineering, Vol. 80, pages 230-237,1982.
(c)
Letter from Mr.
A.
E.
- Lundvall, Jr.
(BG&E) to-Mr. R. W. Reid (NRC), dated January 15, 1980, Spent Fuel Pool Modification: Supplementary Information Gentlemen:
This letter provides Baltimore Gas and Electric (BG&E) Company's response to your request for additional information regarding our License Amendment to change the Spent Fuel Pool enrichment limit (Reference a). Your specific information request and our response are attached.
Our responses do not change or supersede any information contained in the amendment request.
Therefore, the responses to these questions do not change or modify the Determination of Significant IIazards presented in the amendment request.
160036 9211170202 921111 ai DR ADOCK 0500 7
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- Document Control Desk November 11,1992
, Page 2 Shoulu you have any further questions regardirg this matter, we will be pleased to discuss them with you.
i truly your.<,
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STATE OF MARYLAND 1
TO WIT COUNTY OF CALVERT I hereby certify that on the [
day of Novena er,1992, befg&uwn b
re me, the subscriber, a Notary Public of the State of Maryland in and for
/ Min /A A C
, personally-appeared Robert E. Denton, being duly sworn, and states that he is Vice Prq(ident of the Baltimore Gas and Electric Company, a corporation of the State of Maryland; that he provides the foregoing response for the purposes therein set forth; that the statements made are true and correct to the best of his knowledge, inforrnation, and belief; and that he was authorized to provide the response on behalf of said Corporation.
WITNESS my Hand and Notarial Seal:
W 76 Notary Public d
My Commission Expires:
dalLLW /, /77@
U ate RED /LMD/Imd/dtm Attachment cc:
D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC T. T. Martin, NRC P. R. Wilson, NRC R. I. McLean, DNR J. H. Walter, PSC -
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NITACIIMENT (1)
Responsi w NRC Request fcr AdditionalInformation Regarding the Spent Fuel Pool Enrichment Limit License Amendment
.NRC REOUEST ABBICE (letterfrom S. A. Toelle to !.. I, Knopp, LD 92-046, March 27,1992) and others (S. E. Turner, Nuclear Science and Engineering, 6. 80, pgs. 230 237,1932) have etpressed concern about using the PNL series of critical experiments (S. R. Bierman, et, a', PNL-2438, Oct.1977) for methodology confirmation. The basic problem is that the worth of the baron in these experiments is relatively low, about 2% compared to about 20% in an actualstorage rack. Therefore, modestpercent errors in boron worth are mamfest as relatively small errors in reactivity (e.g., for a 10% error in poison worth, the error in reactivity would be 0.2%). For a realistic high density storage rack, however, the same 10% error in calculating the react;vity worth of baron absorberplates could result in an error of as much as 5% in reactivity. Based on this, justify the use of the PNL critical experiments for your qualification of the analytical methods and the evaluation of the calculational uncertainty and bias.
IIACKGROUND Asea Brown Boveri-Combustion Engineering (ABB.CE) uses the CEPAK DOT-XSDRNPM codt.
series tc. analyze our spent fuel pool poisoned rack configuration to ensure subcriticality is mLintained under appropriate storage conditions. CEPAK and XSDRNPM are used to generate the neutron cross sections which are used in the DOT-XY transport code. CEPAK generates the fuel-water cross sections and XSDRNPM generates the Baron 10 (B-10) poison cross sections. In order to verify that the computer codes accurately reDect physical systems, they are benchmmked against experimental critical configurations. CEPAK has been benchmarked against a wide series of critical experiments including those performed at Pacinc Northwest Laboratory (PNL). Asea Brown Boveri-Combustion Engineering acknowledges that the PNL criticals are not entirely appropriate for benchmarking the code for use in a highly borated environment. To ensure that the code series performs adequately for calculations of spent fuel pool k g, ABB CE has done a code comparison e
i between its CEPAK-DOT-XSDRNPM calculations and Oak Ridge National Labn atory (ORNL) calculations donc using AMt'X KENO-XSDRNPM, The AMPX-KENO code st.ics has been benchmarked against both the PNL and the B&W critical experiments, among others. Presented below is a comparison of the two code series for cases ranging from the relatively low B-10 laadings of the PNL criticals to the higher B 10 loadings associated with fuel rack calculations performed using I
AMPX-KENO.
l Comparison of Codes - PNL Criticals it should be noted that ABB-CE uses the same code as ORNL, XSDRNPM, to calculate B-10 cross sections. Therefore, differences between the ABB-CE and ORNL results are attributable to the difference in the CEPAK-DOTand AMPX-KENO codes.
Reference (b) describes a series of calculations performed to benchmark the AMPX-KENO codes to the PNL critical experiments. Table (1) of the reference provides a comparison of calculations performed by Turner and ORNL for the same criticals. Table (2) of Reference (b) provides an expanded set of critical calculations performed by ORNL Asea Brown Boveri Combustion Engineering has calculated k g for some of these same critical experiments. Table (1) (attached) e provides a comparison between the ABB-CE calculations and the available ORNL results. As can be seen from the Table, the mean k rrvalue calculated by ABB CE is consistent with the value calculated e
by ORNL Therefore, this comparison demonstrates the equivalence between the CEPAK DOT and l
AMPX-KENO methode'agies for systems containing relatively low B 10 loadings.
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NITA: 31SNT W Response to NRC Request for Additional Information Regarding the Spent Fuel Pool Enrichment Limit License Amendment Comparison Of Codes - Fuel Hack Calculations Another comparison can be made to AhiPX-KENO calculations which were done to support the first re-racking of our spent fuel pool in 1980 (Reference c). The AMPX KENO methodologies have been adequately benenmarked e: higher B-10 loadings and can be used to perform calculations for poisoned fuel racks. Direct comparison with the AMPX-KENO codes provides validation for the use of the CEPAK-DOT code series for the poisoned fuel rack calculations performed in our most recent submittal (Reference a).
AMPX KENO Bias When evaluating the use of AMPX-KENO to accurately calculate k rr for the Bc '" critical series, e
Turner noted that AMPX-KENO routinely overpredicts k rr(Reference b). P :.med an increasing e
trend of overprediction with increasing boron worth. The highest overprediction occurred with the experiment highest in boron worth (experiment XIll). The bias for that experiment was calculated to be 0.009. Turner extrapolated these results to the boron worths associated with poisoned fuel racks 1 and estimated biases of 0.02 to 0.05 for calculat'ons involving fuel racks. These biases are sometimes used with AMPX-KENO fuel rack calculations. Asca Brown Boveri-Combustion Engineering feels that the trend in biases should be limited to the experimental results (0.009). Therefore, in the following discussion ABB-CE has used the more conservative experimental bias when evaluating the AMPX KENO results.
In Reference (c), Nuclear Energy Services (NES) used the AMPX-KENO methodology to calculate k rr e
for our proposed spent fuel pool racks assuming fresh 4.1 w/o U 235 fuel assemblies were being -
stored. The nominal k rt (without_ bias) was calculated to be 0.9201, NES used a bias of -0.02, e
consistent with that estimated by Turner, and reported a - k rt of 0.92010.02 = - 0.9001 in e
Reference (c). As part of this calculation, NES also determined the scaling factor associated with an increase in fuel enrichment,0.20 w/o U 235 per percent delta k rt. This allows us to determine the e
k rt result as a function ofincreasing enrichment.
e As part of the reanalysis for the current spent fuel racks, ABB-CE modelled the same fuel rack as-Reference (a) using CEPAK-DOT methodology with fresh 4.3 w/o U-235 fuel instead of 4.1 w/o U 235 fue' Asea Brown Boveri-Combustion Engineering obtained a nominal k rrvalue of 0.92308, without e
bias. If we adjust the NES value to account for the increase in fuel enrichment to 4.3 w/o U 235, the NES k g value would become 0.9001+0.01 = 0.9101. The 1% increase in k rr is due to the e
e 0.2 w/o U-235 increase in the fuel enrichment (scaling factor from previous paragraph). Comparing the CEP_AK-DOT k g value of 0.92308 to the AMPX-KENO k g value of 0.9101-for the same e
e configuration with the same fuel allows us _to conclude that the CEPAK-DOT-methodology is -
conservative with respect to the AMPX KENO methodology.
If biases are included in the -answers, t.1cy compare even more favorably.
Taking the NES 4.1 w/o U-235 k rr and applying the more conservative bias of 0.009, k g would be 0.9111 e
e (0.9201-0.009). After accounting for the difference in fuel emichment,tk g' becomes 0.9211 e
(0.9111 +0.01). Recall that the CEPAK-DOT answer for 4.3 w/o U-235 fuel is 0.92308 without bias.
Asea Brown Boveri Combustion Engineering has calculated a bias for CEPAK DOT case of 0.00197.
Including this bias in the answer, the CEPAK-DOT k rr becomes 0.92111 (0.92308-0.00197). These e
answers (0.9211 and 0.92111) compare exceptionally well.
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NITACIIMENT (1) 1(esponse to NRC llequest for Additional Information llegarding the Spent l'oel Pool Enrichment Limit License Amendn.ent To provide further verification of the CEPAK-DOT methodology, ABB.CE used AMPX-KENO methodology to directly calculate k rt for 4.3 w/o U-235 fuel in the fuel racks. The result is e
0.93276 1 0.00346. When the experimentally determined bias of 0.009 is subtracted, the result is -
0.92376 (0.93276-0.009). This compares well with the CEPAK-DOT result obtained above,0.92111.
ONCLUSION Asea Brown Boveri-Combustion Engineering has henchmarked CEPAK-DOT methodology against
- PNL critical experiments. The difficulty with this benchmarking method is that it is only applicable for low B-10 loading configurations. This means that additional work is required to ensure that CEPAK-DOT is acceptable as a methodology for modelling spent fuel pool racks which have a high B-10 loading. Therefore, ABB CE compared their code ac tinst ' :ntical cases run using the AMPX-KENO methodology. The results of the comparison aic givu. above and in Table (2). It is clear from the comparison that the CEPAK DOT provides consistent answers with the AMPX KENO methodology. This comparison, along with the comparison of CEPAK DOT and AMPX KENO calculations given in Table (1), allows us to conclude that the CEPAK DOT methodology produces -
consistent results with the AMPX-KENO methodology over a wide range of B 10 loadings. Therefore, the acceptability of the CEPAK-DOT methodology for use in fuel rack calculations has been demonstrated.
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t ATTACIIMENT (1)
Response to NitC Request for AdditionalInformation Regarding the Spent Fuel Pool Enrichment Limit License Amendment r
TABLE (1)
Comparison of ABB.CE and ORNL Results for the PNL Poisoned Criticals EXPERIMENT ABB-CE ORNL-i 16 1.002 0.003-1.007 0.005 17 0.997 0.003 NA-20 1.004 0.003 1.010 0.004 32 1.004 i OlX)3 1.004 1 0.004 33 1.005 1 0.003 0.999 0.004' 38 1.009 0.003 1.000 0.004 39 1.011 1 0.003 -
1,002 i OJX)4 Mean k 1.004 0.003 1.004 0.004 crg q
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A'lTACIIMENT (1)
Itesponse to NitC lleguest for Additional Information thgarding the Spent Fuel 1%>l Enrichment Limit License Amendment TAllLE (2)
Comparison of CEPAK DOT with AMPX-KENO bias keff NES Calculation 4.1 w/o
.02 0.9001 NES Calculation 4.3 w/o
.02 0.9101 (adjusted)
CEPAK. DOT 4.3 w/o 0.92308 Calculation NES Calculation 4.3 w/o
.009 0.9211 (adjusted)
CEPAK-DOT 4.3 w/o
.00197 0.92111' ABB CE 4.3 w/o
.009 0.92376 AMPX-KENO CEPAK-DOT 4.3 w/o
.00197 0.9211-5
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