ML040850650

Enclosure 4 - ER-03-006, Revision 1, Characterization of D. C. Cook Unit 1 Steam Generator Lower Assemblies.

ML040850650
Person / Time
Site:	Cook
Issue date:	03/02/2004
From:	Whittaker M, Witt C Duratek
To:	Office of Nuclear Reactor Regulation
References
ER-03-006, Rev 1
Download: ML040850650 (22)

Text

Enclosure 4 ER-03-006, Revision 1 Characterization of D. C. Cook Unit 1 Steam Generator Lower Assemblies

DURATEK ENGINEERING REPORT ER-03-006 Revision I Approvals Page -

Characterization of D.C. Cook Unit I Steam Generator Lower Assemblies Prepared by: Z? 4 e )) OY Mark fiflaker, Sr. Analyst Date Reviewed by: -a 31o40 Charles Witt, Principal Engineer ate 11 A

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TABLE OF CONTENTS Page No.

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SUMMARY

......................................... 3

2. PHYSICAL DESCRIPTION OF STEAM GENERATORS ......................................... 3

3. RADIOACTIVE SOURCE CHARACTERISTICS ......................................... 3

4. CHARACTERIZATION ASSUMPTIONS ......................................... 4

5. SOURCE CHARACTERIZATION ......................................... 5 5.1 MICROSHIELD CALCULATIONS ........................................ 6 5.2 SOURCE DISTRIBUTION ........................................ 7

6. WASTE CLASSIFICATION AND DOT SUBTYPING ......................................... 8

7. REFERENCES ......................................... 11 APPENDIX A AEP SUPPLIED INFORMATION .12 APPENDIX B MICROSHIELD MODELS AND OUTPUT .20 LIST OF TABLES AND FIGURES Table 3.1 - Radionuclide Distribution .3 Table 5-1 Co-60 Content in Straight Tube Section .7 Table 5-2 SGLA Co-60 Content Results .7 Table 6-1 DOT Subtyping of D.C. Cook SGLA 12 .9 Table 6-2 Disposal Classification of D.C. Cook SGLA 12.10 Figure 5-1 Microshield Model Representation of Steam Generator Source Region .6 ER-03-006 Rev. I Page 2

1. Summary This report presents the analyses performed in support of the source characterization and classification of four D.C. Cook Unit I Steam Generator Lower Assemblies (SGLAs) for American Electric Power, the owner and operator of the D.C. Cook plant.

The radionuclide content of the SGLAs was determined based on isotopic and dose rate information to demonstrate compliance with applicable criteria for transportation and disposal.

The activity in each SGLA will be re-evaluated after removal of the SGLAs from the storage facility and prior to shipment for disposal. Ifthere is a significant change in the activity from that estimated in this report, a revised characterization will be prepared.

2. Physical Description of Steam Generators The steam generators at D.C. Cook Unit 1 are Westinghouse Model 51, identical to those previously transported for disposal. The basic physical dimensions and design criteria of the SGLAs are taken from the characterization report for the previously disposed SGLAs, ER-98-009 [11].

3. Radioactive Source Characteristics A contamination sample (smear) was taken from the interior of one of the SGLAs on Feb. 5, 2000. The sample was analyzed for radionuclide content. The analysis report is included in Appendix A. The activity was decayed to the date of the radiation survey of the SGLAs, Sept. 12, 2003. The decayed radionuclide content was used as the isotopic distribution of radioactivity within the SGLAs. For two pair of radionuclides, Cm-2431244 and Pu-239/240, a single activity is reported. The distribution was normalized to Co-60 and applied to the Co-60 activity determined from the dose to curie conversion factor from the shielding model. The sample results and the normalized distribution are provided in Table 3-1.

Table 3.1 - Radionuclide Distribution Measured Activity Decayed Activity Normalized Radionuclide (Ci) (Cl) Distribution Am-24f 2.OOE-05 1.99E-05 2.02E-04 Cm-243/244 1.80E-05 1.66E-05 1.69E-04 Co-60 1.51 E-01 9.84E-02 1.OQE+00 Fe-55 4.70E-02 2.06E-02 2.09E-01 Mn-54 2.78E-03 .1.98E-04 2.02E-03 Ni-63 1.1OE-02 1.08E-02 1.09E-01 ER-03-006 Rev. 1 Page 3

Measured Activity Decayed Activity Normalized Radionuclide ( Ci) ( Ci) Distribution Pu-239/240 1.30E-05 1.30E-05 1.32E-04 Pu-241 1.80E-03 1.54E-03 1.56E-02 Tc-99 3.50E-04 3.50E-04 3.56E-03 External radiation surveys were taken on the SGLAs on Sept. 12, 2003. This survey information is included in Appendix A. The average value over the straight tube region of the SGLA was determined. These average values are used in calculating the surface area contamination on the straight tubes.

The characterization will be re-evaluated based on dose rate profiles taken on the SGLAs on removal from the storage facility. However, these dose rates are not expected to change significantly from those measured in September, 2003.

4. Characterization Assumptions Several assumptions are made Inthe course of performing the characterization analyses of the steam generators. These assumptions are utilized to simplify the analysis, while maintaining accuracy in the overall result.

1. Secondary-side steam generator surfaces contain no activity.

Since the secondary side of the steam generator is exposed only to secondary side water, it is assumed that the secondary side contains only negligible quantities of radioactive contamination. This assumption has been used for previous steam generator characterizations.

2. Residual water in plugged tubes contains no activity.

The plugged tubes in the steam generator could contain relatively small amounts of water that seeps into the tubes during operation of the generators. It is assumed that this water contains negligible quantities of radioactive material, and is not considered in this characterization.

3. Uniformity in distribution of primary-side surface contaminates.

Two EPRI reports [2, 3] address the issue of steam generator primary side surface contamination. These reports indicate that, while the straight tube sections with the SGLAs exhibit fairly uniform surface contamination, the U-tube and tube sheet sections of the heat exchanger tubes contain higher surface contamination values than that of the straight tube sections.

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Additional uncertainty exists concerning the relative surface contamination levels between the tubes and the channel head surfaces, including the tube sheet, divider plate, and bowl itself. The studies indicate that the differing materials used for the tubes versus the channel head components, combined with other factors, could result in higher surface contamination values in the channel head region.

To address these issues, this analysis assumes that all surfaces other than the straight tube sections contain surface contamination levels per unit area twice that of the straight tube sections. This factor of two is addressed specifically in the reference [2] study for the various tube sections. It is reasonable to apply this assumption to the channel head sections as well, as they are of a similar geometry and represent only a minimal fraction of the total surface area, and thus only a small portion of the total activity in the SGLAs.

5. Source Characterization Employing the information from the previous sections, the radionuclide content of the SGLAs can be determined from the measured external SGLA dose rates and the SGLA design parameters.

The straight tube section of the lower barrel of the SGLA is modeled with the Microshield [4] point kernel shielding code, using a I curie Co-60 source term. The shortest straight tube length is approximately 357 inches, not including the 21 inch length of tube in the tube sheet. The diameter and thickness of the radial source and shielding regions of the model are taken from ER-98-009 [11].

ER-03-006 Rev. 1 Page 5

Figure 5-1 Microshield Model Representation of Steam Generator Source Region Lower Barrel - 2.82" The source region is modeled as nickel alloy, Alloy 600, at a density of 0.646 g/cc to represent the fraction of the source region cross-section occupied by the tubes. The void regions are modeled as air, and the wrapper and lower barrel are modeled as A 533 steel. The densities are taken from ER-98-009[1 1].

5.1 Microshield Calculations Analyses are performed with Microshield using the model previously described with the I Ci Co-60 source term. The calculation produces an exposure rate, 1 foot from the surface, of 1.181 mRIhr; thus, the dose-to-curie factor is 1.181 mRlhr/Ci. The average exposure rates ate then divided by the dose-to-curie factor to determine the number of curies of Co-60 irthe straight tube section of the SGLA on the date of the survey, 9/12/03. This activity is then divided by the surface area of the straight tubes (3.80E+07 cm2 ) to give the activity per unit area. The results of these calculations are presented in Table 5-1.

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Table 5-1 Co-60 Content in Straight Tube Section SGLA SGLA SGLA SGLA 11 12 13 14 Average 30 cm Exposure Rate (mR/hr) 20.4 26.9 24.2 24.3 Activity in Straight Tube Section (Ci Co-60) 17.31 22.81 20.48 20.53 aity (.CVCM 2 Areal Activit (,~/A Co-60) 0.456 0.601 10.539 0.541 5.2 Source Distribution The straight tube source contamination calculated in Section 5.1 is utilized to determine the contamination on the U-tube and tube sheet sections of the heat exchanger tubes, as well as the channel head components.

The straight tube contamination levels, shown InTable 5-1, are multiplied by the surface area of the other components and the factor of two discussed in Section 4. The resulting Co-60 surface contamination levels on the remaining primary side surfaces of the steam generator are 0.912, 1.201, 1.079, and 1.082 pCi/cm2 , respectively. These surface contamination levels are used to calculate the Co-60 curies in each steam generator as shown in Table 5-2.

Table 5-2 SGLA Co-60 Content Results (as of 12 September2003).

AT SGLA 11 SGLA 12 SGLA 13 SGLA 14 Surface Co-60 Co-60 Co-60 Co-60 Area Activity Activity Activity Activity Contaminated Surface (cm2) (Ci) (Ci) (Ci) (Ci)

Areas Straight Tube Surface Area 3.80E+07 17.31 22.81 20.48 20.53 Tubes in Tube Sheet 2.25E+06 2.04 2.69 2.41 2.42 U-Tube Section Surface 5.19E+06 4.73 6.23 5.59 5.61 Area Channel Head 1.60E+05 0.15 0.19 0.17 0.17 Tube Sheet 5.93E+04 0.05 0.07 0.06 0.06 Divider Plate 8.OOE+04 0.07 0.10 0.09 0.09 Total 24.34 32.08 28.81 28.88 The normalized distribution presented in Table 3.1 is used to determine the full isotopic distribution of activity in each SGLA, i.e., each isotope distribution factor is multiplied by the Co-60 content from Table 5-2. The activity is decayed to the estimated date of shipment, May 15, 2004. The resulting activity is shown in Table 5-3.

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Table 5-3 SGLA Activity.

SGLA#11 SGLA#12 SGLA#13 SGLA#14 9/12/03 5/15/04 9/12/03 5/15104 9/12/03 5/15/04 9/12/03 5/15104 Isotopic (Ci) (Ci) (Ci) (Ci) (Ci) (Ci) (Ci) (Ci)

Am-241 0.005 0.005 0.006 0.006 0.006 0.006 0.006 0.006 Cm-243 0.004 0.004 0.005 0.005 0.005 0.005 0.005 0.005 Co-60 24.341 22.277 32.083 29.362 28.808 26.364 28.882 26.433 Fe-55 5.085 4.285 6.703 5.648 6.018 5.072 6.034 5.085 Mn-54 0.049 0.028 0.065 0.037 0.058 0.034 0.058 0.034 NI-63 2.661 2.648 3.507 3.491 3.149 3.134 3.157 3.142 Pu-239 0.003 0.003 0.004 0.004 0.004 0.004 0.004 0.004 Pu-241 0.381 0.369 0.502 0.486 0.451 0.436 0.452 0.437 Tc-99 0.087 0.087 0.114 0.114 0.102 0.102 0.103 0.103 Total 32.616 29.706 42.989 39.154 38.601 35.157 38.700 35.248

6. Waste Classification and DOT Subtyping The shipping and disposal classifications can be performed for the SGLAs based on the calculated radionuclide content In accordance with regulatory requirements [5, 6, 7, and 8]. This information is important to demonstrate that the SGLAs meet applicable requirements for transportation and disposal.

The DOT subtyping for the highest activity SGLA, SGLA #12, is shown in Table 6-1. As shown, the SGLA #12 contains a greater-than-Type-A quantity of radioactive material, with a cumulativeA 2 value of 7.2 (per the revised regulations the A2 is 3.6). The average Co-60 surface contamination level (0.6 ILCVcm 2, shown in Table 5-2) is much less than the SCO-I1 fixed plus non-fixed P,y limit for inaccessible areas of 20 J4Ci/cm 2.

Applying the isotopic distribution of Table 3.1, the isotopic contamination levels are determined; note that there are no low toxicity alpha emitters in the distribution. The average fixed plus non-fixed p, y contamination levels are 0.8 pLCi/cm 2 and the average fixed plus non-fixed cc contamination levels are < 0.001 pICi/cm 2, both much less than the SCO limits. Even with the expected uncertainty in the distribution of activity over all surfaces in the SGLA, the averages are so much below the limits that there is little uncertainty that all areas are less than the SCO-II limit. As such, no exemption from SCO-Il limits will be requested from the DOT as suggested in Reference 9.

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The total amount of fissile material In all four SGLAs is 0.26g which is less than 15g; therefore, the shipment qualifies as fissile excepted.

Table 6-1a DOT Subtyping of D.C. Cook SGLA 12 (A2 values from current 49 CFR173.435)

Isotope Curies. A2 Value A2 Fraction Am-241 6.48E-03 0.00541 1.198 Cm-243 5.33E-03 0.00811 0.658 Co-60 2.94E+01 10.8 2.719 Fe-55 5.65E+00 1080 0.005 Mn-54 3.75E-02 27 0.001 NI-63 3.49E+00 811 0.004 Pu-239 4.24E-03 0.00541 0.783 Pu-241 4.86E-01 0.27 1.799 Tc-99 1.14E-01 24.3 0.005 TOTAL 3.92E+01 7.173 Table 6-1 b DOT Subtyping of D.C. Cook SGLA 12 (A2 values from 49 CFR 173.435 effective Oct. 1, 2004)

Isotope Curies A2 Value A2 Fraction Am-241 6.48E-03 0.027 0.240 Cm-243 5.33E-03 0.027 0.198 Co-60 2.94E+01 1 2.669 Fe-55 5.65E400 1100 0.005 Mn-54 3.75E-02 27 0.001 Ni63 3.49E+00 810 0.004 Pu-239 4.24E-03 0.027 0.157 Pu-241 4.86E-01 1.6 0.304 Tc-99 1.14E-01 24 0.005 TOTAL 3.92E01 3.583 The disposal classification of SGLA #12, which has the largest total activity, is shown in Table 6-2. The disposal volume is 121.6 m3 and the mass is 2.18E+08g. This classification lists the required nuclides from 10 CFR 61, and demonstrates that the Table. I -and Table 2 isotopes meet the requirements for classification of the SGLAs as ClassAwaste.

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Table 6-2 Disposal Classification of D.C. Cook SGLA 12 SpA, Part 61 Nuclides Activity (Ci) nCIIg SpA, Cilm 3 fraction 14C O.OOE+OO0 O.OOE+O0 O.OOE+00 14C O.OOE+0O O.OOE+0O O.OOE+OO00 59 Ni O.OOE+0O O.OOE+OO O.OOE+OO00 f 94 Nb 9.00E+O0 O.OOE+0O 99Tc 1 01..14E-~o0 9.39E-04 3.13E-04 129 1 O.OOE+O0 O.OOE+00 O.OOE+OO TRU 1.61 E-02 7.37E-02 241 Pu 4.86E-01 2.23E+O( 6.37E-04 242 Cm O.OOE+00 O.OOE+OC O.OOE+00 sum of fractions 1.69E-03 Table I Eval: Class Table 2 Activity (Ci) SpA, Clum 3 Evaluation All.... 5.69E+OO 4.68E-02 ClassA 3H O.OOE+OO O.OOE+00 Class 60Co 2.94E+01 1 2.41 E-01 Class 63Ni 3.49E+OO 2.87E-02 Class A 63Ni act O.OOE+O0 O.OOE+O0 ClassA 9OSr O.OOE+00 O.OOE+00 Class A 137Cs O.OOE+OO O.OOE+0O Class TOTAL: 3.92E+O0I 3.18E--1

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7. References

[1] CNS Procedure EN-AD-010, "Procedure for Waste Characterization of Non-Irradiated Components or Items."

[2] EPRI-NP-2968, "Primary-Side Deposits on PWR Steam Generator Tubes,"

Electric Power Research Institute, Palo Alto, C-A, March 1983.

[3] EPRI-NP-3107, "Gamma-Ray Exposure Rate Distribution in a Steam Generator,"

Electric Power Research Institute, Palo Alto, CA, May 1983.

[4] Grove Engineering, Inc. uMicroshield Computer Code," Version 5.01.

[5] NRC, "Low-Level Waste Licensing Branch Technical Position on Radioactive Waste Classification,' (May 1983).

[6] Code of Federal Regulations, 10CFR Part 61 and IOCFR Part 71.

[7] Code of Federal Regulations, 49CFR Parts 100 to 177.

[8] DHEC License CNSI-SC-097, (Bamwell Site Criteria).

[9] NRC Generic Letter 96-07, "Interim Guidance on Transportation of Steam Generators," U.S. NRC Office of Nuclear Material Safety and Safeguards, December 5, 1996.

[10] NUREG-1608, "Categorizing and Transporting Low Specific Activity Materials and Surface Contaminated Objects," U.S. Nuclear Regulatory Commission, July 1998

[11] Duratek Engineering Report,ER-98-009, Rev.1, Preliminary Waste Characterization of D.C. Cook Steam Generator Lower Assemblies ER-03-006 Rev. 1 Page 11

APPENDIX A AEP SUPPLIED INFORMATION (7 PAGES)

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APPENDIX B MICROSHIELD MODELS AND OUTPUT (1 PAGE)

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ER-03-006 Rev. I Page 20

MicroShield v6.00 (6.0-00005)

Page :1 File Ref :ER-03-006 DOS File :crb-model.ms6 Date  : 27 October 2004 Run Date  : February 17, 2004 By  : M. Whittaker Run Time  : 8:11:50 AM Checked Duration  : 00:00:01 Case

Title:

DC Cook SGLA

Description:

Characterization model, 1 Ci Co-60 Geometry: 7 - Cylinder Volume - Side Shields Source Dimensions:

Height 906.145 cm (29 ft 8.7 In)

Radius* 151.994 cm (4 ft 11.8 In)

Dose Points A *X y z

1. 1 201.93 cm 45:3.0725 cm 0 cm 6 ft 7.5 In 14 Ift 10.4 In 0.0 In Shields S;hield N Dimension Material Density Source 4.01e+06 In 3 Alloy 600 0.646 Shleld 1 2.23 In Air 0.00122 Shleld 2 .38 In A 533 7.86 Shleld 3 2.23 In Air 0.00122 Shield 4 2.82 In A 533 7.86 ransitlon Air 0.00122 Alr Gap Air 0.00122 Source Input: Grouping Method - Actual Photon Energies Nucilde curies becquerels pCi/cms Bq/cm' Co-60 1.0000e+000 3.7000e+010 1.5206e-002 5.6260e+002 Buildup: The material reference Is - Shield 4 Integration Parameters Radial 10 Circumferential 10 rDirection (axial) 20 Results Fluence Rate Fluence Rate Exposure Rate Exposure Rate Energy Activity MeV/cm 2 /sec MeV/cm 2 /sec mR/hr/sec mR/hr/sec MeV Photons/sec No Buildup With Buildup No Buildup With Buildup 0.693'8 6.035e+06 9.497e-04 9.229e-03 1.834e-06 1.782e-05 1.1732 3.700e+10 4.195e+01 ' 2.774e+02 7.497e-02 4.956e-01 1.3325 3.700e+10 6.576e+01 3.948e+02 1.141e-01 6.850e-01 Totals 7.401e+10 1.077e+02 6.722e+02 1.891e-01 1.181e+00 ER-03-006 Rev. 1 g 21 F:'age