Text

Rev 1 to ER-98-012, Evaluation of Dose Rate from U-Tube End of DC Cook SG Lower Assembly
	ML17335A275
Person / Time
Site:	Cook
Issue date:	09/02/1998
From:	Whittaker M, Witt C; CHEM-NUCLEAR SYSTEMS, INC.
To:	;
Shared Package
ML17335A271	List: ML17335A270; ML17335A272; ML17335A273; ML17335A274; ML17335A275;
References
	ER-98-012, ER-98-12, NUDOCS 9810140058
	Download: ML17335A275 (34)
	v • d • e

CHEM-NUCLEARSYSTEMS fRjJ~ggfj, p /fig'lg yg PREPARED BY'NDEPENDENT REVIEWER'RINTED OR TYPED NAME MARKWHITTAKER CHARLES WITT SIGNATURE DATE 8/17/98 8/1 7/98 DOCUMENTTITLE:

EVALUATIONOF DOSE RATE FROM U-TUBE END OF D.C. COOK STEAM GENERATOR LOWER ASSEMBLY DOCUMENT NO.

ER-98-012 REV.

PAGE 1 of4 98iOi40058 98i008 PDR ADQCK 050003ih P

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TABLE OF CONTENTS

~Pa e No.

1.0 INTRODUCTION

2.0 EVALUATIONMETHODOLOGY.

3.0 RESULTS

4.0 CONCLUSION

5.0 ATTACHMENTS

.3 3

3 4

4 ER-98-012 REV. 1 PAGE 2

1.0 INTRODUCTION

American Electric Power (AEP) replaced the D.C. Cook Unit 2 steam generators in 1988. As part of the replacement project, the steam domes were removed and a 3" steel end plate was welded to the transition cone to seal the steam generator lower assembly (SGLA) prior to placing them in storage.

CNS intends to ship these SGLAs from D.C. Cook unpackaged with the approval of DOT. To support the DOT request for exemption from several of the shipping requirements allowing the SGLAs to be shipped unpackaged, the dose rate was estimated at the end of the SGLA for the hypothetical case that the 3" steel end plate was removed during transportation.'his dose rate estimate was compared to the limiting dose rate for a Type A packaged shipment of SCO.

2.0 EVALUATIONMETHODOLOGY The radioactivity in the heat exchanger tubes p;oduces a radiation field which can be detected and quantified external to the SGLA. The amount of radioactivity can be estimated from a model of the SGLA by adjusting the input activity until the calculated dose rate matches the measured dose rate.

Using this estimated activity and adjusting the model by removing the end plate, the dose rate at the now open end of the SGLA can be calculated.

AEP provided survey results of external measurements made on the four SGLAs. Included in the survey was a measurement on contact at the center of the steel plate welded,to the transition cone.

The. maximum dose rate, measured.

was 42 mrem/hr.

The Microshield point kernel computer code was used to model the SGLA and calculate dose rates at the center of the end plate. The contaminated heat exchanger tubes were assumed to be the only source of radiation. The isotope was assumed to be Co-60. At the transition cone end of the steam generator, the tubes bend in a u-shape forming a semi-spherical array of tubes; the remaining straight section of tubes forms a cylindrical array.

Microshield allows a limited number of source geometries, none of which exactly match the shape of the tube bundle.

To approximate the tube bundle, two source geometries were used, a sphere and a cylinder. The sphere was expected to underestimate the actual source and the cylinder to overestimate it. For each geometry, a source was determined that produced a dose rate on the outside of the 3" plate equal to that measured by AEP, i.e., 42 mrem/hr. Without changing the activity, the 3" steel plate was replaced by air and the resulting dose rate calculated.

3.0 RESULTS The activity which results in 42 mrem/hr on the end plate is 6.3 Ci and 27.5 Ci for the spherical and cylindrical model, respectively.

The dose rate without the end plate, calculated with the spherical model, is 580 mrem/hr. The dose rate without the end plate, calculated with the cylindrical model, is 870 mrem/hr.

ER-98-012 I[, REV. 1 PAGE 3

4.0 CONCLUSION

The estimated dose rate at the transition cone end of the SGLA ifthe steel plate were removed would be between 580 and 870 mrem/hr. This result is less than the limitof 1000 mrem/hr at a distance of 3 meters.

5.0 ATTACHEMENTS Microshield Results Sketch SK:46628-001 AEP Surveys ER-98-012 REV.

1 PAGE 4

ATTACHMENTS Microshield Results 4 pages Sketch, SGLA Parameters, SK:46628-001 1 page AEP Surveys 4 pages

'age:

1

)OS File: DCCOKEND.MS5

<un Date: August 14, 1998

<un Time: 1:36:57 PM

)uration: 00:00:01 roShietd v5:01 (5.01-01072) ~

Cheni-Nuclear Systems, Inc.

Case

Title:

DCCOOK END

==

Description:==

DCCOOK dose with end plate Geometry: 6 - Sphere File Ref:

Date:

By:

Checked:

Radius Source Dimensions 151.994 cm 4 ft 11.8 in

¹1 X

203.6 cm 6 ft 8.2 in Dose Points Y

0cm 0.0 in z

0cm 0.0 in Shield Name Source Shield 1

Shield 2 Transition AirGap Shields -,'

Dimension

Material 1.47e+07 cm'lloy 600 42.951 cm Air 7.62 cm Iron Air Air Densitet 0.658 0.00122 7.86 0.00122 0.00122 Nuclide Co-60 Source Input Grouping Method: Actual Photon Energies curies becceuerels t/Ci/cm'ct/cm*

6.3000e+000 2.3310e+011 4.2833e-001 1.5848e+004 Buildup The material reference is: Shield 2 Integration Parameters Rho (Radial)

Angle 10 10

~Ener MeV 0.6938 1.1732 1.3325 Activitl/

hotons/sec 3.802e+07 2.331 e+1 1 2.331e+11 Fluence Rate Results Fluence Rate

~No Buildu 3.985e-02 1.626e+03 2.496e+03 t~dtd B ttd 3.651e-01 1.001e+04 1.392e+04 Me V/cm'/sec MeV/cm'/sec Ex osure Rate mR/hr

~No Buildu 7.694e-05 2.906e+00 4.330e+00

~d

~ t mR/hr t~dth B ttd 7.050e-04 1.789e+01 2.414e+01 TOTALS:

4.662e+11 4.122e+03 2.393e+04 7.237e+00 4.204e+01 Page 1 Of 9

r 1

age OS File: DCCOKEND.MS5 un Date: August 11, 1998 ut tme: 7:57:59 AM ui

.n: 00:00:01 roShield v0.01 (0.01-01072) ~

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File Ref:

Date:

By:

Checked:

Case

Title:

DCCOOK END

==

Description:==

DCCOOK dose without end plate Geometry: 6 - Sphere Radius Source Dimensions N$.994'cm 4 ft 11.8 in Dose Points X

Y 203.6 cm 0cm 6 ft 8.2 in 0.0 in z

0cm 0.0 in Shield Name Source Shield 1

Shield 2 Transition AirGap Shields Dimension 1.47e+07 cm'2.951cm 7.62 cm Material

~Densit Alloy600 0.658 Air 0.00122 Air 0.00122 Air 0.00122 Air 0.00122 Nuclide Co-60 Source Input Grouping Method: Actual Photon Energies curies becciuerele pCi/cm'B/cm'.3000e+000 2.3310e+011 4.2833e-001 1.5848e+004 Buildup The material reference is: Source Integration Parameters Rho (Radial)

Angle 10 10 Engr MeV Activity/

hotons/sec Fluence Rate Results Fluence Rate No Buildu With Buildu MeV/cm'/sec MeV/cm'/sec Ex osure Rate mR/hr

~No Buildu Ex osure Rate mR/hr W~lh B i~Id 0.6938 1.1732 1.3325 3.802e+07 2.331e+11 2.331 e+1 1 6.200e+00 8.267e+04 9.988e+04 1.219e+01 1.510e+05 1.786e+05 1.197e-02 1A77e+02 1.733e+02 2.353e-02 2.698e+02 3.099e+02 IOTALS:

4.662e+11 1.826e+05 3.296e+05 3.210e+02 5.797e+02 Page 2 Of 9

age:

1 lOS File: DCCKENDC.MS5

,un Date: August 11, 1998

.un Time: 8:12:16 AM luration: 00:00:01

~croBhield v5.01 (5.01-01072) ~

Chem-Nuclear Systems, Inc.

File Ref:

Date:

By:

Checked:

Case

Title:

DCCOOK END CYL

==

Description:==

DCCOOK END DOSE CYLINDERMODEL Geometry: 8 - Cylinder Volume - End Shields Height

'adius X

¹1 Ocm 0.0 in Source Dimensions

.'1.1e+3 cm 151.994 cm Dose Points Y

1109.8 cmt 36 ft 4.9 in,.

34ff 8.6 in 4 ft11.8 in Z

0cm 0.0 in Shield Name Source Shield 1

Shield 2 AirGap Shields Dimension Material

~Denstt 7.68e+07 cm'lloy 600 0.659 42.951 cm Air 0.00122 7.62 cm Iron 7.86 Air 0.00122 Nuclide Co-60 Source Input Grouping Method: Actual Photon Energies curiae becceuerets ttCilcm'Blcm'.7500e+001 1.0175e+012 3.5809e-001 1.3249e+004 Buildup The material reference is: Shield 2 Integration Parameters Radial Circumferential Y Direction (axial) 20 10 10 Enemy MeV 0.6938 1.1732 1.3325 Activitlr.

hotons/sec 1.660e+08 1.018e+12 1.018e+12 Fluence Rate Results Fluence Rate

~No Buildu 3.687e-02 1.559e+03 2A17e+03 W~ll B 3.471 e-01 9.948e+03 1.399e+04 MeV/cm'/sec Me V/cm'/sec Ex osure Rate mR/hr

~No Buildu 7.119e-05 2.786e+00 4.194e+00

~E*

il W~lh B lid 6.702e-04 1.778e+01 2 427e+01 TOTALS:

2.035e+12 3.976e+03 2.394e+04 6.980e+00 4.205e+01 Page 3 of 9

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1 OS File: DCCKENDC.MS5 un Date: August 11, 1998 u'me: 8:13:20 AM ut, on: 00:00:01 unl ',"

QroBhietd v5.01 (5.01-01072)

Chem-Nuclear Systems, Inc.

File Ref:

Date:

By:

Checked:

Case,

Title:

DCCOOK END CYL

==

Description:==

DCCOOK END DOSE CYLINDERMODEL Geometry: 8 -.Cylinder Volume - End Shields

¹1 X

0cm 0.0 in Height

'adius Source Dimensions

-1..le+3 cm 151.994 cm Dose Points Y

1109.8 cm 36 ft 4.9 in 34 ft 8.6 in 4 ft11.8 in Z

0cm 0.0 in Nuclide Co-60 Shields Dimension 7.68e+07 cm'2.951cm 7.62 cm Shield Name Source Shield 1

Shield 2 AirGap Source Input Grouping Method: Actual Photon Energies curies becceuerels t/Ci/cm'.7500e+001 1.0175e+012 3.5809e-001 Buildup The material reference is: Source Material

~Denatt Alloy600 0.659 Air 0.00122 Air 0.00122 Air 0.00122 Bct/cm'.3249e+004 Integration Parameters Radial Circumferential Y Direction (axial) 20 10 10 Ene~rtt/

MeV 0.6938 1.1732 1.3325 A~ctivit hotons/sec 1.660e+08 1.018e+12 1.018e+12 Fluence Rate MeV/cm'/sec

~No Buildu 9.872e+00 1.294e+05 1.556e+05 Results Fluence Rate MeV/cm'/sec With Buildu 1.876e+01 2.271e+05 2.671 e+05 Ex osure Rate mR/hr

~No Buildu 1.906e-02 2.313e+02 2.700e+02 Ex osure Rate mR/hr With Buildu 3.621 e-02 4.059e+02 4.635e+02 TOTALS:

2.035e+12 2.851e+05 4.943e+05 5.013e+02 8.694e+02 Page 4 Of 9

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ML17335A275

Contents

Text

1.0 INTRODUCTION

4.0 CONCLUSION

1.0 INTRODUCTION

4.0 CONCLUSION

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ML17335A275

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1.0 INTRODUCTION

4.0 CONCLUSION

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