ML19114A323
| ML19114A323 | |
| Person / Time | |
|---|---|
| Site: | 07103052 |
| Issue date: | 03/05/2019 |
| From: | Willems T TN Americas LLC, Orano USA |
| To: | Division of Spent Fuel Management |
| Shared Package | |
| ML19115A128 | List:
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| References | |
| DOS-18-011415-029-NPV, V2.0 | |
| Download: ML19114A323 (35) | |
Text
Formulaire : PM04-4-MO-6E rév. 02 Orano TN SAFETY ANALYSIS REPORT NON PROPRIETARY VERSION CHAPTER 3A TN MTR Prepared by T.WILLEMS Date Signature Identification :
DOS-18-011415-029-NPV Vers. 2.0 Page 1 / 35 NON PROPRIETARY VERSION RELEASE OF ACTIVITY CONTENTS
SUMMARY
- 1. INTRODUCTION
- 2. CONTAINMENT
- 3. CONTENT DATA
- 4. PACKAGING LEAKAGE RATE
- 5. CAVITY INTERNAL PRESSURE UNDER NCT AND ACT
- 6. CALCULATION OF ACTIVITY RELEASE IN GASEOUS FORM UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT
- 7. CALCULATION OF ACTIVITY RELEASE IN AEROSOL FORM UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT
- 8. CALCULATIONS OF THE RELEASE OF ACTIVITY DUE TO PERMEATION UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT
- 9. CALCULATION OF THE TOTAL RELEASED ACTIVITY UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT
- 10. CONCLUSIONS
- 11. REFERENCES LIST OF TABLES APPENDIX 3A-1:
CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING AND AN MTR-68, MTR-52, MTR-52S, MTR-52SV2, RHF OR FRM-II BASKET, LOADED WITH THE UPPER-BOUNDUPPER-BOUND MTR CONTENT WITH FULL INTEGRITY BEFORE TRANSPORT APPENDIX 3A-5:
CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING AND AN MTR-44 BASKET, LOADED WITH ALLOWABLE CONTENTS APPENDIX 3A-10: CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING LOADED WITH THE CESOX CONTENT
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2.0 Page 2 of 35 NON PROPRIETARY VERSION APPENDIX 3A-11: CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING AND AN MTR-52S OR MTR-52SV2 BASKET, LOADED WITH BROKEN MTR ELEMENTS APPENDIX 3A-12: JUSTIFICATION THAT SPECTRA CONSIDERED FOR CALCULATIONS OF RELEASES FROM MTR PLATE FUELS ARE UPPER-BOUNDUPPER-BOUND SPECTRA APPENDIX 3A-13: CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING AND AN MTR-52 BASKET, LOADED WITH BROKEN OR DISASSEMBLED BR2 CONTENT APPENDIX 3A-14: CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING LOADED WITH CAESIUM TRAP CONTENT APPENDIX 3A-15: CONFINEMENT OF THE CONTENT OF THE PACKAGE FORMED BY THE TN-MTR PACKAGING LOADED WITH GISETE CONTENT
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2.0 Page 3 of 35 NON PROPRIETARY VERSION REVISION STATUS Revision Date Modifications Prepared by/
Checked by Old reference: DOS-16-00173678-300 8
N/A Document first issue. Revision number intentionally set to correspond to the source document revision number.
ALC / TWI New reference: DOS-18-011415-029 1.0 N/A New reference due to new document management system software.
ALC / TWI 2.0 N/A Adding of the Caesium trap content and Gisete content TWI / SAZ
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SUMMARY
The objective of this chapter and its appendices is to verify the release of activity with regard to the regulatory criteria under normal and accident conditions of transport, when the TN-MTR packaging is loaded with various contents defined in chapter 0A.
This chapter presents the method used in the appendices to this Chapter for the calculation of released activity. The following quantities are studied:
- The packaging leakage rate:
- The maximum normal operating pressure (MNOP) reached in the containment ;
- The maximum pressure reached inside the containment under accident transport conditions.
- Activity released in gas form, in aerosol form and by permeation through the seals of the containment.
The total activity released is the sum of activities released in gas form, in aerosol form and by permeation through the seals.
Standard leakage rates (SLR) required for the containment and checked before transport are as follows:
- 4.7 x 10-4 Pa.m3.s-1 when the packaging is loaded with fuel elements unbroken before transport or the gisete content,
- 3.5 x 10-5 Pa.m3.s-1 when the packaging is loaded with beryllium elements,
- 1.33 x 10-4 Pa.m3.s-1 when the packaging is loaded with fuel elements broken before transport of the CESOX content or the caesium trap content, Radioactive materials that can be transported in the packaging can be organised into three groups:
- An upper-bound MTR fuel: this fuel includes all fissile MTR type fuel assemblies that can be transported in the different baskets. The upper-bound nature of the MTR fuel selected for this study is justified in Appendix 3A-12; o the MTR UO2 type fuel can only be transported in the MTR-44 basket; o there may be some broken areas in MTR fuel except for UO2 before transport;
- Beryllium elements: this radioactive non-fissile content is specific to the MTR-44 basket;
- The other types of contents: these contents (CESOX, caesium trap and gisete contents) are dealt with in the appendices specific to this chapter. It is assumed that the sealed capsule surrounding the radioactive material does not confine the radioactive material, which is conservative for the study of releases of the CESOX content.
Appendices 3A-1, 3A-5, 3A-10, 3A-11, 3A-13, 3A-14 and 3A-15 to this chapter present digital applications and the results of analyses of the confinement of the content of the TN-MTR packaging loaded with the different internal fittings and allowable contents.
The calculations of the release of activity are carried out with an external pressure of 0.6 bars.
The release results presented in the appendices to this chapter comply with regulatory criteria, namely: 6 A2 / hour under normal conditions of transport,
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- 1 A2 / week under accident conditions of transport
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- 1. INTRODUCTION This chapter presents the analysis of the confinement of the TN-MTR packaging loaded with fissile or non-fissile radioactive materials under normal and accident transport conditions (NCT and ACT). It starts with a description of the containment and goes on to present calculation methods for evaluating the release of activity in gas form, in aerosol form and by permeation through elastomer seals. Digital applications of studies associated with the various internal fittings and authorised contents are presented in the corresponding appendices.
Confinement studies of the TN-MTR packaging loaded with the different internal fittings and MTR type plate fuel elements are based on a typical fuel material that upper-bounds allowable contents described in Chapter 0A. The characteristics of this typical fuel material are as follows:
- MTR fuel except for UO2:
o Enrichment in 235U: 93.5%,
o burnup: 450,000 MWd/tU o cooling time 1 year,
- Special case for UO2 type MTR fuel:
o enrichment in 235U: 8%,
o burnup: 41000 MWd/t U, o cooling time 10 years Appendix 3A-12 justifies that the material considered upper-bounds contents typically transported with regard to release calculations.
This chapter also presents the characteristics of contents that are not covered (beryllium elements, CESOX content, caesium trap content and gisete content).
Under NCT, the justification of the confinement of the packaging content is based on the containment leakage rate measured before dispatch and the possibility of an external pressure dropping suddenly to 0.6 bars after one year of transport (conservative assumption for the activity release in that the difference between the inside pressure in the cavity and the outside pressure is maximised). Two cases are possible depending on the internal cavity pressure under NCT (PNCT) after one year of transport:
- if PNCT 0.6 bars, the cavity is under negative pressure; in this case, it can be concluded that no activity is released except by permeation through the seals of the containment;
- if PNCT > 0.6 bars, the cavity is under positive pressure; in this case, a calculation of the activity released (in gas form, in aerosol form and by permeation through the seals) must be made.
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- 2. CONTAINMENT The content of the TN-MTR packaging is confined in a containment that also forms the packaging shielding and the structure on which its mechanical strength is based. This containment is described in Chapter 0 and is represented in Figure 0.1.
2.1. Specifications for the containment The containment is the volume delimited by the following elements:
- Bottom of the internal containment;
- Shell of the body internal containment;
- Flange as far as the lid inner seal;
- Lid inner seal;
- inner seals of orifice A & B covers:
- Orifice A and B covers Note that:
- the internal containment is made of stainless steel:
- the lid is made of stainless steel and lead (standard type lid) or stainless steel (SEC type lid);
- the combined components are tested at an internal pressure of 7 bars without affecting the leak-tightness of the containment (see Chapters 1 and 1-10).
2.2. Openings in the containment The containment contains the following openings:
- compartment in the packaging lid
- orifice A called the cavity vent and test orifice (see Chapter 0),
- orifice B called the operations orifice (see Chapter 0).
These orifices are protected by a cover, fixed on the lid by screws and provided with seals for maintaining leak-tightness of the containment.
2.3. Seals and welds of the containment The internal wall of the body of the containment is made entirely of stainless steel. It is welded using a method designed and tested to guarantee that it remains leak-tight.
Each closing device is made leak-tight by EPDM O-rings; this leak-tightness is tested at the end of the manufacturing process and before each transport of the packaging.
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2.0 Page 8 of 35 NON PROPRIETARY VERSION 2.4. Containment closing devices The lid is fixed on the packaging body using 36 M30 screws fitted with captive washers.
Orifice A and B covers are fixed on the lid by 4 M12 screws.
The torques of screws and covers are given in Chapter 0.
2.5. Requirements for normal transport conditions 2.5.1. Efficiency of closing devices with regard to shocks and vibration The strength of screws under routine transport conditions is justified in chapter 1-10.
The strength of screws under accident transport conditions is justified in chapter 1-9:
this justification covers normal transport conditions.
2.5.2. Risk of opening under the effect of increased pressure inside the containment The containment is designed to resist an internal pressure of 7 bars (See Chapters 1 and 1-10).
2.5.3. Compatibility of containment materials with other components of the packaging and with the content of the package and risk of radiolysis The following materials are in contact with the outside of the containment:
cooling fins, tie-down devices and stainless steel plates welded onto the outside wall of the containment. Welding methods are qualified to avoid embrittlement of the metal.
the thermal insulation (resin) and the balsa are not reactive with regard to contact with steel.
The inside of the containment is a stainless steel chamber, which prevents any corrosion phenomenon due to pool water.
Since fuel assemblies are transported dry, there is no risk of galvanic corrosion between the component materials (stainless steel, borated aluminium) of the internal fittings, the inside wall of the containment (stainless steel) and the cladding of the fuel plates (aluminium or zircalloy alloys). All these materials are also inert with regard to the gas filling the containment (air, nitrogen or any other inert gas).
It is possible that the package containment contains products that could be subject to radiolytic decomposition. Boric acid in some pools can crystallise in the cavity during the drying procedure. Data from pools in EDF power stations are used for this demonstration because there are no available general data for the boron content in research reactor pools (see Chapter 5A safety file for the TN12/2 packaging).
Water in pools for storage of fuel assemblies from the core of EDF power plant reactors contains mainly boric acid H3BO3 which does not exceed 2500 ppm by mass or less (i.e. 0.25% by mass). Boron occurs in the form of borate ions, of which the most hydrogenated ions contain two hydrogen atoms for each atom of boron (e.g.
H2BO3
-).
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2.0 Page 9 of 35 NON PROPRIETARY VERSION The TN-MTR packaging is equipped with a dip tube the end of which is located at a
<< low point >> at the bottom of the cavity. Water is pumped or flushed through this low point, so that there is only a small quantity of residual water in the cavity at the beginning of the drying phase. If it is conservatively assumed that 0.5 litres of water remains in the TN-MTR cavity at the beginning of the drying phase and that all the boron is contained in the water crystallises, the number of moles of borate ions does not exceed:
n = 500 0.0025 / 60.81 = 0.0206 moles, where 60.81 is the molar mass of the borate ion (H2BO3
-).
Since the number of moles of borate ions is equal to the number of moles of water molecules formed by radiolysis of the borate ion, this represents an equivalent water mass of 0.0206 18 = 0.369 g, which is a very small mass of water.
Therefore, allowing for conservative aspects of the calculation, the real mass of products that can be decomposed by radiolysis is negligible. Production of H2 by radiolysis of borated water inside the package containment is less than the lower flammability limit of hydrogen in air at the maximum temperature of gases in the cavity under ACT (329°C according to Chapter 2A), namely 1.87%1.
2.5.4. Risk of loss of content under the conditions for regulatory tests simulating normal conditions of transport The tests to be considered are:
water spray, Drop from a height of 0.3 m, compression under a distributed load equal to 5 times the weight of the package, impact on the hemispherical end of a 6 kg bar with diameter 3.2 cm dropping from a height of 1 m.
Chapter 1 demonstrates that these tests will not cause any dispersion of the content or loss of leak-tightness of the packaging that could invalidate the assumptions made in Sections 3 to 7.
Chapter 1A also shows that there is no risk that these tests will cause a break of the cladding. Furthermore, no cladding break during transport has ever been observed.
2.6. Requirements for accident transport conditions 2.6.1. Risk of loss of content under accident transport conditions The tests to be considered are:
1 Calculated from the formula
0 0
0 600 1
T T
T LII LII (see <11>), where LFL and LFL0 are the lower flammability limits of dihydrogen in air at temperatures T and T0 = 20°C respectively (4%).
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2.0 Page 10 of 35 NON PROPRIETARY VERSION drop from a height of 9 metres, drop on a bar from a height of 1 m, fire test (800°C for 30 minutes).
It is demonstrated in Appendices 1-6, 1-7 and 1-9 that these tests do not cause any loss or dispersion of the packaging contents.
It is demonstrated in Chapter 1A that the assemblies resist a drop of 9 m and that no significant deformation is observed.
- 3. CONTENT DATA 3.1. MTR type upper-bound content 3.1.1. Definition of the upper-bound content Chapter 0A in the safety file authorises the transport of MTR plate fuels complying with the following upper-bound characteristics:
MTR fuel except for UO2:
Enrichment in 235U: 93.5%,
Burnup: 450 000 MWd/tU Cooling time 1 year; Special case for UO2 type MTR fuel:
Enrichment in 235U: 8%,
Burnup: 41000 MWd/t U, Cooling time 10 years.
The check on the upper-bound nature of the selected spectrum corresponding to a fuel with the characteristics described above is presented in chapter 3A-12.
Fission products that can be in gas form (at the temperature of cavity gases specified in Chapter 2A) consist of isotopes of bromine (Br), krypton (Kr), iodine (I), xenon (Xe) and also tritium (3H).
Only 85Kr and 3H have a significant activity for this upper-bound spectrum.
The following table gives the total volume of radioactive or non-radioactive fission gases under STP (25°C and 1.013 x 105 Pa), and the activities of these gases and aerosols contained in the upper-bound MTR type fuel. Data are expressed per unit mass of uranium present in the fuel element before irradiation.
MTR fuel except for UO2:
Total volume of fission gases at STP (m3/ g Uinitial)
Vgu Activity of fission gases (A2 / g Uinital)
Activity of aerosols (A2
/ g Uinitial)
Asaero 85Kr gu Kr Kr A
a
85 2
85 3H gu H
H A
a
3 2
3 Total fission gases
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2.0 Page 11 of 35 NON PROPRIETARY VERSION gu i
i A
a
2 1.72.10-5 7.06.10-5 6.62.10-6 7.72.10-5 5.57 NOTE: Standard temperatures and pressures (STP) are taken to be equal to 25°C and 1.013 x 105 Pa respectively.
Data in the following table are upper-bound data for all MTR fuels (except for UO2), with a cooling time longer than 1 year.
Other cooling times are considered for the release study for MTR fuel that might have some broken zones (see chapters 3A-11 and 3A-13). MTR fuel upper-bound data for these particular cooling times are as follows (see Chapter 3A-12):
Cooling time (years)
Total volume of fission gases at STP (m3/ g Uinitial)
Vgu Activity of fission gases (A2 / g Uinitial)
Activity of aerosols (A2
/ g Uinitial)
Asaero 85Kr gu Kr Kr A
a
85 2
85 3H gu H
H A
a
3 2
3 Total fission gases gu i
i A
a
2 2
1.71.10-5 6.62.10-5 6.26.10-6 7.24.10-5 2.42 3
1.71.10-5 6.20.10-5 5.92.10-6 6.80.10-5 1.39 5
1.71.10-5 5.45.10-5 5.29.10-6 5.98.10-5 0.75 10 1.71.10-5 3.95.10-5 3.99.10-6 4.35.10-5 0.55 NOTE: Standard temperatures and pressures (STP) are taken to be equal to 25°C and 1.013 x 105 Pa respectively.
Special case for UO2 type MTR fuel Total volume of fission gases at STP (m3/ g Uinitial)
Vgu Activity of fission gases (A2/g Uinitial)
Activity of aerosols (A2/g Uinitial)
Asaero 85Kr gu Kr Kr A
a
85 2
85 3H gu H
H A
a
3 2
3 Total gu i
i A
a
2 2.70.10-8 2.88.10-6 3.13.10-7 3.25.10-6 0.53 NOTE: Standard temperatures and pressures (STP) are taken to be equal to 25°C and 1.013 x 105 Pa respectively.
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2.0 Page 12 of 35 NON PROPRIETARY VERSION 3.1.2. Volumes and activities of releasable fission gases Volumes and activities of fission gases releasable into the packaging cavity are obtained from the volumes and activities of these gases contained in the upper-bound content (see Section 3.1.1), corrected by release rates of fission gases and by the mass of uranium before irradiation that might participate in the release of these gases.
The following table presents the expressions used to calculate these volumes and activities of releasable gases:
NCT ACT Volume of releasable gases before transport:
VgRi = Vgu MR U t%
during transport Vg = Vgu MU t%
Vg = Vgu (MU - MR U) t%
Activity of releasable gases Before and during transport
i i
A a
2
=
gu i
i A
a
2 (MU + MR U) t%
i i
A a
2
=
gu i
i A
a
2 MU t%
Where:
Vgu: total volume of fission gases contained in the upper-bound MTR type fuel at STP (25°C and 1.013 x 105 Pa) (see Section 3.1.1),
gu i
i A
a
2
- the activity of fission gas contained in the upper-bound MTR type fuel (see Section 3.1.1),
MU and MU: the maximum mass of U before irradiation for which a cladding rupture could occur during NCT and ACT respectively, MR U: the maximum mass of U before irradiation contained in fuel areas broken before transport; t%: the release rate of fission gases.
3.2. Special case of beryllium elements 3.2.1. Gaseous radionuclides According to <5>, the only gaseous radionuclide for which the quantity has a measurable influence on the release of activity is tritium (3H).
The maximum total activity of tritium contained in all beryllium elements is aH-3 = 7 x1014 Bq, as described in Appendix 5 to Chapter 0A.
According to <1>, the value of A2 for tritium is: A2 H-3 = 4 x 1013 Bq.
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2.0 Page 13 of 35 NON PROPRIETARY VERSION The activity of tritium corrected by the value of A2 is then:
13 14 3
H 2
3 H
10
.4 10
.7 A
a
=1.75 x 101 A2 The specific activity of tritium is:
as-H3 = 357.8 TBq/g (see <1>).
The total mass of tritium contained in beryllium elements is then:
mH3 =
8, 357 700 a
a H3
-s H3
= 1.96 g.
The total volume of tritium contained in beryllium elements at STP (25°C and 1.013 x 105 Pa) and therefore that could be released is:
i i
H3 H3 3
P T
R M
m
H V
Where:
mH3: the total mass of tritium contained in beryllium elements (mH3 = 1.96 g),
MH3: the molar mass of tritium, diatomic gas (MH3 = 2 3 = 6 g/mol),
R: the ideal gas constant, (R = 8.31 J.mol-1.K-1),
Ti: the normal temperature of the gas (Ti = 298 K),
Pi: the normal pressure of the gas (Pi = 1.013 x 105 Pa).
Hence VH3 = 7.97 x 10-3 m3.
3.2.2. Volume and activity of releasable tritium under transport conditions The volume and activity of tritium that can be released under transport conditions are obtained by correcting the volume and activity of tritium contained in beryllium elements (see Section 3.2.1) by the tritium release rate.
The release rate is denoted tNCT under normal transport conditions and tCAT under accident transport conditions.
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2.0 Page 14 of 35 NON PROPRIETARY VERSION 3.2.3. Aerosols According to <5>, the following aerosols participate in measurable quantities: 60Co, 10Be and 63Ni.
The following table gives activities of the main aerosols that can be released by beryllium elements.
60Co 10Be 63Ni Total Activity (Bq) 5.97.1011 2.00.1010 2.99.1010 6.47.1011 Specific activity (Bq/g) 4.19.1013 8.28.108 2.19.1012 A2 (Bq) 4.00.1011 6.00.1011 3.00.1013 Mass (g) 1.42.10-2 2.41.101 1.36.10-2 2.42.101 Number of A2 1.49 3.33.10-2 9.97.10-4 1.53 The specific activity of aerosols is then obtained by:
Asaero =
aérosol A
m N
2 Where:
NA2: the total number of A2 (according to the above table, NA2 = 1.53 A2),
maerosol: the total mass of aerosols (according to the above table, maerosol = 2.42 x 101 g).
Hence Asaero = 0.0632 A2/g of aerosols.
3.3. Special case of CESOX content The following assumptions are used for the release study, in accordance with the characteristics of the radioactive material in the CESOX content presented in Chapter 0A-11:
- the maximum activity of the source is equal to 5.55 PBq; each of the 144Ce and 144Pr isotopes accounts for 50% of the total activity,
- emitting impurities and emitting impurities are conservatively treated like 60Co;
- impurities leading to spontaneous fission reactions are conservatively treated like 244Cm.
Thus, the activity of the CESOX content is entirely due to aerosols.
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2.0 Page 15 of 35 NON PROPRIETARY VERSION The following table gives activities of the main aerosols that can be released by the CESOX content.
144Ce 144Pr 60Co 244Cm Total Activity (Bq) 2.78.1015 2.78.1015 2.78.1012 2.78.1010 5.55.1015 Specific activity (Bq/g) 1.182.1014 2.797.1018 4.191.1013 3.000.1012 A2 (Bq) 2.00.1011 4.00.1011 2.00.109 Mass (g) 2.35.101 9.92.10-4 6.62.10-2 9.25.10-3 2.36.101 Number of A2 1.39.104 6.94 1.39.101 1.39.104 The specific activity of aerosols is then obtained by:
Asaero =
aérosol A
m N
2 Where:
- NA2: the total number of A2 (according to the above table, NA2 = 1.39 x 104 A2),
- maerosol: the total mass of aerosols (according to the above table, maerosol = 2.36 x 101 g).
Hence Asaero = 5.90 x 102 A2/g of aerosols.
3.4. Special case of caesium trap content Only isotopes to consider for the release study are the 137Cs and the 241Am, in accordance with the characteristics of the radioactive material in the caesium trap content presented in Chapter 0A-13.
Although these isotopes are traps in the solidified sodium, we consider conservatively a released activity of these only isotopes (without sodium) in aerosols form.
The following table gives activities of the aerosols that can be released by the caesium trap content.
137Cs 241Am TOTAL Activity (Bq) 1.25.1013 3.105 Specific activity (Bq/g) 3.225.1012 1.273.1011 A2 (Bq) 6.00.1011 1.00.109 Mass (g) 3.88 2.36.10-6 3.88 Number of A2 2.08.101 3.10-4 2.08.101 The specific activity of aerosols is then obtained by:
Asaéro =
aérosol A
m N
2 Where:
- NA2: the total number of A2 (according to the above table, NA2 = 2.08 x 101 A2),
- maerosol: the total mass of aerosols (according to the above table, maerosol = 3.88 g).
Hence Asaero = 5.38 A2/g of aerosols.
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2.0 Page 16 of 35 NON PROPRIETARY VERSION 3.5. Special case of gisete content The only isotope to consider for the release study is the 90Sr, in accordance with the characteristics of the radioactive material in the gisete content presented in Chapter 0A-14.
The following table gives activities of the aerosols that can be released by the gisete content.
90Sr TOTAL Activity (Bq) 8.97.1014 Specific activity (Bq/g) 5.057.1012 A2 (Bq) 3.00.1011 Mass (g) 1.77.102 1.77.102 Number of A2 3.103 3.103 The specific activity of aerosols is then obtained by:
Asaéro =
aérosol A
m N
2 Where:
- NA2: the total number of A2 (according to the above table, NA2 = 3.103 A2),
- maerosol: the total mass of aerosols (according to the above table, maerosol = 1.77.102 g).
Hence Asaero = 1.7 x 101 A2/g of aerosols.
- 4. PACKAGING LEAKAGE RATE According to Chapter 6A, the guaranteed leakage rate of the TN-MTR packaging before transport is equal to:
- 4.7 x 10-4 Pa.m3.s-1 SLR when transporting fuel elements without any cladding broken before transport and in the special case of the gisete content,
- 1.33 x 10-4 Pa.m3.s-1 SLR when transporting fuel elements with cladding broken before transport and in the special case of transporting the CESOX content and in the special case of transporting the caesium trap content,
- 3.5 x 10-5 Pa.m3.s-1 SLR in the special case of transporting beryllium elements, When the leakage rate is between 10-8 and 1 Pa.m3.s-1, Knudsens general equation (1) is applied according to <2> to calculate a leakage rate in Pa.m3.s-1.
Pu Pd M
T a
D 204
,1 Pu Pd a
D 0123
,0 Q
g 3
2 2
4
(1):
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 17 of 35 NON PROPRIETARY VERSION Where:
- Pd: the external pressure (atmospheric pressure),
- Pu: the packaging internal pressure (Pa),
- D: the leakage capillary diameter (m),
- a: the leakage capillary length (m),
- Tg: temperature of cavity gases (K),
- M: the molar mass of the leaked gas,
- : the viscosity of the leaked gas.
4.1. Equivalent leakage capillary diameter The equivalent leakage capillary diameter is calculated from SLR leak rates guaranteed before transport of the packaging. Thus, standard SLR conditions are considered (see <2>),
as follows:
- the differential pressure is equal to 1.013 bars;
- the cavity gas temperature is equal to 25°C.
- the gas considered for the leakage rate is air (for which the molar mass is M = 0.029 kg/mol and the viscosity is 1.85 x 10-5 Pa.s at 25°C <6>).
The following assumptions are also made:
- the atmospheric pressure is conservatively assumed to be equal to its maximum value:
Pd = 1.04 bars = 1.04 x 105 Pa. Therefore the internal pressure Pu is taken to be equal to 0.027 bars to have a differential pressure of 1.013 bars;
- the leakage capillary length is assumed to be equal to the diameter of the torus of the packaging lid O-rings, namely a = 7.8 mm (see table 0.4 in Chapter 0).
Therefore the following table gives the equivalent capillary diameter obtained by application of formula (1), for leakage rates guaranteed before transport.
Transported content Broken MTR
- elements, CESOX content and caesium trap content Unbroken MTR elements and gisete content Beryllium elements Guaranteed leakage rate before transport QSLR (Pa.m3.s-1) 1.33.10-4 4.7.10-4 3.5.10-5 Equivalent capillary diameter D (m) 1.91.10-5 2.63.10-5 1.35.10-5
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
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2.0 Page 18 of 35 NON PROPRIETARY VERSION 4.2. Leakage rates under normal transport conditions, The leakage rate of the packaging under NCT is calculated using formula (1):
atm CNT g
3 2
atm 2
CNT 4
CNT P
P M
T a
D 204
,1 P
P a
D 0123
,0 Q
(Pa.m3.s-1)
Where:
- PNCT: the internal pressure in the packaging under NCT (see Section 5.1.6),
- Patm: minimum atmospheric pressure, Patm = 0.6 x 105 Pa,
- D: the leakage capillary diameter (see Section 4.1),
- a : the leakage capillary length (a = 7.8 x 10-3 m according to section 4.1),
- Tg: temperature of cavity gases under NCT (K),
- M: the molar mass of gas in the cavity (for air, Mair = 0.029 kg/mol; for helium, MHe =
0.004 kg/mol),
- : the viscosity of the cavity filling gas at temperature Tg (Pa.s), see Table 3A.1.
Since the gas in the cavity can be air or helium, the worst case gas will be considered in the calculations.
4.3. Leakage rates under accident transport conditions, Similarly, the leakage rate of the packaging under ACT is calculated using formula (1):
atm CAT g
3 2
atm 2
CAT 4
CAT P
P M
T' a
D 204
,1 P
P a
D 0123
,0 Q
(Pa.m3.s-1)
Where:
- PACT: the internal pressure in the cavity under ACT (see Section 5.2.4),
- Patm: minimum atmospheric pressure (Patm = 0.6 x 105 Pa),
- D: the leakage capillary diameter (see Section 4.1),
- a : the leakage capillary length (a = 7.8 x 10-3 m see section 4.1),
- Tg: temperature of cavity gases under ACT (K),
- M: the molar mass of gas in the cavity (for air, Mair = 0.029 kg/mol; for helium, MHe =
0.004 kg/mol),
- : the viscosity of the cavity filling gas at temperature Tg, see Table 3A.1.
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
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2.0 Page 19 of 35 NON PROPRIETARY VERSION
- 5. CAVITY INTERNAL PRESSURE UNDER NCT AND ACT 5.1. Cavity internal pressure under NCT The internal pressure Punder NCT is the result of:
- the increase in the temperature inside the packaging due to the radioactive content under normal transport conditions (Pu0),
- the gas released from initially broken fuel zones if applicable (PgRi),
- leakage into the packaging as a result of the initial cavity negative pressure (Pf),
- breakage of sealed cans, if applicable (Pre),
- breakage of content cladding, if applicable, during transport (Pg).
Therefore, PNCT = Pu0 + PgRi + Pf + Pre + Pg.
It is conservatively assumed that cladding of fuel contained in sealed cans breaks after one year under normal transport conditions.
The maximum normal operating pressure (MNOP) is the maximum pressure reached inside the packaging cavity during a year <1>. It is conservatively considered that the maximum normal operating pressure is: MNOP = PNCT.
5.1.1. Pressure increase related to temperature (Pu0)
The internal pressure is adjusted to P0 = 0.35 bars when the packaging is closed (see Chapter 6A) except for caesium trap content.
The caesium trap content is loaded with atmospheric pressure, but the study of released activity is realised with P0= 1.2 bar in order to take the maximum pressure in the packaging caesium trap.
The gisete content is loaded with atmospheric pressure (0 = 1.04 ).
The average internal temperature, or the cavity gas temperature, under normal transport conditions is denoted Tg (in K).
Therefore, the pressure caused by the increase in temperature is equal to:
i g
T T
P Pu
0 0
Where:
- P0: the internal pressure when the packaging is closed (P0 = 0.35 bars, P0 = 1.2 bar or P0 = 1.04 bar),
- Tg: temperature of cavity gases under NCT (in K),
- Ti: the temperature when the packaging is closed (Ti = 298 K),
5.1.2. Pressure increase due to gas released from fuel zones broken before transport (PgRi)
This section is applicable to the MTR type upper-bound content only.
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 20 of 35 NON PROPRIETARY VERSION A broken element means an element for which at least one of the claddings surrounding the fuel zones has lost its leak-tightness.
The pressure increase due to gas released from fuel zones broken before transport is then iP T
V T
V P
i l
g gRi gRi (Pa),
Where:
VgRi: the volume of releasable fission gases before transport at STP (25°C and 1.013 x 105 Pa) (due to zones broken before transport, see Section 3.1.2) (in m3),
Tg: the temperature of cavity gases under NCT (in K),
VL: the minimum free volume of packaging cavity (in m3)
Ti: the normal temperature of gases at the time of closure (Ti = 298 K),
Pi: the normal pressure of gases (Pi = 1.013 x 105 Pa).
Note: this additional pressure is zero in the case of MTR fuel elements that are not broken before transport.
5.1.3. Pressure increase in the cavity (Pf)
This paragraph is not applicable in caesium trap content and gisete content.
The pressure increase is calculated from the leakage rate from the packaging. When the packaging is at negative pressure, the pressure increase in the cavity is due to the entry of external air into the packaging.
The leakage rate is calculated assuming that the time to reach the cavity gas temperature Tg is very short compared with the period of 1 year (duration used for calculating the MNOP <1>). It is also assumed that fuels broken before transport release their gases as soon as the cavity is closed (if they are not packaged inside sealed cans).
Thus the internal pressure in the packaging is quickly equal to the pressure resulting from the increase in the temperature inside the packaging due to the radioactive content under normal transport conditions and to the gas released from cladding broken before transport. Therefore we have:
Pu = Pu0 + PgRi Therefore we calculate the packaging leakage rate (in Pa.m3.s-1) when the cavity is closed, using the formula (1) (see Section 4):
)
P Pu
(
10 04
,1 0,029 T
7,8.10 D
204
,1
)
P Pu
(
10 04
,1 7,8.10 D
0123
,0 Q
gRi 0
5 g
3 3
2 gRi 0
2 5
3 4
0
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 21 of 35 NON PROPRIETARY VERSION Where:
D: the leakage capillary diameter (see Section 4.1),
- the viscosity of air at temperature Tg (see Table 3A.1).
Pu0: the internal pressure in the packaging due to the temperature increase caused by the radioactive content (see Section 5.1.1),
PgRi: the pressure increase due to the gas released from cladding broken before transport (see Section 5.1.2),
Tg: the temperature of cavity gases under NCT (in K).
The pressure increase due to the leak after the cavity is put under negative pressure is obtained as follows:
l f
V t
Q P
0 Where:
Q0: the packaging leakage rate when the cavity is closed (calculated above),
t : the time elapsed since negative pressure was applied (t = 365243600 seconds for a year),
VL: the minimum free volume of the cavity (in m3) 5.1.4. Pressure increase due to breakage of cans (Pre)
This section is applicable when cans sealed before transport are loaded into the packaging.
It is conservatively assumed that these cans break after 1 year (at the end of NCT).
The additional pressure Pre is due to can filling gas being released into the packaging cavity.
This pressure increase is calculated as:
Pre =
l ie g
le oe e
e V
T T
V P
N t
Where:
te%: the percentage of sealed cans considered to be broken under NCT, Ne: the total number of cans loaded in the packaging cavity.
Poe: the internal pressure in a can when it is closed (in Pa),
VL: the free volume of a can (in m3)
Tg: temperature of cavity gases under NCT (in K),
Tie: the temperature of the can filling gas when the can is closed (in K),
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 22 of 35 NON PROPRIETARY VERSION VL: the minimum free volume of the packaging cavity (in m3)
After the cans have broken, the free volume of the cavity is increased, including the free volume of cans that have lost their leak-tightness. The free volume is conservatively minimised by considering only the free volume of the cavity before the cans break throughout the study.
Note: this additional pressure is zero in the case in which no sealed cans are loaded into the packaging.
5.1.5. Pressure increase due to breakage of cladding during transport (Pg)
It is conservatively assumed that the breakage of cladding during transport takes place after 1 year. The additional pressure Pg is due to fission gases released into the cavity by zones broken during transport.
This pressure increase is calculated as:
Pg =
iP T
V T
V i
l g
g
Where:
Vg: the volume of fission gases that can be released under NCT (see Sections 3.1.2 and 3.2.2),
Tg: temperature of cavity gases under NCT, Pi: the normal pressure of released gases (Pi = 1.013 bars).
VL: the minimum free volume of the cavity Ti: the normal temperature of released gases (Ti = 298 K),
5.1.6. Total pressure under NCT The maximum internal pressure inside the packaging under NCT can be determined from the above sections:
Therefore, PNCT = Pu0 + PgRi + Pf + Pre + Pg.
It is conservatively considered that the maximum normal operating pressure is:
MNOP = PNCT.
This pressure will be compared with that authorized by the regulation <1>, which gives a maximum allowable value for the MNOP of 7 bars for a B(U) type package.
This pressure must also be less than the maximum allowable pressure in the containment (7 bars according to Chapters 1 and 1-10).
If PNCT is less than 0.6 bars (minimum atmospheric pressure), only activity releases by permeation through the seals are considered under normal conditions of transport.
If PNCT is greater than 0.6 bars, the activity released (in gas form, in aerosol form and by permeation through the seals) is calculated.
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
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2.0 Page 23 of 35 NON PROPRIETARY VERSION 5.2. Packaging internal pressure under ACT The internal pressure PACT is the result of:
- the temperature rise with respect to NCT due to the fire test (Pt),
- the overpressure due to the breakage of sealed cans under ACT (Pre),
- the overpressure due to the breakage of content cladding under ACT (P'g),
Therefore: PACT = Pt + Pre + Pg.
5.2.1. Pressure increase related to temperature under ACT (Pt)
The pressure caused by the increase in temperature under ACT is equal to:
g g
CNT t
T T
P P
Where:
PNCT: the internal pressure in the packaging under NCT (see Section 5.1.6),
Tg: the temperature of cavity gases under NCT (in K),
Tg: temperature of cavity gases under ACT (in K),
5.2.2. Pressure increase due to the breakage of sealed cans under ACT),
It is assumed that all sealed cans will break under ACT.
The additional pressure due to the breakage of sealed cans under ACT is given by the following calculation Pre =
l ie g
le oe e
e V
T T
V P
N t
1 Where:
te%: the percentage of sealed cans considered to be broken under NCT, Ne: the total number of cans loaded in the packaging cavity.
Poe: the internal pressure in a can when it is closed (in Pa),
VL: the free volume of a can (in m3)
Tg: the temperature of cavity gases under ACT (in K),
Tie: the temperature of the can filling gas when the can is closed (in K),
VL: the minimum free volume of the packaging cavity (in m3)
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 24 of 35 NON PROPRIETARY VERSION 5.2.3. Pressure increase due to the breakage of cladding under ACT, The overpressure due to the breakage of claddings under ACT is given by the following calculation P'g =
iP T
V T
V i
l g
g
Where:
g V the volume of fission gases that can be released under ACT (see Sections 3.1.2 and 3.2.2),
g T :; temperature of cavity gases under ACT (K),
Pi: the normal pressure of released gases (Pi = 1.013 bars).
VL: the minimum free volume of the cavity (in m3)
Ti: the normal temperature of released gases (Ti = 298 K),
5.2.4. Packaging internal pressure under ACT Therefore the internal pressure under ACT is:
PACT = Pt + Pre + Pg.
The maximum internal pressure under ACT must be less than the maximum design pressure in the containment (7 bars according to Chapters 1 and 1-10).
- 6. CALCULATION OF ACTIVITY RELEASE IN GASEOUS FORM UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT Let ai represent the activity of a gas radionuclide i and t the time. The activity rate r of a set of radionuclides is written:
dt a
d r
i 0
Let n be the number of moles of gas contained in the packaging cavity.
dt dn n
a dt n
n a
d r
i i
0
We obtain the following relations:
- The packaging leakage rate is defined by: Q =
dt dPV, where P is the pressure of gases in the cavity and V is the gas volume in the cavity (free volume);
- For perfect gases: PV = nRT, where P is the gas pressure, V is the gas volume, n is the number of moles of gas, R is the perfect gas constant and T is the gas temperature.
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 25 of 35 NON PROPRIETARY VERSION Hence:
Q PV a
=
dt dPV nRT a
r i
i 0
Therefore:
V P
a Q.
r i
0
The activity rate released by fission gases (corrected by A2 ) is calculated:
V P
A a
Q r
2i i
Where:
- Q: the packaging leakage rate:
- ai = activity of gas radionuclide i
- A2i: the value for A2 for radionuclide i.
- P: the pressure of gases contained in the packaging cavity
- V: the volume of gases contained in the cavity (cavity free volume).
6.1. Under normal conditions of transport Therefore the release of gas activity under NCT is:
3600 V
P A
a Q
r l
CNT 2i i
CNT CNT
(in A2/hour)
Where:
- PNCT: the internal cavity pressure under NCT (see Section 5.1.6),
- QNCT: the packaging leakage rate under NCT (see Section 4.2),
- Vl:
the free volume of the cavity,
i i
A a
2
- the releasable activity (as a number of A2) under NCT for gas nuclide i (see Sections 3.1.2 and 3.2.2).
6.2. Under accident conditions of transport Therefore the release of gas activity under ACT is:
7 24 3600 V
P A
a Q
r l
CAT 2i i
CAT CAT
(in A2/week)
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 26 of 35 NON PROPRIETARY VERSION Where:
- QACT: the packaging leakage rate under ACT (see Section 4.3),
- PACT:
the internal pressure in the packaging under ACT (see Section 5.2.4),
- Vl:
the free volume in the cavity,
i i
A a
2
- the releasable activity (as a number of A2) under ACT for gas nuclide i (see Sections 3.1.2 and 3.2.2).
- 7. CALCULATION OF ACTIVITY RELEASE IN AEROSOL FORM UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT This section considers only the fraction of substances in aerosol form in the cavity, in other words solid or liquid particles originating from the fuel in the gas medium in the cavity.
7.1. Normal Conditions of Transport According to the notes in references <13><3> and <4><14>, the maximum concentration of material in the form of aerosols in the cavity under normal transport conditions is evaluated as follows based on experimental observations:
C = 1 x 10-3 g / m3.
Considering the containment leakage rate, we obtain the activity rate related to the release of aerosols under normal conditions of transport as follows:
3600 P
A Q
r CNT V
CNT aCNT
(A2 / hour)
Where:
- QNCT: the leakage rate under NCT (see Section 4.2),
- AV: the activity concentration of aerosols in the cavity under NCT (
saéro A
C AV
) ;
- C: the maximum concentration of material of the aerosols in the cavity under NCT (C = 1 x 10-3 g / m3),
- Asaero: the activity of aerosols (in A2 / g), see Sections 3.1.1 and 3.2.3),
- PNCT: the cavity pressure under NCT (see Section 5.1.6),
7.2. Accident Conditions of transport According to the notes in references <13><3> and <4><14>, the maximum concentration of material in the form of aerosols in the cavity under accident transport conditions is evaluated as follows based on experimental observations:
- C1 = 9 g /m3 during the half-hour that follows the drop
- C2 = 0.1 g /m3 after the first half-hour after the drop Therefore, the activity rate due to the release of aerosols under ACT is obtained as follows:
CAT V
CAT aCAT P
A Q
r
(A2/ week)
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 27 of 35 NON PROPRIETARY VERSION Where:
- QACT: the leakage rate under ACT (see Section 4.3),
- AV: the activity concentration of aerosols under ACT, AV = Asaero (C1 t1 + C2 t2),
- Asaero: the activity of aerosols (in A2 / g), see Sections 3.1.1 and 3.2.3),
- C: the maximum concentration of material in the form of aerosols in the cavity under ACT during time t1 (C1 = 9 g /m3),
- t1: the time corresponding to the half-hour after the drop, hence t1 = 1 800 s,
- C2: the maximum concentration of material in the form of aerosols in the cavity under ACT during time t2 (C2 = 0.1 g /m3),
- t2: time after the first half-hour after the drop, hence for a duration t1 + t2 equal to 1 week, t2 = 7 24 3600 - t1
- PACT: the cavity pressure under ACT (see Section 5.2.4),
- 8. CALCULATIONS OF THE RELEASE OF ACTIVITY DUE TO PERMEATION UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT This part considers the activity release due to permeation through lid and cover seals. The lid and each cover have two elastomer seals - one inner seal and one outer seal (see Chapter 0).
8.1. Total length of the seals forming the containment The total length of the containment seals is calculated as follows:
)
(
int
jo gorge gorge gorge eq o
d H
D L
according to <9>
Where:
- Dmean groove: the mean diameter of the seal groove,
- Hgroove: the groove depth,
- d: detachment of the clamped part adjacent to the seal zone. According to Chapter 1-9, the maximum residual detachment of the lid under ACT is obtained with case No. 2 (oblique drop with minimum preload and maximum NCT temperature) and is equal to 0.042 mm. Detachment of the lid and the covers is zero under NCT.
- ogroove: the opening of the seal groove.
This calculation considers the lid inner seal and the inner seals of the two covers. It is conservative to consider only the first seal barrier (inner seals of the lid and the two covers)
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 28 of 35 NON PROPRIETARY VERSION to calculate this length. In practice, the gas must cross two barriers of elastomer seals before reaching the exterior.
Two seal barriers are considered for beryllium elements, the behaviour of the inner and outer seals may be treated like a single seal (called the "equivalent seal") for the following reasons:
- the characteristics of the inner and outer seals are the same except for the length;
- the inner and outer seals are installed in series.
The following table shows the characteristics of the equivalent seal for the lid and the two covers:
Geometric characteristics (mm)
Inner seal Outer seal Equivalent seal Lid D: mean diameter of the seal groove 1,130 1170 (1,130+1,170)/2 =
1,150 h: depth of the seal groove, 5,5 5,5 5,5 o: groove opening 7,2 7,2 (7,2+7,2) = 14,4 Cover A D: mean diameter of the seal groove 90,5 121 (90,5+121)/2 = 106 h: depth of the seal groove, 3,65 3,65 3,65 o: groove opening 4,8 4,8 (4,8+4,8)= 9,6 Cover B D: mean diameter of the seal groove 90.5 121 (90.5+121)/2 = 106 h: depth of the seal groove, 3.65 3.65 3.65 o: groove opening 4.8 4.8 (4.8+4.8)= 9.6 The following total seal lengths are then obtained:
Leq (m)
NCT ACT Single seal (inner) 3.14 3.16 Equivalent seal (inner + outer) 1.63 1.64
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2.0 Page 29 of 35 NON PROPRIETARY VERSION 8.2. Permeation coefficient The permeation coefficient P(T) depends on the nature of seals, the gas present in the cavity and the seal temperature.
Release by permeation through the seals is due mainly to 85Kr and 3H. The following table gives permeation coefficients through an EPDM seal for these two gases:
Gas 3H 85Kr P(T) (m2.s-1)
T e
3426 6
10 08
,3
Reference
<10>
<8>
where T is the temperature of the seals.
NOTE: The permeation coefficient of tritium is taken to be the same as that of deuterium.
8.3. Activity release by permeation through the seals According to reference <2>, the permeation rate of a gas through an elastomer seal is expressed as follows:
Qp = P(T).Leq.pp (en Pa.m3.s-1)
Where:
- P(T): the seal permeation coefficient (see Section 8.2),
- T: the temperature of seals (K),
- Leq: total length of seals forming the containment (see Section 8.1),
- pp: the difference in partial pressure of fission gas through the seals (Pa).
We will consider that the partial pressures of fission gases outside the containment are zero.
Therefore for a given fission gas, the difference in partial pressure p is equal to the partial pressure of gas in the cavity Pp.
The release for a fission gas is as follows, regardless of the transport conditions:
l p
i i
p i
p V
P A
a Q
r
2
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 30 of 35 NON PROPRIETARY VERSION Where:
- Qp: the permeation rate of a gas through an elastomer seal,
- Pp: the partial pressure in the cavity (in Pa),
i i
A a
2
- the number of A2 corresponding to the releasable activity of nuclide i,
- V: the minimum free volume of the cavity.
Simplifying:
l i
i eq i
T i
p V
A a
L P
r
2
)
(
Where:
- P(T)i: the seal permeation coefficient of the gas considered at temperature T (see Section 8.2) in m2.s-1,
- T: the temperature of seals (K),
- Leq: total length of seals forming the containment (see Section 8.1),
i i
A a
2
- the number of A2 corresponding to the releasable activity of nuclide i,
- V: the minimum free volume of the cavity.
Since release by permeation through the seals is due mainly to 85Kr and 3H, the total release by permeation will be:
85 3
Kr p
H p
p r
r r
8.3.1. Under normal conditions of transport Therefore the release of activity by permeation under NCT is:
3600
)
(
85 3
Kr p
H p
CNT p
r r
r Hence:
3600 3
2 3
3
)
(
85 2
85 85
)
(
H H
H T
Kr Kr Kr T
l eq CNT p
A a
P A
a P
V L
r (in A2/hour)
Form: PM04-4-MO-6 rev.02 NON PROPRIETARY VERSION Orano TN Identification:
DOS-18-011415-029-NPV Version:
2.0 Page 31 of 35 NON PROPRIETARY VERSION Where:
Leq: total length of seals forming the containment under NCT (see Section 8.1),
P(T)Kr-85 and P(T)H-3: permeation coefficients of 85Kr and 3H respectively at temperature T (see Section 8.2),
T: the maximum temperature of seals under NCT,
85 2
85 Kr Kr A
a and
3 2
3 H
H A
a
- activities (as a number of A2) of 85Kr and 3H respectively that can be released in the cavity under NCT.
8.3.2. Under accident conditions of transport Similarly, the release of activity by permeation under ACT is therefore:
7 24 3600
)
(
)
85 3
Kr p
H p
CAT p
r r
r Hence:
7 24 3600 3
2 3
3
)'
(
85 2
85 85
)'
(
H H
H T
Kr Kr Kr T
l eq CAT p
A a
P A
a P
V L
r (in A2/week)
Where:
Leq: total length of seals forming the containment under ACT (see Section 8.1),
P(T)Kr-85 and P(T)H-3: permeation coefficients of 85Kr and 3H respectively at temperature T (see Section 8.2),
T: the maximum temperature of seals under ACT,
85 2
85 Kr Kr A
a and
3 2
3 H
H A
a
- activities (as a number of A2) of 85Kr and 3H respectively that can be released in the cavity under ACT.
- 9. CALCULATION OF THE TOTAL RELEASED ACTIVITY UNDER NORMAL AND ACCIDENT CONDITIONS OF TRANSPORT The total released activity is the sum of the activity released in gaseous form (leak and permeation) and the released activity related to aerosols.
Let TOT CNT R
and TOT CAT R
be total released activity rates under normal and accident conditions respectively.
pCNT aCNT CNT TOT CNT r
r r
R
(see Sections 6.1, 7.1 and 8.3.1) pCAT aCAT CAT TOT CAT r
r r
R
(see Sections 6.2, 7.2 and 8.3.2)
These values should be compared with regulatory requirements <1> for released activity under normal and accident transport conditions, as follows:
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- Under normal conditions of transport: 10-6 A2/hour;
- Under accident conditions of transport: 1 A2/week
- 10. CONCLUSIONS This chapter presents methods of calculating the maximum normal operating pressure (MNOP) reached in the containment, the maximum pressure reached inside the containment and the maximum quantity of activity that could be released inside the TN-MTR containment.
These methods applied to the different internal fittings and upper-bound contents of allowable TN-MTR contents demonstrate that regulatory requirements concerning the release of activity under normal and accident transport conditions are respected. The associated calculations are presented in the appendices to this chapter.
Regulatory requirements <1> for activity releases under normal and accident transport conditions are:
- under normal conditions of transport: 10-6 A2/hour;
- under accident conditions of transport: 1 A2/week These calculations also show that the maximum internal pressure of 7 bars that can be applied to the containment is respected (see chapters 1 and 1-10) and that the maximum normal internal pressure imposed by the regulations under normal transport conditions (7 bars <1>) is respected.
- 11. REFERENCES
<1> Applicable IAEA regulations: see chapter 00;
<2> International standard ISO 12807:-1996(F) - "Safe transport of radioactive materials -
Package leak-tightness tests;
<3> A guide to Radiological Accident Considerations for Siting and Design of DOE Non Reactor Nuclear Facilities. - LA 10294-MS - UC 41 - January 1986 - Los Alamos National Laboratory, New Mexico, USA;
<4> PATRAM 1980 Article - Leakage of radioactive powders from containers - W.D.
CURREN and R.D. BOND.
<5> CEA report ref. Report 2270/99/308 rev B date 04/11/99 - Characterisation of beryllium present in SILOE;
<6> Initiation for heat transfers - J.F. SACADURA - 4th print 1993;
<7> CRC Handbook of Chemistry and Physics-David R. LIDE - 75rd Edition - 1992-1993;
<8> TN International Note ref. NTC-07-00085519-000 "Synthse des essais de détermination du coefficient de perméabilité sur élastomre FKM et EPDM" (Summary of tests used to determine the permeability coefficient on FKM and EPDM elastomer seals)
<9> TN International fax to IRSN on March 15 2013, TN-MTR package model - Answers to the IRSN/PSN-EXP/SSTC/2012-817 fax dated December 14 2012, reference CEX 00075142-103;
<10> Gas permeation through common elastomer sealing material - H.-P Weise, K.-H Ecker, H.
Kowalewsky, Th. Wolk Bundesanstalt für Materialforschung and prüfung (BAM), Berlin F.R.G. - Vuoto - 1990.
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<11> "Explosive mixtures: gases and vapours, dusts, liquids and solids - National Institute of Research and Safety (INRS), A. Cleuet, P. Gros, 1994.
TN International Ref. DOS-06-00032593-300 Rev. 8 Page 34 / 35 NON PROPRIETARY VERSION LIST OF TABLES Table Description Pages 3A.1 Viscosity of air and helium versus temperature 1
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2.0 Page 35 of 35 NON PROPRIETARY VERSION TABLE 3A.1 VISCOSITIES OF AIR AND HELIUM VERSUS TEMPERATURE Temperature (K)
Viscosity of air (Pa.s)
Viscosity of helium (Pa.s) 300 1.86.10-5 2.00.10-5 321 1.95.10-5 2.09.10-5 343 2.05.10-5 2.19.10-5 400 2.31.10-5 2.44.10-5 445 2.49.10-5 2.62.10-5 468 2.58.10-5 2.71.10-5 482 2.64.10-5 2.77.10-5 500 2.71.10-5 2.84.10-5 522 2.79.10-5 2.93.10-5 536 2.84.10-5 2.98.10-5 557 2.92.10-5 3.06.10-5 574 2.98.10-5 3.13.10-5 589 3.04.10-5 3.19.10-5 600 3.08.10-5 3.23.10-5 602 3.09.10-5 3.24.10-5 NOTE: data presented in bold are derived from <7>; other values were obtained by interpolation/extrapolation of data from <7>.