LEADER meeting WP2 – Task 2.5 DPA, dose and activation calculations D. Gugiu (INR) – C. Petrovich (ENEA) Karlsruhe, November 21 st 2012

Task 2.5 DPA and radiological protection for LFR and ETDR (INR, ENEA, SCK  CEN)  Evaluations of the DPA on the structural materials and main components, replaceable or not, of both ETDR and LFR systems.  The activation of the main components of both ETDR and LFR (including the Pb) will be also computed in order to evaluate their contributions to the  doses in some key points (personnel radioprotection). The activation estimations will also allow the characterization of the respective components (materials) from the waste management point of view. Objectives:

Technical Document T61 (advanced draft – issue within end of 2012) ETDR core: DPA rates in the main components, activation, doses IndexResponsibleParticipantsDate 1. ScopeINR 2. IntroductionINR 3. Radiation damage evaluation SCK  CEN All 4. Pb activationENEAENEA, INR 5. Pb activation contribution to the  dose INRENEA, INR 6. Activity and  dose contribution of the impurities removed by coolant from the reactor Internals INR 7. Neutron and  dose computations during reactor operation-reference core configuration INR 8. ConclusionsINRAll

Technical Document T65 (under preparation) (January is OK??) LFR cores: DPA rates in the main components, activation, doses IndexResponsibleParticipantsInput Need Date 1. ScopeINR 2. IntroductionINR 3. Radiation damage evaluation INR 4. Pb activationENEAENEA, INR 5. Pb activation contribution to the  dose INR D05; T51; T55 6. Activity and  dose contribution of the impurities removed by coolant from the reactor Internals INR 7. Neutron and  dose computations during reactor operation- reference core configuration INR 8. ConclusionsAll

Configuration and tools All calculations are performed with: – MCNPX (3D detailed model) + JEFF 3.1 – FISPACT (UKAEA, activation calculations) + EASY-2005 – ERANOS (CEA)

Radiation damage evaluations for ALFRED The max, over the reactor life, obtained on the Ti cladding (only Iron) : 85 dpa (criteria is  100 dpa) (ERANOS computations by CEA, reported in D7) 1. DPA in cladding

MCNPX calculations: 60 dpa in the central FA The differences could be due to: -ERANOS takes into account the axial and pin-wise distribution factors, while MCNPX has been used upon averaging on the entire FA -ERANOS used a realistic refuelling scheme, while the MCNPX computations have been performed on a completely fresh core - the value of the damage energy (E d ) used in ERANOS might be different; in some references this value is of 25 eV for iron; for ELSY, ALFRED and previously for XS-ADS a value of 40 eV has been used.

DPA values in the inner vessel (T91) -Divided in segments of 20 cm starting from the inner vessel bottom -After 20 y, DPA>2, starting from cm from the bottom -After 40 y, DPA>2, starting from cm from the bottom

DPA values for the internals Pump casing -The pump casing tube has been divided into segments of 20 cm height starting from its bottom ending located at cm with respect to the active core centre -For the lowest segment (closest to active core ) the DPA after 40 y is considerably under the limit (2 DPA)

Inner shell MCNPX model of SG The DPA start to accumulate from the segment located at -12cm with respect to the core centre and are under the design constraint (2 DPA) even after 40y of irradiation

Cladding Activation (Ti 15-15) Nuclide Activity (Bq) Total1.58E+14 Co E+13 Fe E+13 Co 58m2.64E+13 Mn E+13 Mn E+12 Mo E+12 Cr E+12 Tc 99m3.44E+12 Tc E+12 Mo E+12 Fe E+11 Ta E+11 Tc E+11 Ni E+11 V E+11 Co 60m2.93E+11 Nb 94m2.75E+11 Si E+11 Cu E+11 Cr E+11 Rest1.16E+12 The total activity of 1 kg of Ti after 5y of continuous irradiation in the central FA is very high: 1.6E+14 Bq The FISPACT code provides also information about the contribution of each type of radiation to the total activity:  Bq = 4.4E+07  Bq = 1.3E+14  Bq = 3.0E+13 The  decay is the main contributor and, together with the  decay, should be taken into consideration (from personnel radioprotection point of view) during handling and transportation.

After 100 y of cooling the activity is still high; the clearance index remains enough high due to long-lived isotopes (Ni63, C14, Ar39, etc.) Dominant isotopes:

Cladding Activation (Ti 15-15) Another aspect that could be of interest especially for the nuclear materials field is the behavior of the Ti isotopic composition with irradiation.

It could be observed an increase of the V mass (  17%) after 5y of irradiation (central FA) and of the Co element (20%) Additionally, the Ta mass decreases by  20% and transmutes partially into W, whose mass increases by  3% Even if these elements are in small amounts in the initial composition of Ti 15-15, the variation of their concentration could lead to changes (?) in the crystallographic structure and subsequently to the modification of the mechanical, thermal, etc. properties of the steel.

Impurities (removed by lead from the internals) NOTE: it should be of interest to have detailed information about the corrosion rate of various stainless steel types (maybe from KIT ?) which could allow a better estimate of the quantity and the activity level of the impurities transported by the Pb coolant. Example: IAEA-TECDOC-1289 Results of out-of-pile corrosion tests (ferritic-martensitic 12% Cr steel) conducted within 400–650 C range during 8000 h were extrapolated for h (5 y operation of fuel subassembly) gave ~120 μm and 60 μm reduction of cladding wall thickness at 650 C and 550 C respectively. In the present work (T61): - a layer of 50 μm (in 5y) removed only from the fuel claddings (133 cm length) has been considered ( cm 3 ) - a thin layer of impurities (resulted from their volume conservation) has been considered at the lead free surface -the most intense  source (after 5 y irradiation of Ti ) has been considered for this layer. The  dose values obtained show that the impurities carried by Pb could provide a substantial dose. As a result, a more detailed information about the erosion/corrosion rate is needed (μm/y). (also which cooling time to be considered? Shielding ?)

LEAD ACTIVATION the Pb coolant activation analysis is performed for C00 lead brand analysed in BREST reactor (purity level of %) AgCuZnBiAsSnSbMg % wt FeTlCaNaCdAlHgIn % wt  Assumption that Pb is irradiated during the reactor life in the average neutron flux–spectrum evaluated in the entire Pb volume (same approach as PDS-XADS, EFIT and ELSY). Assumption of homogeneous irradiation (no stagnant zones)  The actual lead volume in the reactor is  320 m 3 approximately (as computed by MCNPX). Therefore:  3400 tons of Pb Intrinsic impurities assumed for calculation (other impurities?):

Average neutron flux-spectrum over the whole lead volume  The value of the tot neutron flux is of 1.4  cm -2 s -1 (assumed to be constant during 40 y). 175 energy groups.  A detailed isotopes inventory is available (in ANNEX of T61), with grams, Bq, Sv (ingestion and inhalation). Isotopes with atoms <10 12 are there neglected.  Using this approach, the total Po produced is ~0.03g (for an initial concentration of Bi impurities of 1.E-4 ); for a Bi impurity level of 0.006%, the amount of Po becomes 0.4g.

Total production of atoms in the whole volume

10 dominant nuclides after 40y (no cooling) – 1 kg of Pb Nuclide Activity (Bq) Nuclide Ingestion (Sv) Nuclide Inhalation (Sv) Total5.21E+10Total3.34E+00Total8.16E+00 Pb207m4.22E+10Po E+00Po E+00 Pb E+09Pb E-01Sb E-01 Pb204m2.75E+08As E-01Pb E-01 As E+08Sb E-01Sb E-01 Sb E+08Sb E-01As E-01 Hg E+08Pb204m6.05E-02Bi E-01 In116m1.16E+08Tl E-02Pb204m6.32E-02 Sb E+08Zn E-02Ag110m3.60E-02 Ag E+07Cd E-02Cd113m3.39E-02 In116n6.28E+07Pb E-02Te123m1.52E-02

CONCLUSIONS DPA limits: -Respected in cladding: <85 dpa (limit of 100) -Respected in SGs: <0.3 dpa (limit of 2) -Not respected in the inner vessel: 4.6 dpa after 40y (limit of 2). Change radius? CLADDING ACTIVATION - Calculations show high activity, some % composition change (negligible?). Erosion rates are needed if dose assessment above the reactor is needed. LEAD ACTIVATION -Results depend on the assumed impurities. Complete list of activation products is available (Po <1 g). Lead will be recycled or is it waste?