RAPPORT TECHNIQUE DRN R/ P/ N 357. REACTOR PHYSICS ACTIVITIES IN FRANCE NOVEMbER SEPTEMBER nnirnfiir*. M.

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1 RAPPORT TECHNIQUE DRN R/ P/ N 357 REACTOR PHYSICS ACTIVITIES IN FRANCE NOVEMbER SEPTEMBER 1986 r nnirnfiir*. M. SAI VATDRFS**

2 DIVISION ETUDES ET DEVELOPPEMENT DES REACTEURS Département des Réacteurs à Neutrons Rapides RAPPORT TECHNIQUE CHl\-DRNR/ P/N 357 REACTOR PHYSICS ACTIVITIES IN FRANCE NOVEMBER SEPTEMBER 1986 C. GOLINELLI*. M. SALVATORES** * IRDI - DEDR - DRE BUREAU DE COORDINATION TECHNIQUE BATIMENT 220 CENTRE D'ETUDES NUCLEAIRES DE CADARACHE SAINT-PAUL-LEZ-DURANCE CEDEX FRANCE ** IRDI - DEDR - DRNR SERVICE DE PHYSIQUE, CONTROLE ET INSTRUMENTATION BATIMENT 230 CENTRE D'ETUDES NUCLEAIRES DE CADARACHE SAINT-PAUL-LEZ-DURANCE CEDEX FRANCE 29ème REUNION NEACRP CHALK-RïVER (CANADA) SEPTEMBRE 1986

3 2 - FAST REACTuR PHYSICS t Experimental studies SUPER PHENIX-1 At present (July 1986) 50 X of full power has been attained and full power is expected by the end of the year, with a few months delay with respect to what was announced a year ago. The delay is due to various reasons, not connected to core performances, but essentially to the "prototype" effect of such reactor. Concerning the neutronic experiments, the majority of them has been competed successfully. Control rod experiments have been carried out extensively. The first results, reported a year ago, indicating a C/E of the order of 1.1, has been confirmed alro on the power core, both for the main (SCP) and the complementary (SAC) control rod systems. In the case of SAC, more sophisticated control rod heterogeneity calculation tools have been necessary / 1 /.o have consistent results (e.g. SAC worths with different SCP insertions). Radial and axial power distributions have been measured in the core, with different control rod insertion patterns, and in the blanket/ shield regions (at higher power). The first results of calculation-to-experiment comparisons, have indicated that simple, design-oriented methods can be used, which are forced to reproduce the observed experimental control rod reactivities, and which reproduce correctly reaction rate shapes, and, then, power distributions in the core. Concerning the flux distributions in the shield, the results of C/E comparisons show an excellent performance of the shielding formulaire PROPANE, to which bias factors are associated, derived from neutron propagation experiments. An example of the C/E agreement is shown in fig. 1, relative to the Au(n.y) radial (at mid-plane) distribution, normalized at the blanket interface. The agreement over approximately 2 meters of radial shield (SS/Na) is of the order of 10 i 20 %. Concerning reactivity coefficients, a preliminary estimate of the E/C for the Doppler coefficient is : E/C %.

4 PHENIX i During this year, it has been completed a consistent analysis and re-analysis of irradiation experiments performed with pure samples (PROFIL-I and II experiments) and with fuel pins of different Pu compositions (TRAPU experiments). The, analysis has shovm an excellent consistency of the results and also the good performance of the data of the new JEF file for minor actinides / 2 /. Moreover, the analysis has allowed to draw conclusions on several branching ratios / 2 / and data are expected soon also for the case of Pu-236 producing route. 4 Concerning the definition of a volatile and gazeous fission product migration model, the Cs isotope axial distributions analysis in an irradiated pin, has given the needed complementary informations to validate the model previously proposed / 3 / MASURCA The BALZAC program / 4 / has been re-started after tne completion of the neutronic experiments at SUPER PHENIX, which involved most of the personnel of the MASURCA installation. The first series of experiments were related to the study of control rod heterogeneity / 5 /. The need for these experiments is directly connected to 6ome difficulties encountered in the analysis of some of the control rod experiments performed at the SUPER PHENIX start-up. The first results are reported in / 5 /. In relation to these experiments, the RACINE-IE experiment analysis has been completed, including both natural and enriched boron carbide experiments / 5 /. The observed C/E for control rod worhts is slightly higher than 1 for enriched boron rod, and slightly lower than 1 for natural boron rods. Reaction rate distributies close to rod singularities are reasonable well predicted in both cases / 6 /.

5 Future critical experiment programs f In the frame of the European cooperation on Fast Reactor, an agreement in principle has been reached for a common critical experiment program, involving a large quantity of Pu fuel (^ 2 000* kg) from UK, DEBENE, ITALY and FRANCE, devoted to the study of the physics caracteristics of large LMFBRs. Among the parameters to be studied, there are rod interaction effects and in particular in safety configurations like handling error configurations, and the neutron flux monitoring system validation in large cores. This pro 6 ram, called CONRAD, should last approximately three years and qhould be performed starting in Theoretical studies ' Design calculation methods The design oriented code system CCRR has been up-graded with new capabilities in a new full FORTRAN-77 version. Transport based procedures are being introduced for the calculation of special subassemblies (diluent, control rods, etc..) both for neutron and for photon transport calculations. A series of intercomparison workshops on the European design code systems (UK, DEBENE and FRANCE) has been performed in the frame of the European cooperation for fast reactors, and has resulted in recomandations for the development of a unified code system, with enphasis on portability, flexible user oriented languages and procedures, quality insurance techniques and sofware engineering practices. A final decision for such development is expected early next year Cell code The work for the development of the unified cell (ECCO) code has progressed. Studies have been performed on optimized collision probability algorithms.

6 Specific studies have been devoted to the problem of calculating i streaming effects taking place between standard fuel assemblies, in Nafloaded or Na-voided situations, both for power reactors and for critical facilities. This type of studies can also be related to safety configurations (redistribution of gaps among subassemblies). Theoretical formulations have been proposed and practical examples have been carried out / 7 /. Concerning the well known sub-group method for resonance absorption treatement in heterogeneous lattices, a rigorous formulation has been proposed for the statistical domain and applicable to isotope mixtures / 8 / Perturbation methods The flux reconstruction method based on flux harmonics development, has been extended to the multigroup case, overcoming a long standing difficulty / 9 /. Applications both to LMFBRs and to PWRs have been made. As an example, fig. 2 shows the comparison of the radial flux shape in a PWR, perturbed by the insertion of "grey" rods, as calculated with the harmonics method and directly recalculated. TPG based sensitivity methods, extended to reactivity coefficients (EGPT) / 10 /, have widely being used in connection with design studies and experiment analysis Data assement A preliminary assessment of the performance of the new JEF-1 files has been completed. The test has been made an a number of critical experiment results, as stored in the Integral Data Bank at Cadarache (BDI, see ref. 11). The quality of the data has been found acceptable for many major isotopes. However, a number of deficiencies have been pointed out and will be the subject of evaluation revision for the future version of the JEF-file. A complementary validation has been made an fission product data / 3 / and on minor actinide data 111. Concerning new data evaluation, Pu-239 data in the resonance region have been revised in a common effort of ORNL and Cadarache / 12 /.

7 Efforts are also made in the Pu-241 resonance region data and t Pu-239 data in energy ranges outside the resonance region. 3 A H production data experiment for ternary fission of Pu-239 is also undervay at the Bordeaux University. Finally, (a,n) neutron production data in oxide fuel are being revised an the basis of an improved theoretical model and using fresh fuel neutron emission experimental data REFERENCES / 1 / NEACRP-A-720 (1985). / 2 / A. D'ANGELO et al., paper presented at the ANS Topical Meeting SARATOGA SPRINGS, Sept (1986). / 3 / NEACRP-A-748 (1985). / 4 / R. SOULE et al. ; paper presented at the ANS Topical Meeting, SARATOGA SPRINGS, Sept (1986). / 5 / Y. KIM et al., paper presented at this meeting. / 6 / H. GIESE et al., paper presented at the ANS Topical Meeting, SARATOGA SPRINGS, Sept (1986). I l l P. BENOIST, M. SALVATORES, to be published.

8 / 8 / P. RIBCN et al., paper presented at the ANS Topical Meeting, SARATOGA SPRINGS, kept (1986). / 9 / G. PALMIOTTI, to be published in Annals of Kucl. En. / 10 / A. GANDINI, G. PALMIOTTI, M. SALVATORES, Annals or Nucl. En., _L3, 109 (1986). / 11 / G. RIMPAULT, G. REYNAUD, paper presented at this meetir.g. / 12 / H. DTKRIEN et al. jrnl-tm (1986).

9 Radial blanket lûtftrol ùx ca'cuiq^on. V Hutm.D ottônuûtion. l x calcula fio/\ /yv\abjure /» * * T" J)lST4NCf f m») AviX OFTMi COftf t«d. )00 ICO 4«o

10 FLUX (arbitrary units) O.OOOf - c; direct calculation 2-reconstructed with harmonics("french" method) ',00. jvo. Fig. 2 - Radial flux traverse of the thermal group (in a two group schématisation) of a Pw? with a black absorber inserted. (or