>– IGGOR International Conference,October 28-30, 2009, Beijing , China < 1 The MADERE radio-activity Measurement Platform: Developments for a better addressing to the experimental needs. JM. Girard; H. Philibert; S. Testanière, Ch. Domergue; and D. Beretz 93Nbm reference sample (17 keV Xk emitter). This direct Abstract—The main goal of the Reactor Dosimetry is to provide comparison measurement method allows getting free from the information (reaction rates, fluence, fluence rate...) for the determination of different measurement parameters, since they interpretation of experiments irradiated in critical mock-up, test are considered proportional between the reference and the reactors or power nuclear reactors. Various techniques are used, measured samples, under the hypothesis that geometry, activity including analysis of irradiated activation or fission dosimeters level and measurement conditions are identical. A need has 103 m whose radioactivity is measured afterwards. emerged for measuring the Rh activity. It would have 103 m The MADERE platform (Measurement Applied to DosimEtry required the use of a reference Rh source which is in fact for REactors) is a CEA facility which is dedicated to the activation excluded due to the short half-life (56 minutes) of this dosimeters manufacturing and their activity measurement after radionuclide. It was therefore decided to establish the total irradiation in a nuclear reactor. The laboratory is accredited by absorption yield curve in order to perform absolute activity the French Accreditation Committee for specific activity measurement. measurements of solid samples using gamma and X-rays • One precise micro-balance allowing the measurement of spectrometry. sample mass with an accuracy of few micrograms. The choice of dosimeters takes into account limitations coming • One fissile measurement device equipped with 4 NaI from the characteristics of the measurement devices. To meet detectors associated to an automated samples holder. experimenter’s new demands, the MADERE platform set out to improve its offer by lowering the energy of measured radiations The quality of gamma spectrometry measurements mainly down to 10 keV, and the activity level down to the tenth of depends on the knowledge of the detection efficiency yield Becquerel (Bq). Doing so, the range of usable dosimeters and by associated to the Source-Detector system geometry. Thus, the the way, the energy range of the neutron spectrum is expanded. MADERE platform uses twenty different calibrated Dosimeter, wires or foils, few millimeters large, are measurement geometries. In order to optimize the time spent on manufactured using ultra-pure material (Gold, Iron, Nickel,...). the experimental determination of each associated detection yield, Some of them are encapsulated in quartz containers for a modeling work is underway, using the ETNA software, integration into experimental devices. developed by the Henri Becquerel French National Primary Laboratory, to derived transfer efficiency and correction In order to determine the activity of irradiated metal solid coincidence parameters. samples, the MADERE platform makes use of several The precise determination of the sample activity also requires measurement equipments: the use of correction factors related to the effects of self • Three Gamma spectrometry devices equipped with absorption, sum peak and geometry. Thus, the MADERE semiconductor diode detectors HPGe set to work on an energy platform has developed tools using its large experimental field ranging from 50 keV to 2 MeV. The range of activity covered database which allow the accurate determination of these by these devices spreads from a few tenths of Bq to a few tens of correction factors to be applied to the sample measurements. MBq. The ability to measure samples with activities of the order Finally, in order to meet the various requirements for the of one tenth of Bq may be used to implement a non-destructive monitoring of the total stored activity in the facility, but also for determination of the isotopic composition of low-active objects. the traceability of the measurement results and of all the elements • One X-ray spectrometry device equipped with a LEGE (Low contributing to the elaboration of the results provided to its Energy GErmanium) GeHP semiconductor detector. The settings customers, the MADERE platform has developed computerized of this equipment have been made to work in an energy range management tools that maximize its productivity. from 10 keV to 300 keV. This range allows covering almost all the X energy domain and also easily measuring low energy gamma Index Terms— CEA - Radioactivity measurement – photons – emitters. For a long time, this device has been exclusively used for X-rays spectrometry, gamma Spectrometry - Reactor dosimetry - relative activity measurements of irradiated niobium using a I. INTRODUCTION Manuscript received May 15, 2009 Authors are with the Commissariat à l’Energie Atomique, The MADERE platform is dedicated to the radio-activity DEN/CADARACHE/DEN/DER/SPEx/LDCI – CEA Cadarache, F13108 Saint measurement of metal samples irradiated in test reactors, power Paul Lez Durance – France (e-mail: [email protected]; [email protected]; [email protected] [email protected] .) plants and zero power reactors. These measurements are carried out on a set of samples of different types selected to >– IGGOR International Conference,October 28-30, 2009, Beijing , China < 2 present neutron sensitivity at different energy regions. For handling and storage of dosimeters. Finally, it limits the example, the neutron spectrum rebuilding at the studied induced production of radioactive waste. position can be done. The table below shows the main neutron The MADERE platform is accredited by the COFRAC (French dosimeters used with their energy threshold, the reactions Accreditation Committee) for measuring activity of metal involved and the radioactive periods of the measured radio samples using gamma and X spectrometry. nuclides. III. DOSIMETERS MANUFACTORING Table 1 The MADERE platform has the ability to provide its customers Characteristics of the main neutron dosimeters used on the with all neutron dosimeters corresponding to their needs. MADERE platform Sensibility Radioactive Dosimeter Reaction energy range period (MeV) Iron 54 Fe(n,p)54Mn E >3 MeV 312.13d Cobalt 59Co(n,)60Co Th + epi 5.271 y Copper 63Cu(n,α)60Co E > 6 MeV 5.271 y Nickel 58Ni(n,p)58Co E > 2.7 MeV 70.82 d Gold 197Au(n,)198Au Th + epi 2.6944 d Niobium 93Nb(n,n’)93Nbm E> 0.1 MeV 16.13 y 103 103 m Activation Rhodium Rh(n,n’) Rh E > 0.7 MeV 56.1 m 115In(n,)116Inm Th + epi 54.2 m Indium 115 115 m E > 1.3 MeV 4.486 h In(n,n’) In 27 24 Aluminium Al(n,α) Na E > 7.3 MeV 14.9574 h 237Np 237Np(n,f)137Cs E > 0.6 MeV 30.05 y These dosimeters can be from 0.1 to 2 mm thick disks with diameters generally comprised between 1 and 20 mm or few 238 238 137 Fission U U(n,f) Cs E > 1.5 MeV 30.05 y millimeters long wires with diameters ranging from 0.1 to 1mm or even strips of few millimeters. They are made from very high purity materials, material certificates being available. The main customers of the MADERE platform are: EDF in the framework of the monitoring program of irradiation effects on PWR vessels. CEA, on the one hand, for the purposes of dosimetry experiments carried out in the OSIRIS test reactor and soon in its successor the RJH reactor. On the other hand in the experiment programs carried out in the critical facilities EOLE and MASURCA. AREVA-TA, RES reactor operator, which will be soon in operation at the Cadarache site. The facilities of the platform may also be used occasionally, as in the case of the re-divergence of the test reactor CABRI. II. DESCRIPTION OF THE MADERE PLATE-FORM The platform MADERE is a facility classified for environmental protection. It is composed of different places The wire-type dosimeters are usually enclosed in a 0.4 mm each of them dedicated to a specific activity: thick quartz bulb about 10 mm long and 2 mm diameter. Storage of raw materials and manufacture of dosimeters, IV. MEASUREMENT EQUIPMENTS Storage of irradiated dosimeters, Preparation of dosimeters before measurement, The MADERE platform is equipped with 4 high resolution Weighing, gamma spectrometry devices. Three detection units are Activity measurement using gamma and X-ray dedicated to gamma spectrometry measurement, one of them spectrometry. for measuring low activity samples. A fourth detection unit is The dosimeters design is thought keeping in mind the used for activity measurement by X-ray spectrometry. A minimization of the post irradiation activity. Regardless the gamma spectrometry device with an automatically rotating benefits arising for the measurement process, that minimization holder (PASTAGA) is also available. All these devices are allows the limitation of the doses received by the staff to supplied by the CANBERRA company. extremely low levels. It also allows avoiding the use of heavy A. The PASTAGA device equipments (hot cells, remote manipulator etc ...) for the The PASTAGA device is a sample carrier designed for gamma measurement on radioactive solid samples (fissile or activation) >– IGGOR International Conference,October 28-30, 2009, Beijing , China < 3 irradiated in low neutron flux critical mock-ups with the main These features allow measuring easily samples with an activity objective to characterize the core. of a few tenths of Becquerels. This device consists of a carousel allowing up to 51 samples The associated electronics is identical for all detectors and measurement per campaign. It is equipped with four NaI corresponds to a digital system that supports pulses directly detectors. A 4 to 8 channels electronic permits total gamma or supplied by the preamplifier. It provides the formatting and the absolute counting under some conditions (single- energy peak analog/digital conversion of the signals in order to be directly and low activity).