Page 189 - 00. Complete Version - Progress Report IPEN 2014-2016

Nuclear Science and Technology | Progress Report 189

as evidence for different production locations. Sm, and Yb are measured after a 7-day cooling
time and Ce, Cr, Cs, Eu, Fe, Hf, Rb, Sb, Sc, Tb, Th,
In our laboratory, the Archaeometric Studies Zn and U after 3 or 4 weeks’ time.
Group of the IPEN-CNEN/SP is working with a
research program as a means of physical and By means of XRD, it is possible to determine
chemical characterization of ceramic from sev- the mineralogical composition in the ceram-
eral regions of the country. The researchers are ics, i.e., it indicates the relative proportions of
inserted in an archaeometric program at Ac- minerals in the sample. The chemical and the
tivation Analysis Laboratory – LAN – and are mineralogical compositions of the ceramics are
focused on identifying the behavioural factors both complementary and equally important
that affect chemical variability. The group use in determining its properties. Both are neces-
several analytical techniques, like instrumen- sary to understand the history and properties
tal neutron activation analysis, INAA, X-ray of the material being investigated.
diffraction, XRD, thermoluminescence dating,
electron paramagnetic resonance, among oth- The firing temperature and dating is being
er answering questions like “why?”, “where”? used in our Group by means of electron para-
and “when”? in studies of the natural and man- magnetic resonance and thermoluminescence
made objects. There is no doubt that if an ar- to found the firing and the age of ceramic ma-
tifact is held in hand, its age and authenticity terials found at archaeological sites.
is of utmost interest. The most classical dat-
ing methodology is based on seriation, sty- The quartz and feldspar grains found in piec-
listic technique, clay and pigment. However, es of pottery or other types of fired clay act-
these approaches may reveal which objects ed as dosimeters, i.e., they were able to record
belong together, but not their age in a quan- the amount of radiation to which they had
titative manner. been exposed. In the case of pottery, this ra-
diation dose was that received by the grains
A typical procedure used in our laboratory since the time when they had been heated.
consist in cleaning the ceramics` outer sur- The heating erased the previous TL signal and
face and drilling using a tungsten carbide ro- with it the information on the previous radi-
tary file attached to the end of a flexible shaft, ation exposure, i.e., that related to the time
variable speed drill. After that, this material is elapsed since the minerals had been formed.
dried in an oven at 105°C for 24h and stored The age calculation in luminescence requires
in a desiccator. the estimation of two factors: the equivalent
dose (De) which is the absorbed dose, gener-
For INAA, approximately 100 mg of ceram- ally expressed in Gy (1Gy = 1J) and measured
ic samples, the standard reference materials in a luminescence reader, and the annual dose
NIST-SRM-1633b and IAEA-Soil-7, are weighed (Dan), which is the received dose of ionizing
in polyethylene bags and wrapped in alumi- radiation rate, expressed in mGy/year or Gy/
num foil. Groups of 8 to 10 samples and one of ka. The ratio between both doses, De / Dan,
each reference material are packed in alumi- provides the age.
num foil and irradiated in the research reactor
swimming pool, IEA-R1, from IPEN-CNEN/SP A typical vessel from Amazon is presented in
at a thermal neutron flux of about 8.92 x 1012 the Fig. 11.
cm-2 .s-1 for 8 h. Arsenic, Ba, K, La, Lu, Na, Nd,