Cistern
barrels.
and
groundwater samples were collected in 5- are 15-gal oor
The 15-gallon water samples were acidified in the sid, and = 3
Water samples were returned to LLNL for analysis of !3/cs, 90s-. ang 239-24c04u.
ANALYTICAL METHODS AND QUALITY CONTROL
A brief description of our analytical methods and quality -antrol program
is given here. More details are given in Jennings and Mount (~283).
The LLNL gamma-counting facility #$ housed in a specials construczed
building.
The floor is a 9-inch-thick layer of concrete with <"ack serpentine
as the aggregate. This rests on a 12-inch layer of black serzantine.
This
serpentine was used
because
it’ contains
very
small
amounts <- naturally
occurring radionuclides. The walls and ceiling are extremely well insulated
to maintain constant temperature. The room containing the comuter and the
analyzer electronics has its own temperature and humidity-contrs: system.
There are currently 16 Ge(Li), p- and n-type, detectors in use. They are
housed in steel caves made from selected materials and are spaces to eliminate
any interaction of signals among adjacent detectors.
High-volzage and power
cables are run separately from the signal cables to minimize zny possible
interference.
:
Three Canberra analyzers are used to collect
the
spectra.
4096-channel spectra are written to 1600-bpi 9-track tape.
The
.
The spectra are
reduced using the program GAMANAL (Gunnink and Niday, 1972) znd a Cray
computer. The resulting numbers are then entered into various cata bases.
A standard containing !33pa, 137cs, and ©9Co is counted on each detector
each day to provide an ongoing calibration record. Any counter that exhibits
#0.5-channel difference from the standard channel location is acjusted back to
the proper channel.
fach
Monday,
the
same
standards
80 minutes and a background is counted overnight.
are
counted
for
These data ave processed by
GAMANAL like any other sample and are entered into a data base.
This allows -
an experimenter to access the whole history of the detector.
Gamma spectroscopy for !37cs and other gamma-emitting raconuclides is
performed primarily at LLNL.
Sometimes, when our sample load is particularly
heavy, we have other laboratories perform gamma-spectroscopy aralyses for us.
All of our detectors have been calibrated and cross-checked fcr '3?cs and
41am with detectors at three other laboratories.
9000313
Blind dug icates and