practical aspects of operating a neutron activation analysis laboratory

251 Pages·2002·14.22 MB·English

IAEA-TECDOC-564
PRACTICAL ASPECTS OF OPERATING
A NEUTRON ACTIVATION
ANALYSIS LABORATORY
A TECHNICAL DOCUMENT ISSUED BY THE
INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1990
PRACTICAL ASPECTSF OO PERATING
A NEUTRON ACTIVATION ANALYSIS LABORATORY
IAEA, VIENNA, 1990
IAEA-TECDOC-564
ISSN 1011-4289
Printee htI dyAb EAn i Austria
July 1990
PLEASE BE AWARE THAT
E MHTIAS FSLOILN G PAGN ETISH IS DOCUMENT
WERE ORIGINALLY BLANK
FOREWORD
This bs oioik nten odteadd vin isee veryday practical problems relatoetd
operating a neutron activation analysis (NAA) laboratory. It gives answers
to questions like "what to use NAA for", "how to find relevant research
problems", "how to find users for the technique", "how to estimate the cost
of the analysis and how to finance the work", "how to organize the work in
a rational wd an"yah" o optw ere fhqoutra mlity contrt ogIli"v .es advice
o desitgn fa cilitwies ohin chodosinng d sctoaanfsnfu,m a ebaqlueispm ent,
and procedures accd oanro vndaateiien ldgable resources.
e s hbdioeTos o kigdtnies dcuss prt obdoleneaml st n woiirAtd hiAnNar y
textbooks, but also, in order to prevent it from being too voluminous, to
avoid duplication of material described in normal NAA text books.
There erhfeotarde e,r will find that some matf erioinat s lemriiess sting
from this book and it is recommended that one or two of the textbooks
listed in chapter 11 be read in addition to this one.
e hT authors representa wide rangef o experience with biological,
environmental, gd eionnldouagsitcrai la,l n scaoimnptlee xst,s from basic
research to commercial analytical service. Their backgrounds also range
from universo itgto yvernmental research instid tnpurati evate enterprise.
Their summed experience exe cehtetidm se since Hd envLeaesv yy's first
publication on activation analysis; nevertheless, other workers in the
field may not agree with all the statements made herein. It is their hope
that this publication will be of value, both in respect to practical
aspects of running a modern NAA laboratory, and in recommending relevant
appli aca ttniimioen s with abundant analytical teach ndinqaues
requira ew mreeolnflt -founded cost/benefitl al acr taritovifio ties.
EDITORIAL NOTE
In preparing this me aphtrtee rrsiosaf,l staffe Ihnottf ernational Atomic Energy Agency have
mound ptneaadg ina ethoetrd iginal manuscrd ignpaitvs en some attentioo ptn resentation.
The viet wnoes cneexs psoraerdsislye d reflect the gohosevt eor fnm eeMnhtesmt ob fer States
or organizations under whose auspices the manuscripts were produced.
The use in this book of particular designations of countries or territories does not imply any
judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their
authord iitnnie aesdhs tetit lufiomti iortnoast if oothn eir boundaries.
The mentf ioospn ecific comf optha enrioire ps rodur cbotrs and names t dyoiomnneaps ly
endorsement or recommendation on the part of the IAEA.
CONTENTS
1. INTRODUCTION ..................................................................................... 7
. 2 PRINCIPLEF SOI NSTRUMENTAL NEUTRON ACTIVATION ANALYSIS ..........9..
2.1. Historical background .........................................................................9....
2.2. Characteristicf osn eutron activation analysis ..............................................9...
2.3. Sensitivities available with NAA .............................................................. 18
. 3 POTENTIAL APPLICATIONF OES CONOMD SNIACO CIAL IMPORTANCE ...0.2...
3.1. Major applications ................................................................................ 20
3.2. Other applications .............................................................................92...
4. IRRADIATION FACILITIES ........................................................................ 33
4.1. Research reactor types ........................................................................3.3..
4.2. Sample encapsulation ............................................................................ 37
4.3. Irradiation sites ................................................................................3.4...
4.4. Irradiation in modified flux ..................................................................... 47
.5 COUNTIND DNGAA TA PROCESSING FACILITIES ....................................05...
5.1. Typical counting systems ...................................................................0.5....
5.2. Semiconductor detectors ......................................................................... 51
5.3. Basic electronics ..............................................................................5.6...
5.4. Multichannel pulse height analyzer (MCA) ................................................. 81
5.5. Data processing .............................................................................5.8.....
5.6. Automation ...................................................................................8.8.....
5.7. Choicf oel ocation ............................................................................3.9...
6. RELATED TECHNIQUES .........................................................................69..
6.1. Delayed neutron activation analysis ....................................................6..9.....
6.2. Prompt gamma neutron activation analysis .................................................. 99
6.3. Measurement of environmental radioactivity ................................................ 99
7. MAKING NAA AVAILABLE TO THE SCIENTIFIC AND
TECHNICAL COMMUNITY ...............................................................1..0.1.....
7.1. Identification of possible consumers .......................................................... 101
7.2. Collecting background informatiod nnai dentificationf o applications ................4.01.
7.3. Consultation with potential consumers ....................................................... 104
7.4. Modesf o providingA AN services ...........................................................501
7.5 Cost analysis ...................................................................................... 108
. 8 ORGANIZATIOF WON ORK .................................................................5..1.1...
8.1. Staff .............................................................................................5.1.1..
8.2. Sample bookkeeping and coding .............................................................. 116
8.3. Sample preparation .........................................................................9.1.1....
8.4. Standards ........................................................................................... 126
8.5. Irradiation procedures ........................................................................... 128
8.6. Decay .......................................................................................6.3..1.... .
8.7. Measurements .............................................................................8..3.1.... .
8.8. Data processing ...................................................................................841
8.9. Reporting ........................................................................................... 150
. 9 QUALITY ASSURANCE ............................................................................65.1
9.1. Nr eoqefuda lity assurance .............................................................6..5..1....
9.2. Methods for quality assurance ................................................................. 156
9.3. Assignement of uncertainty ..................................................................... 161
9.4. Location of sources of errors .................................................................. 163
10. RADIATION PROTECTION ........................................................................ 169
11. SUGGESTED READING ............................................................................. 172
REFERENCES ................................................................................................. 175
APPENDIX A. TABLES FOR NEUTRON ACTIVATION ANALYSIS ......................... 193
Introduction ......................................................................................3..9.1.....
Refereno cItens troduction ....................................................................6..9.1.....
Table I. Thermal neutron cross-sections and resonance integrals .......................... 197
Table II. Cross-sections averaged in a 235U fission neutron spectrum ..................... 202
Table III. Radioactive isotopes arranged by atomic number .................................. 203
Ta. VbGlIe amma rays arrang yeebnd ergy 1d a( <ty,) ............................1..2.2....
/2
Table V. Gamma rays arranged by energy (t > Iday) .................................... 228
1/2
. TIaVRblee commended gammar aornad faythnls yeasiirs interferences
(t,5 <h ours) .........................................................................8.32.
/2
Table VII. Recommended gamma rayr osfa nalysid nsat heir interferences
(5 ho7 u< drta s <ys ) ......................................................0..4..2... .
1/2
Table VIII. Recommended gamma rays for analysis and their interferences
(t > 7 days) ............................................................................ 243
1/2
Referenceo tst ables ................................................................................8.4.2..
CONTRIBUTORS TO DRAFTING AND REVIEW .................................................. 251
1. INTRODUCTION
Nuclear research reactors are commonly purchased by governments or
universities to form the basis for multidisciplinary research institutes. In
many countries ther sei onle nyo research reas ci ttiio ndnrat endeodt
support the scientific and technical development of the whole country. A
research ra ema acsjtioorr s iail nstvoie s tedmxnepanent so itvre un.
Therefore it is important to use it efficiently.
Analytical chemistry is an essential part of science and technology. In most
cases an analytical chemistry laboratory is established and used in the
institutes whie htc ershue sults. Neutron activation analysis (NAAna) si
exception to this. The expensive research reactor necessary to conduct NAA
cannot be purchased by every analytical laboratory. Therefore NAA is commonly
only perfort maerd eactor laboratories although some laboratories without
reactors simple ht yyub irradiations. When short-lived nuclidese ra used
close access to the reactor is obligatory.
Although very sensitive and accurate non nuclear analytical techniques exist,
Ns aAhsA everal advantages whicha csaso umeppsupl oestrmite o ntto ther
techniques, as has been clearly shown on several occasions [i]. Therefore
it is the duty of the institute running the reactor to make NAA available to
ewhhotl e nucsioeurn stry., hl socTwt ilohesouivau nsecn tcr re,nisesisfu l
or reactor laboratories. Several NAA laboratories are run in a way that is
far from optimum as regards the needs of the country. One or several of the
following reasons can be identified.
- The NAA group has no motivation to make the technique available to
outsides e waihuocsraT edkresm .ically ore ighernTotuepd .develops
analytical methods to be published in scientific journals and only runs
itsn wo research projects.
- Co-operation with scientific institutid oninans dustrial enterprisseis
limiA tANeg edhrTt .oo nu asipw e ahtrn feeo e ehtdc fsoo untrdnya
the possible counterpart has no knowledge about the possibilities of
using NAA to solve their analytical problems.
There dt ooeenxs isa t mechanism thatA AsmNea rekhvetis ces avai Laebl
to outside users. The increased use of NAA requires manpower and
instrumentation, the cost of which must somehow be covered.
e hTlaboratory dt ooenhse ahvtcea pabilr iotfly arge scale work.
Delivery time of results is long and only a limited number of samples
can be analyzed annually, because of lack of skill, manpower,
instrumentation or proper procedures. The cost of services may also be
high for this reason.
et htogd no nuof see de oshwe ritoe hseqrnTu h koaTfulgoiht . y -
analytical daethat caee nsrnhueotsd t u t ntlhnraoteeo srnl e yfoodr e
NAA services.
s aipo NpAe lttAld ieoe se r nmtadwnheemoahn cptitfhl ces en hisrqaue s
optimal compared to available non-nuclear analytical techniques.
e hT authors feel thate ht available articlesd na bookst on od AAN no deal with
e phrtoblems outlined hn eItrhewi .n eston he beehtoromtooorp kn yh assii s
techniques.
Radiochemical NAA is not dealt with because (1) radiochemical NAA, with the
exceptif oosn ome preirradiation applicat toeinc oosnniso, mically competitive
with non-nuclear techniques, and (2) description of the numerous chemical
separation techniques and radiochemical laboratory practices would enlarge the
book too much.
This book addresses itself to scientists who are starting with NAA or who are
establishiA ANn lwegan boratori, esihs toI. wever, foreseen that ti will also
be useful to scientists who have already been working a few years with NAA.
2. PRINCIPLES OF INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS
2.1 HISTORICAL BACKGROUND
Neutron activation analysis (NAe Ab dna)ca ethtet odti mf eoH evesd nyaL evi
o ph[uw2b] l,ished their firste mhretet n phf1oio9or d3 t6.
Followie hntdg evelopmef notn uclear reace ht1to 9nr4d is0n sas odium-iodide
scintillation dee theetca rtnloirys 195 e0hpsto, ssibilitr aiofpeps lyAiAnNg
to trace element analysis of samples from many disciplines were recognized.
Early development of NAA was rapid. The invention of high resolution
solid-state Ge(Li) detectors in the 1960s and more recent advancements of
computed rnasa utomation durie hntg1 970s aad 1080s have made possible
o rtes eaAaprpAclNih c asfttoiuod nies involving very large numf bseoar msples.
2.2 CHARACTERISTIF NCOE SUTRON ACTIVATION ANALYSIS
Neutron activation analysis has become a mainstay of geochemical and
biochemical trace element research because the technique possesses several
important advantages.
(a) Substantial freedom from systematic errors. The physical processes
involvee rda well understood. Radioactive growtd nha decaerya
rigorously exponee nthniTuam flboe .en rergetically possible nuclear
reactions fra om given target nucl ls lipiadsoe msdasnlialb,l e
reace btie nonanucms erat yebdi nspec at itfooanb f loen uclides.
High-resolution gamma-ray spectroscopy affords qualitative
identification of the nuclides present as well as their quantitation.
The density of known gamma-ray lines in energy space is small compared
wit ehth resolutio fon modern detectot onr msdnaa,n y analytically
important decay gamma raye s bdir seocmoe atvihpe nrTreesdfe .noc e
possible interferences may often be readily tested when multiple lines
of either component are emitted.
(b) Complementarity to other methods. A different suite of elements is
measurable by using nuclear rather than chemical reactions, and the
detection limit esra quantitatively different. Equally important,eht
kinds of errors to which nuclear methods are subject are due to
different physical phenomena and are therefore likely to give a
different bias in the results.