ML19224A943
| ML19224A943 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/03/1976 |
| From: | Metropolitan Edison Co |
| To: | Mullinix W NRC/IE |
| References | |
| 1951, TM-0190, TM-190, NUDOCS 7906130264 | |
| Download: ML19224A943 (4) | |
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'n'ilda R. Mullinix, NRC i 78 3G' O
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MASTER COPY Revisme 3 DO NOT REMOV4ATION
- /0mo THREE Milt ISLAND NUCLE AR S STATI0'l CHEMISTRY PROCEDURE NO. 1951 Determination of Tritium CONTROLLED COPY, Table of tEffective Pages Page Date Revision Page Date Revision Pace Date R evision 1.0 11/03/75 3
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1951 Revision 3 11/03/76 STATION CHEMISTRY PPOCEDURE NO. 1951 Determination of Tritium 1.0 SU". MARY Tritium is a low energy beta emitter with a maximum beta energy of 18.6 Kev. This energy is not sufficient to penetrate even the thinnest detector windows.
Of the various counting methods available, liquid scintillation offers several advantages for use on tritium concentrations of 10-5 umCi/ml or greater.
Two significant advantages are reasonably high counting efficiencies (greater than 30%) and a minimum of sample preparation time.
If a liquid scintillation counter having two or more channels is used, a compensation can be made for any high energ beta contributicn to the tritium energy region. Air samp as may be counted if _the air _is pas ad throuch water and t."e water is counted.
A collection eff ciincy for this
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process must be applied. An alternate method of eliminating high energy beta interference is to demineralize and boil samples prior to counting for tritium.
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2.0 APPARATUS 2.1 Packard tri-carb liquid scintillation counter.
2.2 Liquid scintillation vials with caps.
2.3 Assorted pipets.
3.0 REAGENTS
~~i 3.1 Prepared scintillator cocktail (Packard Insta-Gel Cat. No. 6C02173).
4.0 PRCCECURE a.1 Check the tri-cart to insure that it is s,et up per calibration 1
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-- procedure HPP 1741, and background ar.d efficiency counted as per
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.:51 Revision 3 ll/03/7d 4.2 Pipet 10 ml of cocktail into a vial for each sample to be measured.
4.3 Pipet 1 ml of sample into each vial, cap and shake thoroughly. Any marks for purposes of identification should go on the vial cap.
If significant quantities of high energy beta are present, (i.e. > 10%
of the counts in the tritium cnannel appear in the high energy beta channel) the sample should be passed through a mixcd bed resin column twice, heated to boiling. and cooled prior to pipetting into the vial.
Or, if calibration has been performed to determine the high enargy beta contribution to the tritium channel then corrections can be made as shown in step 4.11.
NOTE:
Equal amounts cf Dowex l-x3 anion resin and Cowex 50W-x8 cation resin or ecuivalent can be mixed and placed in a poly drying tube to serve as a mixed bed resin column.
4.4 Place the vial (s) in the sample changer ccapartment of the tri-carb ar.d allow at least si hour for the sarole to reach thermal equilibrium.
4.5 Place the sample in the chaager.
Place a " start" tower in the sample position immediately before the sample (s) and a "stop" tower in the sample position immediately after.
4.6 Select the desired counting time and set the Preset Time switches accordingly.
4.7 Set the Mode Selector switch to auto.
4.3 SettheAutoStandardizationsbitchtoout.
4.9 Turn the Samole Chancer switch to the coerate position.
The instrument will count and print other information for each sample as folicws:
a.
_lst line is sample changer positicn, number.
S-b.
2nd line is count time in hur.dredth's of a minute
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1951 Revision 3 11/03/76 c.
3rd line is counts in the tritium channel d.
4th line is counts in the high energy beta channel e.
5th line is counts in the channel used for external stcndardi-zation.
It is not used at this time.
4.10 When the sample (s) has been counted, turn the Preset Time switch to 100 min.
4.11 Calculate the contribution of the higher energy beta to the tritium and compute corrected tritium counts as follor:s:
If,the counts in the high energy beta channel are less than 10% of these in tritium channel, no correction for high energy beta r.eed be made.
Corrected Tritium Ccunts = Counts in Tritium Channel -
(Counts in High --
energ: bt:ta channel) X (% Contribution from Calibration Data) 4.12 Calculate +.he tritium concentration as follows:
f Corrected Tritium Counts
=
nCi/ml 6
(Time in min.) (Vol. in ml) (eff) (2.22x10 dpm/uCi) 5.0 REFERENCE 5.1 Packard Tri-Carb Instruction Manual 5.2 B&W Radiochemistry Ma:.ual
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