Analysis results for PPO samples irradiated 7/13/2001 at MITR



Zelimir Djurcic and Andreas Piepke
University of Alabama
(Status 7/28/2001)
(Updated 9/7/2001)


We report the data obtained when counting the ion exchange columns as obtained after post irradiation sample treatment. This analysis is optimized for the detection of U/Th which are accumulated in Eichrom TRU Resin ion exchange columns. The most prominent side activities do not remain in the column resulting in a more than ten fold reduction of the source related background at only marginal loss in target isotope. Repeated analysis of Packard PPO batch 21-634 in several activation runs yield consistent and reproducible extraction results both for different activations and when comparing results derived at Caltech and UA. A Np/Pa retention efficiency of 75% has been measured in March 2001 using a U/Th spiked PPO sample.

Results


U and Th are not observed in any of the tested PPO samples. The following table lists the concentration we derive from the data assuming 100% extraction efficiency. A short description of the samples may be found in the chemical analysis page. The overall efficiency of the ion exchange has been measured to be 75%. PPO data is listed in red , blanks in blue.
Sample Th
[pg/g] 		U
[pg/g]
Packard PPO mix -5.1±1.9
3.3±1.5 		-2.5±6.5
14.5±3.3
Unpurified
evaporated PC-PPO 		25±12
6.4±1.6
-1.7±8.
Purified
evaporated PC-PPO 		-4±1.1
6.4±1.6 		0.4±2.7
-1.7±8


Interpretation of these data
Differences in the U/Th concentration were not observed because they were beyond our current sensitivity. However, all PPO batches do have sufficient purity for KamLAND's reactor phase. At a concentration of 1.5 g/l the PPO constitutes only 1.9·10-3 of the scintillator mass. A purity requirement of 10-14 g/g for U/Th in the scintillator hence translates into limit of no more than 5 pg/g of U/Th in the PPO. This requirement is met by the tested samples. We hence conclude that the PPO is suited for KamLAND.

Analysis Results


All activities reported correspond to a delay of 84 hours after end of irradiation. Apparent concentrations are derived assuming 100% extraction efficiency. Isotopes listed in red are accumulated by the column. Note that the extraction efficiencies for Np/Pa, the activation products of U/Th, has been measured to be 75%. All measurements presented here were done with the "new low background Ge detector". The errors reported are the quadratic sum of the statistical and a 10% systematic error.

Remarks


Upon receipt it was noted that the irradiation vial of sample UA53 was cracked. To not have any of the acid used in the external cleaning contaminate the sample it was cleaned by hand dipping it partially into the acid bath leaving the crack out of the liquid. UA53 therefore underwent a non-standard cleaning procedure which might result in external contamination interfering with the sample counting.
Sample UA46 was subjected to the standard cleaning procedure. It was then found that the irradiation vial had a small crack too leaving the possibility that some of the external cleaning acid did migrate into the interior of the vial.
Although not listed here an invisible crack was also identified in the vial containing the flux standard UA56. This crack could only be identified by the fact that the acid used for the cleaning was contaminated.

As we received 9 irradiated samples this time we decided to process two samples in parallel. This was necessary to get early counting data for all important samples. After processing of a sample pair the fume hood was cleaned and all instruments except the hot plate replaced. Only new glass ware was used in all cases. The following samples were processed together:
7/17/2001 17:25 - 7/18/2001 1:10: UA45 sample of Packard PPO 21-634 and UA47 mix of all Packard batches used in KamLAND.

7/18/2001 14:00 - 17:45: UA46 UA sample preparation blank, an empty vial. UA55 the Caltech evaporation blank, also an empty vial.

7/18/2001 18:50 - 8/18/2001 1:40: UA53 PPO dissolved in PC, collected in Kamioka (5/2/2001) after water extraction and then evaporated at Caltech. CIT54: same material but collected before water extraction (4/27).

7/20/2001 15:08 - 19:00: UA54 the Caltech bottle blank.
No spiked sample has been processed at all.

UA45 Packard 21-634 ti=1 h, m=1.2638 g UA46 UA preparation blank ti=11 h, m=0 g use 0.9756 g UA47 Packard UA mix ti=11 h, m=0.9756 g 11 h CIT54 CIT evapor. PPO
before water extraction
ti=1 h, m=0.89 g 		UA53 CIT evapor. PPO
after water extraction ti=11 h, m=0.8634 g 		UA55 CIT evaporation blank ti=11 h, m=0 g use 0.8634 g
Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g]
Na -3.1±0.37 (-5.6±0.67)·10-9 5.9±0.7 (1.6±0.18)·10-9 0.05±0.09 (13±24)·10-12 -0.47±0.16 (-141±50)·10-12 1.3±0.45 (389±135)·10-12 Na
K -10.6±4.1 (-324±125)·10-9 -2.1±0.7 (-9.8±3.3)·10-9 0.9±0.7 (4±3)·10-9 -4.6±1.6 (-24±8)·10-9 1.1±3.4 (5.8±18)·10-9 K
Sc 0.069±0.007 (12.2±1.3)·10-12 0.14±0.014 (2.9±0.29)·10-12 0.38±0.038 (7.9±0.79)·10-12 0.0084±0.0021 (2.2±0.55)·10-12 0.18±0.018 (4.2±0.42)·10-12 0.11±0.01 (2.6±0.26)·10-12 Sc
Cr -0.039±0.045 (-118±136)·10-12 -0.005±0.049 (-1.9±17.5)·10-12 0.45±0.08 (161±27)·10-12 (0.004±0.046) (16±178)·10-12 0.20±0.05 (81±21)·10-12 0.025±0.044 (10±18)·10-12 Cr
Fe 0.28±0.028 (300±30)·10-9 0.74±0.08 (92.4±9.3)·10-9 2.3±0.23 (287±29)·10-9 0.079±0.010 (121±16)·10-9 1.9±0.19 (268±27)·10-9 1.4±0.14 (198±20)·10-9 Fe
Co 0.0049±0.0011 (5.8±1.3)·10-12 0.035±0.004 (4.8±0.5)·10-12 0.0043±0.0014 (0.6±0.2)·10-12 0.034±0.004 (5.3±0.6)·10-12 0.032±0.0034 (5±0.5)·10-12 Co
Zn 0.027±0.004 (1494±238)·10-12 0.026±0.005 (170±34)·10-12 0.028±0.006 (183±40)·10-12 0.030±0.006 (2414±483)·10-12 0.029±0.004 (214±32)·10-12 0.029±0.005 (214±38)·10-12 Zn
Br 6.4±0.65 (2.6±0.27)·10-9 3.6±0.4 (191±19)·10-12 100±10 (5.3±0.5)·10-9 47±0.47 (2.8±0.28)·10-9 2.3±0.23 (138±14)·10-12 Br
Sb 0.0037±0.028 0.025±0.026 0.21±0.06 0.069±0.035 -0.016±0.035 Sb
Hf 0.0029±0.0034 0.031±0.005 0.025±0.005 0.013±0.004 0.13±0.014 0.032±0.0.005 Hf
Au 0.23±0.04 (2.8±0.52)·10-12 6.2±0.06 (9.5±0.95)·10-12 1.4±0.14 (2.1±0.2)·10-12 23±2.3 (40±4)·10-12 1.2±0.12 (2.1±0.21)·10-12 Au
Th 0.017±0.009 (15.9±8.2)·10-12 0.030±0.014 (3.3±1.5)·10-12 -0.046±0.017 (-5.1±1.9)·10-12 0.018±0.0083 (25±12)·10-12 -0.032±0.009 (-4±1.1)·10-12 0.051±0.013 (6.4±1.6)·10-12 Th
U 0.29±0.20 (58±40)·10-12 0.58±0.13 (14.5±3.3)·10-12 -0.10±0.26 (-2.5±6.5)·10-12 0.015±0.096 (0.4±2.7)·10-12 -0.06±0.28 (-1.7±8.0)·10-12 U
Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g] Activity [Bq] Conc. [g/g]
UA45 Packard 21-634 ti=1 h, m=1.2638 g UA46 UA preparation blank ti=11 h, m=0 g use 0.9756 g UA47 Packard UA mix ti=11 h, m=0.9756 g 11 h CIT54 CIT evapor. PPO
before water extraction
ti=1 h, m=0.89 g 		UA53 CIT evapor. PPO
after water extraction ti=11 h, m=0.8634 g 		UA55 CIT evaporation blank ti=11 h, m=0 g use 0.8634 g



Consistency of the measured sample blank


The UA sample preparation blank has been determined twice in the 3/22/2001 and 7/13/2001 beam times at MITR. The table below lists the activities and element masses derived from these two runs. The data correspond to shipping delays of ts=60.0336 and 84 hours, respectively. The table contains data after ion exchange and assumes 100% extraction efficiency for all elements listed. As above, errors reported are the quadratic sum of the statistical and a 10% systematic error. The March 2001 blank consisted of 3 vials, while the June data was derived using only one vial. The measured element masses of the March run were therefore divided by three to obtain the "per vial" value.

UA9-11 March 2001 data ti=5 h, 3 vials UA46 July 2001 data ti=11 h, 1 vial
Activity [Bq] Mass per vial [g] Activity [Bq] Mass per vial [g]
Na -3.6±0.5 (-156±20)·10-12 5.9±0.7 (1600±180)·10-12
K -2.1±0.7 (-9.8±3.3)·10-9
Sc 0.032±0.005 (0.38±0.06)·10-12 0.14±0.014 (2.9±0.29)·10-12
Cr -0.10±0.055 (-20±11)·10-12 -0.005±0.049 (-1.9±18)·10-12
Fe 0.18±0.02 (12±1.3)·10-9 0.74±0.08 (92±9)·10-9
Co 0.035±0.004 (4.8±0.5)·10-12
Zn 0.026±0.005 (170±34)·10-12
Br 4.9±0.5 (55±5.5)·10-9 3.6±0.4 (191±19)·10-12
Hf 0.031±0.005
Au 5.5±0.55 (2.4±0.24)·10-12 6.2±0.06 (9.5±0.95)·10-12
Th -0.028±0.016 (-1.2±0.7)·10-12 0.030±0.014 (3.3±1.5)·10-12
U 0.062±0.15 (0.3±0.7)·10-12 0.58±0.13 (14.5±3.3)·10-12
Activity [Bq] Mass per vial [g] Activity [Bq] Mass per vial [g]
UA9-11 March 2001 data ti=5 h, 3 vials UA46 July 2001 data ti=11 h, 1 vial


This page is maintained by A. Piepke
Last update September 7, 2001