If it looks like 7Be and says it’s 7Be it doesn’t always mean that

it is 7Be

Robert Hardy

Jackie Pates

Overview

• Context of the work

– 7Be as a environmental tracer

• Data that was recorded

– Looking good

– Wait that can’t be 7Be…

• What was really measured

– The mystery nuclide

7Be Production

7Be N2 O2

What 7Be is used for

Blake et al. (1999) Applied Radiation and Isotopes. 51, 599–605

Clean-up of Tracer

Gamma spectrum

Resin binding experiments

• Used tracer to investigate how “Be” binds under different acid concentrations

Horwitz and McAlister (2005) Solvent Extraction and Ion Exchange. 23, 611-629

“Let’s just check”

Recounted vials after ~300 day. All Be should be gone

Some 54Mn in tracer so recounted to assess 54Mn contribution to count rate

It’s not 7Be but what is it? Let’s make a model

When optimised model includes NO Be and half-life of X of ~340 days

Model Variables: Counts of Be, Counts of X, Half-life of X

Possible candidates

Searched every element with half-life 300-360 days

Element Z N Decay Half-life (days)49V 23 26 ε 330

54Mn 25 29 ε+β+, β-   312.3

145Sm 62 83 ε 340

248Cf 98 150 α, SF 333.5

249Bk 97 152 β-,α, SF 320

Back to Gamma Spectroscopy 145Sm, 61 keV, 12%

54Mn, 835 keV, 99%

7Be, 477 keV, 10%

49V no gamma

Conclusion

• 7Be not easily detected with LS

– Counting efficiency too low

• Contamination may be present

– Issues with safety

• What are you really handling/disposing of

– Calibration problems

• Counting efficiency

RH funded by studentship from NERC and ACTF Resins supplied by Steffen Happel (Triskem)