…continued from solar neutrino presentation,

NESS02, Sept. 2002

• 6 papers presented tomorrow morning

• Many thanks to Wick Haxton for giving us the extra time

• 14C in deep oilfields

• Homestake rails as a source of radiopure structural and shielding material

14C in deep oilfields (paper 5, to be submitted to NIM)

• Paper by G.B., E. Carter (RET), N. Harris, V. Paolone

• Borexino results and partial interpretation

(Schoenert-Resconi)

• Single carbon chemistry, gas field

• Tests and further research (by others)

14C in petroleum

• The original (atmospheric) 14C in petroleum is long gone

• 14C recharged underground by neutron flux from rock

• The Solar Neutrino TPC needs at least 14C/12C=r<10-18 to work in the (pp) region, Borexino/Kamland need r<10-21

The Borexino result

• Borexino, using the CTF facility, found (G. Alimonti et al., Phys. Lett. B 422, 349, 1998) r=(1.94+-0.09)10-18 for Lybian petroleum

• However, a previous test on methane gave a limit of r< 10-18

• They have since measured petroleum from the Corpus Christi, TX, area at r=11X10-18

• Borexino and Kamland have overwhelming 14C backgrounds below 250 keV

Interpretation (Schoenert-Resconi)

• Identifies dominant reaction as 14N(n,p)14C

• Petroleum has typical 2% nitrogen content due to biological origin (i.e, DNA)

• Identifies the best oilfields as having low U/Th, low N

• Predicts 10-16 <r< 10-20

Nuclear reactions

Reaction mbarn) Comment

17O(n,)14C 235

14N(n,p)14C 1830

13C(n, )14C 1.4

11B(,n)14C 20-200 2-5 MeV energy

226Ra =>14C - tripartition

Our approach: focus on methane

• Methane is easy to separate by boiloff

• Methane has different chemistry than other hydrocarbons

• Isotopical separation does not work unfortunately

• Chain must proceed as:

2 2 1 2 2

2 2 2 2 2 2

3

4

n n n n

n n n n

C C H C H

H CH

H CH C H C H

H CH

H CH

Single C reaction products in CH4

Impurities None 2% O2 1.2% C2H4

CO <0.2 26.8 <0.2

CH4 13.9 <0.15 <0.2

C2H2 17.7 32.3 25.2

C2H4 12.4 30.5 23.5

C2H6 23.9 <0.5 3.4

C3H8 11.1 0.2 1.7

Higher 20.9 16 46.2

Methane yield by hydrocarbon

Hydrocarbon Methane yield (%)

CH4 13.9

C2H6 2.1

C3H8 2.9

cyclohexane 6.7

N-hexane 5.6

Consider a simple model for 14C(predicts 10-17 >r>10-22)

144( )rock CH

UMC N

B

Some facts about gasfields

• Petroleum starts as crude and becomes a gas as it ages (hotter, deeper)

• Light alkanes migrate and move away – gasfields with zero nitrogen can be found

• Natural gas is typically 90% methane, with some ethane and propane

Specifying the perfect gasfield

• 90% methane, with some ethane (factor 50 purity)• proven low U content (several) (factor 30)• No kerogen, no nitrogen (factor 50) (some)• No bacterial activity

• No H2S

• Probably no water is better• Double boiloff recommended (CO)

Conclusions

• Two new ways to strongly suppress 14C in hydrocarbons – both use methane as feedstock

• TPC almost certainly immune to 14C backgrounds

• Our colleagues have work to do, including devising a clean industrial reducing process, but r=10-22 appears feasible

Homestake rails as a source of radiopure structural and shielding

material (Paper 7)

• Paper by G. Aberle, G. B., R. Brodzinski, E. Loh

• Major steel contaminants

• Quantity and quality

Steel major radiocontaminants

• 54Mn (half life=312 days, E=835 keV). Activated by cosmic rays at surface, equilibrium activity 5mBq/Kg (equivalent U=10-10g/g)

• 60Co (half life=5.27 days, E=1.2 MeV). Also cosmic-activated, but mostly due to contamination. Usually dominant radiocontaminant, wide variance.

• U limits at the 10-11g/g level exist for some steels. Some variance expected once measurements are refined

Homestake steel (older than 50 years)

• Free of both 54Mn and 60Co ( 60Co measured by R.B. on 125 yrs old steel)

• 75 miles of rails older than 50 years can be readily harvested (5 kTons)

• 1 kTon available in I-beams and pipes of various sizes

• Many advantages (spikes, no travel, standard sizes, several sizes, records, upper levels, very cheap)

Goals and possible uses

• 10-11-10-13g/g U/Th may be feasible (need measurements)

• To be used as part of the neutron shield for DRIFT (G.B.)

• If 10-11g/g, Solar Neutrino TPC detector plane frames (G.B.)

• If 10-12g/g, Solar Neutrino TPC inner shield support (deionized ice) (G.B.)

Conclusions

• Homestake rails are potentially a great treasure which could serve the need for radiopure structural and/or solid shielding material of EVERY NESS02 PARTICIPANT

• The funding agencies should consider funding preliminary testing of the hypothesis