1Laboratoire National Henri Becquerel Decay data evaluation of Radium – 226 and its daughters V. Chisté, M. M. Bé, C. Dulieu

1Laboratoire National Henri Becquerel

Decay data evaluation ofRadium – 226 and its daughters

V. Chisté, M. M. Bé, C. Dulieu


Introduction

* Important naturally occurring radioactive chain: 1 – calibration of gamma-ray detectors2 – environmental controls

* Ra-226 chain is included in the Coordinated Research Program – IAEA


99.9 %

Ra-226 1600 (7) a

100 %

Rn-222 100 %

Po-218 100 %

Pb-214 Bi-214

At-218 Rn-218

Po-214

Tl-210

100 %

100 %0.02 %

0.022 %

0.1 %

100 %

99.98 %

Pb-210 Bi-210 Po-210

Hg-206 Tl-206 Pb-206

Stable

T1/2 = 22.23 (12) a

Ra-226 radioactive chain

T1/2 = 36.0 (19) ms

T1/2 = 162.3 (12) s


Global Characteristics of the Ra-226 chain.

10 disintegrations and 9 - disintegrations down to Pb-206 (stable nuclide).

Half-lives between some years (Ra-226 and Pb-210) and some fraction of a second (Rn-218 (ms) and Po-214 (µs)).

~ 275 -rays, mainly in: Pb-214 - decay to Bi-214 (26 -rays), Bi-214 - decay to Po-214 (212 -rays) and Tl-210 - decay to Bi-214 (24 -rays).


Evaluation difficulties: 1st Group - Lack of data set (4 examples).

- I) Half-lives

Isotope Half-life (T1/2)

% of T1/2

N° of measuremen

ts

Most recent experimental value

Ra-226 1600 (7) a 0.4 12 [5] 1966, H. Ramthun

Rn-222 3.8232 (8) d 0.02 9 2004, H. Schrader

Po-218 3.094 (6) min 0.20 4 [3] 1986, G. V. Potapov

At-218 1.4 (2) s 14 2 1989, D. G. Burke

Rn-218 35.5 (13) ms 4 5 [4] 1971, A. Erlik

Pb-214

26.8 (9) min 3.4 1 1931, M. Curie

Bi-214 19.9 (4) min 2 1 1956, H. Daniel

Po-214 161.7 (15) s 0.9 10 [6] 1993, J. W. Zhou

Tl-210 1.30 (3) min 2.3 3 [2] 1964, P. Weinzierl

Pb-210 22.23 (12) a 0.5 14 [11] 2002, G. A. Rech

Bi-210 5.012 (5) d 0.1 6 1959, J. Robert

Po-210 138.3763 (17) d

0.001 9 [7] 1964, J. F. Eichelberger[]: n° of measurements with uncertainty.


- II) and - Emission probabilities: lack of measured values.

Isotope Type of decay Situation

Ra-226 (100 %) Two measurements in 1963 and 2001.

Rn-222 (100 %) Last measurements in 1958.

Po-218 (99.978 %) (0.022 %)

Last measurements in 1958.Last measurements in 1952.

At-218 (99.9 %) (0.1 %)

Last measurements in 1958.Last measurements in 1948.

Rn-218 (100 %) No direct measurements available.

Pb-214 (100 %) No direct measurements available.

Bi-214 (0.02 %) (99.98 %)

Last measurements in 1960. No direct measurements available.

Po-214 (100 %) No direct measurements available.

Tl-210 (100 %) Last measurements in 1964.

Pb-210 (1.9 10-6 %) (~ 100 %)

Three measurements in 1961, 1962 and 1964.

Five measurements between 1953 and 1963.

Bi-210 (1.4 10-4 %) (~ 100 %)

Five measurements between 1947 and 1962.No direct measurements available.

Po-210 (100 %) No direct measurements available.


- III) X-ray emissions.

Isotope Type of emission Situation

Ra-226 X-rays Three measurements in 1973, 1983 and 2002.

Rn-222 -raysX-rays

No direct measurements available.

Po-218 X-rays No direct measurements available.

At-218 X-rays No direct measurements available.

Rn-218 X-rays No direct measurements available.

Pb-214 X-rays Two measurements in 1969 and 1983.

Bi-214 X-rays No recent measurements since 1983.


Tl-210 -raysX-rays

No recent measurements since 1964.

Pb-210 X-rays Four measurements in: 1957, 1971, 1987 and 1990.

Bi-210 -raysX-rays

No direct measurements available.



- IV) Example of decay scheme particularly unknown:Tl-210 -decay to Pb-210


This decay scheme is based

on the measurements of

P. Weinzierl (1964):

Energy (keV) Relative -ray Emission intensity (%)

83(a) 2.0

97 4 (2)

296 80 (10)

356 (a) 4 (2)

382 (a) 3 (2)

480 2 (1)

670 (a) 2 (1)

799 100

860 7 (2)

910 (a) 3 (2)

1070 12 (5)

1110 7 (2)

1210 17 (4)

1316 21 (5)

1410 5 (2)

1490 (a) 2 (1)

1540 (a) 2 (1)

1590 2 (1)

1650 (a) 2 (1)

2010 7 (2)

2090 (a) 5 (2)

2270 3 (2)

2360 8 (3)

2430 9 (3)

Experimental data set of the relative -ray

emission intensities.

(a) Not placed in the decay scheme


Experimental values of - transition probabilities.

Level Energy (keV)P. Weinzierl (1964We06)

11 1380 (12) 25 %

10 1603 (12)

9 1860 (12) 56 %

8 2024 (12)

7 2413 (12) 19 %

3 4290 (12)

2 4386 (12)

Q(Audi) = 5482 (10) keV

Qeff = 4390 (1600) keV

Adoptedvalues

2 %

7 %

24 %

10 %

10 %

31 %

13 % PQeff = 5470

(1000) keV

Conclusion: New measurements are strongly suggested.


Evaluation difficulties: 2nd Group- -ray emission intensity.

Ra-226 radioactive chain: ~ 275 -rays.

1. Good examples: many and recent articles found about direct measurements.

A) Pb-214 - decay to Bi-214, Bi-214 - decay to Po-214 and Ra-226 decay to Rn-222

We have: * 5 measurements of absolute -ray emission intensities: E. W. A. Lingeman (1969), D. G. Olson (1983), U. Schötzig (1983), W. -J. Li (1991) and J. Morel (2004) * 14 measurements of relative -ray emission intensities, where: 8 measurements not used because: a) a lack of information in articles – K. Ya. Gromov (1969), G. Wallace (1969) and M. A. Farouk (1982) b) values comes from the same laboratory: A. Hachem (1975), G. Mouze (1981), H. Akcay (1982), G. Mouze (1990) and G. Diallo (1993). Finally, 6 measurements used: G. T. Ewan (1964), V. Zobel (1977), G. Mouze (1990), D. Sardari (2000), J. U. Delgado (2002) and G. L. Molnar (2002).


B) Pb-210 - decay to Bi-210

We have 9 measurements of relative -ray emission intensities (the most recent one in 1990), where 4 measurements were not used because of a lack of information in articles (D. K. Butt (1951), C. S. Wu (1953), P. E. Damon (1954) and I. Y. Krause (1958)).

C) Po-210 decay to Pb-206

We have 8 (no recent) measurements: M. A. Grace (1951), M. Riou (1952), W. C. Barber (1952), O. Rojo (1955), R. W. Hayward (1955), A. Ascoli (1956), N. S. Shimanskaia (1957) and V. V. Ovechkin (1957).


Evaluation difficulties: 2nd Group - -ray emission intensity.

2. Difficult examples: no articles found in the literature for direct gamma–ray measurements.

A) Measurements of -ray emission intensity found in the literature come from indirect measurements:

* Rn-218 decay: -ray emission intensity was deduced from the U-230 decay chain.* Po-214 decay: -ray emission intensity was obtained from the Ra-222 decay.

OR

B) Adopted -ray emission intensity comes from and - intensity measurements:

* Rn-222, Po-218 and Bi-210 decays


Evaluation difficulties: 3rd Group- Decay scheme balance.

1) Pb-214 - decay.

Internal conversion coefficients (ICC’s) for -ray transitions of Bi-214have been deduced from Rösel’s tables.These coefficients lead to a better decay scheme.ICC’s given by Rösel PICC’s given using BRICC computer code (Band’s values) P = 102 %

E (keV) Multiporality T (Rösel) T (BRICC)

53.2275 (21)

M1 + E2, = 0.030 (10)

1.288 (39) E+01 1.214 (19) E+01

241.997 (3) M1 (+E2), = 0.00 (15)

8.88 (27) E-01 8.38 (18) E-01

295.224 (2) M1 + E2, = 0.30 (13)

4.82 (14) E-01 4.6 (3) E-01

351.932 (2) M1 (+E2), = 0.00 (32)

3.19 (10) E-01 3.00 (25) E-01

Q(Audi) = 1019 (11) keV

Qeff = 1024 (11) keV

Rel. Error = 0.51 %

Qeff = 1029 (15) keV

Rel. Error = 0.99 %


Evaluation difficulties: 3rd Group - Decay scheme balance.

2) Tl-210 - decay.

All decay scheme is based on the only measurement found in the literature given by P. Weinzierl (1964) and several inconsistencies appeared, as shown previously.

Because of these inconsistencies, there is a lack of 3 % in decay scheme balance (P = 97 %) and we wait for new measurements to solve these problems.


Conclusions

Taking into account the experimental values of -ray emission intensities, we have done a new evaluation of the Ra-226 decay chain down to Pb-206. A total of twelve radionu-clides have been reviewed ( ~ 275 -rays).

For other nuclear data like half-life, X-rays, - and emission intensities, the situation is as follows:

A - Half-lives. Critical cases: Pb-214 (1 measurement by M. Curie in 1931) Bi-214 (1 measurement by H. Daniel in 1956). For four nuclides (Ra-226, Tl-210, Bi-210 and Po-210): no recent measurements since the 1960’s. B – X-rays. Only few measurements for Ra-226, Pb-214, Bi-214, Tl-210 and Pb-210. For the other radionuclides: no direct measurements available.

C - - and emission intensities. Except for Ra-226 (last measurement in 2001), no recent measurement were found in the literature since 1960’s.

To solve all problems in decay scheme of nuclides that belong to Ra-226 decay chain,we need new measurements of these nuclear data.


More information about evaluations can be obtained at:

http://www.nucleide.org/NucData.htm

Documents

1Laboratoire National Henri Becquerel Decay data evaluation of Radium – 226 and its daughters V. Chisté, M. M. Bé, C. Dulieu