ReferenceMartin B. Kalinowski; Anders Axelsson; Marc Bean; Xavier Blanchard; Theodore W. Bowyer; Guy Brachet; Simon Hebel;Gilbert Le Petit; Justin I. McIntyre; Jana Peters; Christoph Pistner; Maria Raith; Anders Ringbom; Paul Saey; Clemens Schlosser;Trevor J. Stocki; Thomas Taffary; R. Kurt Ungar. (2010). Discrimination of nuclear explosions against civilian sources based onatmospheric xenon isotopic activity ratios. Accepted by Pure and Applied Geophysics Topical Volume “Recent Advances inNuclear Explosion Monitoring”, submitted on 17 December 2008, revision submitted on 18 May 2009.

Martin B. Kalinowski; Christoph Pistner. (2006). Isotopic signature of atmospheric xenon released from light water reactors.Journal of Environmental Radioactivity, 88 (3), 215-235.

Supported by

German Foundation for Peace Research

Carl Friedrich von Weizsacker Centre for Science and Peace Research

Beim Schlump 8320144 HamburgGermany

Tel. +49 40 42838 4335Fax. +49 40 42838 3052

http://www.znf.uni-hamburg.deMartin.Kalinowski@uni-hamburg.de

ConclusionThe multiple isotopic ratio plot is a very robust tool for discriminating nuclear reactor sources from thesignature of a nuclear explosion release. Emissions from isotope production facilities are expected to showan isotopic characteristic similar to that of nuclear test explosions due to the short irradiation time. However,in atmospheric observations this has never been seen, because of ambient concentrations of 131mXe stillremaining from the radioactive decay of previous releases or originating from additional sources of thisparticular isotope.

The multiple xenon activity ratios provide a major methodology for source discrimination. It will be used ina suit of several different complementary screening approaches. The other two main screening methodsare anomaly detection in the station specific concentration distribution of the historic measurements at thatsite as well as the explanation of elevated concentrations with known sources according to source-receptor-sensitivities as determined by atmospheric transport simulations.

Observations by measurement stations of INGEThe dashed red line marks the time-invariant screening separation:

• Isotope ratio relations found left to this line:can be screened out because they cannot be explained by a nuclear explosion.

• Samples that have ratio dependencies found right to the line:might be relevant for CTBT monitoring purposes.

Only very few data points are outliers in the nuclear test domain. They are subject to further investigation.

INGE Stations 2009The International Noble Gas Experiment (INGE) was established in 1999. Of the 40 noble gas installationsplanned, 22 INGE stations are in operation in 16 countries.

http://www.ctbto.org/

Data used for this poster was collectedat the following stations (stations, whichreported 3 or more isotopes are printedbold):

• aux04

• aux09• brx11• cax05• cax16

• cax17• cnx22

• dex33• jpx38• nox49• nzx46• sex63• usx74• usx75

Simulations of reactors and nuclear explosionsReactor ratio trajectory of the first one-year power cycle of fuel plus a 30-day revision period with 3.2%enrichment in 235U. Description of the isotopic ratio track during the first reactor power cycle:

(Kalinowski & Pistner, 2006)

1. Start-up with fresh fuel only

2. Approaching equilibrium

3. Short-time increase of 135Xe after power shut-down

4. Radioactive decay

5. Low neutron flux during revision period

6. Restart of reactor to full power

7. Circling back to equilibrium

Comparison of simulated and reportedxenon isotopic activity ratios releasedfrom nuclear tests.

Preconditions for the multiple istopic ratio methodThe following conditions and limitations are associated with the multiple isotope ratio method for sourcecharacterization:

• Suitable combination of isotopes need to be detected;

• Background needs to be precisely known, in particular 131mXe;

•No mixing in of fresh releases from other sources.

Further work is required in order to put this method in operation. The decision procedure whether or not anuclear explosion is likely indicated by the ratio as demonstrated by a separation line needs to be clarifiedand the uncertainties of xenon isotopic activity ratios need to be accounted for.

The purpose: Use atmospheric xenon to verify the CTBTCTBT relevant xenon isotopes: 135Xe, 133mXe, 133Xe and 131mXe

isotope T1/2

131mXe 11.9 d133Xe 5.2 d

133mXe 2.2 d135Xe 9.1 h

The purpose is to distinguish nuclear explosion sources from civilianreleases. The proof of concept for the isotopic ratio based method forsource discrimination is based on:

• Simulations of reactors and nuclear explosions

• Empirical data for both test and reactor releases

•Observations by measurement stations of INGE

Motivation: Proper source characterisation is importantOnly radionuclides can prove the nuclear character of an event. But the presence of xenon is not sufficientto indicate a nuclear explosion. Civilian sources of radioxenon are:

Nuclear Power Plants

Grafenrheinfeld

Isotope Production Facilities

Chalk River Laboratories

· · ·

IntroductionThe isotopic ratio plots have been proposed as one of several methods for categorization of noble gassamples. This poster demonstrates the concept and its applicability based on data from different radionuclidestations. It is based on the forthcoming paper by Kalinowski et al. (2010). The multiple isotopic activityratio plots are applied to new data taken by various IMS stations as part of the International Noble GasExperiment (INGE). These data were analysed by the International Data Centre (IDC) and provided to theauthors as part of their work for the International Scientific Studies Project (ISS).

Discrimination of nuclear explosions against civilian sources based onatmospheric xenon isotopic activity ratios

Martin B. Kalinowski1∗, Jana Peters1, et al.2

1 Carl Friedrich von Weizsacker Center for Science and Peace Research, University of Hamburg, Germany, ∗ Corresponding Author2 International Noble Gas Experiment station operators and analysts