Preparation and Development of New Pu Spike Isotopic Reference Materials at IRMM

Reliable isotope measurements of nuclear material and reference materials with small uncertainties of the certified values are of great importance for security and safeguards of nuclear installations. They provide the basis for a strong verification and detection system to safeguard nuclear activities. Worldwide needs for continued and improved Isotopic Reference Materials (IRM) are the main reason for developments of new nuclear reference materials at IRMM. Measurement capabilities of laboratories have evolved considerably over the years hand in hand with progress in modern analytical techniques. But some plutonium reference materials are already on the market for decades. The availability of new reference materials with appropriate small uncertainties of the certified values is essential for measurement laboratories striving to meet the International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials (ITVs). The preparation and the certification of such materials are demanding and challenging tasks that require state-of-the-art measurement procedures and equipment. The Institute for Reference Materials and Measurements (IRMM) has repeatedly demonstrated its capabilities in plutonium analysis and represents one of the few institutes that supplies plutonium IRMs worldwide. IRMM has recently performed an inter-calibration campaign inter-linking selected plutonium spike IRMs on a metrological basis, applying state-of-the art measurement procedures. In the scope of this compatibility study new reference materials have been prepared for Isotope Dilution Mass Spectrometry (IDMS) in nuclear fuel cycle measurements. A new series of large-sized dried (LSD) spikes IRMM-1027n has been prepared and certified for plutonium and uranium amount content and isotopic composition. These mixed spikes are applied to measure the uranium and plutonium content of dissolved fuel solutions using isotope dilution mass spectrometry. They are prepared by IRMM to fulfil the existing requirements for reliable spike IRMs in fissile material control from European Safeguards authorities and customers from industry. IRMM-046b, a mixed uranium-plutonium spike IRM of highly enriched 233U and 242Pu that dates from 1995 was recertified for isotope amount content and isotopic composition, each with considerably smaller combined uncertainties. IRMM-046c, a new mixed uranium-plutonium spike and IRMM-049d, a highly enriched 242Pu spike have been prepared and certified. IRMM-049d was prepared from the same stock solution as its predecessor IRMM-049c, dating from 1996, but this 242Pu spike has certified values with smaller combined uncertainties. These reference materials were prepared by dissolving the base materials in nitric acid and are certified for the amount content by gravimetry or isotope dilution mass spectrometry (IDMS). The traceability of the certified values to the SI is established through an unbroken chain of comparisons all having stated uncertainties. IRMM is also cooperating with the Institute for Transuranium Elements (EC-JRC-ITU) in a feasibility study on the development of Pu reference materials for “age dating” in nuclear forensics. In the course of this work the reference materials NBS SRM 946, 947 and 948 (NBL CRM 136, 137 and 138) will be investigated among others.

JAKOPIC Rozle;  BAUWENS Jeroen;  RICHTER Stephan;  STURM Monika;  VERBRUGGEN Andre;  WELLUM Roger;  EYKENS Roger;  KEHOE Frances;  KUEHN Heinz;  AREGBE Yetunde; 

2012-01-17

ESARDA and the Joint Research Centre of the European Commission

JRC65089

0392-3029,