Mixed item formats are in extensive use in large-scale assessment today and widely accepted as a means to improve assessment validity. Many studies have investigated the differential effect of Item Format on gender and ethnic subgroups in mathematics, yet few of these studies have attended to their impact on students with limited language proficiency and linguistic abilities in the area of reading. As educational policy increasingly mandates the inclusion of minorities such as English Language Learners (ELL) and students diagnosed with Specific Learning Disability (SLD) in federal and state assessment, many question the validity of achievement test scores because the degree to which the test score is a function of language proficiency is not clearly understood (Mahoney, 2008). To fill that research void, this study investigated Item Format effect and its interaction with (a) group membership as an ELL and/or SLD student and (b) assessment format differences related to genre and reading content. The software program ConQuest (Wu et al., 2007) was used to conduct Item Response Modeling on the 2007 NAEP 4th grade reading achievement data. Analysis demonstrated an overall hierarchy of Item Format difficulty. Contrary to expectation, DIF analysis demonstrated that flagged CR items favored both ELL and SLD students, while flagged MC items generally favored the Non-SLD group. But, multidimensional regression analysis demonstrated that there is no interaction between Item Format and group membership because the effect was virtually equivalent across MC and CR formats for the reference and focal groups. In looking to the future of assessment design, more research is needed to fully understand how Item Format differences contribute to assessment difficulty, the limited application of various Item Formats, specifically how they are suited to particular content, and how to blend Item Formats in a manner that utilizes their unique benefits while also producing fair results (Hastedt & Sibberns, 2005).

The response to high linear energy transfer (LET) radiation of a variety of aqueous systems such as biological systems and the Fricke dosimeter has frequently been studied in the literature. Linear energy transfer is a unique property of radiation which describes the special distribution with which energy from radiation is deposited and concentrated as it travels through matter and can have implications on degradation within the matter itself. The four types of ionizing radiation alpha, beta, gamma, and neutrons have different LET, classified from low for gamma and beta, to high for alpha. All types of ionizing radiation are encountered in used nuclear fuel. This radiation induces damage to solvent extraction processes designed to recycle used nuclear fuel which results in impaired selectivity and reduced process efficiencies. While the effects of low LET radiation on organic solutions have been widely studied, the effects of high LET radiation have not due to difficulties in studying this type of radiation such as short radiation path lengths on the order of 50 μm. This study investigates the effects of high LET radiation deposited in situ from fission products lithium and helium emitted in the ¹⁰B(n,α)⁷Li reaction. The reaction, studied previously in aqueous systems, is applied here to organic solvents containing ligands used in solvent extraction. Ligands studied were TBP, CMPO, and TODGA utilized in the PUREX and TRUEX processes. Results demonstrate that high LET radiation has the tendency to reduce degradation to the parent compound due to reactive products being consumed within the radiation track, while encouraging secondary degradation products to occur within the radiation track. Products of these secondary degradation reactions may be more detrimental to the solvent extraction process than primary degradation products and are therefore important to understand and monitor. Results also demonstrate the utility of using the ¹⁰B(n,α)⁷Li reaction to study the effects of high LET radiation on organic solutions encountered in used nuclear fuel recycling processes. Understanding the effects of both high and low LET radiation on solvent extraction processes will facilitate early screening of novel ligand susceptibility to radiation induced degradation while also providing a more comprehensive picture of degradation encountered during radiolysis.