Monte-Carlo calculations for the development of a BNCT neutron source at the Kyiv Research Reactor.

The results presented in this paper display our continuing steps toward development of a neutron source with parameters required by boron neutron capture therapy (BNCT) at the Kyiv Research Reactor (KRR). The purpose of this work was: 1. calculation of the neutron flux which can be achieved at the greatest possible approach of a patient to the reactor core; 2. analysis of the influence of a nickel collimator and a nickel-60 filter on the characteristics of the neutron beam; 3. creation and validation of the MCNP calculational pattern for an actual core fuel load in the KRR. Results of calculations were carried out by means of the MCNP4C code included: 1. An epithermal neutron flux of 3x10(9)-5x10(9)neutron/cm(2)s with an epithermal-to-fast flux ratio of 80-230 could be obtained at the KRR, using a natural nickel layer on the interior borated polyethylene collimator wall and a (60)Ni filter. 2. Use of the (60)Ni filter may be useful to increase the ratio epithermal-to-fast flux without a substantial decrease in the magnitude of the epithermal neutron flux. 3. The MCNP model proposed in this paper could also be useful for reactor safety calculations.

Investigation of host-guest stability constants of calix[n]arenes complexes with aromatic molecules by RP-HPLC method.

Under reversed-phase high-performance liquid chromatographic conditions [Spherisorb ODS 1 stationary phase, UV detection at 254 nm, and acetonitrile-dichloromethane-acetic acid-methyl-tert-butylether (84.6/4.5/0.9/10, v/v/v/v) as the mobile phase], adding p-tert-butylcalix[8] (10(-5)-3.10(-5))-[12]arenes (10(-5)-4.10(-5) mol/L) to the mobile phase leads to decreased sorption of aromatic solutes on the surface of the sorbent because of the formation of host-guest inclusion complexes between the calixarenes and the aromatic molecules. Stability constants of the complexes (781-9338M(-1)) are determined from the relationship between the solute capacity factors and the calixarene concentration in the mobile phase.

Optical resolution of phosphorus containing calix[4]arenes by additive RP HPLC method.

The RP HPLC method (LiChrosorb RP18 or Separon SGX C18 column, acetonitrile-water 86:14 v/v mobile phase) was applied for enantiomeric separation of topologically chiral 5-bromo-25,26-bis(diethoxyphosphoryl)calix[4]arene 9 or 25-ethyl-26-dihydroxyphosphoryl-calix[4]arene 5. Separation of calixarene 9 was achieved by the addition of D-(-)-tartaric acid which formed hydrogen bonded diastereomeric associates with 9 to the mobile phase. Calixarenephosphoric acid 5 was transformed into diastereomeric salt 6 by addition of L-(-)-alpha-phenylethylamine before RP HPLC separation.

HPLC and GLC determination of residual solvents in busulphan.

Quantitative methods using HPLC and GLC for the determination of residual pyridine and ethanol in busulphan have been developed. The measurement errors for pyridine and ethanol in busulphan samples (p = 0.95) were found to be 10% and 7%. It was shown that one recrystallization enabled pure busulphan to be prepared.