[en] SISAK is a new continuous technique for rapid radiochemical separations. The SISAK system consists of three main parts, a target system, a chemical separation system and a nuclear detection system, connected by liquid flow lines, transporting the species. In the target system, a substance dissolved in a liquid or fixed on an ion exchanger is continuously irradiated. The products formed are transported by a liquid to the chemical separation system, where they are distributed between an organic solvent and the aqueous phase, after which the two liquid phases are separated in a continuous flow centrifuge. By proper chemical control of the two-phase system, very selective, high yield separations can be completed within some 2 seconds. The technique may be extended to multistage processing, if necessary. In the nuclear detection system, the separated species are collected on ion exchange or extraction column collectors in front of detectors measuring gamma radiation. The delay properties of the different components are discussed in terms of mathematical models. The two detector delay method, which is a new technique for the determination of radionuclide half-lives in continuously flowing media, is presented and its applications are discussed. The SISAK technique has been applied to studies of the following nuclides: ⁷⁰Cu, ¹¹³Pd, ^115-116Pd, ^144-146La, ^147-150Ce and ^148-150Pr. In addition, the kinetics of the solvent extraction system palladium-acetylacetone have been studied with the SISAK equipment. Future developments to decrease the delay in the separations and transports are proposed, along with sampling techniques enabling the measurement of beta particles. (Auth.)

[en] It is well known that good control of the primary chemistry in a PWR is essential in order to minimize material problems and fuel damages. It has also been well established that the water chemistry has a great influence on accumulation of corrosion products on the fuel and the radiation build-up on primary system surfaces. Ringhals was one of the pioneers to increase operating pH in order to reduce radiation build-up and has now been operating for ten years with pH at 7.4 or (in later years) 7.2. Our experience is favourable and includes low radiation levels in the new (1989) steam generators of Ringhals 2. Ringhals 4 has operated almost its whole life at pH 7.2 or higher and it remains one of the cleanest PWRs of its vintage. In addition to strict adherence to a stable operating chemistry, Ringhals is now working on a program with the aim to find optimum shut-down and start-up chemistry to reduce activity levels in the primary systems. A particular goal is to use the shut-down and start-up chemistry at the 1994 outage in Ringhals 3 in order to reduce doserates in preparation for the planned steam generator replacement in 1995. The paper summarizes the experience to date of the established operating chemistry, on-going tests with modified shut-down and start-up chemistry and other measures to limit or reduce the activity build-up

[en] The objective of the strategy for CDA is to obtain information as soon as possible and to continue the assessment until stable conditions are established. CDA methods are: 1) information of process parameters; 2) dose rates within the containment; 3) activity content (Swedish post accident sampling system PASS); 4) hydrogen concentration. (orig.)

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[en] γ-γ-coincidence measurements have been performed on neutron-rich Ce isotopes using the fast radiochemical separation system SISAK in combination with a gas jet recoil transportation system. The results include assignments of new γ-rays and proposal of partial decay schemes for 3 min ¹⁴⁵Ce, 56 s ¹⁴⁷Ce and 48 s ¹⁴⁸Ce. The existing decay system of 14 min ¹⁴⁶Ce has been verified, except for a few transitions. (author)

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[en] Ringhals Nuclear Power Plant in Sweden comprises one Boiling Water Reactor and three Pressurised Water Reactors. This paper describes the experience in monitoring fuel failures and discusses the criteria for shutting down to avoid excessive contamination. (UK)

No abstract available

[en] At Ringhals 1, a high resolution Ge(HP)-detector was installed for on-line monitoring of system activity contamination. A vertical RWCU-pipe, DN 300, was monitored during operation of the reactor. 30-minutes spectra were continuously recorded during one fuel cycle. The statistical scattering of Co-60 and Co-58 for 30 minutes measurement is 0.5 and 2 %, respectively. For 24 hours measuring time the statistical scattering is 0.1 % for Co-60, 0.4 % for Co-58, 3 % for Mn-54, 4 % for Cr-51 and about 10 % for Zn-65, Zr-95 and Sb-124. Thus, changes significantly less than 1 % for Co-60 and Co-58 of the surface contamination levels on primary system pipes, can be continuously recorded during normal operation of a BWR. The contribution to the net measured detector signal from background sources is very low. As an example, the relative contribution to the measured Co-60 (and Co-58) signal from activity in the reactor water in the monitored pipe is less than 4^*10^-6. The relative contribution to the Co-60 signal from all other sources was less than 6^*10^-3. With the on-line activity (OLA) measuring method it is possible with high time resolution and with significant sensitivity to follow-up tests of various kinds, for instance iron injection, zinc-injection, HWC, pH changes, and how chemical transients in the reactor water affects the activity uptake on the surfaces. The measuring system can provide an early warning if unexpected activity uptake will take place and also reveal operational condition, which may cause increased activity deposition. OLA-equipment will be installed in a number of Nordic BWRs by the start of the fuel cycle 1998-99. (author)

[en] γ-ray singles and coincidence measurements have been performed on the neutron-rich nuclides ¹⁴⁴La, ¹⁴⁵La and ¹⁴⁶La, produced in thermal neutron-induced fission of ²³⁵U. The studies were facilitated by the combination of a gas jet recoil transportation (GJRT) system with the rapid on-line chemical separation system SISAK. Half-lives of 42.1 +- 0.7 s, 25.2 +- 2.6 s and 8.5 +- 1.0 s were obtained for ¹⁴⁴La, ¹⁴⁵La and ¹⁴⁶La, respectively. Several new γ-ray enrgies have been assigned to each of the nuclides, and partial decay schemes are proposed for ¹⁴⁴La and ¹⁴⁶La together with a preliminary partial decay scheme for ¹⁴⁵La. (author)