Objective

The objective of the project was to improve the sump inlet conditions of the Emergency Core Coding System (ECCS) in VVER 1000 containments in order to enable unclogged operation of ECCS pumps in case of insulation disintegration.
The deliverable was to be a report of an investigation on a reference plant, with concrete proposals for prevention or mitigation of the effects.

The work was divided into 7 parts:

1. General

• Definition of the detailed project time schedule, the work plan and the project related QA programme in agreement with the Beneficiary.
• Evaluation of background information supplied by the Beneficiary.

2. Design basis for improved sump screen structures

• Find a basis for redesign of the sump screen structures taking into account:

material survey with respect to sump blockage risk and debris generation;

sump water inventory and suction conditions of safety system pumps;

net Positive Suction Head (NPSH)-requirements;

mechanical loads.

• Prepare an assessment report on the design basis for the work under section 3 below, including justification of the chosen scale of the model.

3. Sump strainer conceptual design

• a) Elaborate a conceptual design for a sump strainer and specification of the system parameters considering the design basis development in section 2 above.
• b) Issuing a report in which the results of section 3a are documented and which then serves as a basis for the decision on how to proceed with prototype (model) and baseline tests on this model.

4. Hydraulic model tests

• Manufacture a strainer prototype (model) based on the conceptual design developed in the previous sections.
• Establish a test programme, perform model testing in collaboration with the Subcontractor.
• Carry out tests considering most adverse effects of temperature, chemicals (boron content) and insulation material composition.
• Insulation thermal ageing shall be included.

5. Prepare test report

6. Conclusions

7. Final Report

Evaluation of the tests results and making a proposal for modifications in Russian VVER.

Result

The main outputs were:

Analytical work:

• design basis for the development of the new filtering structure;
• modification proposal for implementation.

Experimental work:

• engineering basis for the development of new filter structures;
• basis for the justification of the designed performance of the proposed filter structures.

Adequate information has been received to understand the behaviour of the filter structure.
All specific deliverables have been produced. The output was in accordance with the TOR. The modification proposal for the new filter structure was accepted by the Federal Nuclear and Radiation Safety Authority of Russia (GOSATOMNADZOR) and the Beneficiary as a basis for implementation at Balakovo NPP.

Based on this result the next step has been performed with Project R1.02/96C.

The Project was completed on 01.01.1997.