Low Temperature Overpressure Protection



Low Temperature Overpressure Protection

of the

Reactor Coolant System

Abstract

Author: Zoran Račič

Company: NUMIP Krško d.o.o

NUMIP Krško is a small sized company located at Krško. The company was founded in 1996 and it employs highly experienced experts. NUMIP specializes in maintenance, construction projects, installation works, and production of spare parts for nuclear power plants, electric power plants and other industrial plants. With the cooperation of our subcontractors home and abroad we are capable of leading the most demanding projects up to 500 people.

In last five years NUMIP participated in the implementation of several modifications in the Krško Nuclear Power Plant (Krško NPP). As an example we would like to present our scope of work within LTOP modification, implemented during Outage 2001.

The LTOP modification was required as a result of the resolution to EEAR 95-043 (Engineering Evaluation Assistance Request) prepared and issued by Krško NPP Engineering Service Department. EEAR 95-043 requested Low Temperature Overpressure Protection (LTOP) of the Reactor Coolant System (RCS) after Krško Onsite Event Report 14/94 regarding the RCS pressure excursion experienced after the inverter ESELIV01 static Switch failure on September 25.

The modification package was prepared by company Parsons from United States of America and reviewed and approved by NEK. It was used as basis document for preparation of installation documentation prepared by NUMIP.

NUMIP scope of work was:

Preparation of the installation package in accordance with NEK procedures

➢ Fabrication of pipe spools at NUMIP workshop

➢ Installation activities inside Reactor Building during Outage2001 - Existing 2x3 RF relief valves and 2" inlet pipe and 2" socket weld connections were removed and replaced by a 3" weldolet, 3" pipe and new larger relief valves. The new 3x4 relief valves were added to the RF suction piping, and new 6" relief piping was run to the 10" PRT inlet piping from the pressurizer safety valves and PORVs.

Procurement, fabrication and installation was performed in accordance with the applicable ASME Boiler and Pressure Vessel Code Sections II, III, V, IX & XI – 1989 Edition including Addenda through 1990.

The applicable code for the NDE and visual examination (VT-2) of safety related piping and supports was the ASME Boiler and Pressure Vessel Code Sections III& XI – 1992 Edition (per Code Case N-416-1).

All above-mentioned activities were performed on time and successfully.

Author's Address: Zoran Račič

NUMIP Krško d.o.o

CKŽ 135e

8270 Krško, Slovenia

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