atw 2018-04v6


atw Vol. 63 (2018) | Issue 4 ı April

Experimental and Analytical Tools

for Safety Research of GEN IV Reactors

G. Mazzini, M. Kyncl, Alis Musa and M. Ruscak

Current research on nuclear safety in the world, in addition to supporting existing nuclear power plants (PLEX,

mitigation of severe accidents, the development of accident tolerant fuel, decommissioning, etc.), is focused on the

more detailed aspects of the new reactors. The new generation reactors are expected inter alia to use innovative types

of fuel and new types of coolants, such as e.g. Super-Critical Water (SCW), supercritical CO 2 , liquid metals, fluoride

salts or high-temperature Helium. The paper will describe new experimental infrastructure build recently in Research

Centre Řež under the SUSEN (Sustainable Energy) project and available analytical tools for supporting safety research

of GEN IV reactors. Two experimental loops - SCWL (Supercritical Water Loop) and HTHL (High Temperature Helium

Loop) will serve as in-pile loops in the active core of the research reactor LVR-15. The loops insertion in the reactor

LVR-15 requires performing additional safety analyses studying the mutual interference of the loops and the reactor,

especially in conditions of abnormal operation or accident conditions of the loops. The paper will provide examples of

these analyses made using codes ATHLET (supercritical water) and TRACE (high temperature He) illustrating process

of their assessment and practical use. These activities provide significant opportunity for TSO team in building its new


Revised version

of a paper presented

at the Eurosafe,

Paris, France, 6 and

7 November 2017.


1 Introduction

The Centrum Výzkumu Řež (CVŘ) and

its partners in the Czech Republic and

abroad are supporting the development

[1] of the Generation IV and

Fusion concepts as well as demonstrators

of these technologies such


others. For this reason, the CVŘ has

had a large R&D program financed

from SUStainable Energy (SUSEN)

project and from its continuation

Research 4 Sustenibility (R4S) [2].

The construction and the operation of

the new SUSEN infrastructure was

supported by the grant of the Ministry

of Education, Youth and Sports as the

part of state help for the large research

infrastructure in the Czech Republic

dedicated to the period 2011–2019.

The SUSEN project consists of 4


1. Technological Experimental Circuits


2. Structural and System Diagnostics


3. Nuclear Fuel Cycle (NFC)

4. Material Research (MAT)

Within this program, several facilities

were designed and built in order to

study and to address new challenges

of such new technologies. In particular,

the paper focuses on two new

loops which are going to be inserted

inside the LVR-15 research reactor

existing in Řež. The LVR-15 is a light

water tank-type research reactor in

operation since 1957. It is placed in a

stainless steel vessel under a shielding

cover, has forced cooling, uses IRT-4M

type fuel and an has an operational

power level of 10 MWt. The reactor

operations run in campaigns that

usually last for 3 weeks, followed by

an outage lasting for 10 to 14 days

necessary for maintenance and fuel

reloading. There can be also other

campaigns which can operate for

‘short-time’ experiments. Some of the

LVR-15 applications are in the field of

material irradiation research and services,

neutron physics, development

and production of new radiopharmaceuticals

[3]. The loops in concern are

the High Temperature Helium Loop

(HTHL) and the Super Critical Water

Loop (SCWL) and their main scope

are to analyse the cladding behaviour

and structural materials under different

pressure, temperature and coolant

media conditions different from the

standard Light Water Reactors (LWR)

technology [2].

In order to get the regulatory

permit for in-pile operation of these

loops in LVR-15, CVŘ has to prepare

an amendment to the Final Safety

Analyses Report (FSAR) containing

safety analyse of the loops under

| | Fig. 1.

CVR Facilities list.

operational and accidental conditions.

Aim of this paper is to present

the methodology and the analyses

done in support of this process, starting

from code benchmarking/assessment

and the methods adopted in preparing

the safety case.

2 Facilities description

The map of experimental facilities put

into operation in 2016 and those

under preparation to be finalized in

2017 is shown in Figure 1 in the

technology – knowledge map.

In particular, the SCWL and HTHL

represent a pioneer and unique experimental

facility for Gen. IV and Fusion.

2.1 SCWL

The SCWL is going to be a part of a

research facility dedicated to GIV

technologies which will focus on

obtaining data in several areas of the

supercritical fields like: corrosion

processes of construction materials in

supercritical water, with influence of

Operation and New Build

Experimental and Analytical Tools for Safety Research of GEN IV Reactors ı G. Mazzini, M. Kyncl, Alis Musa and M. Ruscak

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