TVS-2M is a consistent development of TVS-2 Generation 2 “zirconium” fuel assembly design (with a rigid skeleton) in aspects belonging to an increase in fuel loading and service reliability enhancement that allow rising the capacity factor. TVS-2M is intended for operation in the environment of VVER-1000 reactor core both with the central and lateral positioning of the instrumentation tube. At present TVS-2М is the basic type of fuel operated at the Russian NPPs with VVER-1000 and the basis for fuel to be applied at NPPs with VVER-1200 (AES 2006). FA for V-187 RP

FA

MTVS

UTVS

TVS-2

TVS-2M

TVS-AES-2006

FA with a rigid skeleton TVS-2M design provides:

 high reliability;

Significant features of TVS-2M:

 а possibility of Unit operation in “fl exible” fuel cycles (4х12; 5х12; 3х18 months), including the cycles with low neutron leakage;

 geometrical stability of the core;

 а possibility of Unit operation at power uprated up to 104% of nominal;

 fast core refueling during preventive maintenance;

 compatibility with the previous FA designs (with 15 and 12 spacer grids), approved by the experience of replacement of Units with UTVS (15 spacer grids) and TVS-2 (15 or 12 spacer grids) by TVS-2M;

 maximum permissible burn-up to 68 MW•D/kg U in a TVS-2M and up to 72 MW•D/kg U in a fuel rod;  specific consumption natural uranium up 0,185 kg U/MW•D;

 reliable actuation of reactor trip system;

 capability for being disassembled and repaired with fuel repair and inspection equipment.

of to

 invulnerability during handling procedures;

fuel

 optimized pitch of spacer grids providing TVS-2M rigidity and stability of shape and absence of fuel rod cladding frettingwear.

Basic characteristics of TVS-2M Fuel rod TVS-2M

 The extended length of fuel column reduces the average load onto fuel rod which contributes to safety.

2

 The fuel column length extension along with an increase in the outer diameter and a decrease in the inner diameter of the fuel pellet increments the mass of UO2 in the core which allows reducing the number of make-up FAs or extending the length of the fuel cycle.

 Fuel rods with claddings made from E110 zirconium alloy with increased content of UO2, with a collet-type lower plug.  Fuel column height is 3680 mm.

TVS-2M

Rigid welded skeleton for TVS-2M  The rigid skeleton formed by spacer grids welded to the guide tubes.  The guide tubes of zirconium alloy E635.  The basis of TVS-2M is a rigid skeleton formed of spacer grids welded to the guide tubes. The rigid welded skeleton is the basic innovation in the TVS-2 design not previously applied in Russian FAs.

 The spacer grids rigidly connected to the guide tubes form a skeleton, a truss structure with a bending resistance significantly greater that the resistance in case such ties are not available. The in-service bending rigidity of the skeleton remains actually at the same level due to rigid connection of spacer grids to the guide tubes. Tie weakening (mechanical friction) between the fuel rods and the spacer grid cells in the course of the operation does not result in a critical decrease in the TVS-2M bending rigidity which ensures the possibility for FA to resist to the bending loads during the entire service life.  An additional spacer grid was introduced in the lower part of the skeleton to perform the function of an antivibration grid, which has increased the vibration resistance of the lower part of TVS-2M.  The spacer grids are located along the TVS-2M height with the basic pitch of 340 mm in such a way that the TVS-2M can be loaded into VVER-1000 core loaded with FAs containing other number of spacer grids (8, 12, 15).

TVS-2M spacer grid  Spacer grids made of zirconium alloy E110 providing fuel rod slipping without sticking, а reinforced rim.

3

TVS-2M top nozzle  A detachable cap without d eta ch a b l e/re p l a cea b l e fasteners as well as the design of the upper and lower plugs of the fuel rod allow a remote removal and replacement of the failed fuel rod under the conditions of NPP using the standard fuel repair and inspection equipment.

TVS-2M bottom nozzle with anti-debris filter

 A short-cut bottom nozzle of TVS-2M with an anti-debris fi lter which ensures trapping the particles with a size above 2 mm and a considerable part of smaller particles.

4

TVS-2M

Basic characteristics of TVS-2M Parameter

Value

TVS-2M shape

Hexahedral prism

Fuel rod (Gd fuel rod) arrangement

Uniformly triangular

TVS-2M height, mm

4570±1

Maximum allowable width across the fl ats for fresh TVS-2M, mm

235,1

Mass of TVS-2M, kg, nominal

738

Height of the fuel column active part, mm: - in TVS-2M with blankets - in TVS-2M without blankets

3530 3680

UO2 (UO2+Gd2O3)mass in the active part of the fuel column, kg: - in TVS-2M with blankets - in TVS-2M without blankets

505,4 527,0

Pitch between fuel rods (across the triangle grid), mm

12,75

Spacer grid: - quantity, pcs. - material

13 alloy E110

Guide tube: - quantity, pcs. - material

18 alloy E635

Instrumentation tube: - quantity, pcs. - material

1 alloy E635

Fuel rod/Gd fuel rod: - quantity, pcs. - material - outer diameter of the cladding, mm - inner diameter of the cladding, mm

312 E110 9,1 7,73

Maximum permissible burn-up averaged on TVS-2M, MW•D/ kg U

68

5

High reliability characteristics of the cores with TVS-2M were experimentally verified:  in testing facilities (pre-irradiation studies);

 by operational experience (inpile verification).

Pre-irradiation studies Mechanical tests of two-span FA dummies:  forcing the bundle of fuel rod claddings through a two-span FA dummy (with a transverse bow of 0, 1, 2, 3 mm) with a determination of the parameters of spacer grid deplanation;

Mechanical tests on fragments:  tests of fuel rod dummies for rotation;  tests of fuel rod dummy pulling through;  tests to determine the rigidity for GT turning;

SG

 tests of the two-span FA dummy for spacer grid rim tear-off;

 tests for GT pushing through (determination of the force of GT-to-SG welded joint);

 tests for spacer grid compression in plane.

 tests for GT-to-lower grid mating pair destruction.

Scope of justification using FA experimental specimen (dummy)

6

Test

Purpose

Shop tests

Dummy parameter monitoring in the course of manufacturing

Mechanical tests

Measurement of rigidity and shape of the skeleton and dummy bowing under transverse loading

Hydraulic tests

Determination of actual values of pressure loss coeffi cients for FA and separate fragments

Endurance tests

Justifi cation of FA service life under the conditions that simulate actual ones

Vibration tests in the air

Determination of frequencies, shapes and damping coeffi cients of natural vibrations of FA dummy and fuel rods

Termomechanical (thermocyclic) tests

Determination of transverse deformations of dummy at cyclic variation of temperature and simulation of non-simultaneous elongation of fuel rods and GT

Vibration tests in cold water fl ow

Determination of frequencies, shapes and natural vibration damping coeffi cients for FA dummy in coolant fl ow. Determination of resonance frequencies and response characteristics of the dummy

Seismic tests in coolant fl ow at (40±5)0C

Determination of FA vibration response for seismic impacts in coolant fl ow. Determination of the time taken by RCCA to drop

TVS-2M

Reactor justification  TVS-2M have been operated since 2006 at six power units with RP V-320 in Russia (Balakovo NPP and Rostov NPP) gradually replacing TVS-2.  In 2011 six pilot TVS-2M were loaded into the core of Tianwan NPP Unit 1 (China) fuelled with UTVS fuel assemblies.  Five power units with TVS-2M have been operated at uprated power (104 % of nominal).  Load factor of the power units has reached more than 90%.  Since 2006 till August 2011 720 TVS-2M (with axial blankets and without axial blankets) were loaded into the reactors.

 The refueling of the core with TVS-2M takes place at elevated rates without exceeding the setpoint of 75 kgf assigned for the fuel handling machine.

 The reactor core of Rostov NPP Unit 1 has been completely formed by TVS-2M without blankets since the fi rst loading.  Not a single TVS-2 or TVS2M has been mechanically damaged within the entire service life. The tests performed have shown that the tear of the spacer grid rims in TVS2M is actually impossible as it takes place at forces not less than 5220 N which is more than twice above the maximum allowable change in FA weight at fuel handling procedures at a NPP.

 The zero defect concept has been actually implemented at the power units with TVS-2M.

 The time of RCCA drop in the cores with TVS-2 and TVS-2M are steadily at the level of 2 seconds. The time taken by each RCCA to drop is strictly controlled before and after the core refueling.  The forces of RCCA motion are less than 6 kgf.

TVS-2M introduction schedule 2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

Balakovo NPP Power unit 1

Balakovo NPP Power unit 2

Balakovo NPP Power unit 3

Balakovo NPP Power unit 4

Rostov NPP Power unit 1

Rostov NPP Power unit 2

Tianwan NPP Power unit 1 TVS-2 loading Loading of TVS-2M with blankets Loading of blanket-free TVS-2M

Transfer to a 18-month cycle Power uprating to 104 %

7