Extensive infrastructure exists for the transport of natural gas and it is an obvious step to assess its use for themovement of hydrogen. The Naturalhy project?s objective is to prepare the European natural gas industry forthe introduction of hydrogen by assessing the capability of the natural gas infrastructure to accept mixturesof hydrogen and natural gas. This paper presents the ongoing work within both Durability and IntegrityWork Packages of the Naturalhy project. This work covers a gap in knowledge on risk assessment requiredfor delivering H2+natural gas blends by means of the existing natural gas grids in safe operation.Experiments involving several parts of the existing infrastructure will be described that are being carried outto re-examine the major risks previously studied for natural gas, including: effect of H2 on failure behaviourand corrosion of transmission pipes and their burst resistance (link to the Work Package Safety), onpermeability and ageing of distribution pipes, on reliability and ageing of domestic gas meters, tightness toH2 of domestic appliances and their connexions. The information will be integrated into existing Durabilityassessment methodologies, originally developed for natural gas.An Integrity Management Tool will be developed taking account of the effect of hydrogen on the materialsproperties. The tool should enable a cost effective selection of appropriate measures to control the structuralintegrity and maintaining equipment. The main measures considered are monitoring, non destructiveexamination (pigging and non pigging) and repair strategies. The tool will cover a number of parameters,e.g.: percentage of hydrogen in the gas mixture, material of construction, operating conditions and conditionof cathodic protection. Thus, the Integrity Management Tool will yield an inspection and maintenance planbased on the specific circumstances.