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SHIELDING FOR PLUME RADIATION AND ASSESSMENT OF FACTORS INFLUENCING INDOOR RADON EXPOSURE

Objective

PROJECT 1: SHIELDING FACTOR CALCULATION FOR PLUME RADIATION.
THE FIRST PROJECT AIMS AT OBTAINING SHIELDING FACTORS FOR PERSONS STAYING INDOORS RELATIVE TO EXTERNAL GAMMA-RADIATION FROM NOBLE GASES IN A PLUME DERIVED FROM A REACTOR ACCIDENT.
PROJECT 2: INVESTIGATION OF FACTORS INFLUENCING INDOOR RADON CONCENTRATION. THE OBJECTIVE OF THE SECOND PROJECT IS TO INVESTIGATE THE FACTORS INFLUENCING INDOOR RADON CONCENTRATIONS. AMONG THESE FACTORS ARE EXHALATION FROM BUILDING MATERIALS, INGRESS OF RADON FROM THE GROUND AND AIR EXCHANGE RATE IN THE HOUSE.
A computer model has been developed for calculating the protection, both indoors and outdoors, afforded by buildings against gamma radiation from a passing radioactive plume. Important parameters such as building structure dimensions, window apertures, plume and building geometries and photon energy have been identified by means of parametric studies. Protection factors for typical European houses have been calculated and representative shielding factors for European housing conditions have been estimated.
PROJECT 1: - THE RESEARCH WORK FALLS INTO THREE PARTS:
1. DEVELOPMENT OF A COMPUTER MODEL THAT CALCULATES THE INDOOR DOSE RATE IN DIFFERENT HOUSE TYPES FROM A GAUSSIAN PLUME.
2. A SENSITIVITY ANALYSIS OF THE INDOOR DOSE RATE DEPENDENCE ON ATMOSPHERIC STABILITY, PLUME HEIGHT, DOWN-WIND AND CROSS-WIND DISTANCE FOR SELECTED HOUSE TYPES AND PHOTON ENERGIES.
3. CALCULATION OF REPRESENTATIVE SHIELDING FACTORS FOR TYPICAL EUROPEAN HOUSES.
AD 1. THE MODEL WILL CALCULATE KERMA IN AIR INDOORS FROM A VOLUME INTEGRATION OF THE POINT-SOURCE KERNEL CONSISTING OF INVERSE SQUARE AND EXPONENTIAL ATTENUATION FACTORS AND A BUILD-UP FACTOR THAT ACCOUNTS FOR SCATTERED PHOTONS. A METHOD BASED ON APPLICATION OF ADAPTIVE NUMERICAL QUADRATURE IS ALREADY IN USE IN THE DANISH PLUME DOSE MODEL PLUCON. THIS WILL FORM THE BASIS FOR THE SHIELDING FACTOR MODEL.
AD 2. A PARAMETER STUDY WILL BE MADE FOR SELECTED HOUSE TYPES AND PHOTON ENERGIES. THE STABILITY, PLUME HEIGHT, DOWN-WIND DISTANCE, AND CROSS-WIND DISTANCE WILL BE VARIED IN ORDER TO FINDSHIELDING FACTORS REPRESENTATIVE FOR DIFFERENT HOUSE TYPES AND AREA TYPES(URBAN/SUB-URBAN AREA).
AD 3. FOR TYPICAL EUROPEAN HOUSES SHIELDING FACTORS WILL BE CALCULATED. THESE RESULTS TOGETHER WITH THE RESULTS FROM THE PARAMETER STUDY WILL BE USED TO RECOMMEND SHIELDING FACTORS FOR SOME TYPICAL HOUSES WITHIN THE COMMUNITY.

PROJECT 2- THE SUBJECT OF THE INVESTIGATION IS A GROUP OF DETACHED HOUSES BUILD ON THE SAME LOCATION. THE HOUSES ARE OF IDENTICAL STRUCTURE, BUT MARKET DIFFERENCES OF RADON CONCENTRATIONS IN THE HOUSES HAVE BEEN FOUND. PRELIMINARY MEASUREMENTS OF RADON IN SOIL GAS AND RADON EXHALATION RATES FROM SURFACE TO AIR SHOW GREAT DIFFERENCES WITHIN THE SITE OF THE HOUSES. LIKEWISE GREAT DIFFERENCES IN AIR EXCHANGE RATE HAVE BEEN FOUND.
THE INVESTIGATION SHALL REVEAL THE CONNECTIONS BETWEEN THE INFLUENCING FACTORS. SIMULTANEOUS MEASUREMENTS WILL BE MADE OF RADON CONCENTRATIONS IN SOIL GAS, EXHALATION RATE FROM SOIL TO AIR, AIR EXCHANGE RATE FOR THE HOUSES AND INDOOR RADON CONCENTRATIONS.
THE SOIL MEASUREMENTS WILL BE DONE BY EXTRACTING SOIL GAS FROM A SUITABLE DEPTH THROUGH SCINTILLATION FLASKS. FOR THE MEASUREMENTS OF EXHALATION RATES AROUND THE HOUSES A PASSIVE DOSEMETER WILL BE USED.
THE GEOLOGICAL CLASSIFICATION WILL BE BASED ON SOIL AND SUBSOIL SAMPLES. THIS PART OF THE PROGRAMME WILL BE CO-ORDINATED WITH INVESTIGATIONS DONE BY THE DEPARTMENT OF ELECTROPHYSICS, TECHNICAL UNIVERSITY OF DENMARK OF THE PERTINENT CHARACTERISTICS OF THE SOIL, I.E.CONTENT OF RADIUM 226, EMANATING POWER AND PERMEABILITY.
THE RATE OF AIR EXCHANGE IN THE HOUSES WILL BE MEASURED BY THE TRACER GAS (SF6) TECHNIQUE UNDER DIFFERENT, CONTROLLED VENTILATION CONDITIONS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

RISOE NATIONAL LABORATORY
Address
P.o. Box 49
4000 Roskilde
Denmark