Contaminated concrete scabbling at the Shippingport Station Decommissioning Project

At turnover, there were several areas in the plant where radioactive contamination was entrained in concrete surfaces. The walls and floors of the refueling canal representing the primary source of contaminated concrete at the SSDP. The residual contamination levels in the refueling canal were low and it was not certain that concrete decontamination would be required, as the site release criteria had not been formally established. The primary isotope of concern was Co-60. The mean concentration of radioactivity entrained in the concrete surface was measured at 11,200 pCi/gm. Exposure rates adjacent to the walls averaged 3 mRem/hr. The technical specification for concrete decontamination was initially prepared as a contingency measure in parallel with the development of the site release criteria. The Decommissioning Operations Contractor (DOC) prepared this specification to be utilized if the final approved release criteria required it; or, to avoid future project delays in the absence of an approved site release criteria. With the receipt of DOE guidance for development of the site release criteria (100 mrem/yr to the maximum exposed individual), it was determined that the refueling canal did not meet the occupancy scenario requirements. The DOC subsequently issued the bid package and awarded the subcontract for the removal of contaminated concrete. This summary highlights some of the management decisions and engineering considerations for the removal of the contaminated concrete at the SSDP. The paper will give further background to the engineering decisions, concrete decontamination practices and experience. 2 refs