United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No.80-09 – Possible Occupational Health Hazard Associates with Closed Cooling Systems for Operating Power Plants

                                                            SSINS: 6870 
                                                            Accession No.: 
                                                            7912190681

                                UNITED STATES
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                               March 7, 1980  

                                            Information Notice No. 80-09 

POSSIBLE OCCUPATIONAL HEALTH HAZARD ASSOCIATES WITH CLOSED COOLING SYSTEMS 
FOR OPERATING POWER PLANTS 

As a result of information that the causative agent for meningoencephalitis,
the amoeba Naeglaria fowleri, had been found in warm water ponds in Florida 
and Texas where two fatalities were reported, NRC initiated a study by Oak 
Ridge National Laboratory on the occurrence of Naeglaria in power plants 
with closed cycle cooling systems. For seven power stations examined (6 
fossil, 1 nuclear), this study confirmed the presence of pathogenic 
Naeglaria at three plants including the nuclear plant (Dresden). 

Recently, Northern States Power Company (NSP), while monitoring the Prairie 
Island Nuclear Generating Plant closed cooling system for the amoeba, did 
identify the presence of Naeglaria. Although the Minnesota Department of 
Health does not  consider the existence of the organism to be a public 
health threat, it was recognized as a possible occupational health hazard. 
Plant personnel were instructed to wear rubber gloves when coming into 
contact with the circulating water and to wear respirators when working in 
the area of the cooling towers. In November 1979, NSP conducted a special 
chlorination program at Prairie Island that was designed by Dr. Richard 
Tyndall of Oak Ridge to eradicate this organism. Chlorine concentrations in 
the circulating water system was raised to 2.0 mg/l (measured as free 
chlorine) for a period of six hours to destroy both the amoebae and its 
encysted form. This program also included dechlorination prior to discharge 
and intensive monitoring to document chlorine concentrations, the impacts of 
chlorinated cooling tower draft and sampling to determine the efficacy of 
the special chlorination program in destroying Naeglaria. Preliminary 
results indicate that the program was successful in reducing the number of 
organisms present by two to three orders of magnitude. 

It is recognized that there have been no reported cases of 
meningoencephalitis reported among power plant personnel to date; however, 
the seriousness of the disease (if contracted) and the confirmed presence of
Naeglaria at four plants, leads us to inform all licensees with closed cycle
cooling water systems of the potential occupational hazard and advise that 
they take appropriate action. 

No written response to this Information Notice No. is required. If you desire
additional information regarding this matter, contact the Director of the 
appropriate NRC Regional Office. 

Page Last Reviewed/Updated Tuesday, November 12, 2013