qualified expert in the subject of corrosion, Rudolf Hausler, has reported in a
memo to objectors to Oyster Creek Nuclear Generating Station that the base of
the steel liner of the containment is at risk of corrosion, and that if it is
"THE ENTIRE STRUCTURE IS NOT ONLY IN DANGER OF BUCKLING, BUT INDEED OF COLLAPSE."
Although they have known of the vulnerability of the steel liner to corrosion since the 1980's, the NRC and reactor operators have neither required nor performed ultrasound inspections on the portion of the steel liner most obviously vulnerable to corrosion -- the interface between the steel liner and its concrete base.
What they have done -- more than ten years ago -- is to perform ultrasound testing on other portions of the steel liner, which they found to be less than 0.1" above minimum required thickness, and considerably corroded since original construction during the 1960's.
Objectors are asking that the NRC require comprehensive ultrasound testing as a prerequisite for a 20 year license extension to 2029 [which would make the plant 60 years old.]
My opinion is that if a competent expert thinks the plant may be at risk of buckling and collapse, and if the NRC is so feckless as never to have required testing of the area most vulnerable to corrosion, then the plant should be taken offline today and tested immediately before being allowed to restart.
Unfortunately Governor Corzine, Senator Menendez, Senator Lautenberg, Congressman Saxton, and the others do not care to engage in leadership on this issue.
Rudolph Hausler's 2 1/2 page memo and diagram are attached. (below)
Unplug Salem Campaign; Coalition for Peace and Justice;
321 Barr Ave; Linwood NJ 08221
8081 Diane Drive Rudolf H. Hausler Kaufman, TX 75142 Tel: 972 962 8287 (office)firstname.lastname@example.org Fax: 972 932 3947
Tel: 972 824 5871 (mobile)
To: Mr. Paul Gunter, Director February 4, 2006
Reactor Watchdog Project
Nuclear Information and Resource Service
Washington DC 10036
Mr. Richard Webster, Esq.
Rutgers Environmental Law Clinic
123 Washington Street
Newark, NJ 07102-5695
From: Dr. Rudolf H. Hausler, President
Subject: Oyster Creek Drywell Liner Corrosion
The present memorandum is a follow-up to my earlier communication regarding the subject of the Oyster Creek Nuclear Reactor Drywell corrosion in the area of the sand bed, also called the sand pocket region ). This earlier Memorandum essentially focused on severe localized corrosion, which had been first observed in 1980, and quantitatively assed in the accessible areas of the sand bed region during the period of 1992 to 1993, and the resulting need for extensive direct assessment of the extent of corrosion prior to re-licensing the Oyster Creek Nuclear Plant for and additional 20 years.
The sand bed had been removed during the period of 1988 to 1992, and the outer surface of the liner in this area coated with an epoxy coating. As a consequence of these actions it is held that corrosion very likely shifted from the upper sand bed region to the lower sand bed region. In view of the fact that it had been determined that past NRC guidance relating to deterioration of the imbedded steel containment shell or liner was insufficient , it appears to be timely to revisit the question of corrosion in the concerned areas.
The attached Figure 1 shows a schematic of the lower part of the drywell liner and details of structure sitting in a concrete (bed) foundation. This schematic is an abstraction of a similar schematic shown in the notes of Reference 2. The abstraction was made to clarify the areas of concern. The liner essentially sits in a concrete foundation and is filled with concrete on the inside (the concrete floor). The level of the concrete on the inside is higher than the level of concrete on the outside. This difference in height necessitated the sand pocket in order to prevent the liner from bulging outward (buckling).
As long as the sand bed was present, the bulk of the corrosion occurred at the top of, or just below, the sand bed region and could be monitored by UT measurements from the inside above the concrete floor (see Fig. 1). However, corrosion occurring on the outside in the sand bed region below the level of the inside concrete floor, could only be observed visually, and only to the extent that the corroded areas were accessible to visual inspection. It was basically assumed that the corrosion in the inaccessible areas on the outside of the liner in the sand bed region would be equal and no more severe than what had been assessed with the UT measurements in the accessible region (see Fig.1). In order to prevent further corrosion on the outside of the liner in the sand bed region this area was coated with an epoxy coating, presumably in all areas that were accessible to this operation.
It is now proposed to verify the integrity of the coating and its prevention of further corrosion with renewed UT inspections. However, as can be seen from Fig. 1, this can only be done for a fraction of the area in question, and the limited usefulness of visual inspection from the outside has been discussed earlier (ref. 1).
However, a potentially more dangerous situation has developed through the removal of the sand bed. Corrosion always occurred in the sand bed region through leakage of water from various sources above in the cylindrical portion of the liner. There is no reason to believe that such leakage was entirely stopped, and therefore it is equally reasonable to believe that water accumulations at the bottom of the earlier sand bed continued to be present, and there is no assurance that the drainage channels were entirely effective to evacuate such water accumulations. As a consequence corrosion developed at the concrete steel boundary on the outside of the liner in the area which would not ever have been accessible to UT inspection from the inside (see Fig. 1). Although the outside to the liner had originally been coated with corrosion-preventive red lead paint, such corrosion protection was not effective over time, as the corrosion in the sand bed area demonstrated.
It is therefore submitted that localized corrosion necessarily occurred on the outside of the liner at the concrete-steel boundary. It is well known that steel in contact with concrete, water and air, will start to corrode fairly rapidly, particularly if cracks develop. This is known from the fact that rebar imbedded in concrete will start to corrode if water can penetrates the concrete through cracks. Thermal expansion at the location indicated in Fig. 1 as the “UT inaccessible areas” will cause the concrete to disbond from the steel, resulting in cracks and crevices, and thus initiate local corrosion. Since the volume of the resulting iron oxide is larger than the volume of the steel from which it grew, the corrosion products will force the crack to widen, hence accelerating the process. It is well known that concrete thus affected by corrosion of rebar will eventually spall off and expose the rebar to the environment. It can reasonably be expected that the same thing has happened on the outside of the liner in this three-phase boundary (steel/concrete/water-air) designated as the “inaccessible areas”.
If in fact these processes occurred, and this is precisely the subject of much needed verification, the entire structure is not only in danger of buckling, but indeed of collapse from the weight of the liner and the weight of the concrete floor, much aggravated by the absence of the sand bed, i.e. additional support on the outside of the liner. Clearly such inspection requires the most sophisticate tool and is a challenge to the industry. However, the challenge arising from a collapse of the liner will be order of magnitude greater.
Respectfully submitted by
Rudolf H. Hausler