ML20151W740

Responds to Re Concerns of 750801 Oroville Earthquake & 860721 Bishop Earthquake W/Respect to Safety of Facility.Allegations Provided No Basis for Safety Concern W/Respect to Seismic Design of Plant

ML20151W740
Person / Time
Site:	Rancho Seco
Issue date:	04/26/1988
From:	Murley T Office of Nuclear Reactor Regulation
To:	Southard E AFFILIATION NOT ASSIGNED
Shared Package
ML20151W743	List: ML20151W740 ML20151W768
References
NUDOCS 8805030476
Download: ML20151W740 (6)

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APR 2 61988-Ms. Elaine Southard 5691 Connie Court Loomis, CA 95650

Dear Ms. Southard:

This is in response to your letter addressed "To Whom It May Concern," dated February 18, 1988, a copy of which you mailed to Victor Stello, Jr., the Executive Director for Operations of the Nuclear Regulatory Comission (NRC).

The concerns you expressed in your letter about the August 1,1975 Oroville earthquake and the July.21, 1986 Bishop earthquake with respect to the safety of the Rancho!Seco"plantiare similar to those you expressed in your 1986 postcard to Senator Alan Cranston. These issues were addressed in the letter to Senator Cranston from Victor Stello, Jr., dated November 12, 1986, which you referred to in your February 18, 1988 letter. The letter from Stello to Cranston contained a sumary of the NRC staff's evaluation of these two earthquakes with respect to the Rancho Seco plant and an explanation of why they are not considered a safety concern to the plant. Since then, the NRC staff has continued its review of the geology and seismology of the Rancho Seco area. As a result of the NRC staff's request for additional information in June 1986, Sacramento Municipal Utility District (SMUD) undertook additional geologic field work. SMUD submitted a report on this work in October 1987.

As part of the review program, NRC and State of California staff participated in a geologic field trip and plan another field trip (with SMUD consultants in attendance) in the near future.

The Poorman Gulch fault, which is currently assumed to be the nearest

, capable fault, is about 20 miles from the Rancho Seco plant site. SMUD i estimated a maximum earthquake magnitude for this fault of 6 and calculated the mean peak ground acceleration at the plant from this size earthquake as 0.12 g. The NRC staff has not completed its review of this item. However, at this time, we do not consider it to be a significant safety concern that had to be resolved before restart of the plant. The China Gulch fault, a minor fault, appears to be about 13 miles from the Rancho Seco site. We have not as yet determined whether this fault is capable. One reason for the upcoming field trip is to inspect this fault. If the China Gulf fault is determined to be capable, the maximum earthquake magnitude for this fault will be calculated. Then the estimate of the resulting vibratory ground motion will be compared to the seismic design of the plant to see if it is of safety i significance.

, Your letter also refers to an article in the November 19, 1979 New West Magazine about allegations made by Mr. Ron Clary as to errors made in the seismic design of the cooling towers and spent fuel building for Rancho Seco.

In May 1978, the Nuclear Regulatory Comission's Office of Inspection and Enforcement investigated these allegations. The investigation included '.

interviews with the alleger, with SMUD personnel, and with Bechtel Power Corporation employees. The following is a sumary of the findings and conclusions of that investigation.  ;

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Ms. Elaine Southard Among the findings with respect to the allegation made about the spent fuel storage building are the following:

Records of design calculations and checks do not indicate that the alleger performed calculations or checks for the spent fuel storage building design.

All the calculation sheets for the spent fuel storage building were examined for evidence of involvement by the alleger. None of these sheets bore the alleger's name or initials, nor do any of the drawings for this structure bear his name or initials. The original design and design calculations were checked between July 1968 and May 1970. Records of design calculations for the spent fuel building during this period are contained in a single, bound record. After the original design work was completed, more checks were performed. In March 1971, wind loading on the building was checked. In February 1972, thermal stresses were checked. In March 1972, the ability of the structure to withstand a cask drop was analyzed. In 1975, the building structure was again analyzed in connection with the increase in capacity to store spent fuel.

Employment records do not indicate that the alleger would have performed design or design check calculations.

NRC investigators asked for employment statistics. Bechtel's check of personnel files showed that the alleger was employed from July 14, 1969 to May 12, 1972. He was initially employed for non-nuclear design work on a military project. He was first assigned to Rancho Seco in March 1971.

Bechtel personnel refute the contention that the alleger was ever assigned work on the spent fuel storage building.

The Vice President and Manager of Operations, Los Angeles Division; the Chief Civil Structural Engineer; and the Engineering Group Supervisor did not recall having assigned the alleger work on the spent fuel storage building.

Bechtel personnel do not recall any incident involving an error-of-one magnitude which was ignored in the spent fuel storage building design.

The incident as described by the NRC investigators did not coincide with any incidents in the memory of Bechtel personnel regarding the spent fuel storage building design. However, they noted that the alleger was an extremely conservative designer and that he often accepted direction to design more conventionally with reluctance.

The spent fuel storage building design has been subjected to checks by competent designers.

The structure was reanalyzed in 1975 by a competent structural engineer to determine its adequacy for increased fuel storage capacity. No problems were noted. Also, in 1978, the original fuel storage pool

Ms. Elaine Southard design engineer examined all changes that had been made to his original calculations and he was satisfied that the changes that had been made were appropriate. This engineer is a professional engineer who has both civil and structural qualifications in California.

The NRC investigators concluded that the above findings indicate that the design of the spent fuel storage building could not have been adversely affected by the incident described, if in fact it did occur. None of these findings provide any evidence that such an incident actually took place in the manner described by the alleger.

Among the findings with respect to the allegation made about the natural draft cooling towers are the following:

The natural draft cooling towers are not safety-related structures.

According to Section 5.5.3 of the final safety analysis report (FSAR),

these structures are classified as Class II. This means that the loss of function of these structures would interrupt power generation.

However, this does not pose a threat to the health and safety of the public, since the plant could still safely shut down and the integrity of the reactor coolant pressure boundary would not be adversely affected.

The controlling design criterion for the natural draft cooling towers is wind loading.

Section 5.5.3 of the FSAR states that wind load was the controlling factor in cooling tower design. However, in the same section it states that "an independent check of the design indicates that the towers can withstand the Class I operating basis earthquake." The operating basis earthquake has a peak aorizontal ground acceleration of 0.13 g.

In the event of their collapse. the cooling towers will not affect other equipment.

The NRC (AEC) addressed this issue at the time of the nperating license review. Bechtel had analyzed the type of collapse that would most likely occur. The failure mode correlated with the available experience on cooling tower failure.

The above findings led the NRC investigators to conclude that the collapse of the cooling towers was not a threat to nuclear safety and the allegation was not substantiated. In searching for possible sources for the alleger's concern about the San Fernando earthquake, the NRC investigators noted that the scientific community had paid particular attention to the high acceleration readings at the Pacoima Dam and that Bechtel itself was very interested in the damage to the nearby Sylmar Converter Station which Bechtel had designed. The investigators stated that such items as this would certainly have resulted in general speculation about other structures and possibly hsve led to the concern expressed by the alleger. However, it should be noted that Federal regulations do not require that nuclear power plant structures be designed to

Ms. Elaine Southard the largest ground motion ever recorded anywhere in the world but, rather, to an earthquake that is based upon an evaluation of the maximum earthquake potential considering the regional and local geology and seismology and specific characteristics of local subsurface materials for the plant -ite. Therefore, the San Fernando earthquake Pacoima Dam data would not necessarily be used as the design basis for Rancho Seco. In fact, the seismic design basis for nuclear power plants is usually dettrmined by the statistical analysis for a suite of ground motion data from apprcpriate size earthquakes made at suitable distances.

The following are other findings that the investigating team thought night possibly be related to the allegations:

Use of incorrect grou'id acceleration in design of the plant vent structure.

Investigators found that the principal Rancho Seco design activity of the alleger concerned the plant vent. In attempting to locate a source for the alleger's concern, it was noted that the calculations for the buttress configuration (vertical portion of the vent) contained a note reading - "Use .036 g design min, per Bill Brandes, Proj. Engr. (over the above designer's objections)."

On the following page, it was noted that the use of this low acceleration value (obviously in erior by a decimal point) resulted in a very small load for the vent duct bracing. Immediately following this notation was a calculation for wind loading which exceeded the erroneously calculated seismic loading by a factor of 11. Since wind loading was more than a factor of 10 greater than the seismic loading, the investigators found the question of whether to use .036 g or .36 g for the seismic loading was academic.

As previously stated, the geology and seismology studies for the Rancho Seco plant are continuing. On the basis of its currant knowledge, the staff concludes that there is no innediate seismic hazard at the site and it is not necessary for the seismic study to be completed prior to plant startup.

l However, we intend to make a complete evaluation of all the new information to determine its impact on the plant. With respect to the New West Magazine report you referred to in your letter, the NRC Office of Inspection and Enforcement investigated the allegations.

This investigation included interviewing the alleger. The NRC concluded that the allegations provided no basis for a safety concern with respect to the seismic design of the plant.

Sincerely, Thomas E. Hurle , irector Office of Nuclear Reactor Regulation

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Ms. Elaine Southard 5-4 DISTRIBUTION:

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CONCERNING SAFETY AT RANCHO SECn NllCLEAR POWFP JMARTIN PLANT MURRAY DATE: 02/7'2/88 ASSIGNED Tn: NPR CONTACT: Mt.lRL E Y SPECIAL INSTRUCTIONS OR REMARKS:

FOR APPROPRIATE ACTION NRR RECEIVED: FEBRUARY 23, 1988 I ACTION: N NB DIh'. g6 b f( '

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