ML20073S459

Research News.Volume 7,Number 1

ML20073S459
Person / Time
Issue date:	05/31/1994
From:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:
References
NUREG-BR-0112, NUREG-BR-0112-V07-N1, NUREG-BR-112, NUREG-BR-112-V7-N1, NUDOCS 9406060091
Download: ML20073S459 (10)

Text

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Q$$.)RESE ARCH NEWS OFFICE OF NUCLEAR REGULATORY RESEARCH U.S. NUCLEAR REGULATORY COMMISSION l

MAY 1994 l

VOLUME 7, NUMBER 1 i

i The Move to Two White Flint North can work better and be more productive We can arrange meetings more easily and get to them Eric S. Beckjord, Director, RES quicker. Our business with NRR, NMSS. AEOD, and other offices will improve through more fre-l The Office of Nuclear Regulatory Research will quent face-to-face exchanges, stronger working relationships, and better coordination of research l

move in late May and early June to the newly com-and regulatory products. I am confident that pleted Two White Flint North Building, a move that TWFN will be a big plus for RES and for the NRC.

will gather in one place the N RC's entire headquar.

ters staff. For the first time the Research Office will As we get ready to move in the days ahead, I ask be collocated with other program offices.

you to keep the positive factors of the move in Personally I look forward to the new office environ.

mind. We have a big opportunity ahead.

ment where we can carry out our responsibilities better, because we will be near the offices that w Reliability and Risk Methods Can work with daily.

improve Techn.ical Specif.ications l

I am aware of inconveniences connected with our and Operational Safety move, but I ask you to think for a moment about the many advantages we will have, including:

Carl Johnson, RES/DSR/HFB a magnificent view, almost full circle, from Most reactor technica! specifications reflect the l

e around the periphery of the 9th and 10th premise that if safety equipment fails, the safest Hoors action is to shut down the reactor. However, if the e

new and modern furniture safety equipment is needed during shutdown, would continuing power operation be safer than new clean carpeting and surroundings shutting down?

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new modern restroom facilities The Office of Nuclear Reactor Regulation (NRR) temperature control and a clean air system e

l asked the Office of Nuclear Regulatory Research well designed work places (RES) to develop risk-based methods to evaluate e

an improved computing network this question and several similar issues regarding e

surveillance test intervals, allowed outage times, e

a better environment for RES visitors and the use of allowed outage times for preventive maintenance.

Most important to me, however, is the opportunity of the headquarters location. Because of it, we This article describes the research results.

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Supplement PRAs with Reliability Analysis boiling water reactor, shutting down the reactor to Tools repair failed trains of standby service water, residu-al heat removal, or emergency diesel generators The technical approach is to supplement existing did not necessarily reduce the estimated likeli-probabilistic risk assessments (PR As) with reliabil.

hood of core damage, compared to promptly re-ity analysis tools to address specific issues. These painng the equipment during power operation.

reliability tools can evaluate operational safety is-sues in terms of their impact on the availability of To confirm this preliminary result for the AFW ex-safety systems and the frequency of initiating ample, additional analysis will include cross con-events. These parameters serve as input to exist.

nections among systems at a multeunit site and ing PRAs. Figure 1 illustrates this conceptual ap.

will evaluate whether this preliminary result applies proach.

to only one plant or to other plants as well.

t Regulatory Applications Example of Approach To Optimize Maintenance Intervals NRR's Technical Specifications Branch and Prob-abilistic Safety Assessment Branch have used The maintenance rule requires licensees to bal-these methods to he!p evaluate proposed ance competing objectives. Licensees must en-changes in technical specifications. Also, another sure that the objective of preventing equipment RES Branch, the Probabalistic Risk Analysis failures is appropriately balanced against the ob-Branch, recently used these methods to review the jective of minimizing equipment unavailability South Texas technical specifications.

caused by preventive maintenance.

Also, the tools may have broader application. For To analyza this balance, the following approach is example, in 1992, the New York Power Authority used. Whereas many reliability analyses consider briefed the Commission on the feasibility of using equipment in two states, i.e., operational or f ailed, these tools in a joint pilot project with N RC to evalu-this analysis includes a third state, degraded. In ate risk-based regulation.

this degraded state, equipment can still function.

but needs maintenance to continue functioning re-Two examples illustrate these tools' capabilities.

liably. This degraded equipment can be restored by periodic maintenance. With data on failure Example of Action Statements Requiring rates and degradation rates, the model (called a Plant Shutdown Markov model) can estimate the effect of mainte-nance intervals on the probability that the equip-At one plant that was analyzed, technical specifi-cations require immediate shutdown if two trains in principle, the method has the potential to esti-of auxiliaryfeedwater(AFW)areinoperable. How-mate optimal maintenance intervals to minimize ever, preliminary research results indicate that system unavailability and the likelihood of core shutting down the reactor to repair AFW increases damage. However, the method has not yet been the likelihood of core damage compared to contin-tested with plant data.

uing power operation with prompt AFW repair dur-ing power operation. A comparison by B N L is illus-trated in Figure 2, The reason is that AFW may be Outlook needed during shutdown if a transient occurs, and the frequency of transients increases during ma-The reliability tools illustrated in these examples neuvering the reactor from full power to shutdown.

can supplement plant-specific PRAs to evaluate the risk implications of specific issues, e g., sur-Examples of other systems needed during shut-veillance test intervals, allowed outage times, down show a similar trend. For example, in limited scheduling of preventive maintenance, and action analyses of one pressurized water reactor end one statements requiring shutdown.

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e Maintenance Performance Assessment Figure 1. Conceptual approach to develop methods to evaluate the risk impact of requirements in technical specifications 1.0E - 0 2 r l

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The resulting risk perspective can aid in reviewing The field guide was Dr. Lawrence McKague, these issues to make NRC requirements more ef-CNWRA, an author of the field guidebook, "The fective while avoiding unnecessary burden, thus Geology of the Nevada Test Site and Surrounding enhancing operational safety.

Area" (American Geophysical Union,1989). High-lights of the geologic portions of the field trip in-cluded observations of exposed volcanic units Research Results along the flanks of Yucca Mounta,in Crest and in the adjoining Solatario Canyon, the volcanic Research information Letter Number 173 summa-cones in Crater Flats, the upland plateaus of Rain-J rizes the research results. Detailed technical re-ier Mesa and Pahute Mesa, the exposed Ghost ports will present the results,n detail. About half of Dance Fault on the south side of Antler Ridge, and i

these reports are completed, the remainder will be an overview of the regional physiographical set-issued during 1994 ting from Yucca Mountain Crest (a view ranging from the Funeral Mountains bordering Death in addition a handbook, to be available late in Valley to the Spring Mountains of the Nevada Test 1994, will summarize the principles involved, the Site to Pahute Mesa, see Figure 1).

variables to be addressed, and some examples.

The handbook is intended to help NRC staff review changes that licensees propose in technical speci-The hydrologic points of interest were the Amargo-fications.

sa River to the west of Yucca Mountain, Prow Pass descending to Yucca Wash, Fortymile Canyon The research was performed by Brookhaven Na-emptying into Fortymile Wash, and a series of nat-tional Laboratory, Sandia National Laboratory, ural springs in Ash Meadows and at Devils Hole in Idaho National Engineering Laboratory, Science Death Valley National Monument. The observa-f Applications International Corporation, and Ava-tions of fracture systems and associated seeps in plan Oy (in Finland). This research is managed by N-Tunnel of Rainier Mesa were of particular inter-the Human Factors Branch in the Division of Sys-est. Scientists from the Desert Research Institute tems Research.

provided tours of their experimental recharge facil-ity at Dead Horse Flat in the north central portion of Hydrologic Field Trip To Yucca Pahute Mesa and the ongoing drilling projects west of Yucca Flat for identifying ground-water Mountain and Environs characteristics as part of the NevadaTest Site envi-ronmental restoration program.

Thomas J. Nicholson, RES/DR A/WMB U.S. Geological Survey scientists working in sup-(

Researchers from the Center for Nuclear Waste Regulatory Analyses (CNWRA); Dr. Philip Justus, p of s Qa Mountain sh characWza-tion program provided a tour of their hydrologic re-Senior On-Site NRC Licensing Representative for search facility to discuss their current laboratory the Yucca Mountain Project; and Thomas Nichol-studies for rock core charactenzation, instrument son, the RES project manager on the high-level development, prototype downhole instrumenta-waste (HLW) hydrology studies at the CNWRA, tion testing, and meteorological surveillance. The conducted a site visit to Yucca Mountain, Nevada, researchers visited an excavated trench on the and environs in November. Yucca Mountain is the flanks of Exile Hill to examine carbonate deposits proposed site under investigation by DOE for use that may be,ndicative of paleo recharge. The i

as a HLW repository. The objective of the field trip group also visited paleo-discharge sites at Horse was for the CNWRA scientists studying the region-Tooth Spring deposits, and those deposits near al and subregional hydrogeologic systems to Travertine Point in Furnace Creek Wash, observe the principal regional ground-water re-charge and discharge areas as well as the geolo-gy, physiography, and hydrology at Yucca Moun-A Lawrence Livermore Laboratory scientist dis-tain and the surrounding Death Va!Iey Region (see cussed the in situ Large Block Test (3x3x4 meters) map in Figure 1).

at Fran Ridge for studying coupled effects created 4

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by hydro thermal-mechanical-induced conditions stration would use a cancelled plant at Marble Hill, on the partially saturated volcanic fractured rock.

Indiana, as a test bed to investigate and validate The tour group also examined fractures and faults the acceptability of the engineering aspects of an-exposed in the newly excavated Exploratory Stu-nealing.

dies Facilities (ESF) Tunnel (see Figure 2). The ESF is being developed by DOE to characterize One concern raised in several presentations was a Yucca Mountain using a range of hydrologic.

need to make the economic case to utility man-pneumatic, and geochemical tests.

agement that annealing is an advantageous step.

It is hoped the demonstration would adequately

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The field trip significantly helped the NRC and address this advantage.

,j CNWRA staff to better understand the technical

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bases for the ongoing DOE site characterization activities. The information gathered from this field Visit To Northridge Earthquake Site trip will be used in the newly initiated CNWRA re-gional hydrogeMogic research project, which On January 17, 1994, a destructive earthquake seeks to evaluate alternative conceptual models of w th a Richter magnitude of 6.7 occurred in the Los the regional ground-water flow system. A report on Angeles Basin beneath the suburban town of the field inp was wn,tten by Dr. Gordon Wittmeyer, Northridge in the San Fernando Valley. Significant CNWRA Principal Investigator on the regional hy-damage was caused up to 64 kilometers (40 miles) drogeologic studies.

from the epicenter. Numerous aftershocks have l

been recorded, several of magnitude 5 and great-er. These aftershocks are continuing and are ex-A second field trip covering the subregional hydro-pected to continue for several months.

logic and geologic points of interest, including on-going DOE studies, was conducted in rnid-April.

In an are'a where approximately 12 million people Field tnp participants included hydrologists work-reside,61 deaths, more than 8,000 injuries, and ing for CNWRA, the University of Arizona, RES, more than $15 billion dollars worth of damage and NMSS staff.

have been attributed to the earthquake and sever-al of the larger aftershocks. This is a relatively moderate-sized earthquake by California stan-Industry Workshop on Reactor dards; however, some of the highest vertical accel-Pressure Vessel Thermal Annealing erations (up to 1.2g) over recorded were recorded at several seismograph stations located in the A workshop on reactor pressure vessel thermal area. Analysis of the ground motion records of the annealing was sponsored by the Department of main shock and aftershocks, some of which are Energy and the Electric Power Researcn Institute still being gathered, is under way and will be for on February 17 and 18,1994. This workshop is some time in the future.

timely since the RES staff is preparing a proposed rule and a draft regulatory guide on thermal an-Roger M. Kenneally, DE/RES, and Pei-Ying Chen, nealing, which they plan to issue for public com-DE/NRR, were part of a team from NRC, Depart-ment.

ment of Energy, Lawrence Livermore National Laboratories, Battelle National Laboratory, Elec-Theworkshopcoveredavarietyof technicaltopics tric Power Research Institute, and EOE (an earth-on annealing, including irradiation embrittlement quake consulting firm) that visited (on Febru-and the need for annealing, European and Rus-ary 7-9,1994) sites damaged by the January 17, sian experience with annealing their pressure ves-1994, Northridge earthquake. This is the same sets, projected technical needs before a commer-general area damaged by the magnitude 6.5 San cial U.S. pressure vessels could be annealed, and Fernando earthquake in 1971. In general, the team descriptions of several proposed methods for an-members visited sites that contained structures, nealing. In addition, plans were described for a equipment, and piping similar to that found in nu-demonstration of thermal annealing. This demon-clear power plants.

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7

Damage to Residential arid Commercial Nuclear Plants Structures Ground motions were felt at the San Onofre Nu-clear Power Plant site, located about 129 kilome-There were widespread occurrences of typical ters (80 miles) from the epicenter. The peak earthquake damage, including broken glass, fall-ground acceleration recorded there was 0.02g.

en chimneys, and fallen unreinforced masonry The earthquake occurred 233 kilometers (145 wa!Is. In addition, there were many severely dam-miles) from the Diablo Canyon Nuclear Power aged apartment buildings, especially those with Plant site. Peak ground accelerations recorded parking garages at the first floor level because of a there were 0.0022g (N-S), 0.0023g (E-W), and

" soft first story" effect. Simplistically, this means 0.00159 (Vert).

that there is adequate shear resistance above the first floor; however, the first story is weakened be-Observations cause of the large cutouts provided for garages or other architectural features. Within the epicentral Many structures, systems, and components, even region, some low-rise houses moved off their those close to the epicentral region, had little sig-foundations; many of the mobile homes fell from nificant damage and could be occupied or were their jacks resuhing in ruptured gas lines and fire functional after the earthquake. The lessons f

damage.

learned from this and other earthquakes, princi-pally the need to upgrade anchorage, are being Commercial buildings that did not collapse were implemented.

not necessarily functional because of internal damage such as overturned bookcases, dis-placed ceiling tiles, or lack of power or water. Fail-RESEARCH NEWS is published bY the USNRC l

ure of sprinkler system piping caused excessive Office of Nuclear Regulatory Research, Ann F.

Beranek, Editor.

water damage.

Comments, suggestions, and articles for future issues should be directed to the Editor.

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Damage to Industrial Facilities RESEARCH NEWS, Office of Nuclear Regulatory Pesearch, U.S. Nuclear Regulatory Commission, Washing' ton, DC 20555-0001.

Well-engineered structures and equipment that may have experienced ground motion far in ex-Copies of NRC and other Government publica-J cess of their design remained functional Compo-tions may be purchased from the Government nents made of brittle materials, such as ceramic Printing Office at the current GPO price. Informa-insulators and cast iron components, received tion on current GPO prices may be obtained by damage consistent with other earthquakes. Two contacting the Superintendent of Documents, piping system failures were noted. Moreinvestiga-U.S. Government Printing Office, Post Office Box tion is needed to confirm the applicability of this in-37082, Washington, DC 20013-7082, telephone formation to nuclear power plant systems.

(202) 512-2249 or (202) 512-2171.

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