Application of Hazard Assessment Techniques in the ClSF Design Process

October 29, 1997

W r i I Icri by: Jirri I ? . I IiorriIon, Nuclcclr CorisulI(iril

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DISCLAIMER

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This report was prepared as an account of work sponsored by 'an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus. product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, m m - menduion. or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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APPLICATION OF HAZARD ASSESSMENT TECHNIQUES IN THE ClSF DESIGN PROCESS

Introduction

The Department of Energy has submitted to the NRC staff for review a topical safety analysis

report (TSAR) for a Centtdized Interim Storage Facility (CISF). The TSAR will be used in licensing the

ClSF when and if a site is designated. ClSFl design events are identified based on thorough review

of design-basis events (DBEs) previously identified by dry storage system suppliers and licensees and

through the application of hazard assessment techniques. A Preliminary Hazards Assessment (PHA)

is performed to identify design events applicable to a Phase I non site-specific CISF. A PHA is

deemed necessary since the Phase I ClSF is distinguishable f rom previous dry store applications in

several significant operational scope and design basis aspects. In addition to assuring all design

events applicable to the Phase I ClSF are identified, the PHA served as an integral par t of the ClSF

design process by identifying potential important- to-safety and defense-in-depth facility design and

administrative control features. This paper describes the Phase I ClSF design event identif ication

process and summarizes significant PHA contributions to the ClSF design.

Reference Dry S t o r a a e y s t e m Design Events

I vorils corisitfcrcd lor Iurlhcr ciricilysis iricludc 1)IjI s cissocicilcd wilh liqhl wcilcr rociclor SNI

dry s I or (1 qo [(IC il i I ios pr (Iviou SI y id (2 ri I i I iod in iri d 11 s I r y (1 rid r (I(J IJ I(1 Io r y docu rri cri Is, (1 s w (11 I (1 s corri rri or cici I

determined to be potentially applicable to the Phase I ClSF include natural phenomena events and

other system specific events identified in reference system SARs and regulatory documents such a s

cask tipover, failure of instrumentation, and canister misalignment.

Preliminary Hazards Assessment

It is recognized that the Phase I ClSF design effort requires special attention in areas which

may not have been reviewed previously in SNF dry store applications. Relatively bounding generic site

characteristics, transportation cask receipt operations, large number of operations and storage units

and the lack of onsite bare fuel transfer capability are issues identified as somewhat unique to the

Phase I ClSF design effort and may not have been addressed previously in reference system safety

evaluations. Therefore, in addition to the reference dry storage system design event review, a PHA

is performed to ensure that all credible accident and off-normal events applicable to the Phase I

ClSF have been identified. Systematic hazard analysis techniques are employed to provide reasonable

assurance that all possible off-normal and accident-level events are identified and appropriately

evaluated and considered as part of the facility design process.

The PHA is performed in a two-step process of hazard identification and hazard evaluation.

Hazard identification is the process of highlighting material, system, process and facility

c ti (1 r (I c I or is I ics ti (1 viri (1 ! ti tl po IC ri I i(i I lor iri i I i(i I i ri (1 (I cc id (iri Is w i I ti IJ ri dos ir (1 Mi cori scq II (I ri (:(IS. I 11 (I

ti(i /(I r d id or1 Ii Iicci l ion pr oc(iss r oqu ir (is (1 Ihor ou(1 ti 11 ridor slaridiriq o I laci l i l y dcsiq r i loci I ur (is , dcsiq r i

crilcrici arid opcrciliorial procoss Ilow. I wo cipproachcs arc ulili/otf ir i idcrilificciliori ol I’ticiso I (XI

po Ion I i(i I h (1 /(I r d s , I ti (I li r s I (1 p pr o(1 (:ti Io r ti (1 /(I r d id (iri I i f icci I io ri i rivolvos (ixa rri in i rig d (I I(1 il ( I d

slop by slop doscriplioris ol ( w r y oporaliori lo ovalucilc ltic irripacl ol slal ic porlorrriciricci ol

s I r 11 c I II r (is, s ys [(I rri s (1 ri tj corn pori (i ri 1s ( sSCS) or1 s(i I (I l y . I 11 (I socori d 0 p pr o(1 c ti for tic1 /(I r d

i(j(irililicciIior1 is Io ovciIuciIc SSCs wticri dolailod procoss IIow doscriplions (ire r iol civciiI(it)Ic (kc.,

suppor I SSCs). I his rovicw procoss irivolvos (iri oxcirriiriciIiori ol supporl subsyslorris or (ir(i(is iri ordor

to identify potential hazards in the form of energy sources (e.g., chemical), which could directly or

indirectly initiate of f -normal or accident-level events with nuclear safety implications. Energy

sources are identified within each subsystem for review as potential event initiators. Natural

phenomena events which may affect the operability of the subsystems themselves, or which may

initiate events involving interaction with important-to-safety SSCs, are also evaluated.

Hazard evaluation constitutes the primary focal point of the PHA. The purpose of the hazard

evaluation is to identify significant events that require further evalgation for determination of risk

acceptance, and to help identify facility design features or operational administrative controls which \

can significantly enhance facility safety. A preliminary qualitative evaluation is performed for each

identified event by identifying potential causes and consequences for each hazard event. Events are

identified for further evaluation if important-to-safety design functions are potentially affected (i.e.,

criticality control, SNF confinement, radiation protection, SNF retrievability, thermal).

Hazard evaluation measures overall safety significance based on a combined qualitative

measure of event frequency and consequence. This qualitative measure is used to screen low

probability and/or inconsequential events f rom further detailed evaluation. Design events identified by

the Phase I ClSF PHA for further evaluation which may not have been previously reviewed by

irid (I pori d or1 I S N I s I o r (1 (1 (I lac i I i I y r (y II I(1 lory 0 11 I hor i I ios , or rri ci y t)c t)cyori d I tic sco po o I p r ovio 11 s

r ovic w s, i ri c I II d o r (id io1 oq ic(i I r (11 (!(I so tf 11 r i ri (1 I r (1 ri s por la l ion pci c ka (1 (I I id r (~rriovo I iri I )ti (1 so I C I SI

rccoiviriq ( i rom, cirid (1 lirriilod r imbc i r ol dry slorciqc; syslcrri spccil ic Ircirisporlciliori ccisk lid h o p

(1 rid vcr Iicci I l r (1 ris lor sys Iorri loc id drop ov(!ri Is.

I k s i q ri (1 rid Ad rri i ri is I r (1 I ivc Co ri I r o I I (!(I I II r c s

I I(i/cird ov(iIu(i~iori is pcrlorrriod wilhoul Iakiriq crcdi l lor I)ti(is(i I CISI dcsiqri lc(iIuros or

(1 d rri i ri is I r (1 I ivo cori I r 01 s prior I o I bi o scr (!(I ri iri (1 pr oc(~ss, I I ow ovor , (1 ri o I ti or pr irri (1 r y I II ri c I io r i o I I h (I

hazard evaluation process is identifying potential important-to-safety and defense-in-depth facility

design and administrative control features with nuclear safety relevance for subsequent consideration

in the design process.

Conclusion

Hazard assessment techniques have been successfully applied in the Phase I ClSF design

process. In conjunction with a thorough review of previous SNF dry store applications and associated

reference documents, the PHA assures all credible accidents and off-normal events applicable to the

ClSF have been identified. The PHA was also useful in identifying Phase I ClSF important-to-safety

and defense-in-depth design and operational control features as an integral part of the design

process.

References

1 . Cenkuhjed hfeflh Sforuge FUc/lR hpkd Sofefi. Anuhsis Ripor/ , U . S . D 0 E, Doc k e t N 0. 72-21. May 1997.

2. NU R EGIC R - 2 300. PRA Procedures Gui2e: A Gude fo fhe Perhrmunce o f Probubdshc hsk As:s~~s:sr~cv/s hi Mmhr hwcr /?ads . U.S. N I X Jariuciry 1985.

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