ML20056D963
| ML20056D963 | |
| Person / Time | |
|---|---|
| Issue date: | 07/20/1993 |
| From: | De Planque E NRC COMMISSION (OCM) |
| To: | Chilk S NRC OFFICE OF THE SECRETARY (SECY) |
| References | |
| NUDOCS 9308190090 | |
| Download: ML20056D963 (3) | |
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RELEASED TO THE PDR
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SAMUEL J. CHILK, SECRETARY OF THE COMISSION l
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FROM:
C0l44ISSIONER DE PLANQUE
SUBJECT:
SECY-93-108 - REVISED GUIDELINES FOR PRIORITIZATION OF GENERIC SAFETY ISSUES
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APPROVED xx DISAPPROVED ABSTAIN l
i NOT PARTICIPATING REQUEST DISCUSSION C0l44ENTS:
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I agree with the change proposed by Commissioner Rogers for the priority ranking grid.
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i The attached markups are some editorial changes.
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~,mmgm m u m.s hgurei2MPriority3 ant 1RgGedWAux111ayTAbscissae 5.
Other Considerations The formula-based rankings represent the primary concern of the NRC:
public safety. The secondary concern is the impact on licensees, evaluated in terms of cost. However, the tentative priority rankings are subject to the limitations of an often incomplete and imprecise data base and to possible distortions due to the nature of the necessarily highly simplified quantitative formula underlyin,.g them.
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c:te;;;rie:.) Special situations with respect to some issues may cause added difficulty in priority assignment. While the formula-based tentative rankings must generally indicate that the safety significance is sufficient to justify NRC actica, other considerations not adequately reflected, or not reflected at all, in the numerical formula are often needed to corroborate or adjust the results. Decision-making is helped by explicit identification of such other considerations and explanation of how they bear on the resulting final priority ranking, whether the effect is one of corroborating or of changing the estimates.
Listed below are some factors that may be important in arriving at a sound priority ranking and may lead to adjustment of a tentative, formula-derived ranking.
Possible effects of occupational doses,-averted-plant-damage-eesets, and
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uncertainty bounds [(a)(1), (a)(2), (eyn.and (b)(1) below] require particularly careful consideration for all issues. The factors listed are not considered all inclusive. Others thought significant are discussed W/NTs3 24 NUREG-0933
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and, wh:n practical, quantificd apprcpriataly in the evarall ri:rity
- nd it; adsntifiedsiisEsi~gnificanciFamiiUFsiindNEpiEtf615siritTis scer:
andithii6 associated ^snciFtainties.~$ometiines,~thiFe^ife spec'ial~" '
conside^rTfions that are quite specific to an issue or some aspect of it.
~Ghe EartiaL11st of other factors is listed below. IWsh661dibeI63tB
' thatdM3stifilhFwhitherransisissiEsS6613?iFsEiiVisi?HIGHipriority?ong those ?ofThe Tactorsithat?rel ate ttoisafetfl fire]gijesiconsidefation T (a) Special risk and cost aspects not included in or potentially masked by the numerical formulas:
(1) The net change in occupational doses i=plicit in 5tal]edy implementing the current,versus the proposed requirements; 21: 0,
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.f (2) Any significant non-radiation-related occupational risk EffeEtedilifLth]e propossdTr'~eToTdtf5hii (3)
'ce:rted :::t :f plant d = ;: fr:: th: p::tul:ted :::id:r.t.-
(43) Loss or severe degradation of a layer in the defense-in-depth
~ concept (e.g., one mode of core cooling or containment cooling).
(54) Issues for which solutions of widely differing costs may be applicable to different classes of plants or various plants are otherwise affected in vastly different ways.
(b) Factors related to uncertainties stemming from an incomplete or imprecise data base for the priority formula:
(1) Uncertainty bounds, imbalance in uncertainty factors, certainty of cost to fix versus uncertainty that safety is really improved and the true extent of such improvement.
(2) Situations where uncertainty is extraordinarily large (in accident probability, consequences, or cost, or any or all of these).
(3)
Problems which are ill-defined and problems for which solutions are not evident so that at least the resources necessary to understand the problem are assigned!
(4) The potential for a proposed change to affect more than one accident or transient sequence, thus affecting risk to a greater or lesser degree than assessed in the description of the issue; notably, the potential for a new safety decrement, or increase in risk, due to unidentified effects of a proposed change, or added complexity, or for other reasons]
4 (5) Circumstances imparting unusual significance to accident consequences (such as ingestion-pathway effects) or mitigating l
measures (such as evacuation) that are not directly included in the public dose calculationsy.
0{f22/9js 25 NUREG-0933