SUBJECT: COMMENTS ON NRC PROPOSED RULE ...

6.6 - Evaluation Summarl:
The atructu ponse of s substantinl nuclesr power plant structure to
the impact of aircraft has been dir~cussed bn the previous subnectlona
with reapect to (1) the establishment of the impulsive load that the
aircraft imposes upon the structure- under a normal flight impact
condition, (ii) the wailable atructur a1 re-ponre models or llcthodologiee
for examining the local i.. punc ,,re) and the gross response of the
structure, (iii) tha current state-of-tht!-art of the constitutive models for
concrete/reinforced steel. systems experisncing plastic deformation, and (iv)
the vibrational respoirsa of the structure and its attendant equipment.
These deterministic aspects of the response need to be aueented by a series
of stochastic variabl~mr relating to the aircraft typo a weight),
aircraft speed, flight impact direction, aircraft orientation (pitch and
yaw), and impact location on any given ntructure or structural system. 'Ihe
level of daterainistic analyses currently available and being applied to
this problem appears to ba adequate in most cases, except perhaps for those
dealing with the systlm vibratior. Tt~ese analyses are alro adequate to
establish the level of the hazard imporrd upon the plant or the degree of
enginseritlg safety syaterm required to mltigate this hazard to an acceptable
level. Ibwevur, it 111 clear that thetle methodologies should include the
thc problem to better define the hazard.