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NATIONAL LABORATORY

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memorandum

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X- Theoretical Design
XTD-2 Navy Systems

CONFIRMED TO BE UNCLASSIFIED
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DATE

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XTD-2:10-012C
June 24, 2010

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SUBJECT: Peer Review of W78 CSA Life Expectancy (U)
Introduction
On May 2i1\ 2010, a peer review of the W78 CSA (canned sub-assembly) Life Expectancy
was held. The peer review committee appreciated the work done by the life expectancy team,
and appreciated the lively and frank discussions during the 2+ hours of presentations.
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Presenting for the milestone closure team were
Team
members
also
present
included
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The peer review committee consisted of XTD's

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eer review committee was that this general statistical approach used is
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Actua i e expectancy or t e W78 wou
longer than that predicted. The peer review committee says this, understanding the W78
team's wish to ensure they have a conservative estimate of the life expectancy.

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Peer review committee analysis of the general method

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!This is then folded into a further distribution that provides a "life-

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expectancy" for the system.

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1

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These maximum yields then defme Y+ line in the probability density plot in figure 3.

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Figure 2.

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Figure

3.,

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With this in mind, the peer review committee made observations that relate to the sensitivity
and applicability of the PDFs chosen for this life-expectancy analysis. I

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clearl complicates any prediction.

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The peer review committee communicated to the W78
team that more information should be looked at to get a more realistic idea of how to derive
the lower-yield section of the PDFs.

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\ Thus, understanding the sensitivity of the

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life-expectancy to these lower yields is important. The peer review committee is concerned
that a ''too-conservative" determination of degraded yield will lead to a life expectancy that is
unrealistic (too short).

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Peer review committee analysis, other observations
Some other observations during the review are listed below. Some of these may be helpful in
future oresentations on this imoortant tooic.

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- mtroauce the general approach (see tlgure 4) at the beginning of a (physics) presentation,
with each term" of fioure 4 heino identified with a short description of what that term is in
this analysis. \

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Conclusion
This statistical approach used for the W78 CSA Life Expectancy is a reasonable approach.
The conservative formulation of possible yield degradation employed seems overly
conservative. Actual life expectancy for the W78 would be longer than that predicted by the
results shown in figure 1. The peer review committee says this, understanding the W78
team's wish to ensure they have ·a conservative estimate ofthe life expectancy.

Distribution:

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