ML20052D506
| ML20052D506 | |
| Person / Time | |
|---|---|
| Issue date: | 02/15/1982 |
| From: | Langhaar J Advisory Committee on Reactor Safeguards |
| To: | Duraiswamy S Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1419, NUDOCS 8205060519 | |
| Download: ML20052D506 (4) | |
Text
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s 15 Fchruary, 1982
/fA Mr. Sam Duraiswamy, Staff Eagineer f
U. 8. Nuclear Regulatory Commission SV Advisory Committee on Beactar Safeguards R/.
G Washington, D. C. 20555 il 3
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Dear Mr. Duraiswamys SAFETY ISSUES RAISED BY 'NC FOR!IER D71CTEES E NRC t
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COUCERNINC REGULAM REVIEWS OF PACKA:iE FOR
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RADICACTIVE MA1ERIAIS y
s As requested in your letter of November 22, 1981, I have reviewed the technica] issues raised by the two forner NRC saployees, and offer comments l
below.
l General he issues should be viewed in the light of the intent of the regulations.
It was recognized that some small risk of radiological injury must be accepted.
i Just how amall is sonewhat subjective, but one generally accepted rule is that
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the probability of realological injury should be auch smaller than the proba-bility of non-radiological or " common cause" injury in the transport of radioactive material.
his was to be achieved by requirin6 that containers would pose alnost zero risk under a range of conditions representing normal transport, and would survive nearly all accidents without causing serious radiological injury to any member of the general public.
Some cost-benefit philosophy is inherent in establishing the requirements.
If the intent can be fulfilled with containers of " reasonable" size and cost, it would be imprudent to require containers ao costly that auch greater safety benefit could be realized by directing the effort elsewhere, or to require the radioactive contents to be so small that the increased number of shipments would result in increased " common cause" injury out of all proportion to the reduction, if any, of radiological injury.
In the absence of data for reliable technical assessment of the risks, l
those panels of experts who developed the re6ulatory requirements attempted to be conservative. Bis does not imply that all aspects of the reculations have the mane degree of conservatism, because judgment is necessarily involved.
Se proof of the pudding is the eating experience to date indicates ht the overall degree.of safety is very high, and that ensuring proper use of the containers is of dore concaut ihr maaLYs snadequacy of design.
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It is o pract.eal impossibility to write regulo irns which.do not p;rmit como Ittituda cf interpretation, and which anticipate all future developments in technology. D ere is a tendency, as time goes on, to apply the regulations in a more stringent and literal fashion, and to use more and more sophisticated techniques for demonstration of compliance, even thogh the effect on actual safety any be negligible.
The hypothetical accident conditions were not intended to simulate real accidents, and even the specified normal conditions in sose respects would not nornally be considered nor=al. However, it is expected that containers satisfying these design requirements will in actual use perform as intended.
Dere it nothing magic about the 30 ft drop onto an essentially unyielding surf.cc or the 40 inch drop onto a penetrater, or so.tc of the other specc.
'The cix inch dia;.cter penetrator wa: oricinally celected to reprc:ent, more or l e.,. the end cf a railro d rail.
hc 40 inch drop was arrived at in a roundabout fa:hion; suffice it to say that.the r.unber nicht just as wcII have conc out 33 ir.che or 50 incher..
Wia cort of situstioz. nt,y bc disturbirs to those whose trLinin6 and work have been directed to ard inproving precicios. and accuracy.
It say also te disturbi:g to thosc who ni ht have to defend the po:ition that the design 6
of a pr.rticule.r cor.taincr dceu in fact satisfy the letter of the law.
Eeverthc2c::, all that car. te expected is a hi h degree of assurance that a 6
cor.tal:.er a: fatricated satisfic: all of the requirenents. We justifiable dc;rce cf refir.c.cnt for analy:Is and to:tinc depend: in part on whether a pa-ticular fcotu e is clocc to borderline, and even in borderlinc case: the practic:.1 ca'cty :1,nificance M ould be taken into account.
_Srecifie te :
ilnde.- ths circun:tance described above, a denon:tr: tion acceptable to ora revicwu ni-hi not be acceptable to another reviewer, even thouch in eith e c: c ths re d t could bc a container which would perfore a: interded.
In que:tionat2u cases about the extent to which ana3ycit or fact-finding should be cu ried, a de-cicion by cupervicion le appropristc. C1 cry's iten: #2, #4, and #33 ceen to ne to be in this category.
Clary's itens #1, #3 in part, #6, #7, #8, f), #10, #11, #1b, and #15 seen to represent a misunderstanding of the regulatory requirements of 10CFR Part 71 and of the responsibilities of the Transportation Certification Branch I bc11 eve that 1:r 1:acDonald's memo 6f February 15 1978 and Mr.
Bernero. 's report of the findings of the Review Group provirle prop,er explanation.
With regard to Clary's iten #3, the regulations are not clear about how the dead weight chould be taken into account.
mis is not important, because the 10-5-2 s figure: do not have a cound basis, do not appear in the IAEA re;tdatione, and are expected to be eliminated fron 10CFP. Part 71.
For the I
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bed of a truck, the figures are excessively hight for the bed of a rail car during coupling operations, they appear to be high for the lateral component and low for the vertical component. Furthermore, forces on the container attachments say be auch different, depending on the design of the tiedoisi system. h e subject has been under study by the NRC, DOE, and ANSI meantitile,
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l there sepears to be no basis for requirements more restrictive than at present.
he problem of characterizing vibration in nozual transport (Clary ites d%)
has also been under study.
I do not know the current status, but am unaware of any container failure to date as a result of such vibration, nus staff discretion seems appropriate until there is evidence of damage due to vibrations when and if that occurs, the benchnarks for judp ent will change accordingly.
The incentive for study is partly if not largely concern about damage to fragile fontents rather than dant.ge to the contciner.
Clary doe: not specifically mention secondary impact in itec #5 or #6, but may have had this in mind. It is correct that secondary impact, due to fallir.6 over after the initial inpact, can sometimes be more damaging than the initial inpact. Be regulatien do not state that this should be considered, and I believe it was net discucsed when the reculations were developed. Sus, it appearc appropriate for EP.SS-TC6 nanacenent to exercise judgnent. At the sane tine, an atter.pt chould be made to deterr.ine if this iten is of any real safety si nificance.
o Clary's ite.w #5 and #12, and Shich's ite 15b of " sone spoeial Events",
abcut the ec trave 211nc a little further than the specifjed drop distances, see.- technically valid. Rey are of minor significance except for the design of impact limiters which undergo large deformation, and in such cases it is custo=arily taken into account.It does seat proper to tah it into account alco in other caces when it is knowoor predictable in advance; this can easily be done by assur.ir. a slightly greater anount of energy to be dissipated.
"he or.3y techr.ical matter clear)y identified in the notes and letters of Dr. Chich relates to prediction of puncture. Reganiing iten i!2 of his, different references G ve somewhat different values for the i
strength of stecIs. What minicu?. value to use unless a hi her value can be 5
justified depends partly on the desired degree of conservatism. 75 kai for Type 3% stainless has been a commonly accepted figures if some other value is to be used, applicants should be so advised.
On items #3 through #7, there appears to be a need to update the infor-nation on puncture given in OREL-USIC 68, Cask Designer: Cuide, particularly l
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cith regard to laminated chdlo, local ctiffeners, and backing cther than lead. he2e factors have been the cubject cf more speculation, necessitating many tests of prototypes and scale models because of lack of reliable methods of calculation. ho 50,5 figure cited in item #5 is rather surprising, and if not already done should be further investigated by IGC.
Conclusionn (1)
Some of the point raised by Mr. Clary and Dr. Shich represent differing opinions in situations where the regulations permit some flexibility or latitude in method of cpplications in such case:, the staff position shculd prevt.11. AlthouGh Cla y's implied concern relating to secondary inpcet efter the 30 ft drop 10 of thi: nature, tahinc it into account in ca3cu2 stave a :e:snent could a'fect the design of come containere, and to wcrrant further consideration of its practical importance.
It 10 seen:
usually automaticc23y t:J:en into accotet in te:t.
(2) Several other of C1 cry's points were c, to a misu.dcrstandin: of the regulations and of 12:33-TCE re:ponsibilities.
(3) he only other itens of inportance are the need for more data in connection with vibratien, a ncted by : r. Clary, and in connection with resistance to puncture, as ncted by Dr. Shich. "his has been reco nized by NRC, and studien have accordin;3y been funded.
It would be of interest to learn the current tatus and the results to date.
'o Very 4.ruly ur /
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John 'J. las 1
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