ML20215D971
| ML20215D971 | |
| Person / Time | |
|---|---|
| Issue date: | 04/03/1985 |
| From: | Ross D NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Ernst M, Gillespie F, Silberg M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20215D926 | List: |
| References | |
| FOIA-86-483, RTR-NUREG-0956, RTR-NUREG-956 NUDOCS 8610140378 | |
| Download: ML20215D971 (3) | |
Text
cO E
,j UNITED STATES F
.i s"'
1, NUCLEAR REGULATORY COMMISSION i o msmuorou. o. c.rosss
....+
April 3, 1985 NOTE:
M. Silberberg, ASTP0 F. Gillespie, DRA0 M. Ernst, DRA0 J. Mitchell, ASTP0 R. Denning, BCL R. Bernero, NRR R. B. Minogue, RES FROM:
D. F. Rcss, Deputy Director, RES Consider the following statements 1.
"To date, however, the technology has not progressed to the point where it T.
is possible to assign quantitative numbers to all the significant factors relative to safety or to predict with surety the probabilities of malfunctioning of engineering features of plant design under all operating conditions thit might exist."
2.
......, such systematic analyses of potential accidents often lead to discovery of ways in which safeguards against particular accidents can be provided."
3.
"The amount of each kind of radioactive material present in a reactor system can be estinated fairly closely, as a function of the power level history, but the quantity of this material that would be released as a result of an accident is unpredictable."
4.
"Further, there is a multiplicity of possible combinations of the physical and chemical form of the radioactive materials released into the containment vessel and of the ways that atmospheric conditions might cause these radioactive materials to be transported to regions beyond'the site boundary."
5.
"Some ejected materials may conceivably burn on contact with air, and thus increase the volatiles and fractions of fine particles."
6.
"At the same time, a certain amount of the airborne fission products would be removed by such phenomena as adsorption, deposition, plate-out and steam condensation within the reactor building or containment scructure."
7.
" Removal by adsorption and settling processes would be affected by turbulence."
8.
"The objective of estimating the radioactive inventory without the outer containment barrier is to attain a starting point for calculating the potential radiological hazard in the surrounding environs."
{8860726 TOLA66-4g3 PDR
.. 9.
"As the last exercise, there is the problem of establishing some acceptable exposure dose criteria. within the context of this procedural operation, for a comparative measure of the acceptability of unacceptability of the estimated exposures resulting from the hypothetical accident."
10.
"There is a substantial degree of judgment involved in establishing the basic assumptions and assigning definitive values to variable parameters."
11.
"The results obtained are approximations, sometimes relatively poor ones, to the result which would be obtained if the effects of the full play ef all the variables and influencing factors could be recognized and fixed with certainty--an impossibility in the present state of the art."
i' 12.
..... it is estimated that removal of airborne iodines by various physical phenomena such as adsorption, adherence and settling could give an effect of 3-10 reduction in the final result.
Credit has not been taken for the effects of washdown or filtering from protective safeguards such as cooling and internal air recirculating systems. Washdown features and filtering networks could provide additional reduction factors of 10-1000."
13.
"Thus, even if the postulated maximum credible accident occur, the resulting exposure doses would probably be many times lower than those calculated by the indicated method."
14.
"Other potentially more hazardous factors than those represented by the example calculation include the following conditions.
1.
.... Release of long-lived fission products to the containment vessel could theoretically be up to 99 times as large as that assumed.
Such releases would increase doses to the lung, bone, and total body."
15.
"3.
If the external containment structure should be rendered completely ineffective at the outset of the accident, the consequences of the
" maximum credible" accident would be increased many orders of magnitude....."
The 15 numbered paragraphs are not as anticipated from NUREG-0956, or extracted from APS or ANS or UCS, but from the 23-year old TID-14844. How much progress have we made?
Y
'Y D.
. Ross, Deputy Director Office of Nuclear Regulatory Research
o v.-,
ENCLOSURE F ILLUSTRATIVE PRESSURE-TIME CURVES FOR SEVERE ACCIDENTS
'i h
4 e
4 e
- - - -