ML20133K456
| ML20133K456 | |
| Person / Time | |
|---|---|
| Issue date: | 04/04/1985 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Cranston A SENATE |
| Shared Package | |
| ML20132C556 | List:
|
| References | |
| FOIA-85-199, FOIA-85-A-15 NUDOCS 8508120237 | |
| Download: ML20133K456 (2) | |
Text
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Lt > ; gg The Honorable Alan Cranston United States Senate Washington, DC 20510
Dear Senator Cranston:
Thank you for your letter of March 11, 1985 accident research results in reactor regulation.concerning the use of severe I want to assure you that the Commission and the staff are firmly committed to protection of the public health and safety.
No changes to regulations would UF contemplated without the belief that they were based on scientifically accepted principles and methodology.
The issue of source terms and especially its impact on emergency plans is of great interest at the present time because the results of the Commission's own reviews and those of other groups have recently becone available.
At the request of the Commission, the American Physical Society (APS) has provided a broad-based review of the adequacy of the underlying science and the method-ology for estinating source terns.
They found "that considerable progress has been nade since publication of the Reactor Safety Study..." and they concluded that "fi]n a number of cases, new calculations indicate that the quantity of radionuclides that would reach the environment is significantly lower than that calculated in the Reactor Safety Study."
the rajor factors leading to this reduction and one mechanism that couldAfter discussing increase the calculated release, they further concluded that "[ilt is impossible to nake the sweeping generalization that the calculated source term for any accident sequence involving any reactor plant would always be a small fraction of the fission product inventory at reactor shutdown."
that "further studies may improve this situation."
They did rote, however, With increased emphasis on ccdes which model the physical phenomena in detail, it is likely that differences among plants will have to be taken into account, where such differences did not previously exist in the simplified evaluations of the past.
The Commissinn has recognized that the uncertainties associated with the source tern methodology are large and that consideration of those uncertainties is mandatory for any application.
The uncertainties that you mention, relating to containment performance and initiating event probabilities, are only a part of the complete uncertainty picture.
The APS has discussed the uncertainties in the supporting science and modeling for such areas of the methodology as the core-concrete interactions and the performance of mitigative features, for instance, the ice condensers or pressure suppression pools. The NRC has been conducting an extensive research program ained at addressing all of these y
uncertainties.
in emphasis may be needed.We are assessing the program to determine where some changes 7
! Q.' s 8508120237 850627 PDR FOIA BELAIR85-A-15 PDR
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r The Honorable Alan Cranston 2
I believe that the state of our knowledge today about the fundamental aspects of nuclear safety is greatly improved relative to our understanding a few years We have had a most thorough review of this work and have had general ago.
confirmation that our research is well founded and is in the right direction.
We have had conclusions confirmed that for most radionuclides and most sequences, the source terms are much lower than had been previously predicted. While the APS explicitly took no position on such major uses of source term research as emergency planning or backfits, the report did conclude that we should use the new information as we determine what is necessary in the regulatory arena.
Again, thank you for your letter. Be assured that only technology with broad-based scientific acceptance will be used in any proposed regulatory changes.
I or members of my staff would be available to discuss the source term issue with you or your staff at any time.
Sincerely, (Siped) William J.Direks William J. Dircks Executive Director for Operations Distribution: This memo closes ED0-000451 and RES-850501.
Subj JMitchell, RES Circ MSilberberg, RES Chron Dross, RES Branch r/f RMinogue, RES ED0 r/f YSl EConti, RES I,
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