ML19291C198
| ML19291C198 | |
| Person / Time | |
|---|---|
| Issue date: | 12/20/1979 |
| From: | Basdekas D NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Ahearne J NRC COMMISSION (OCM) |
| References | |
| NUDOCS 8001230112 | |
| Download: ML19291C198 (5) | |
Text
.
SECy
~
bn REQy
'o UNITED STATES
~,,
8 NUCLEAR REGULATORY COMMISSION
+q,'
n
{
- E WASHINGTON, D. C. 20555 A'
( C lb k DEC 2 01979 MEMORANDUM FOR:
Chairman Ahearne FROM Demetrios L. Basdekas Experimental Fast Reactor Safety Research Branch, RES
SUBJECT:
1.
SAFETY IMPLICATIONS OF CONTROL SYSTEM FAILURES AND PLANT DYNAMICS 2.
RECOMMENDATION TO DERATE OPERATING PLANTS TO 65 PERCENT OF RATED POWER The December 17, 1979, meeting covering the subject matters was very useful, and I thank you for the opportunity to participate.
The following comments are intended to put in a better and updated perspective the concerns I expressed to you earlier.1-4 An ACRS subcommittee also held a discussion on these matters on December 13, 1979.5 Although there is an increased level of agreement between my views and those of the NRR management on the nature of the problems of control systems and plant dynamics, the differences of the perceptions of its severity, and approaches to deal with it remain substantial.
Specifically, I believe that:
e The short tenn FMEA of control systems for all plants and its attendant development of dynamic analysis capability within the NRC are imperative and long overdue.
e The proposed derating to 65 percent will produce a measured and indespensible reduction in risk.
The "zero risk reduction" claim by the NRR staff management is not correct because it continues not to take into account the systemic considerations inherent to control systems and plant dynamics that may lead to unprotected sequences of events or " snowballing effect" that will quickly offset any conservative margins that may be attributed to the previsions of 10 CFR Part 50, Appendix K.
.The analytical safety envelope, as defined by the LOCA/ Steam Line Break Accident is not
~
i791 282 80012301I7--
7 Chairman Ahearne 2
DEC ?,0 W9 sufficient for accident sequences which include compound systemic distur-bances.
It is primarily these systemic disturbances resulting from or compounded by loss (es) of control sequences that would be less severe at a reduced power level.
This is so basically because of the reduced stored energy in the system.* TMI cannot be too distant of a reminder of this unforgiving law of physics.
We must deal with this problem on a high priority basis, previously taken positions by the staff notwithstanding.
The merits of the proposed approach are strengthened by the fact that the operating experience, at least with the B&W plants, shows that the " corrective" measures taken in these operating plants, as a result of the TM1 accident, have resulted in a net loss in safety.5 Neither the " band-aid" approach nor the long and wide range plans, such as IREP, will deal with this issue realistically.
An interim derating of all unreviewed operating plants is prudent, if not e
imperative.
It will not only ralieve the burden on safety from this one safety issue, but it will do su to varying degrees, for the rest of the 133 unresolved safety issues.
Even on the basis of the probabilistic risk assessment study performed by the staff sometime ago, we cannot.
ignore the cumulative risk contribution of most of them on the basis that their individual contributions to total risk may be one percent or less.6 On the question of operational and societal costs related to a derating, e
it should be realized that in the long run the energy produced under derated operation will be substantially the same as with full-rated power operation as shown in the attached graph.
Initial dislocations in power production and loss of some peak power production will be the only ar-guable aspects of derating; but in my judgment, they are a price worth paying.
It is not a question of whether we can afford to do this; it is one of whether we can afford not to.
e The points made by Mr. Minogue in his July 20, 1979 memorandum to Commissioner Gilinsky offer a good insight into problems associated with rapid size 7
and power level escalation in the development of nuclear power.
These problems do have an important bearing on our lack of understanding of plant dynamics.
- This is quite analogous to having an automobile loss-of-control accident, involving say a front tire blowout, at 100 mph or 65 mph.
Although the risk in both cases is substantial, the course and consequences of the accident will most likely be different and may very well make the difference between life and death, even if the seat belts, for instance, remain intact.
Furthermore, driving at 65 mph would decrease the likelihood of having the accident in the first place.
1 1791 283
1 Chairman Ahearne 3
DEC 2 01979 If I can assist you and your colleagues on the Commission further on this matter, I will be happy to do so at your conveinience.
AA A M.
Demetrios L. Basdekas Experimental Fast Reactor Safety Research Branch, RES
Enclosure:
As stated cc:
Commissioner Gilinsky Commissioner Kennedy Commissioner Hendrie Commissioner Bradford L. V. Gossick, EDO M. W. Carbon, ACRS W. Kerr, ACRS H. R. Denton, NRR S. Levine, RES R. J. Budnitz, RES R. Minogue, OSD OGC OPE SECY r
1791 284-
t Chairman Ahearne 4
DEC 2 01979 References 1.
Note to the Commissioners from D. L. Basdekas, May 25, 1979.
2.
Memorandum to Commissioner Ahearne from D. L. Basdekas, September 4, 1979.
3.
Ibid, October 25, 1979.
4.
Briefing for Chairman Ahearne, December 17, 1979.
5.
ACRS Subcommittee on Power and Electrical Systems Meeting, December 13, 1979.
6.
Memorandum to R. J. Budnitz from D. L. Basdekas, January 8,1979.
7.
Memorandum tc Commissioner Gilinsky from R. Minogue, July 20, 1979.
1791 285
9.82 l62l I
l
/////////////
$1 i
mmw i
EEEf8EE,!
r g
8.
k\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
83 mod %
9