ML19311A897
| ML19311A897 | |
| Person / Time | |
|---|---|
| Issue date: | 06/12/1992 |
| From: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Ward D Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML19311A898 | List: |
| References | |
| ACRS-GENERAL, NUDOCS 9206300153 | |
| Download: ML19311A897 (4) | |
Text
. _ _ _ _ _.
,A f^@M2g%,
i
^
3" UNITED STATES E
NUCLEAR REGULATORY COMMISSION i
WASHINGTON. D.C. 20666
\\*****/
June 12, 1992 Mr. David A. Ward, Chairman Advisory Committee on Reactor Safeguards U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Ward:
SUBJECT:
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS) COMMENTS REGARDING THE DRAFT COMMISSION PAPER, " ISSUES PERTAINING TO EVOLUTIONARY AND PASSIVE LIGHT WATER REACTORS AND THEIR RELATIONSHIP TO CURRENT REGULATORY REQUIREMENTS" In your letter of May 13, 1992, you provided the U. S. Nuclear Regulatory Commission (NRC) staff with ACRS comments regarding the NRC staff's positions on several of the issues discussed in the draft Commission paper, " Issues Pertaining to Evolutionary and Passive Light Water Reactors and Their Rela-i tionship to Current Regulatory Requirements."
The NRC staff notes that the ACRS agrees with the staff's proposed positions on several of the issues discussed in the draft paper. We also note the ACRS' comments and recommendations on the tornado design basis (Item II.F), post-accident sampling system (PASS) (Item II.I), and site-specific probabilistic risk assessment (PRA) (Item II.N) issues. We will consider your comments as we revise and finalize the subject Commission paper.
In Item II.F of the draft Commission paper, the staff stated that it will ensure that other loads that may have been enveloped within the tornado design basis will be identified and, if necessary, considered in the design basis.
The staff will ensure that, if an actual site hazard exceeds the design envelope in a certain area, the applicant will perform an analysis to verify that the design remains acceptable for the site.
The staff has reviewed its basis for requiring that.the' PASS have high-pressure sampling capability in order to measure the concentrations of dissolved gas and chloride in the reactor coolant. The staff believes that the need for high pressure sampling. stems from the possibility of partially mitigated severe accidents which do not: involve early reactor depressuriza -
1 tion. This is fundamentally a PWR concern since, for a'PWR, there appears to be a-substantially greater probability of a severe accident being arrested while the reactor coolant system remained at pressure.
In~ fact,-the TMI-2 accident--is just such an example.- In addition, there-is'a significantly greater concern-for maintaining reliable natural. circulation and decay heat '
removal in the presence of the gases which would evolve as a PWR was depressu-rized.- The evolution of a large amount.of non-condensable gas in a passive PWR would appear to be the most sensitive scenario since the passive plant decay heat removal systems are so dependent on: natural circulation.
It should I
also'be.noted that the passive-safety systems on a passive PWR would not take-b the plant to a cold shutdown condition following;a partially mitigated severe 4[f 200053 kh g 63 g 53 g Og2
.I PDR
Mr. David A. Ward June 12, 1992-
-accident. The active non-safety systems wsuld need to be used by the opera-tors to perform the final cooldown and dearessurization. When such actions are called for, the staff believes that tie operators need to have a full appreciation of the consequences of depressurizing the plant and possibly
)
introducing non-condensable gases which could complicate or interfere with the successful termination of the event. The operator can then make informed-decisions relating to issues such as: reactor coolant pump start-up and jl operation; instrumentation reliability; and the use of active or passive decay heat removal systems.
For the longer term, determining the oxygen and chloride concentrations would help ensure that plant personnel take appropriate actions to minimize the likelihood of accelerated primary system corrosion following the accident.
This is a secondary consideration since long term samples could likely be
+
taken at low pressure. However, once the need to take the high pressure i
sample has been established, because of the non-condensable gas concern, it does appear appropriate to test such a sample for oxygen and chlorides in order to get an early indication of potential corrosion problems. Therefore, the staff has concluded that PASS high pressure sampling capability is necessary.
The staff has reviewed the proposed requirement for boron sampling and will clarify the requirement to specify that the analyses include determi-nation of the boron concentration.
In addition, the staff will clarify the term *end of power operations" to help ensure that the sampling time' require-ments are clearly understood.
The staff is developing a position on the treatment of external events in-site-specific PRAs for advanced light water reactor designs.
The staff will incorporate this position into a draft Commission paper which is scheduled to-be forwarded to the ACRS by July 1992. The staff plans to develop a separate Commission paper discussing the form and content of the combined license (COL). This Commission paper should help address any questions the ACRS may have on resolving findings made during the COL review process.
Sincerel,
James ylor Executive Director for Operations cc:
The Chairman Commissioner Rogers Commissioner Curtiss Commissioner Remick Commissioner de Planque SECY DISTRIBUTION:
See next page
- SEE PREVIOUS CONCURRENCE OFC:
NM:PDST:ADAR LA:PDST:ADAR
- TECH EDITOR KSC:PDST:ADAR
.NAME:
THiltz:sg PShea JMain RBorchardt DATE:
06/3/92 06//
05/27/92 06/3/92
- PDST:ADAR dADAR FADT:NRR N:NRR ED pRPierson 0FC:
NAME:
DCrutchfield WRusjell TMurley
-JT lor DATE:
06/g/92 06/t//92 066 /92 06/p/92 06($L92 0FFICIAL RECORD COPY:
DOCUMENT NAME:
GT07766.TH
June 12, 1992 I '.
DISTRIBUTION:
{ Central File EDO #0007749 EDO R/F NRC PDR (w/ine)
JTaylor, 17G21 MTaylor, 17G21 JSniezek, 17G21 HThompson, 17G21 TMurley,12G18 FMiraglia, 12G18 WRussell, 12G18 JPartlow,12G18 FGillespie, 12G18 DCrutchfield WTravers RPierson PDST R/F PDST GT/F JMoore, 15B18 OPA BToms, GT7766 PMagnanelli, GT7766 PShea, GT7766 ESBeckjord, RES RMBernero, NMSS ELJordan, AEOD THiltz NRR Mail Room, (ED0#0007766) (w/inc)
JBlaha, 17G21 EBeckjord, RES RBernero, NMSS JScinto, OGC GBagchi JWiggins
t' G
- -.,'g UNITED STATES t
i;
. NUCLEAR REGULATORY COMMISSION Y
Ej EDO Principal Correspondence Control j
[g g' **
S W ASHINGTON, D. C. 20555 g
l FROM:
DUE: 06/09/92 EDO CONTROL: 0007766 DOC DT: 05/13/92 FINAL REPLY:
D0vid A. Ward ACRS TO:
Jcmes M. Taylor FOR SIGNATURE OF:
- GRN CRC NO:
--EXCcutive Director DESC:
ROUTING:
ISSUES PEP" JNING TO EVOLUTIONARY AND PASSIVE Taylor LIGHT W/
REACTORS AND THEIR RELATIONSHIP TO Sniezek CURRENT kdGULATORY REOUIREMENTS Thompson l
Blaha DATE: 05/15/92 Nat Taylor l
Beckjord, RES l
ASSIGNED TO:
CONTACT:
Bernero, NHSS
_NRR Murley Jordan, AEOD Scinto, OGC SPECIAL INSTRUCTIONS OR REMARKS:
PREPARE RESPONSE TO ACRS FOR EDO SIGNATURE.
PUT COMMISSIONERS AND SECY ON CC (SHOWN ON ORIGINAL) FOR REPLY.
l fl4& ffsd W.* $~)V/w
/: rsp~
7 tsp &&,:
DMR/ && kc)c(
f/M 7,M ACTION r
b*
~ RECTOR'S 0?R^"
l t. _:,u.,...s..
p
& Jso-~
/2se