ML20237B555
| ML20237B555 | |
| Person / Time | |
|---|---|
| Issue date: | 03/05/1987 |
| From: | Messieres Candace De Advisory Committee on Reactor Safeguards |
| To: | Okrent D Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML20237B537 | List: |
| References | |
| FOIA-87-640 ACRS-GENERAL, NUDOCS 8712160346 | |
| Download: ML20237B555 (6) | |
Text
{{#Wiki_filter:l .
-/ 'k UNITED STATES -
!\ . cgi' n . NUCLE AR REGULATORY COMMISSION
.!-( # E ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
*N }[,j '
o nAsm uncion. o. c. 20sss s., . .s. March 5,1987 MEMORANDUM FOR: Dr. David Okrent ACRS Member FROM: Dr. Monide-ep K. De, ACRS Fellow 8D
SUBJECT:
Risk Benefits for Regulatory Actions Taken in Various Co untries to Enhance LWR Safety (Appendix to Draft Report issued January 28, 1987) 4 i As_ you requested, please fimd attached a report on the risk benefits
.for some of the design im;revements in foreign reactors.
The report is written as an Appendix to the main draft report which was issued to you on January 28, 1987. cc: ACRS Members ACRS Technical Staff l 8712160346 871210 PDR FOIA SDRG187-b40 PDR f {j _ _ _ - - - - - - _ _ - - - - - - - - - )
l l
.a . l l
l l i-APPENDIX A RISK BENEFITS FROM FOREIGN REACTOR IMPROVEMENTS
l
, Appendix A Risk Benefits from Foreign Reactor Improvements Page A.2 I FRANCE The NRC Staff in Reference 1 provides estimates of the decrease in core melt frequency as a result of the addition or modification of systems in foreign reactors. Table A.1 lists some of these estimates by the Staff. It should be noted that Table A.1 presents estimates and not the results of analytical computations. The effect of external events have not been accourted for in these estimates.
Among all the French improvements, the addition of a steam-driver generator has the most impact in decreasing the CMF. A factor of about 15 decrease in CMF due to station blackout is achieved. The impact of the addi:fon of the , steam-driven generator on total CMF would depend on the contributicm of station blackout to total CMF. For example, based on the LLNL/Nic assessment of Millstone 3 FRA; Total CMF = 2 E-4, Blackout sequerce = 1 E-4, a 50% contribution of the blackout sequence to total CMF. In such a case the addition of the steam-driven generator would decrease the contribution of station blackout to total CMF to a negligible amount. The to:a1 CMF would decrease by a factor of 2 to 1 E-4. III UNITED KINGDOM The NRC Staff in Reference 2 provides estimates of the decrease in total CMF as a result of various design changes for the Sizewell B plant relative to the SNUPPS design. Table A.2 lists some of these estimates. Among the design changes for the Sizewell B plant, the addition cf a steam-driven charging pump has the most significant impact in decreasirg the total CMF. The total CMF is decreased by an amount greater than 1 E-4. This again would mean a factor of 2 decrease in total CMF for a plant with a large contribution from station blackout to total CMF. IV SWEDEN The risk benefits that would be achieved from the installation of a pressure relief device and a filtered vent system have been estimated by the Swedish State Power Board (SSPB) [3]. Ringhals 1 Figure A.1 shows the risk benefit for the installation of a pressure relief device, e.g. safety valve (withcut filtering). The SSPB has con:1uded that a pressure relief device preventing gross rupture of the containment leads to a significant reduction in the frequency of large releases.
I
. . Appendix A Risk Benefits from Foreign Reactor Improvements Page A03 Rirghals 2, 3 and 4 PWRs Figure A.2 shows the decrease in risk as a result of the installation of a filtered vent system. The overall conclusion drawn by the SSPB is that from the point of view of risk it is not justified to introduce a large scale filtered vent for these plants. However, in order to meet accident 4 meragement requirements (release of less than 0.1 % of core fission product !
inventory), facilities for venting will have to be installed, j l V SWITZERLAND Leibstadt BWP,/6 The owner of this plant, Kernkraftwerk Leibstadt AG, has calculated [4] that the installation of the dedicated decay heat removal system (described in the main report) decreases the CMF due to LOCAs by a factor of 100. The resulting total CMF is 6XE-6. REFERENCES
- 1. NUREG-1206: Analysis of French (Paluel) FFR Design Differences Compared tc Current U.S. PWR Designs.
- 2. NUREG-0999: Sizewell B-Analysis of British Application of U.S. PWR Technology.
- 3. R. Espefalt, L. Gunsell and G. Lowenhielm," Risk Analyses of the Ringhals Plant: Containment Behaviour and Filtered Vent", Proceedings of the Third Workshop on Containment Integrity, NUREG/CP-0076 or SAN 086-0618, August 1986.
- 4. Th. Schaub and H.P. Hanni, " Containment Integrity is a Major Part of KKL-Safety Systems PRA", Proceedings of the Third Workshop on Containment Integrity, NUREG/CP-0076 or SAND 86-0618, August 1986.
1
.- . Appendix A hisk Benefits from Foreign Reactor Improvements Page A.4 TABLE A.1 SAMPLES OF THE APPROXIMATE DECREASE IN CORE MELT FREQUENCY AS A RESULT OF FRENCH PLANT IMPROVEMENTS (From Reference 1)
Plant Improvement ; Decrease In Core From Blackout Melt Frequency) Sequences (Factor A. AC Power Effects Stean-Driven Generator 15 Gas Turbine Generator 10 (On Site) B. Decay Heat Renoval Effects Two Turbine Driven Auxiliary Feedwater Pumps 10 Gravity Feed backup for Condensate Storage Tank 10 TABLE A.2 ) i SAMPLES OF THE APPR0XIMATE DECREASE IN CORE MELT FREQUENCY AS A RESULT OF -{ PLANT IMPROVEMENTS FOR SIZEWELL B (From Reference 2) Plant Improvement Decrease In Core Melt Frequency I Steam-Driven Charging . Pumps High l 1 Emergency Boration System Moderate I Four Segregated 100% , Diesel Generators Moderate { High: Decrease in total CMF of greater than 1 E-4 Moderate: Decrease in total CMF between 1 E-4 and 1 E-5
, hebebstr Cor feecter=) ur larperthem a % PROBABILITY OF RELEASE TO THE ENMONMENT (treguencr] RINGHALS 1 o
- v. ,.,e,,e . e 2- et the testenanment (se 169ter) p6 0- swn r;- wasse stoo s- -7 ges 1 J- g 2- ~ Cs] l
.e' L_ Ringhals 1 l
10 Ringhsts 1 I 7} . Ell.h E.Y
- present status
.:, , i ,
J- 3 1 2- l l Robesse to Id ^ ' I 888 **'ir*aaneet et 10 20 30 40 50 60 70 80 90 f*,fy,',',*, testernet searce sund 1 l FIGURE A.?, hobabwty 90! reacter year
,, ,, PROBABILITY OF RELEASE TO THE ENMONMENT (treevencv) RINGHALS 2 it 6-l l
3 l 2- PWR WA SH- s t oo 5 Cs *] yf . ;
~~~
y ~'~%,. 6- l s- Csl ! I I
+8 l 10 i 1: I present status l
O' With littered eent i 2-R. / t
/ '
l Masse to 10
.y '-- J-~]1.Cs , x L
es, ,,,y,,,,,, ,, Cs ends,% or hobabwt,10 20 30 40 50 60 70 80 90 e wo meostory l l per reacter yeer **'*'**'***'****Y r et robesse \ Jerger then s % j (trequeacy) ' { l. FIGURE A.2 I. 1 _ - - _ - _ _ _ _ _ _ - - - - -}}