ML20052F307
| ML20052F307 | |
| Person / Time | |
|---|---|
| Issue date: | 04/08/1977 |
| From: | Taylor M NRC |
| To: | Levine S NRC |
| Shared Package | |
| ML19219B002 | List: |
| References | |
| FOIA-81-417 NUDOCS 8205120333 | |
| Download: ML20052F307 (6) | |
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ROUTING AND TRANSMITTAL $ LIP
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a m ass Per our a.m. discussions, enclosed is a cut at a listing of some potential LWR safety improvements.
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Taylor 4/8/77 Some Potential Ways to Enhance UfR Safety Broadly speaking, there are two ways in which safety of the UfR can be enhanced through added research and development or through f
UVR design modifications. These are:
(1) Mitigate the effects of core melt accidents, and (2) Reduce the probability of the core melt accidents.
Together or individually, these two ways serve to improve the existing (and small) accident risks from UVRs. Specific exahles of some f areas where risk improvements might be gained are given below:
Core Melt Hitigation (1) Install vutting and filtration systems to control potential overpressure modes of containment failure.
(2) Construct containments having significantly larger design pressure and/or large free voltanes.
(3) Construct containment base mat designs so as to bias core melt induced failitre of containment to a melt through mode. Use limited base-mat thickness and minimize the use of 00 f Iming concretes.
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Reduce Core Melt Probability i
i (1) Develop regulatory design criteria for acceptable designs involving i
l valve arrangements that interface between high and low pressure systems.
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(2) Reduce probability contributions to core melt that arise from:
a) Transients Events Resolve the /.1W5 events Improve plant ability to cope with loss of AC power events I
(e.g., full load rejection capability).
Improve plant ability to cope with events requiring shutdown heat removal and makeup.
(e.g. improved auxiliary f
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feedwater system.)
Reduce frequency and the cagnitude of operational over-
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pressure transients.
b) loss of Coolant Accidents f
- Reduce human error and the test and maintenance contributions
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to the failure of ECCS.
,- Improve redundancy of ECC subsystems.
i (3) Procedural and testing improvements Optimize testing intervals for engineered safety features
- Optimize pre-operational testing trat would validate correct
, design and installation.
- Improve operator training and emergency operating procedures for those events that pr'esently dominate the core melt probability.
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Some Potential Ways for LNR Safety Enhareccent A.
Design Areas I.
Core Melt Mitigations (1) Install Venting and filtration systems to control potential overpressure modes of contalment failure. Des 4;a,"
-to annhie ve_n_ ting operation withDoutation-of-pimps.
(Chill water. NPRi._ ate.)
I (2) Construct contalments having significantly larger n y -(.z,- e :y,,' m.
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pr: Err =7;;inir, design pres concepts of-containmenty-that%. vmy ammu wue erJ:sises.
(3) Construct contalment base mat designs so as to bias core melt induced failure of containment to a melt through mode.
Limited base-mat thickness and minimize use of CO2 forming concretes.
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(5) r ESFs, require installations of indicators, annunciators ard preferable override capabilities for valves (or other such equipment) that are vulnerable to test and maintenance errors.
, 6) F11minate LHI to minimite. Vessel failure probability that may
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intervals. Use realistic ifCA modeling to assess on realistic t,.
basis, the benefits of IMI in large IDCA.
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2-(7) Reqpire diversity of ARG actuation for A33 events, b(8) Optimize AFIG delivery characteristics for ABS events g
considering stuck open relief valve for steam generators.
'(9) Optimize ARG delivery to midimize water Nb, events
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and design damage as has been evidenced by W PWRs.
W...~f.$ -(10) Optimize ARG design to improve redundancy of condensate
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[k valving (, suction) and AF;G water supplies.
(11) Optimize ARG design to include redundancy of steam turbine driven ptsps that are self sustaining for conditions of
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loss of AC power to the unit.
(12) Install adequate safety valves on RCS to mitigate ADG
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(13) Install redundant R GT supplies in order to minimize human error chances during the IDCAhrculation phase operations.
Evaluate pros and cons of automatic initiation of recirculation phase for both large and small IDCAs.
(14) Improve reliability of pressure relief valving to operate for RfRs.
4 (15) Optimize on the reliability makeup systems and letdom isolation e
for selected transient conditims (e.g., loss of AC).
(16) BWR ADG fixes, e.g., i% rove makeup capability, boron injection, etc.
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Procedural Areas (17) Optimize ESF test intervals, staggering of testing, etc.
to optimize on system availability and on accident sequences.
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3 (18) Optimize on pre-operational testing to ensure verification of design adequacy for ESF design and actuation logic.
(19) Improve data analyses to enable check on whethe.r safety is md being senset and to enable h~dC to spot the outliers in systems unavailability, etc.
(20) Improve on operator training and emergency operating procedures to focus on those accidents (transients) found to A=fnate risk. OJnfocus from large tocA).
(21) Develop emergency preparedness progran to cope with liquid pathways (on core melty to mitigate pathway concentrations.
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