ML20238D983
| ML20238D983 | |
| Person / Time | |
|---|---|
| Issue date: | 09/09/1987 |
| From: | Randy Erickson Office of Nuclear Reactor Regulation |
| To: | King T NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| PROJECT-672F, PROJECT-673F, PROJECT-674F NUDOCS 8709140029 | |
| Download: ML20238D983 (2) | |
Text
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Project Nos. 672, Oll' 1 109I 673, and 674 MEMORANDUM FOR: Thomas L. King, Acting Chief
-Advanced Reactors Generic Issues Branch Office of Nuclear Regulatory Research FROM: Robert A. Erickson, Chief Safeguards Branch Office of Nuclear Reactor Regulation
SUBJECT:
ADVANCED REACTOR SAFEGUARDS REVIEWS As a result of our continuing safeguards review of the three DOE advanced reactor projects, each of which uses a form of passive air-cooling of the reactor vessel as the safety-related decay heat removal system, we have come to recognize that the contataments of these designs may entail different sabotage risks from LWRs in which the reactor vessel is enclosed within a conventional containment structure. Enclosed is a set of questions that we would appreciate being sent to DOE in order to facilitate our PSID reviews of these reactors.
Robert A. Erickson, Chief Safeguards Branch Division of Reactor Inspection and Safeguards Office of Nuclear Reactor Regulation
Enclosure:
DISTRIBUTION As stated Central Files (DCS 016)
RSGB r/f cc: Ralph Landry RSGB Advanced Reactors s/f Cardis Allen R.A.Erickson Pete Williams R.J.Dube L. Bush B.T.Mendelsohn PDR CONTACT J.G.Partlow B.T.Mendelsohn, NRR/RSGB B.K. Grimes ext. 29671 OFC :NRR/RSGB :NRR/RSGB :NRR/ GB : : : :
NAME:BMehaelsohn:RJDube T :RAE kson: : : :
DATE: 9/3/87 9/$/87 : 9/)/87 : - -
OFFICIAL RECORD COPY fy 3,i D? jh 8709140029 870909 'ys D aaos. & .f <1 e,:'
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[] ENCLOSURE Additiont?. Information Needed On Containment / Reactor Vessels l I 1
! As a result of our continuing safeguards review of the three DOE advanced reactor projects, each of which enhances the inherent safety of t6e reactor by use of passive air-cooling of the reactor vessel as the safety-rela.ted decay heat removal system, we have come to recognize that the containments of these designs inay entail different sabotage risks from LWRs in which M reactor vessel is enclosed within a massive reinforced concrete containment structure.
Although existing regulations and guidelines will be used in evaluating protection against radiological sabotage, additional criteria and guidance to address those characteristics which differ from LWRs are also to be consid-ered. Accordingly, responses for each of the advanced reactors would be appreciated from DOE and/or its contractors to the following questions:
- 1. Unauthorized acceas to equipment in containment could be more serious than unauthorized access to any single other vital area. Unauthorized personnel access into conventional containments is protected against both by the inherent resistance of the containment portals and by alarms on those
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portals. In the advanced reactor designs, air passages of the safety grade decay heat removal systems provide man-sized passages (man-sized openings "
are defined in NUREG-0908 as 96 square inches with the smallest dimension
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equal to or greater than 6 inches) from the protected area yard to loca- -
tions where relatively small amounts of explosives in the form of shaped charges could breach the reactor vessel. For example, an approximately one pound explosive device placed against a one inch thick steel barrier surrounding a three inch thick steel reactor vessel, with a 12 inch space
.E between the reactor vessel wall and the protective barrier, is estimated to~
be able to penetrate the external barrier and cause a one inch diameter hole in the reactor vessel. A 15 lbs. device is estimated to be able to make a one foot diameter hole in the same vessel. If an adversary with the capabilities defined in 10 CFR 73.l(a)(1)(1) were to penetrate undetected into a decay heat removal air shaft, what would be the consequences of a breach from the air shaft into the reactor vessel? Would heat or radiation make it impossible (self-protecting) during reactor operation for a a person to penetrate the air intake shaft down to a level where reactor
- , vessel breach could otherwise be accomplished? Would the scenario remain a-concern after the reactor had been shutdown lo.ig enough for temperatures in the shaft to be endured?
- 2. Louvers, grills, and screens included in the air intakes would impede personnel entry into the air shafts. Other or additional barriers can be included in the design to greatly increase the time it would take a pe son to penetrate the barrier while still permitting airflow. See, for example, the appendix to Reg. Guide 5.65. What criterion for personnel penetration delay does DOE propose be established for containment barriers ? Are intrusion detection devices on these barriers proposed, or on the approach-es to these barriers, to enhance the value of barrier delay? Can the airflow and maintenance requirements of the safety-grade decay Acat removal system accommodate the type of barrier with the longer penetration times (e.g., Technique No. 3 of Reg. Guide 5.5) ? ?f
.~* 'Themas L. King, Enclosura
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3.-What design criteria for the barrier, or for the air-shaft shape, are
-proposed to preclude explosive satchel charges from being dropped down the intake or exhaust shafts?
- 4. What provisions are planned for authorized personnel access td"these safety-grade decay beat removal systems for inspection and maintenance?
How will these be made compatible with the need to have effective barriers against unauthorized access? ~"'--
- 5. Although not part of current safeguards regulatory requirements, we request that you address the sabotage protection design features discussed in the January 15, 1987 ACRS letter to Chairman Zech, "ACRS Recommendations on !
Improved Safety For Future Light Water Reactor Plant Design." l
- 6. Design features to provide' inherent protection against sabotage is the focus of Generic Safety Issue A-29. In this regard, how do reactor vessels and containments of the advanced reactor designs compare to that of LWRs?
What structural design criteria for advanced reactors do you propose should apply for protection against attacks on the reactor buildings? Explain why
_ . , _ . . . liners on the reactor building walls are not necessary to protect vital ,
equipment from concrete spalls that could result from such attack. Do the designs in which a reactor vessel is underground (MHTGR and PRISM) offer the vessel more protection against an attack on the reactor building than -
- the one (SAFR) where the reactor vessel is above grade?
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