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{{Short description|Failed medical isotope reactor in Canada}}
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'''MAPLE''', short for the '''Multipurpose Applied Physics Lattice Experiment''', later renamed '''MDS Medical Isotope Reactors''' ('''MMIR'''), was a dedicated isotope-production facility built by [[Atomic Energy of Canada Limited|AECL]] and [[MDS Inc.|MDS Nordion]]. It included two identical reactors, I and II, as well as the isotope-processing facilities necessary to produce a large portion of the world's medical isotopes, especially [[molybdenum-99]], medical [[cobalt-60]], [[xenon-133]], [[iodine-131]] and [[iodine-125]].<ref>[http://www.aecl.ca/Commercial/DIF/MAPLE/DIF-MAPLE.htm How the MAPLE Reactors Work] {{webarchive|url=https://web.archive.org/web/20080322074155/http://www.aecl.ca/Commercial/DIF/MAPLE/DIF-MAPLE.htm |date=2008-03-22 }}</ref>

An operational license for the MAPLE I reactor was granted in 1999, and the reactor went critical for the first time in early 2000. MAPLE II followed in the fall of 2003. Problems with the reactors during the testing period, most notably an unexpected positive [[Nuclear chain reaction|power co-efficient of reactivity]], led to the cancellation of the project in 2008 and the shutdown of both reactors.

==History==

===Background===
With the completion of the [[NRX]] reactor in 1947, [[AECL]]'s [[Chalk River Laboratories]] possessed the world's most powerful research reactor. While the large neutron fluxes available in the reactor led to advances in such fields as [[condensed matter physics]] and neutron spectroscopy, many experiments were carried out involving the production of new [[isotopes]]. The field of [[nuclear medicine]] developed when it was realized that some of these artificially created isotopes could be used to diagnose and treat many diseases, especially cancers.

Pioneering medical work done in the late 1940s and early 1950s established [[cobalt-60]] as a useful isotope, as the relatively high-energy [[gamma rays]] produced when it undergoes [[beta decay]] are able to penetrate the skin of the patient, and deliver a greater portion of the dose directly to the tumor. The high neutron efficiency of the NRX's [[heavy water]]-moderated design, coupled with the high neutron flux of the reactor, made it relatively inexpensive for AECL to produce medical-grade cobalt-60. For example, the cost of the entire unit used to perform the first cobalt-60 treatment was about $50,000. By way of contrast, it would cost $50,000,000 just to produce enough [[radium]] (which had been previously used as a therapy source) to perform the same procedure.<ref>{{cite news| url=http://archives.cbc.ca/400d.asp?id=1-75-346-1855-20&wm6=1 | work=CBC News | title=CBC Archives}}</ref>

With this promising start, AECL came to be a major world supplier of medical isotopes, using both the [[NRX]] reactor, and the [[National Research Universal Reactor|NRU]] reactor, which came on-line in 1957. However, as these reactors began to age, it became clear that a new facility would be needed to continue the production of medical isotopes.

===Beginnings===
In the late 1980s, AECL began to acknowledge that continued isotope production would require the construction of a new reactor to replace capacity lost by the planned closing of the [[NRX]] in 1992, and the planned closing of the [[National Research Universal Reactor|NRU]] early in the new millennium. Design work on a replacement, originally under the name "Maple-X10", began in the late 1980s.<ref name=myers/>

As part of a restructuring taking place around the same time, the medical isotopes side of AECL was reorganized as Nordion in 1988. Work on the X10 project essentially ended at this point. Nordion company was purchased by MDS in 1991, and an agreement was reached between AECL and MDS Nordion that a new facility dedicated to the production of medical isotopes would be needed.<ref name=myers/> A formal agreement was signed to begin the project in August 1996. Following a year-long environmental assessment, construction began in December 1997.<ref>{{cite web |url=http://anes.fiu.edu/Pro/s4ma1.pdf |title=Archived copy |website=anes.fiu.edu |access-date=22 May 2022 |archive-url=https://web.archive.org/web/20040122024353/http://anes.fiu.edu/Pro/s4ma1.pdf |archive-date=22 January 2004 |url-status=dead}}</ref>

The design that resulted involved a facility with two identical reactors, each capable of supplying 100% of the world's medical isotope demand. The second reactor would function primarily as a backup, to ensure that the supply of isotopes would not be interrupted by maintenance or unplanned shutdowns. This is made necessary by the nature of medical isotopes; many have short [[half-lives]], and must be used within a few days of production. With treatments being constantly carried out around the globe, an uninterruptible supply was essential.

There had been some local opposition to the use of highly enriched uranium ([[Highly enriched uranium|HEU]]) in the reactor,<ref>[http://www.ccnr.org/maple_heu.html Website of local group opposed to HEU in MAPLE]</ref> as well as from activists in the United States who fear that the uranium could be stolen by terrorists and used to fabricate a bomb.<ref>[http://www.nci.org/c/c21999.htm 2/19/99 Letter from American group concerned about HEU use in MAPLE]</ref>

===Project cancellation===
Originally planned to complete construction in 1999 and 2000, both reactors were instead completed in May 2000. An operational license was granted in August 1999 for the MAPLE I reactor, and extended to include the MAPLE II reactor in June 2000. Commissioning testing was begun immediately, with the MAPLE I achieving its first sustained reaction in February 2000, and MAPLE II following in October 2003.

However, during testing, it was noted that some of the emergency shut-off rods in the MAPLE I reactor could fail to deploy in certain demanding situations. This failure was ascribed to workmanship and design issues, and related to fine metal particles accumulating in the control rods' housing and interfering with their free movement.{{Citation needed|date=May 2008}}

In addition, later testing found that the reactors have a positive [[Nuclear reactor physics#Moderators and reactor design|power co-efficient of reactivity]] (PCR), which was in disagreement with the prediction of the modelling, and was a significant barrier to commissioning.<ref name=myers>{{cite news |url=http://www.magma.ca/~drcanrt/aeclscrapmaple.htm |newspaper=North Renfrew Times |title= AECL scraps Maple project |first= Terry |last=Myers |date=21 May 2008 |archive-url=https://web.archive.org/web/20080602140723/http://www.magma.ca/~drcanrt/aeclscrapmaple.htm |archive-date=2 June 2008 }}</ref> A positive power co-efficient means that the reactor becomes more reactive when it heats up; in the case of an unplanned power spike, such a design can "run away" and potentially cause a [[Nuclear meltdown|meltdown]].<ref name=mccarthy/>

Consequently, significant efforts were made to resolve the outstanding issues, but progress towards commissioning the reactors was markedly slowed.<ref>[http://www.invap.net/news/novedades-e.php?id=20060628192056 Press release of an agreement with INVAP for numerical modelling work] {{webarchive|url=https://web.archive.org/web/20080616124416/http://www.invap.net/news/novedades-e.php?id=20060628192056 |date=2008-06-16 }}</ref><ref>[http://www.aecl.ca/Regulatory/Activities/Maple-Update.htm Index of AECL submissions to the CNSC for licensing, and the subsequent decisions.] {{webarchive|url=https://web.archive.org/web/20080524211437/http://www.aecl.ca/Regulatory/Activities/Maple-Update.htm |date=2008-05-24 }}</ref> During the subsequent eight-year-long delay in the start of commercial production, the project significantly overran its budgeted cost. The original budget was $140 million, but by 2005 it had already cost $300 million.<ref name=myers/> Disputes over responsibility for the overruns between [[AECL]] and MDS Nordion added a further layer of complexity to the process. After considerable negotiation, AECL assumed full responsibility for the reactor in a settlement.<ref>[http://www.accessmylibrary.com/coms2/summary_0286-13214549_ITM PR Newswire report of AELC-MDS Nordion Settlement (in brief)]</ref>

The MAPLE facility was granted an extension on its operating license on 25 October 2007, which would permit operations until 31 October 2011.<ref>[http://www.nuclearsafety.gc.ca/eng/newsroom/releases/news_release.cfm?news_release_id=285 Release confirming licence extension.] {{webarchive|url=https://web.archive.org/web/20080105180516/http://www.nuclearsafety.gc.ca/eng/newsroom/releases/news_release.cfm?news_release_id=285 |date=2008-01-05 }}</ref> This (final) submission envisioned that the MAPLE I reactor would be operational in late 2008.<ref>[https://web.archive.org/web/20071115040202/http://www.aecl.ca/Assets/Publications/CNSC/Presentation-070912.pdf October 2007 AECL submission to the CNSC, see Slide 8 on Page 4.]</ref>

On 16 May 2008, AECL released a statement announcing that the MAPLE program had been terminated, as it had become "no longer feasible to complete the commissioning and start-up of the reactors".<ref name=mccarthy>{{cite news |first=Shawn |last=McCarthy |title= AECL pulls plug on reactors after millions spent |date=17 May 2008 |newspaper=The Globe and Mail |url=https://www.theglobeandmail.com/news/national/aecl-pulls-plug-on-reactors-after-millions-spent/article17986228/}}</ref> In this statement, AECL indicated that they would move to further extend the licence of the operating [[National Research Universal Reactor|NRU]] reactor to continue the production of medical isotopes. The statement left unclear what long-term direction AECL would take for its medical isotope production business.

==References==
{{reflist}}

==External links==
*[http://archives.cbc.ca/400d.asp?id=1-75-346-1855-20&wm6=1 Article on early cobalt therapy]
* https://web.archive.org/web/20080618221319/http://www.aecl.ca/NewsRoom/News/Press-2008/080516.htm
* {{cite journal | last1 = Magnus | first1 = B. | title = Over budget, overdue and, perhaps, overdesigned | journal = Canadian Medical Association Journal | volume = 178 | pages = 813–4 | year = 2008 | doi = 10.1503/cmaj.080320 | issue = 7 | pmid = 18362369 | pmc = 2267837}}

{{Nuclear power in Canada}}

[[Category:Atomic Energy of Canada Limited]]
[[Category:Nuclear reactors]]